A microtubule structure that forms during CELL DIVISION. It consists of two SPINDLE POLES, and sets of MICROTUBULES that may include the astral microtubules, the polar microtubules, and the kinetochore microtubules.
A broad category of nuclear proteins that are components of or participate in the formation of the NUCLEAR MATRIX.
A type of CELL NUCLEUS division by means of which the two daughter nuclei normally receive identical complements of the number of CHROMOSOMES of the somatic cells of the species.
Slender, cylindrical filaments found in the cytoskeleton of plant and animal cells. They are composed of the protein TUBULIN and are influenced by TUBULIN MODULATORS.
The cell center, consisting of a pair of CENTRIOLES surrounded by a cloud of amorphous material called the pericentriolar region. During interphase, the centrosome nucleates microtubule outgrowth. The centrosome duplicates and, during mitosis, separates to form the two poles of the mitotic spindle (MITOTIC SPINDLE APPARATUS).
The orderly segregation of CHROMOSOMES during MEIOSIS or MITOSIS.
A microtubule subunit protein found in large quantities in mammalian brain. It has also been isolated from SPERM FLAGELLUM; CILIA; and other sources. Structurally, the protein is a dimer with a molecular weight of approximately 120,000 and a sedimentation coefficient of 5.8S. It binds to COLCHICINE; VINCRISTINE; and VINBLASTINE.
A type of CELL NUCLEUS division, occurring during maturation of the GERM CELLS. Two successive cell nucleus divisions following a single chromosome duplication (S PHASE) result in daughter cells with half the number of CHROMOSOMES as the parent cells.
Skeletal muscle structures that function as the MECHANORECEPTORS responsible for the stretch or myotactic reflex (REFLEX, STRETCH). They are composed of a bundle of encapsulated SKELETAL MUSCLE FIBERS, i.e., the intrafusal fibers (nuclear bag 1 fibers, nuclear bag 2 fibers, and nuclear chain fibers) innervated by SENSORY NEURONS.
A stack of flattened vesicles that functions in posttranslational processing and sorting of proteins, receiving them from the rough ENDOPLASMIC RETICULUM and directing them to secretory vesicles, LYSOSOMES, or the CELL MEMBRANE. The movement of proteins takes place by transfer vesicles that bud off from the rough endoplasmic reticulum or Golgi apparatus and fuse with the Golgi, lysosomes or cell membrane. (From Glick, Glossary of Biochemistry and Molecular Biology, 1990)
Proteins that control the CELL DIVISION CYCLE. This family of proteins includes a wide variety of classes, including CYCLIN-DEPENDENT KINASES, mitogen-activated kinases, CYCLINS, and PHOSPHOPROTEIN PHOSPHATASES as well as their putative substrates such as chromatin-associated proteins, CYTOSKELETAL PROTEINS, and TRANSCRIPTION FACTORS.
Test for tissue antigen using either a direct method, by conjugation of antibody with fluorescent dye (FLUORESCENT ANTIBODY TECHNIQUE, DIRECT) or an indirect method, by formation of antigen-antibody complex which is then labeled with fluorescein-conjugated anti-immunoglobulin antibody (FLUORESCENT ANTIBODY TECHNIQUE, INDIRECT). The tissue is then examined by fluorescence microscopy.
The first continuously cultured human malignant CELL LINE, derived from the cervical carcinoma of Henrietta Lacks. These cells are used for VIRUS CULTIVATION and antitumor drug screening assays.
Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.
The phase of cell nucleus division following METAPHASE, in which the CHROMATIDS separate and migrate to opposite poles of the spindle.
Large multiprotein complexes that bind the centromeres of the chromosomes to the microtubules of the mitotic spindle during metaphase in the cell cycle.
The phase of cell nucleus division following PROMETAPHASE, in which the CHROMOSOMES line up across the equatorial plane of the SPINDLE APPARATUS prior to separation.
A microtubule-associated mechanical adenosine triphosphatase, that uses the energy of ATP hydrolysis to move organelles along microtubules toward the plus end of the microtubule. The protein is found in squid axoplasm, optic lobes, and in bovine brain. Bovine kinesin is a heterotetramer composed of two heavy (120 kDa) and two light (62 kDa) chains. EC 3.6.1.-.
High molecular weight proteins found in the MICROTUBULES of the cytoskeletal system. Under certain conditions they are required for TUBULIN assembly into the microtubules and stabilize the assembled microtubules.
Nocodazole is an antineoplastic agent which exerts its effect by depolymerizing microtubules.
Mad2 is a component of the spindle-assembly checkpoint apparatus. It binds to and inhibits the Cdc20 activator subunit of the anaphase-promoting complex, preventing the onset of anaphase until all chromosomes are properly aligned at the metaphase plate. Mad2 is required for proper microtubule capture at KINETOCHORES.
A family of highly conserved serine-threonine kinases that are involved in the regulation of MITOSIS. They are involved in many aspects of cell division, including centrosome duplication, SPINDLE APPARATUS formation, chromosome alignment, attachment to the spindle, checkpoint activation, and CYTOKINESIS.
In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)
A family of multisubunit cytoskeletal motor proteins that use the energy of ATP hydrolysis to power a variety of cellular functions. Dyneins fall into two major classes based upon structural and functional criteria.
The final phase of cell nucleus division following ANAPHASE, in which two daughter nuclei are formed, the CYTOPLASM completes division, and the CHROMOSOMES lose their distinctness and are transformed into CHROMATIN threads.
The cellular signaling system that halts the progression of cells through MITOSIS or MEIOSIS if a defect that will affect CHROMOSOME SEGREGATION is detected.
The process by which the CYTOPLASM of a cell is divided.
Microscopy of specimens stained with fluorescent dye (usually fluorescein isothiocyanate) or of naturally fluorescent materials, which emit light when exposed to ultraviolet or blue light. Immunofluorescence microscopy utilizes antibodies that are labeled with fluorescent dye.
Female germ cells derived from OOGONIA and termed OOCYTES when they enter MEIOSIS. The primary oocytes begin meiosis but are arrested at the diplotene state until OVULATION at PUBERTY to give rise to haploid secondary oocytes or ova (OVUM).
A group of enzymes that catalyzes the phosphorylation of serine or threonine residues in proteins, with ATP or other nucleotides as phosphate donors.
An amorphous region of electron dense material in the cytoplasm from which the MICROTUBULES polymerization is nucleated. The pericentriolar region of the CENTROSOME which surrounds the CENTRIOLES is an example.
Proteins obtained from the species SACCHAROMYCES CEREVISIAE. The function of specific proteins from this organism are the subject of intense scientific interest and have been used to derive basic understanding of the functioning similar proteins in higher eukaryotes.
Proteins found in the microtubules.
Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.
Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.
Proteins found in the nucleus of a cell. Do not confuse with NUCLEOPROTEINS which are proteins conjugated with nucleic acids, that are not necessarily present in the nucleus.
Motor neurons which activate the contractile regions of intrafusal SKELETAL MUSCLE FIBERS, thus adjusting the sensitivity of the MUSCLE SPINDLES to stretch. Gamma motor neurons may be "static" or "dynamic" according to which aspect of responsiveness (or which fiber types) they regulate. The alpha and gamma motor neurons are often activated together (alpha gamma coactivation) which allows the spindles to contribute to the control of movement trajectories despite changes in muscle length.
Self-replicating, short, fibrous, rod-shaped organelles. Each centriole is a short cylinder containing nine pairs of peripheral microtubules, arranged so as to form the wall of the cylinder.
The complex series of phenomena, occurring between the end of one CELL DIVISION and the end of the next, by which cellular material is duplicated and then divided between two daughter cells. The cell cycle includes INTERPHASE, which includes G0 PHASE; G1 PHASE; S PHASE; and G2 PHASE, and CELL DIVISION PHASE.
The first phase of cell nucleus division, in which the CHROMOSOMES become visible, the CELL NUCLEUS starts to lose its identity, the SPINDLE APPARATUS appears, and the CENTRIOLES migrate toward opposite poles.
A species of the genus SACCHAROMYCES, family Saccharomycetaceae, order Saccharomycetales, known as "baker's" or "brewer's" yeast. The dried form is used as a dietary supplement.
The phase of cell nucleus division following PROPHASE, when the breakdown of the NUCLEAR ENVELOPE occurs and the MITOTIC SPINDLE APPARATUS enters the nuclear region and attaches to the KINETOCHORES.
An organization of cells into an organ-like structure. Organoids can be generated in culture. They are also found in certain neoplasms.
The clear constricted portion of the chromosome at which the chromatids are joined and by which the chromosome is attached to the spindle during cell division.
Orientation of intracellular structures especially with respect to the apical and basolateral domains of the plasma membrane. Polarized cells must direct proteins from the Golgi apparatus to the appropriate domain since tight junctions prevent proteins from diffusing between the two domains.
The property of nonisotropic media, such as crystals, whereby a single incident beam of light traverses the medium as two beams, each plane-polarized, the planes being at right angles to each other. (Cline et al., Dictionary of Visual Science, 4th ed)
The process of moving proteins from one cellular compartment (including extracellular) to another by various sorting and transport mechanisms such as gated transport, protein translocation, and vesicular transport.
Highly conserved proteins that specifically bind to and activate the anaphase-promoting complex-cyclosome, promoting ubiquitination and proteolysis of cell-cycle-regulatory proteins. Cdc20 is essential for anaphase-promoting complex activity, initiation of anaphase, and cyclin proteolysis during mitosis.
A monomeric GTP-binding protein involved in nucleocytoplasmic transport of proteins into the nucleus and RNA into the cytoplasm. This enzyme was formerly listed as EC 3.6.1.47.
The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.
The interval between two successive CELL DIVISIONS during which the CHROMOSOMES are not individually distinguishable. It is composed of the G phases (G1 PHASE; G0 PHASE; G2 PHASE) and S PHASE (when DNA replication occurs).
Proteins obtained from various species of Xenopus. Included here are proteins from the African clawed frog (XENOPUS LAEVIS). Many of these proteins have been the subject of scientific investigations in the area of MORPHOGENESIS and development.

Drosophila oogenesis: versatile spn doctors. (1/4092)

Recent work on Drosophila oogenesis has uncovered connections between cell-cycle checkpoints and pattern formation. Genes of the spindle class, which encode double-strand break repair enzymes and RNA helicases, affect oocyte polarity and the decision whether to differentiate as an oocyte or a nurse cell.  (+info)

C-myc overexpression and p53 loss cooperate to promote genomic instability. (2/4092)

p53 monitors genomic integrity at the G1 and G2/M cell cycle checkpoints. Cells lacking p53 may show gene amplification as well as the polyploidy or aneuploidy typical of many tumors. The pathways through which this develops, however, are not well defined. We demonstrate here that the combination of p53 inactivation and c-myc overexpression in diploid cells markedly accelerates the spontaneous development of tetraploidy. This is not seen with either N-myc or L-myc. Tetraploidy is accompanied by significantly higher levels of cyclin B and its associated cdc2 kinase activity. Mitotic spindle poisons accelerate the appearance of tetraploidy in cells either lacking functional p53 or overexpressing c-myc whereas the combination is additive. Restoration of p53 function in cells overexpressing c-myc causing rapid apoptosis, indicating that cells yet to become tetraploid have nonetheless suffered irreversible genomic and/or mitotic spindle damage. In the face of normal p53 function, such damage would either be repaired or trigger apoptotis. We propose that loss of p53 and overexpression of c-myc permits the emergence and survival of cells with increasingly severe damage and the eventual development of tetraploidy.  (+info)

Defects in Saccharomyces cerevisiae protein phosphatase type I activate the spindle/kinetochore checkpoint. (3/4092)

A conditional allele of type 1 protein phosphatase (glc7-129) in Saccharomyces cerevisiae causes first cycle arrest in G2/M, characterized by cells with a short spindle and high H1 kinase activity. Point-of-execution experiments indicate Glc7p function is required in G2/M just before anaphase for the completion of mitosis. Loss of the spindle/kinetochore checkpoint in glc7-129 cells abolishes the G2/M cell cycle arrest with a concomitant increase in chromosome loss and reduced viability. These results support a role for Glc7p in regulating kinetochore attachment to the spindle, an event monitored by the spindle/kinetochore checkpoint.  (+info)

The conserved protein kinase Ipl1 regulates microtubule binding to kinetochores in budding yeast. (4/4092)

Chromosome segregation depends on kinetochores, the structures that mediate chromosome attachment to the mitotic spindle. We isolated mutants in IPL1, which encodes a protein kinase, in a screen for budding yeast mutants that have defects in sister chromatid separation and segregation. Cytological tests show that ipl1 mutants can separate sister chromatids but are defective in chromosome segregation. Kinetochores assembled in extracts from ipl1 mutants show altered binding to microtubules. Ipl1p phosphorylates the kinetochore component Ndc10p in vitro and we propose that Ipl1p regulates kinetochore function via Ndc10p phosphorylation. Ipl1p localizes to the mitotic spindle and its levels are regulated during the cell cycle. This pattern of localization and regulation is similar to that of Ipl1p homologs in higher eukaryotes, such as the human aurora2 protein. Because aurora2 has been implicated in oncogenesis, defects in kinetochore function may contribute to genetic instability in human tumors.  (+info)

Abnormal spindle protein, Asp, and the integrity of mitotic centrosomal microtubule organizing centers. (5/4092)

The product of the abnormal spindle (asp) gene was found to be an asymmetrically localized component of the centrosome during mitosis, required to focus the poles of the mitotic spindle in vivo. Removing Asp protein function from Drosophila melanogaster embryo extracts, either by mutation or immunodepletion, resulted in loss of their ability to restore microtubule-organizing center activity to salt-stripped centrosome preparations. This was corrected by addition of purified Asp protein. Thus, Asp appears to hold together the microtubule-nucleating gamma-tubulin ring complexes that organize the mitotic centrosome.  (+info)

Influence of centriole behavior on the first spindle formation in zygotes of the brown alga Fucus distichus (Fucales, Phaeophyceae). (6/4092)

The influence of centrioles, derived from the sperm flagellar basal bodies, and the centrosomal material (MTOCs) on spindle formation in the brown alga Fucus distichus (oogamous) was studied by immunofluorescence microscopy using anti-centrin and anti-beta-tubulin antibodies. In contrast to a bipolar spindle, which is formed after normal fertilization, a multipolar spindle was formed in polyspermic zygote. The number of mitotic poles in polyspermic zygotes was double the number of sperm involved in fertilization. As an anti-centrin staining spot (centrioles) was located at these poles, the multipolar spindles in polyspermic zygotes were produced by the supplementary centrioles. When anucleate egg fragments were fertilized, chromosome condensation and mitosis did not occur in the sperm nucleus. Two anti-centrin staining spots could be detected, microtubules (MTs) radiated from nearby, but the mitotic spindle was never produced. When a single sperm fertilized multinucleate eggs (polygyny), abnormal spindles were also observed. In addition to two mitotic poles containing anti-centrin staining spots, extra mitotic poles without anti-centrin staining spots were also formed, and as a result multipolar spindles were formed. When karyogamy was blocked with colchicine, it became clear that the egg nucleus proceeded independently into mitosis accompanying chromosome condensation. A monoastral spindle could be frequently observed, and in rare cases a barrel-shaped spindle was formed. However, when a sperm nucleus was located near an egg nucleus, the two anti-centrin staining spots shifted to the egg nucleus from the sperm nucleus. In this case, a normal spindle was formed, the egg chromosomes arranged at the equator, and the associated MTs elongated from one pole of the egg spindle toward the sperm chromosomes which were scattered. From these results, it became clear that paternal centrioles derived from the sperm have a crucial role in spindle formation in the brown algae, such as they do during animal fertilization. However, paternal centrioles were not adequate for the functional centrosome during spindle formation. We speculated that centrosomal materials from the egg cytoplasm aggregate around the sperm centrioles and are needed for centrosomal activation.  (+info)

Self assembly of NuMA: multiarm oligomers as structural units of a nuclear lattice. (7/4092)

NuMA is a nuclear matrix protein in interphase and relocates to the spindle poles in mitotis. Different NuMA constructs, in which either N- or C-terminal domains were deleted, and the full-length construct were expressed in Escherichia coli, and the NuMA polypeptides were purified to homogeneity and allowed to assemble in vitro. Electron microscopy showed that NuMA can build multiarm oligomers by interaction of the C-terminal globular domains. Each arm of the oligomer corresponds to a NuMA dimer. Oligomers with up to 10 or 12 arms have been observed for both full-length NuMA and for constructs that still contain the proximal part of the C-terminal tail domain. Other results from this laboratory have shown that transient overexpression of NuMA in HeLa cells induces a nuclear scaffold with a quasi-hexagonal organization that can fill the nuclei. Here we show that computer modelling of the three-dimensional packing of NuMA into such scaffolds can explain the different spacing of the hexagons seen when constructs with different coiled-coil lengths are used. Thus, the 12 arm oligomer, for which we have in vitro evidence, may be the structural unit from which the nuclear scaffold in transfected cells is built.  (+info)

Control of mitotic spindle position by the Saccharomyces cerevisiae formin Bni1p. (8/4092)

Alignment of the mitotic spindle with the axis of cell division is an essential process in Saccharomyces cerevisiae that is mediated by interactions between cytoplasmic microtubules and the cell cortex. We found that a cortical protein, the yeast formin Bni1p, was required for spindle orientation. Two striking abnormalities were observed in bni1Delta cells. First, the initial movement of the spindle pole body (SPB) toward the emerging bud was defective. This phenotype is similar to that previously observed in cells lacking the kinesin Kip3p and, in fact, BNI1 and KIP3 were found to be in the same genetic pathway. Second, abnormal pulling interactions between microtubules and the cortex appeared to cause preanaphase spindles in bni1Delta cells to transit back and forth between the mother and the bud. We therefore propose that Bni1p may localize or alter the function of cortical microtubule-binding sites in the bud. Additionally, we present evidence that other bipolar bud site determinants together with cortical actin are also required for spindle orientation.  (+info)

by Changsen Leng, Arend W. Overeem, Fernando Cartón-Garcia, Qinghong Li, Karin Klappe, Jeroen Kuipers, Yingying Cui, Inge S. Zuhorn, Diego Arango, Sven C. D. van IJzendoorn. Recycling endosomes regulate plasma membrane recycling. Recently, recycling endosome-associated proteins have been implicated in the positioning and orientation of the mitotic spindle and cytokinesis. Loss of MYO5B, encoding the recycling endosome-associated myosin Vb, is associated with tumor development and tissue architecture defects in the gastrointestinal tract. Whether loss of MYO5B expression affects mitosis is not known. Here, we demonstrate that loss of MYO5B expression delayed cytokinesis, perturbed mitotic spindle orientation, led to the misorientation of the plane of cell division during the course of mitosis, and resulted in the delamination of epithelial cells. Remarkably, the effects on spindle orientation, but not cytokinesis, were a direct consequence of physical hindrance by giant late endosomes, which ...
Exit from mitosis in animal cells is substantially delayed when spindle assembly is inhibited, spindle bipolarity is disrupted, or when a monopolar spindle is formed. These observations have led to the proposal that animal cells have a spindle assembly checkpoint for the metaphase-anaphase transition that monitors bipolar spindle organization. However, the existence of such a checkpoint is uncertain because perturbations in spindle organization can produce unattached kinetochores, which by themselves are known to delay anaphase onset. In this study we have tested if cells monitor bipolar spindle organization, independent of kinetochore attachment, by analyzing the duration of mitosis in sea urchin zygotes and vertebrate somatic cells containing multipolar spindles in which all kinetochores are attached to spindle poles. We found that sea urchin zygotes containing tripolar or tetrapolar spindles progressed from nuclear envelope breakdown to anaphase onset with normal timing. We also found that ...
Microtubule organization is essential for bipolar spindle assembly and chromosome segregation, which contribute to genome stability. Kinesin-5 Eg5 is known to be a crucial regulator in centrosome separation and spindle assembly in mammalian somatic cells, however, the functions and mechanisms of Eg5 in male meiotic cell division remain largely unknown. In this study, we have found that Eg5 proteins are expressed in mouse spermatogonia, spermatocytes and spermatids. After Eg5 inhibition by specific inhibitors Monastrol, STLC and Dimethylenastron, the meiotic spindles of dividing spermatocytes show spindle collapse and the defects in bipolar spindle formation. We demonstrate that Eg5 regulates spindle bipolarity and the maintenance of meiotic spindles in meiosis. Eg5 inhibition leads to monopolar spindles, spindle abnormalities and chromosome misalignment in cultured GC-2 spd cells. Furthermore, Eg5 inhibition results in the decrease of the spermatids and the abnormalities in mature sperms. Our results
Microtubule nucleation for anastral spindle assembly is dependent on chromatin, differing from astral spindles; however, the mechanism of nucleation is still not certain. The initial stages in formation of anastral Drosophila oocyte MI spindles have been studied by imaging live oocytes injected with rhodamine-tubulin [33] or expressing the kinesin-14 Ncd motor fused to GFP to visualize the spindle [20]. Microtubule growth from the condensed MI chromosomes or karyosome was observed in both cases, providing evidence that microtubule nucleation occurs from chromatin, as first observed in Xenopus extract spindles [1]. Time-lapse images obtained with Ncd-GFP showed small fluorescent foci or asters that migrated towards and associated with the karyosome, after which spindle microtubules grew out in all directions from the chromosomes [20]. The asters were also observed labeled with rhodamine-tubulin but were thought not to play a role in spindle assembly, in part because they were not associated with ...
The journal shows that mitotic spindle orientation is powered by cortical dynein and regulated by two signal gradients during mitosis, Plk1 and the RanGTP [3]. However, many things still remain elusive such as the molecular level of how RanGTP interacts with LNG-NuMA and causes it to delocalise off the cell cortex. Understanding still remains underdeveloped, especially of other eukaryotic cells, such as plants, which dont have centrosomes [1]. Greater understanding in these processes and other complementary signals can be applied into targeted therapy and chemotherapy for various diseases [6]. Inhibitors and targeting drugs can provide effective therapeutic applications to cancers, which can target specific cells, important signals (such as Plk1, cortical dynein and LGN-NuMA) and microtubules in different cell cycles of cancerous cells to cause mitotic arrest/death [6]. One of the main goals of anti-mitotics (a branch of chemotherapy drugs) is to disrupt the mitotic spindle. Two common classes ...
In cell biology, the spindle apparatus (or mitotic spindle) refers to the cytoskeletal structure of eukaryotic cells that forms during cell division to separate sister chromatids between daughter cells. It is referred to as the mitotic spindle during mitosis, a process that produces genetically identical daughter cells, or the meiotic spindle during meiosis, a process that produces gametes with half the number of chromosomes of the parent cell. Besides chromosomes, the spindle apparatus is composed of hundreds of proteins. Microtubules comprise the most abundant components of the machinery. Attachment of microtubules to chromosomes is mediated by kinetochores, which actively monitor spindle formation and prevent premature anaphase onset. Microtubule polymerization and depolymerization dynamics drive chromosome congression. Depolymerization of microtubules generates tension at kinetochores; bipolar attachment of sister kinetochores to microtubules emanating from opposite cell poles couples ...
Formation of the mitotic spindle involves a tightly regulated series of coordinated events that ultimately leads to chromosome segregation and cytokinesis. On p. 435, Stephen Huisman and colleagues investigate the role of the essential cell cycle kinase Cdc28-Clb5 in polarity of the mitotic spindle and describe a novel role for spindle pole body component Spc110 in the regulation of spindle morphogenesis in yeast. The authors performed a genetic screen to identify targets of Cdc28-Clb5 kinase involved in spindle polarity and identified a truncated version of Spc110. The truncated version, Spc110Δ13, can suppress the lethal phenotype of the cdc28-4 clb5Δ strain. Cdc28-Clb5 localises to spindle poles and intranuclear microtubules, which is consistent with a role in spindle morphogenesis. The authors find that the Clb5-dependent kinase phosphorylates Spc110 in a cell-cycle-dependent manner at two CDK consensus sites, which is crucial for correct spindle integrity. Their data support a model ...
Every cell division in budding yeast is inherently asymmetric and counts on the correct positioning of the mitotic spindle along the mother-daughter polarity axis for faithful chromosome segregation. A surveillance mechanism named the spindle position checkpoint (SPOC), monitors the orientation of the mitotic spindle and prevents cells from exiting mitosis when the spindle fails to align along the mother-daughter axis. SPOC is essential for maintenance of ploidy in budding yeast and similar mechanisms might exist in higher eukaryotes to ensure faithful asymmetric cell division. Here, we review the current model of SPOC activation and highlight the importance of protein localization and phosphorylation for SPOC function.
In conclusion, we propose that the mitotic spindle protein She1 functions as an MT cross-linking protein to maintain proper spindle stability during metaphase (Fig. 6 H). There are three major lines of evidence supporting this conclusion: (1) she1-ΔN89 and she1-ΔN126 cells display dynein-independent spindle defects, (2) She1 cross-links MTs in vitro, and (3) the she1-ΔN126 spindle phenotype is complemented by inactivation of Ipl1/Aurora B or by overexpression of she1-ΔN126. The latter shows that premature loading of Ipl1/Aurora B in metaphase inhibits the spindle stabilization effect of she1-ΔN126. Furthermore, we show that this novel activity of She1 is negatively regulated by Ipl1/CPC translocation during anaphase.. Recent work suggested that, during the establishment of a functional metaphase spindle midzone (Hepperla et al., 2014), passive cross-linking proteins are required to maintain proper bundling within the spindle once ipMTs are aligned along the spindle axis by kinesin-14 ...
The mitotic spindle is a highly specialized macromolecular machinery that ensures equal segregation of genetic information between daughter cells during mitosis. The assembly and operation of this complex and very dynamic structure have to be appropriately regulated to avoid generation of aneuploid cells. Numerous signaling molecules participate in this regulation, and they include the Aurora A kinase. Some of the functions of the Aurora A kinase during mitotic spindle assembly are now well established; they operate in G2 when the kinase is recruited to centrosomes. Aurora A participates in centrosome maturation by recruiting NDLE1 (Mori et al., 2007) and TACC3 (Kinoshita et al., 2005). In prometaphase, Aurora A participates in regulation of microtubule dynamics by contributing to the recruitment of factors involved in the dynamic instability of microtubules, including DDA3 (Jang and Fang, 2011), MCAK (Zhang et al., 2008), ch-TOG (De Luca et al., 2008; Asteriti et al., 2011), and KIF2A (Jang et ...
RanGTP is important for chromosome-dependent spindle assembly in Xenopus extracts. Here we report on experiments to determine the role of the Ran pathway on microtubule dynamics in Drosophila oocytes and embryos. Females expressing a dominant-negative form of Ran have fertility defects, suggesting that RanGTP is required for normal fertility. This is not, however, because of a defect in acentrosomal meiotic spindle assembly. Therefore, RanGTP does not appear to be essential or sufficient for the formation of the acentrosomal spindle. Instead, the most important function of the Ran pathway in spindle assembly appears to be in the tapering of microtubules at the spindle poles, which might be through regulation of proteins such as TACC and the HURP homolog, Mars. One consequence of this spindle organization defect is an increase in the nondisjunction of achiasmate chromosomes. However, the meiotic defects are not severe enough to cause the decreased fertility. Reductions in fertility occur because ...
Spindle checkpoint proteins monitor the interaction of the spindle apparatus with the kinetochores, halting anaphase even if the microtubule attachment of only a single chromosome is altered. In this study, we show that Bub3p of Saccharomyces cerevisiae, an evolutionarily conserved spindle checkpoint protein, exhibits distinct interactions with an altered or defective kinetochore(s). We show for the first time that green fluorescent protein-tagged S. cerevisiae Bub3p (Bub3-GFP) exhibits not only a diffuse nuclear localization pattern but also forms distinct nuclear foci in unperturbed growing and G2/M-arrested cells. As Bub3-GFP foci overlap only a subset of kinetochores, we tested a model in which alterations or defects in kinetochore or spindle integrity lead to the distinct enrichment of Bub3p at these structures. In support of our model, kinetochore-associated Bub3-GFP is enriched upon activation of the spindle checkpoint due to nocodazole-induced spindle disassembly, overexpression of the
Mitosis is a key event in the life of a cell, where duplicated chromosomes are separated into the daughter cells. Defects associated with chromosome segregation can lead to aneuploidy, a hallmark of cancer. Chromosome segregation is achieved by the mitotic spindle, which is composed of microtubules (MTs), motors and microtubule associated protein (MAPs). Motors such as kinesins generate forces within the spindle while MAPs perform functions such as organize the spindle pole and maintain the bipolar spindle. Both motors and MAPs contribute to spindle mechanics. Here I used the relatively simple fission yeast to address how defects in spindle mechanics affect chromosome segregation. The metaphase spindle is maintained at a constant length by an antagonistic force-balance model yet how the regulation of metaphase spindle length contribute to subsequent chromosome segregation remains unexplored. To test the force-balance model, I applied gene deletion and fast microfluidic temperature-control with live-cell
Although the gradient of Ran-GTP around chromatin is critical to promote spindle formation in the absence of centrosomes in many systems (OConnell and Khodjakov, 2007), it is not essential for formation of the first bipolar meiotic spindle upon meiotic resumption in the acentriolar mouse oocyte, even though it does contribute to the increase in density of microtubules after NEBD (Dumont et al., 2007; Schuh and Ellenberg, 2007). By analyzing the very first events in spindle formation upon NEBD, we find that two protein kinases, Aurora A and Plk4, both contribute to trigger microtubule growth and formation of the first meiotic spindle. Inhibition of either kinase dramatically reduces microtubule growth, leading to a reduction in the velocity of the outward expanding chromosomes that are pushed apart by nascent microtubules as the spindle forms. Plk4 inhibition diminishes microtubule growth upon resumption of meiosis, but bipolar spindle formation does eventually occur in a process that requires ...
Cell division in mitosis and meiosis is governed by evolutionary highly conserved protein kinases and phosphatases, controlling the timely execution of key events such as nuclear envelope breakdown, spindle assembly, chromosome attachment to the spindle and chromosome segregation, and cell cycle exit. In mitosis, the spindle assembly checkpoint (SAC) controls the proper attachment to and alignment of chromosomes on the spindle. The SAC detects errors and induces a cell cycle arrest in metaphase, preventing chromatid separation. Once all chromosomes are properly attached, the SAC-dependent arrest is relieved and chromatids separate evenly into daughter cells. The signaling cascade leading to checkpoint arrest depends on several protein kinases that are conserved from yeast to man. In meiosis, haploid cells containing new genetic combinations are generated from a diploid cell through two specialized cell divisions. Though apparently less robust, SAC control also exists in meiosis. Recently, it has emerged
The metaphase spindle is a dynamic bipolar structure crucial for proper chromosome segregation, but how microtubules (MTs) are organized within the bipolar architecture remains controversial. To explore MT organization along the pole-to-pole axis, we simulated meiotic spindle assembly in two dimensions using dynamic MTs, a MT cross-linking force, and a kinesin-5-like motor. The bipolar structures that form consist of antiparallel fluxing MTs, but spindle pole formation requires the addition of a NuMA-like minus-end cross-linker and directed transport of MT depolymerization activity toward minus ends. Dynamic instability and minus-end depolymerization generate realistic MT lifetimes and a truncated exponential MT length distribution. Keeping the number of MTs in the simulation constant, we explored the influence of two different MT nucleation pathways on spindle organization. When nucleation occurs throughout the spindle, the simulation quantitatively reproduces features of meiotic spindles ...
Conventional centrosomes are absent from a female meiotic spindle in many animals. Instead, chromosomes drive spindle assembly, but the molecular mechanism of this acentrosomal spindle formation is not well understood. This study screened female sterile mutations for defects in acentrosomal spindle formation in Drosophila female meiosis. One of them, remnants (rem), disrupted bipolar spindle morphology and chromosome alignment in non-activated oocytes. It was found that rem encodes a conserved subunit of Cdc2 (Cks30A). Since Drosophila oocytes arrest in metaphase I, the defect represents a new Cks function before metaphase-anaphase transition. In addition, it was found that the essential pole components, Msps and D-TACC, are often mislocalized to the equator, which may explain part of the spindle defect. The second cks gene cks85A, in contrast, has an important role in mitosis. In conclusion, this study describes a new pre-anaphase role for a Cks in acentrosomal meiotic spindle formation ...
We show here that CIN colon cancer cells undergo transient mitotic arrest in response to spindle damage. However, the maximum mitotic indices achieved by the CIN cells is lower than that of the MIN cells. Thus, we argue that the aneuploid colon cancer cells examined here have a robust spindle checkpoint. Consistently, it now appears that mutations in known spindle checkpoint genes are extremely rare in human tumours (Cahill et al., 1998, 1999a; Imai et al., 1999; Yamaguchi et al., 1999; Myrie et al., 2000; Sato et al., 2000). The reason for the apparent lack of such mutations may be that they are lethal. Although spindle checkpoint genes are non‐essential in yeast (reviewed in Taylor, 1999) mutations in MAD2 and BUB3 result in embryonic lethality in mice (Dobles et al., 2000; Kalitsis et al., 2000). Furthermore, disrupting Bub1 and Mad2 function accelerates mitotic exit in human cells suggesting that spindle checkpoint function may be required to complete normal somatic cell divisions (Taylor ...
TY - JOUR. T1 - Histone H3K4 methylation regulates deactivation of the spindle assembly checkpoint through direct binding of Mad2. AU - Schibler, Andria. AU - Koutelou, Evangelia. AU - Tomida, Junya. AU - Wilson-Pham, Marenda. AU - Wang, Li. AU - Lu, Yue. AU - Cabrera, Alexa Parra. AU - Chosed, Renee J.. AU - Li, Wenqian. AU - Li, Bing. AU - Shi, Xiaobing. AU - Wood, Richard D.. AU - Dent, Sharon Y R. PY - 2016/5/15. Y1 - 2016/5/15. N2 - Histone H3 methylation on Lys4 (H3K4me) is associated with active gene transcription in all eukaryotes. In Saccharomyces cerevisiae, Set1 is the sole lysine methyltransferase required for mono-, di-, and trimethylation of this site. Although H3K4me3 is linked to gene expression, whether H3K4 methylation regulates other cellular processes, such as mitosis, is less clear. Here we show that both Set1 and H3K4 mutants display a benomyl resistance phenotype that requires components of the spindle assembly checkpoint (SAC), including Bub3 and Mad2. These proteins ...
FZR1 is an anaphase-promoting complex (APC) activator best known for its role in the mitotic cell cycle at M-phase exit, in G1, and in maintaining genome integrity. Previous studies also established that it prevents meiotic resumption, equivalent to the G2/M transition. Here we report that mouse oocytes lacking FZR1 undergo passage through meiosis I that is accelerated by ∼1 h, and this is due to an earlier onset of spindle assembly checkpoint (SAC) satisfaction and APCCDC20 activity. However, loss of FZR1 did not compromise SAC functionality; instead, earlier SAC satisfaction was achieved because the bipolar meiotic spindle was assembled more quickly in the absence of FZR1. This novel regulation of spindle assembly by FZR1 led to premature bivalent attachment to microtubules and loss of kinetochore-bound MAD2. Bivalents, however, were observed to congress poorly, leading to nondisjunction rates of 25%. We conclude that in mouse oocytes FZR1 controls the timing of assembly of the bipolar ...
Eg5, a member of the bimC subfamily of kinesin-like microtubule motor proteins, localizes to spindle microtubules in mitosis but not to interphase microtubules. We investigated the molecular basis for spindle localization by transient transfection of Xenopus A6 cells with myc-tagged derivatives of Eg5. Expressed at constitutively high levels from a cytomegalovirus promoter, mycEg5 protein is cytoplasmic throughout interphase, begins to bind microtubules in early prophase, and remains localized to spindle and/or midbody microtubules through mitosis to the end of telophase. Both N- and C-terminal regions of Eg5 are required for this cell-cycle-regulated targeting. Eg5 also contains within its C-terminal domain a sequence conserved among bimC subfamily proteins that includes a potential p34cdc2 phosphorylation site. We show that mutation of a single threonine (T937) within this site to nonphosphorylatable alanine abolishes localization of the mutant protein to the spindle, whereas mutation of T937 ...
ORDERED temporal degradation of proteins is an important regulatory mechanism that controls progression through the eukaryotic cell cycle (Reed 2006). The anaphase promoting complex/cyclosome (APC/C) is the E3 subunit of an ubiquitin-conjugating enzyme composed of at least thirteen subunits that targets proteins for proteolysis during the cell cycle (Peters 2006). APC/C function is critical for progression through mitosis where it degrades Pds1 (securin in higher eukaryotic cells) and other substrates to promote anaphase and the exit from mitosis (Pines 2006). APC/C cofactors Cdc20 and Cdh1 are important for conferring substrate specificity during different stages in the cell cycle (Peters 2006). It is unclear, however, how the APC/C chooses substrates for ubiquitylation and the specific role of each subunit in this process (Acquaviva and Pines 2006). The spindle assembly checkpoint (SAC) ensures the formation of a bipolar spindle and proper attachment of kinetochores (Lew and Burke 2003). The ...
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Weaver and Cleveland and Taylor et al. contend that our data on the involvement of the γ-tubulin ring complex (γ-TuRC) in the spindle assembly checkpoint (SAC) can be fully explained by kinetochore-derived checkpoint signaling. We maintain that (i) the interactions of γ-TuRC with Cdc20 and BubR1, and (ii) the activation of SAC by γ-TuRC depletion, in addition to the abrogation of kinetochore-microtubule interactions, argue for a more complex mechanism of SAC signaling.. ...
The BRCA1/BARD1 heterodimer modulates Ran-development mitotic spindle assembly. A mitotic role for BRCA1/BARD1 in tumor suppression?
The molecular role of the centrosome in the spindle checkpoint has been debated for some time. Müller et al. have now identified a function for a subset of core centrosomal proteins, namely their involvement in the spindle checkpoint. γ-tubulin ring proteins are functionally and biochemically integrated into checkpoint control, together with two of the major players in this pathway, BubR1 and Cdc20. However, the function of the γ-tubulin ring components was not linked to centrosome integrity, nor did it require localization to this organelle.. H. Müller, M.-L. Fogeron, V. Lehmann, H. Lehrach, B. M. H. Lange, A centrosome-independent role for γ-TuRC proteins in the spindle assembly checkpoint. Science 314, 654-657 (2006). [Abstract] [Full Text]. ...
The cell in the middle exhibits the normal biphasic pattern of spindle rotation (planar alignment/planar maintenance) regulated by the lateral (...)
A current theory for the generation of fate asymmetry is based on the discrete localization of cytoplasmic fate-determining molecules within the mother cell and their unequal distribution to daughter cells during division. The molecules so far identified, such as Notch, Numb, Miranda, Staufen, and Prospero (10, 20, 45, 46), have been shown to exhibit either basal or apical capping before division in static studies. Importantly, the fate molecule parcellation model only works in conjunction with variable orientations of the final cleavage plane. Assuming that the localization of fate molecule is fixed, only if the plane of cleavage can be modified can divergent cell fates be generated. If, on the other hand, fate molecules are not tethered in the same intracellular location throughout neurogenesis, or if there are multiple signaling pathways as the late vertical neurogenic divisions suggest, then spindle rotation is an even more critical requirement for modulating mode of division.. The nature ...
TY - JOUR. T1 - Par3 controls epithelial spindle orientation by aPKC-mediated phosphorylation of apical pins. AU - Hao, Yi. AU - Du, Quansheng. AU - Chen, Xinyu. AU - Zheng, Zhen. AU - Balsbaugh, Jeremy L.. AU - Maitra, Sushmit. AU - Shabanowitz, Jeffrey. AU - Hunt, Donald F.. AU - MacAra, Ian G.. N1 - Funding Information: We thank the Trono laboratory, T. Stukenberg, and G. Ojakian for reagents and the Macara laboratory for advice. This work was supported by National Institutes of Health grants GM070902 (to I.G.M.), GM037537 (to D.F.H.), and GM079506 (to Q.D.). PY - 2010/10/26. Y1 - 2010/10/26. N2 - Background: Formation of epithelial sheets requires that cell division occurs in the plane of the sheet. During mitosis, spindle poles align so the astral microtubules contact the lateral cortex. Confinement of the mammalian Pins protein to the lateral cortex is essential for this process. Defects in signaling through Cdc42 and atypical protein kinase C (aPKC) also cause spindle misorientation. When ...
Colocalization experiments of Pfark-1-GFP with a-tubulin. Fluorescence microscopy of fixed schizont stage transgenic parasites expressing Pfark-1-GFP. A and B. An anti-a-tubulin mAb recognizes discrete foci (red) near DAPI-stained nuclear DNA (blue). The red fluorescent pattern is consistent with early-stage mitotic spindle formation developing from the spindle pole bodies anchored in the nuclear membrane. In colour merge images, the Pfark-1-GFP protein appears to localize at opposite sides of the early mitotic spindle, consistent with a localization at the mitotic spindle poles. C and D. In these two panels the anti-a-tubulin mAb recognizes partly disassembled bipolar mitotic spindles (red) aligned with DAPI-stained nuclear bodies (blue), representing daughter nuclear bodies in the process of completion of nuclear division. The Pfark-1-GFP protein does not appear now to be confined to mitotic spindle poles. A diffuse cytosolic green fluorescence is observable, presumably representing the GFP ...
The inhibition of KSP causes mitotic arrest by activating the spindle assembly checkpoint. While transient inhibition of KSP leads to reversible mitotic arrest, prolonged exposure to a KSP inhibitor induces apoptosis. Induction of apoptosis by the KSP inhibitor couples with mitotic slippage. Slippag …
Bipolar spindle assembly and failure of chromatin stretching in oocytes expressing αtub67CP40. A, Drosophila female meiotic spindles were examined by indirect
Original Entry: Peter Foster, AP 225, Fall 2011 [[Image:Dn90fig1.png,thumb,300px, Figure 1, taken from [1].]] [[Image:Dn90fig2.png,thumb,300px, Figure 2, taken from [1].]] [[Image:Dn90fig3.png,thumb,300px, Figure 3, taken from [1].]] [[Image:Dn90fig4.png,thumb,300px, Figure 4, taken from [1].]] ==General Information== Authors: Daniel J. Needleman, Aaron Groen, Ryoma Ohi, Tom Maresca, Leonid Mirny, and Tim Mitchison Publication: Needleman et al. Fast microtubule dynamics in meiotic spindles measured by single molecule imaging: Evidence that the spindle environment does not stabilize microtubules. Molecular Biology of the Cell (2010) vol. 21 (2) pp. 323 ==Summary== The meiotic spindle is a piece of cellular machinery composed of microtubules (which are in turn composed of tubulin subunits) that serves to separate chromosomes during cell division. The spindle is incredibly dense with tubulin, containing a concentration much higher than found in the cytoplasm (~60 uM vs ,1uM). Different ...
Fidelity of chromosome segregation is monitored by the spindle assembly checkpoint (SAC). Key components of the SAC include MAD1, MAD2, BUB1, BUB3, BUBR1, and MPS1. These proteins accumulate on...
TY - THES. T1 - Advance to GO: Regulation of mitotic progression by the spindle checkpoint kinase MPS1. AU - Pachis, Spyridon T. PY - 2019/9/24. Y1 - 2019/9/24. N2 - Due to its extreme importance in maintaining a stable genome, chromosome segregation is highly regulated and complex process which is driven by the mitotic spindle. The spindle is comprised of microtubules whose role is to make contacts with chromosomes, capture them and eventually drag duplicated chromosomes (or sister chromatids) to opposite poles of the cell, ensuring the inheritance of a full set of chromosomes by the two daughter cells. The contact points for microtubules on chromosomes are called kinetochores. These are large protein scaffolds comprised of multiple complexes that are built on top centromeric DNA just before mitosis begins. Microtubule-kinetochore contacts can occur in many different configurations, but only a certain kind of attachments (amphitelic) can lead to the equal distribution of chromosomes. For this ...
The female meiotic spindle is commonly formed in a centrosome-independent manner. Here we report the identification of proteins at acentrosomal poles in the female meiotic spindle of Drosophila. The acentrosomal poles contain at least two proteins, Mini-spindles (Msps) and D-TACC, which are also ass …
In this thesis, I reported a membraneless structure that permeated a major region of the female meiotic spindle and formed droplet-like protrusions around the spindle poles. Proteins within this previously unknown structure were highly dynamic and could redistribute rapidly throughout the entire spindle region. I found that this unusual structure behaves similar to a liquid and forms by phase separation and hence, termed it the liquid-like meiotic spindle domain (LISD). Interestingly, the LISD was not only present in the spindle of mouse oocytes, but also cow, pig and sheep oocytes and is thus widely conserved among mammals. Similar structures were not observed in wildtype or centrosome-depleted somatic cells, suggesting that the LISD is likely exclusive to the specialized spindle in oocytes. To identify the key proteins driving LISD assembly, I further optimized Trim-Away, the technique for acute depletion of endogenous proteins in mammalian cells. By combining in vitro and in vivo assays, I ...
BackgroundNormal cell division is coordinated by a bipolar mitotic spindle, ensuring symmetrical segregation of chromosomes. Cancer cells, however, occasionally divide into three or more directions. Such multipolar mitoses have been proposed to generate genetic diversity and thereby contribute to clonal evolution. However, this notion has been little validated experimentally.Principal FindingsChromosome segregation and DNA content in daughter cells from multipolar mitoses were assessed by multiphoton cross sectioning and fluorescence in situ hybridization in cancer cells and non-neoplastic transformed cells. The DNA distribution resulting from multipolar cell division was found to be highly variable, with frequent nullisomies in the daughter cells. Time-lapse imaging of H2B/GFP-labelled multipolar mitoses revealed that the time from the initiation of metaphase to the beginning of anaphase was prolonged and that the metaphase plates often switched polarity several times before metaphase-anaphase
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The key molecules involved in regulating the assembly and function of the mitotic spindle are shared by evolutionarily divergent species. Studies in different model systems are leading to convergent conclusions about the central role of microtubule nucleation and dynamics and of kinesin-related motor proteins in spindle function.
TY - JOUR. T1 - Dependence of Paclitaxel Sensitivity on a Functional Spindle Assembly Checkpoint. AU - Sudo, Tamotsu. AU - Nitta, Masayuki. AU - Saya, Hideyuki. AU - Ueno, Naoto T.. PY - 2004/4/1. Y1 - 2004/4/1. N2 - Paclitaxel stabilizes microtubules, causing mitotic arrest and activating the spindle assembly checkpoint. We determined whether suppression of the checkpoint genes Mad2 and BubR1 affects paclitaxel resistance and whether overexpression of Mad2 protein in checkpoint-defective cells enhances paclitaxel sensitivity. Suppression of Mad2 and BubR1 in paclitaxel-treated cancer cells abolished checkpoint function, resulting in paclitaxel resistance that correlated with suppression of cyclin-dependent kinase-1 activity. In contrast, overexpression of Mad2 in cells with a checkpoint defect attributable to low Mad2 expression restored checkpoint function, resulting in enhanced paclitaxel sensitivity that correlated with enhanced cyclin-dependent kinase-1 activity. However, overexpression of ...
In eukaryotic cells, accurate chromosome segregation requires the spindle assembly checkpoint, a surveillance system monitoring kinetochore attachment to microtubules of the mitotic spindle (Lara-Gonzalez et al., 2012; Musacchio, 2015). The spindle checkpoint kinase MPS1 binds to unattached kinetochores and phosphorylates kinetochore proteins, thus directing the accumulation of spindle checkpoint proteins of the MAD and BUB families (Musacchio, 2015; Ciliberto and Hauf, 2017). A subset of the MAD and BUB proteins then assemble into the mitotic checkpoint complex (MCC; Musacchio, 2015). The mitotic checkpoint complex then diffuses away from the kinetochore to inhibit the ubiquitin E3 ligase anaphase promoting complex/cyclosome (APC/C), thus preventing mitotic exit (Sivakumar and Gorbsky, 2015). The two crucial targets ubiquitylated by the APC/C to promote mitotic exit are securin, the inhibitor of separase, and most important for this work, cyclin B, the activating subunit of a cyclin-dependent ...
In oocytes, where centrosomes are absent, the chromosomes direct the assembly of a bipolar spindle. Interactions between chromosomes and microtubules are essential for both spindle formation and chromosome segregation. This study examined oocytes lacking two kinetochore proteins, NDC80 and SPC105R, and a centromere-associated motor protein, CENP-E, to characterize the impact of kinetochore-microtubule attachments on spindle assembly and chromosome segregation in Drosophila oocytes. The initiation of spindle assembly was shown to result from chromosome-microtubule interactions that are kinetochore-independent. Stabilization of the spindle, however, depends on both central spindle and kinetochore components. This stabilization coincides with changes in kinetochore-microtubule attachments and bi-orientation of homologs. It is proposed that the bi-orientation process begins with the kinetochores moving laterally along central spindle microtubules towards their minus ends. This movement depends on ...
Abstract. Planar spindle orientation in polarized epithelial cells depends on the precise localization of the dynein-dynactin motor protein complex at the lateral cortex. The contribution of cell adhesion molecules to the cortical localization of the dynein-dynactin complex is poorly understood. Here we find that junctional adhesion molecule-A (JAM-A) regulates the planar orientation of the mitotic spindle during epithelial morphogenesis. During mitosis, JAM-A triggers a transient activation of Cdc42 and PI(3)K, generates a gradient of PtdIns(3,4,5)P3 at the cortex and regulates the formation of the cortical actin cytoskeleton. In the absence of functional JAM-A, dynactin localization at the cortex is reduced, the mitotic spindle apparatus is misaligned and epithelial morphogenesis in three-dimensional culture is compromised. Our findings indicate that a PI(3)K- and cortical F-actin-dependent pathway of planar spindle orientation operates in polarized epithelial cells to regulate epithelial ...
TY - JOUR. T1 - Plk1 bound to Bub1 contributes to spindle assembly checkpoint activity during mitosis. AU - Ikeda, Masanori. AU - Tanaka, Kozo. N1 - Funding Information: The authors thank K. Mizuno for YFP-Plk1, J.G. Deluca for Hec1-GFP, M. Lampson for mCherry-Knl1 and Hec1-mCherry-Plk1, G.J. Kops for anti-phospho-Mps1 antibody against T676 and anti-phospho-BubR1 antibody against T680, Y. Watanabe for anti-phospho-Knl1 antibody against T875 and T. Hirota for mCherry-Mis12. We also thank members of the K.T. laboratory for discussions and A. Harata for technical assistance. This work was supported by JSPS KAKENHI Grant Numbers 24370078, 26640067, 26870054, 15H04368, and 16K14604; MEXT KAKENHI Grant Numbers 24114502 and 26114702; and grants from the Takeda Science Foundation, Princess Takamatsu Cancer Research Fund (10-24210).. PY - 2017/12/1. Y1 - 2017/12/1. N2 - For faithful chromosome segregation, the formation of stable kinetochore-microtubule attachment and its monitoring by the spindle ...
Adapter protein able to interact with different proteins and involved in different biological processes. Mediates the interaction between the error-prone DNA polymerase zeta catalytic subunit REV3L and the inserter polymerase REV1, thereby mediating the second polymerase switching in translesion DNA synthesis. Translesion DNA synthesis releases the replication blockade of replicative polymerases, stalled in presence of DNA lesions. May also regulate another aspect of cellular response to DNA damage through regulation of the JNK-mediated phosphorylation and activation of the transcriptional activator ELK1. Inhibits the FZR1- and probably CDC20-mediated activation of the anaphase promoting complex APC thereby regulating progression through the cell cycle. Regulates TCF7L2-mediated gene transcription and may play a role in epithelial-mesenchymal transdifferentiation.
In the mitotic cell cycle, it is only when all chromosomes have appropriately established bipolar attachment to the mitotic spindle that the metaphase-to-anaphase transition can occur (Chen, 2004; Yu and Tang, 2005). Because kinetochores capture microtubules in a stochastic manner, three types of erroneous kinetochore attachments, including monotelic (only one of the sister kinetochores is attached to one spindle pole), syntelic (both sister kinetochores are attached to the same spindle pole), and merotelic (one kinetochore is attached to two opposing spindle poles) attachment, frequently occur (Gregan et al., 2011). Thus, there must be a surveillance mechanism that prevents the precocious separation of sister chromatids until all the improper kinetochore attachments are corrected, ensuring the fidelity of chromosome segregation (Meraldi and Sorger, 2005; Yu and Tang, 2005). The spindle assembly checkpoint (SAC) is such a mechanism that delays anaphase onset when any kinetochore is not properly ...
The blockbuster chemotherapy drug paclitaxel is widely presumed to cause cell death in tumors as a consequence of mitotic arrest, as it does at concentrations routinely used in cell culture. However, we determine here that paclitaxel levels in primary breast tumors are well below those required to elicit sustained mitotic arrest. Instead, cells in these lower concentrations of drug proceed through mitosis without substantial delay and divide their chromosomes on multipolar spindles, resulting in chromosome missegregation and cell death. Consistent with these cell culture data, most mitotic cells in primary human breast cancers contain multipolar spindles after paclitaxel treatment. Contrary to the previous hypothesis, we find that mitotic arrest is dispensable for tumor regression in patients. These results demonstrate that mitotic arrest is not responsible for the efficacy of paclitaxel, which occurs because of chromosome missegregation on highly abnormal, multipolar spindles. This mechanistic ...
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In animal cells, mitotic spindles are oriented by the dynein/dynactin motor complex, which exerts a pulling force on astral microtubules. Dynein/dynactin localization depends on Mud/NUMA, which is typically recruited to the cortex by Pins/LGN. In Drosophila neuroblasts, the Inscuteable/Baz/Par-6/aPKC complex recruits Pins apically to induce vertical spindle orientation, whereas in epithelial cells, Dlg recruits Pins laterally to orient the spindle horizontally. Here we investigate division orientation in the Drosophila imaginal wing disc epithelium. Live imaging reveals that spindle angles vary widely during prometaphase and metaphase, and therefore do not reliably predict division orientation. This finding prompted us to re-examine mutants that have been reported to disrupt division orientation in this tissue. Loss of Mud/NUMA misorients divisions, but Inscuteable expression and aPKC, dlg and pins mutants have no effect. Furthermore, Mud localizes to the apical-lateral cortex of the wing ...
BACKGROUND Meiosis is a unique form of cell division in which cells divide twice but DNA is duplicated only once. Errors in chromosome segregation during meiosis will result in aneuploidy, followed by loss of the conceptus during pregnancy or birth defects. During mitosis, cells utilize a mechanism called the spindle assembly checkpoint (SAC) to ensure faithful chromosome segregation. A similar mechanism has been uncovered for meiosis in the last decade, especially in the past several years. METHODS For this review, we included data and relevant information obtained through a PubMed database search for all articles published in English from 1991 through 2011 which included the term meiosis, spindle assembly checkpoint, or SAC. RESULTS There are 91 studies included. Evidence for the existence of SAC functions in meiosis is provided by studies on the SAC proteins mitotic-arrest deficient-1 (Mad1), Mad2, budding uninhibited by benzimidazole-1 (Bub1), Bub3, BubR1 and Mps1; microtubule-kinetochore
The SPOC regulates the phosphorylation of Bfa1 by Cdc5 at SPBs. (A and B) DYN1 CDC5-GFP and dyn1Δ CDC5-GFP cells in anaphase with a correctly aligned or misoriented anaphase spindle were analyzed by fluorescence microscopy. (A) Measurement of the relative fluorescence intensity of the Cdc5-GFP SPB signal of DYN1 CDC5-GFP cells with a correctly aligned anaphase spindle and dyn1Δ CDC5-GFP cells with the anaphase spindle misaligned in the mother cell body. The signals associated with the preexisting old (orange) and new (blue) SPBs were measured. (B) Cdc5-GFP signal at SPBs of DYN1 CDC5-GFP and dyn1Δ CDC5-GFP cells. Spc42-eqFP611 was used as an SPB marker. Note that Spc42-eqFP611 labeled the old SPB in the mother cell body more strongly because of a delay in the folding of the eqFP611 molecule (Pereira et al., 2001; Wiedenmann et al., 2002). DNA was stained with DAPI. (C) CDC5 and cdc5-10 cells were synchronized in G1 with α factor at 23°C and released at 37°C, the restrictive temperature of ...
Each mitotic chromosome is constituted by two sister chromatids whose correct segregation to the daughter cells is ensured by amphitelic attachment, in which the two sister kinetochores (KTs) are attached to microtubules (MTs) from opposite mitotic spindle poles. KT mis-attachments can occur in early mitosis and cause chromosome mis-segregation and aneuploidy if not corrected. These mis-attachments include monotelic (one attached and one unattached sister KT), syntelic (both sister KTs attached to the same spindle pole), and merotelic (a single KT attached to MTs from opposite spindle poles) attachments. A biochemical pathway named the Spindle Assembly Checkpoint (SAC) is responsible for delaying anaphase onset to allow correction of KT mis-attachments. SAC activation is believed to occur due to KT localization of certain SAC proteins and/or lack of tension, but only monotelic attachment has been proven to activate the SAC. To determine if and how other KT mis-attachments may activate the SAC, ...
This book describes current knowledge about the mechanisms by which cells segregate their already duplicated chromosomes in preparation for cell division. Experts in the field treat several important aspects of this subject: (1) the history of research on mitotic mechanisms, to serve as a background; (2) assembly of the mitotic spindle; (3) Kinetochore assembly and function; (4) the mechanisms of chromosome congression to the metaphase plate; (5) the spindle assembly checkpoint; (6) mechanisms to avoid and correct erroneous chromosome attachments to the spindle; (7) a molecular perspective on spindle assembly in land plants; (8) chromosome segregation in anaphase A; (9) spindle elongation in anaphase B; and (10) the consequences of errors in chromosome segregation. Each chapter provides the reader with a comprehensive and accurate picture of current research in a form that is both readable and authoritative. The volume is suitable for scholars in this and related fields and for teaching at an ...
TY - JOUR. T1 - Sirt1 Regulates Microtubule Dynamics Through Negative Regulation of Plk1 in Mitosis. AU - Kim, Jin Ju. AU - Gil, Na Yeon. AU - Zhang, Xiang Hua. AU - Chun, Kwang Hoon. AU - Fang, Guowei. AU - Kim, Joon. AU - Cho, Hyeseong. AU - Jang, Chang Young. AU - Cha, Hyuk Jin. PY - 2015/9/1. Y1 - 2015/9/1. N2 - Although loss of Sirt1 leads to chromosome aneuploidy, which accounts for higher tumor susceptibility, the molecular mechanisms remain unclear. Herein, we demonstrate that Sirt1 directly regulates Plk1, of which activity is critical for mitotic progression and spindle dynamics. Depletion or inhibition of Sirt1 significantly perturbs the formation of the mitotic spindle, leading to defective chromosome segregation. Elevated depolymerization of the mitotic spindle following loss of Sirt1 was associated with the deregulation of Plk1 activity. Thus, we conclude that Sirt1 may contribute to a mitotic regulator that controls spindle dynamics through Plk1 activity, resulting in fine-tuning ...
Nonpolarized cultured cells that adhere to the substrate on which they are growing orient their spindles parallel to the substratum, thereby allowing both daughter cells to maintain contact with the substrate. Interactions between the astral microtubules and various microtubule-organizing proteins, including the minus end-directed motor complex and the dynein-dynactin complex, are involved in connecting the spindle to the actin cytoskeleton and the cell cortex. Now Toyoshima et al. find that, in HeLa cells, integrin-mediated stimulation of phosphoinositide 3-kinase (PI3K) leading to the production of phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P3] at the midsection of the cell cortex in metaphase cells was required for proper spindle orientation. PI(3,4,5)P3 concentration was monitored with a green fluorescent protein fused to the pleckstrin homology domain of Akt (Akt-PH-GFP), and the midsection cortical localization, as well as proper spindle orientation, was lost if PI3K activity was ...
Cytokinesis is the final stage of the cell cycle. It partitions sister genomes and separates the cytoplasm of nascent daughter cells. Cytokinesis is initiated by the formation of a cleavage furrow whose ingression is powered by an actomyosin network known as the contractile ring. Following furrow ingression, the process of cell separation is completed by a membrane scission reaction. For the accurate inheritance of genetic information, it is crucial that furrow formation is initiated at the cell equator between segregating chromosomes and that this occurs after chromatin has cleared the cleavage plane. In animal cells, the mitotic spindle plays a pivotal role in the formation and placement of the cleavage furrow. The coupling of cytokinesis and chromosome segregation to the mitotic spindle ensures that nuclear and cytoplasmic division are tightly coordinated. The spindle midzone, a structure that is formed at anaphase onset between segregating sister genomes, is thought to play an important ...
Centrosomes organize the bipolar mitotic spindle, and centrosomal defects cause chromosome instability. Protein phosphorylation modulates centrosome function, and we provide a comprehensive map of phosphorylation on intact yeast centrosomes (18 proteins). Mass spectrometry was used to identify 297 phosphorylation sites on centrosomes from different cell cycle stages. We observed different modes of phosphoregulation via specific protein kinases, phosphorylation site clustering, and conserved phosphorylated residues. Mutating all eight cyclin-dependent kinase (Cdk)-directed sites within the core component, Spc42, resulted in lethality and reduced centrosomal assembly. Alternatively, mutation of one conserved Cdk site within γ-tubulin (Tub4-S360D) caused mitotic delay and aberrant anaphase spindle elongation. Our work establishes the extent and complexity of this prominent posttranslational modification in centrosome biology and provides specific examples of phosphorylation control in centrosome ...
Genetic instability is a common feature of many human cancers. This condition is frequently characterized by an abnormal number of chromosomes, although little is known about the mechanism that generates this altered genetic state. One possibility is that chromosomes are missegregated during mitosis due to the assembly of dysfunctional mitotic spindles. Because centrosomes are involved in spindle assembly, they could contribute to chromosome missegregation through the organization of aberrant spindles. As an initial test of this idea, we examined malignant tumors for centrosome abnormalities using antibodies to the centrosome protein pericentrin. We found that centrosomes in nearly all tumors and tumor-derived cell lines were atypical in shape, size, and composition and were often present in multiple copies. In addition, virtually all pericentrin-staining structures in tumor cells nucleated microtubules, and they participated in formation of disorganized mitotic spindles, upon which chromosomes ...
Bir1p localizes to interpolar microtubules and interacts with Ndc10p. (A) Bir1-GFP was imaged in premetaphase cells (top, arrow) and in anaphase cells (bottom,
A novel role for the GTPase-activating protein Bud2 in the spindle position checkpoint.: The spindle position checkpoint (SPC) ensures correct mitotic spindle p
During the process of cell division, the spindle checkpoint prevents separation of the duplicated chromosomes until each chromosome is properly attached to the spindle apparatus. In order to preserve the cells identity and proper function, it is necessary to maintain the appropriate number of chromosomes after each cell division. An error in generating daughter cells with fewer or greater number of chromosomes than expected (a situation termed aneuploidy), may lead in best case to cell death, or alternatively it may generate catastrophic phenotypic results. Examples include: In cancer cells, aneuploidy is a frequent event, indicating that these cells present a defect in the machinery involved in chromosome segregation, as well as in the mechanism ensuring that segregation is correctly performed. In humans, Down syndrome appears in children carrying in their cells one extra copy of chromosome 21, as a result of a defect in chromosome segregation during meiosis in one of the progenitors. This ...
The present invention relates to a steering column (1) for a motor vehicle, comprising a support unit (10, 104) which can be connected to the chassis of the motor vehicle and an actuating unit (10, 104) which is held on this support unit (10, 104) and can be adjusted relative to the support unit (10, 104). 16), which supports a steering spindle (14) for transmitting a steering torque from a steering wheel to a steerable wheel, wherein the actuating unit (16) relative to the support unit (10, 104) via an adjustment (2, 2 ) is adjustable, which is a Threaded rod (26, 26 ) which is in engagement with a female thread (32) having a spindle nut (3) and further comprising a drive motor (20) which acts on an outer toothing (30) of the spindle nut (3) the spindle nut (3) is formed in at least two parts, wherein a toothing part (300) carries the external toothing (30) of the spindle nut (3) and a threaded part (320) the internal thread (32) of the spindle nut (3), and V toothing part (300) and threaded
Looking for online definition of spindle epithelial tumour with thymus like differentiation in the Medical Dictionary? spindle epithelial tumour with thymus like differentiation explanation free. What is spindle epithelial tumour with thymus like differentiation? Meaning of spindle epithelial tumour with thymus like differentiation medical term. What does spindle epithelial tumour with thymus like differentiation mean?
Microtubules play a prominent role in plant morphogenesis (Kost et al., 1999; Kost and Chua, 2002). Unlike other eukaryote cells, vacuolated and cell wall-confined plant cells follow a specialized mode of cytokinesis, exhibiting four major microtubular arrays at different cell cycle stages with a variety of functions (Goddard et al., 1994). During interphase, a cortical array consisting of parallel microtubules oriented perpendicular to the cell expansion axis assists cellulose deposition (Cyr, 1994) and responds to stimuli (Wymer et al., 1996). At the onset of mitosis, the cortical array is replaced by a densely packed ring of microtubules encircling the nucleus called the preprophase band (PPB), which defines the location of the cell plate formed during cytokinesis (Mineyuki, 1999). Subsequently, the PPB is replaced by a mitotic spindle apparatus consisting of bundles of kinetochore microtubules separating the duplicated chromosomes in daughter cells (Yu et al., 2000). Finally, a phragmoplast ...
The Ran GTPase controls many cellular functions, including nucleocytoplasmic trafficking, spindle assembly, nuclear assembly and cell-cycle progression. Considerable evidence suggests that diffusible Ran-GTP near mitotic chromatin facilitates the release of critical factors from nuclear transport receptors, thereby promoting organization of mitotic spindles with respect to chromosomes. In addition to this role of soluble Ran-GTP, Ran has two important but less understood roles at mitotic kinetochores. Namely, it is essential for regulation of the spindle assembly checkpoint and for assembly of microtubule fibres that attach kinetochores to spindle poles. Here, I will briefly summarize evidence for these kinetochore-associated functions and mention some of the issues that remain to be addressed regarding them. ...
Its with sorrow that we share the news that Emeritus Professor Brian Setchell (BVSc, PhD, ScD) passed away peacefully on July 11. Brian was Professor of Animal Sciences at the Waite Agricultural Research Institute, University of Adelaide, from 1982 until his retirement in 1996. He published The Mammalian Testis, a translation of the original text in Italian by Enrico Sertoli which discusses the cells in the testis now bearing his name. He was involved in translations with H.D. Jocelyn from Latin of Regnier de Graafs two 17C books, on the anatomy of the reproductive systems of men and women, and wrote 76 reviews or chapters in books, 152 articles and 213 abstracts on the physiology, biochemistry and endocrinology of the testis and epididymis, as well as 46 articles on metabolism of the brain and other organs.. He was a passionate musician, a patient accompanist and willing participant in any musical opportunity that came his way. He was a wonderful husband to Marcia, father to Jo, Angus and ...
15 Jan 2020. Researchers at Princeton University have successfully recreated a key process involved in cell division in a test tube, uncovering the vital role played by a protein that is elevated in over 25% of all cancers.. The researchers findings, described in a pair of papers published in the journals eLife and Nature Communications, are a key step toward recreating the entire cell division machinery and could lead to new therapies aimed at preventing the growth of cancer cells.. When cells divide, a spindle-like structure composed of thousands of filaments called microtubules attaches to chromosomes and pulls equal numbers of them into each newly forming cell.. Each microtubule is assembled from individual tubulin molecules and, because errors in chromosome segregation can lead to cancer, it is vital that they assemble into microtubules at the right time and place to form a functional spindle apparatus.. Branching microtubule nucleation, in which a new microtubule forms from the side of an ...
TY - JOUR. T1 - Ibd1p, a possible spindle pole body associated protein, regulates nuclear division and bud separation in Saccharomyces cerevisiae. AU - Lee, Jeongkyo. AU - Hwang, Hyung Seo. AU - Kim, Jinmi. AU - Song, Kiwon. PY - 1999/4/1. Y1 - 1999/4/1. N2 - The proper spatial and temporal coordination of mitosis and cytokinesis is essential for maintaining genomic integrity. We describe the identification and characterization of the Saccharomyces cerevisiae IBD1 gene, which encodes a novel protein that regulates the proper nuclear division and bud separation. IBD1 was identified by the limited homology to byr4, a dosage-dependent regulator of cytokinesis in Schizosaccharomyces pombe. IBD1 is not an essential gene, and the knock-out cells show no growth defects except for the reduced mating efficiency [1]. However, upon ectopic expression from an inducible promoter, IBD1 is lethal to the cell and leads to abnormal nuclear division and bud separation. In detail, approximately 90% of the IBD1 ...
To preserve genome integrity, the two sister chromatids of each mitotic chromosome must be distributed equally between daughter cells. Movement of sister chromatids to opposite poles of a dividing cell requires attachment to spindle microtubules of opposing orientation. Errors in the attachment process can lead to chromosome missegregation and aneuploidy (i.e. an aberrant number of chromosomes). Aneuploid karyotypes are the major cause of spontaneous miscarriages in humans [1] and often observed in cancer genomes [2]. A multi-complex protein interface between mitotic chromosomes and the spindle apparatus called the kinetochore is responsible for both the establishment and regulation of the microtubule attachment process [3]. The kinetochore consists of approximately 30 core structural proteins that are arranged into several functional subcomplexes. Structural kinetochore proteins constitute the physical link between chromosomes and spindle microtubules. They also act as a signalling platform by ...
Vitrified-warmed immature equine oocytes are able to complete the first meiotic division, but their subsequent developmental competence is compromised. Therefore, the present study investigated the effects of vitrifying immature horse oocytes on the chromosome and spindle configuration after IVM. Cumulus-oocytes complexes (COCs) were collected and divided into two groups based ... read more on mare age (young ≤14 years; old ≥16 years). COCs were then either directly matured invitro or vitrified and warmed before IVM. Spindle morphology and chromosome alignment within MII stage oocytes were assessed using immunofluorescent staining, confocal microscopy and three-dimensional image analysis. Vitrification reduced the ability of oocytes to reach MII and resulted in ultrastructural changes to the meiotic spindle, including shortening of its long axis, and an increased incidence of chromosomes failing to align properly at the metaphase plate. We hypothesise that aberrant chromosome alignment is an ...
Detailed annotation info for ENST00000235310; Mitotic spindle assembly checkpoint protein MAD2B (MAD2-like 2) (hREV7). [Source:Uniprot/SWISSPROT;Acc:Q9UI95 ...
Spindle apparatus ‎ (→‎Spindle structure) *17:03, 20 November 2013 (diff , hist) . . (+6)‎ . . Spindle apparatus ‎ ...
Ptacin, JL; Lee, SF; Garner, EC; Toro, E; Eckart, M; Comolli, LR; Moerner, WE; Shapiro, L (Aug 2010). "A spindle-like apparatus ... "Stochastic Self-Assembly of ParB Proteins Builds the Bacterial DNA Segregation Apparatus". Cell Systems. 1 (2): 163-73. doi: ...
During mitosis Par14 associates to the spindle apparatus. In vitro experiments demonstrated that Par14 may be involved in ...
The spindle apparatus then rotates in the round cell and after several minutes the spindle position is stabilised ... It is at this rounding stage that the decision on the orientation of the cell division is made by the spindle apparatus. ... The cell then divides along the spindle apparatus orientation. The first insights into how cells could remember their long axis ... The rule emphasizes the cell shape to be a default mechanism of spindle apparatus orientation. Hertwig's rule predicts cell ...
This requires the spindle apparatus in these cells to be asymmetric. She discovered a role for proteins that control actin ... She found that human oocytes have a surprisingly slow and error-prone mechanism for assembling the meiotic spindle, increasing ... In studying how actin helps position the spindle, she discovered that vesicles carrying specific signals can change the ... Schuh, Melina; Ellenberg, Jan (23 December 2008). "A new model for asymmetric spindle positioning in mouse oocytes". Current ...
The funnel locking-apparatus are small and oval to spindle-shaped. A single cartilaginous tubercle is present at the mantle ... In this posture, they rotate around their spindle-shaped digestive glands, the only internal organs of the squid clearly ...
This gene encodes a protein associated with the mitotic spindle apparatus. The encoded protein may be involved in the ... 2003). "The mitotic-spindle-associated protein astrin is essential for progression through mitosis". J. Cell Sci. 115 (Pt 21): ... Shao X, Xue J, van der Hoorn FA (2001). "Testicular protein Spag5 has similarity to mitotic spindle protein Deepest and binds ... 2007). "hNinein is required for targeting spindle-associated protein Astrin to the centrosome during the S and G2 phases". Exp ...
The two centrosomes polymerize tubulin to help form a microtubule spindle apparatus. Motor proteins then push the centrosomes ... With respect to the symmetry of the spindle apparatus during metaphase, an approximately axially symmetric (centered) shape is ... Although centrosomes help organize microtubule assembly, they are not essential for the formation of the spindle apparatus, ... Finally, a third criterion is the location of the central spindle in case of closed pleuromitosis: "extranuclear" (spindle ...
This spindle apparatus consists of microtubules, microfilaments and a complex network of various proteins. During metaphase, ... the chromosomes line up using the spindle apparatus in the middle of the cell along the equatorial plate. The chromosomes move ... Both require vesicular secretions by the Golgi apparatus for resealing and formation of the cytoskeletal network in addition to ... Prophase is the initial phase when spindle fibers appear that function to move the chromosomes toward opposite poles. ...
The spindle apparatus of the second meiotic division appears at the time of ovulation. If no fertilization occurs, the oocyte ...
During the first division, chromosomes may lag behind and become lost from the spindle apparatus. Extra nuclei are occasionally ... During the second division the extra chromosomes tend to form their own spindle apparatus and divide. Megasporogenesis is ...
... maintains bipolar microtubule spindle apparatus in dividing cells and shares redundant functions with KIF11. KIF15 is ... KIF15 maintains half spindle separation by opposing forces generated by other motor proteins. KIF15 co-localizes with ... Vanneste D, Takagi M, Imamoto N, Vernos I (November 2009). "The role of Hklp2 in the stabilization and maintenance of spindle ... Courtois A, Schuh M, Ellenberg J, Hiiragi T (August 2012). "The transition from meiotic to mitotic spindle assembly is gradual ...
During mitosis, clathrin binds to the spindle apparatus, in complex with two other proteins: TACC3 and ch-TOG/CKAP5. Clathrin ... "Coordination of adjacent domains mediates TACC3-ch-TOG-clathrin assembly and mitotic spindle binding". Journal of Cell Biology ... "Coordination of adjacent domains mediates TACC3-ch-TOG-clathrin assembly and mitotic spindle binding". J Cell Biol. 202 (3): ... "Clathrin is required for the function of the mitotic spindle". Nature. 434 (7037): 1152-1157. doi:10.1038/nature03502. PMC ...
... microtubules and the spindle apparatus". European Journal of Cell Biology. 79 (4): 240-51. doi:10.1078/S0171-9335(04)70027-8. ... During interphase, CKIδ associates with the Golgi Apparatus and appears to regulate the budding of clathrin coated vesicles ... Bingham EW, Farrel HM (June 1974). "Casein kinase from the Golgi apparatus of lactating mammary gland". The Journal of ... and cytoplasm of eukaryotes and additionally in the mitotic spindle in mammalian cells. The family members have the highest ...
"Transforming acidic coiled-coil-containing protein 4 interacts with centrosomal AKAP350 and the mitotic spindle apparatus". J. ... Alternate splicing of this gene results in many isoforms that localize to the centrosome and the Golgi apparatus, and interact ... Shanks RA, Larocca MC, Berryman M, Edwards JC, Urushidani T, Navarre J, Goldenring JR (2002). "AKAP350 at the Golgi apparatus. ... "AKAP350 interaction with cdc42 interacting protein 4 at the Golgi apparatus". Mol. Biol. Cell. 15 (6): 2771-81. doi:10.1091/mbc ...
"Transforming acidic coiled-coil-containing protein 4 interacts with centrosomal AKAP350 and the mitotic spindle apparatus". J. ... "The transforming acidic coiled coil 3 protein is essential for spindle-dependent chromosome alignment and mitotic survival". J ...
... sister chromatid adhesion and rearrange the spindle apparatus. During meiosis, there are 2 sets of cell divisions, the second ... and mitotic/meiotic spindle defects that could result in insertions, deletions, abnormal segregation, DNA bridging, and ...
In the first meiotic division, the homologs are segregated to separate daughter cells by the spindle apparatus. The cells then ... Over time the MTOCs merge until two poles have formed, generating a barrel shaped spindle. In human oocytes spindle microtubule ... Unlike mitotic cells, human and mouse oocytes do not have centrosomes to produce the meiotic spindle. In mice, approximately 80 ... The microtubules that make up the spindle network disappear, and a new nuclear membrane surrounds each haploid set. The ...
CK1δ is involved in the regulation of microtubule polymerization and stability of the spindle apparatus and centrosomes during ... microtubules and the spindle apparatus". European Journal of Cell Biology. 79 (4): 240-51. doi:10.1078/S0171-9335(04)70027-8. ... Roof DM, Meluh PB, Rose MD (July 1992). "Kinesin-related proteins required for assembly of the mitotic spindle". The Journal of ... centrosomes or spindle poles. While the present NLS is not sufficient for nuclear localization of CK1δ, the presence of the ...
During cytokinesis the spindle apparatus partitions and transports duplicated chromatids into the cytoplasm of the separating ... The central spindle (or spindle midzone) forms when non-kinetochore microtubule fibers are bundled between the spindle poles. A ... In short, the self-assembly of central spindle is initiated through the phosphoregulation of multiple central spindle ... where signals from two poles are somehow focused into a ring at the spindle. A second possibility, called the central spindle ...
... was recognized particularly for contributing to discovery of the attachment of chromosomes to the mitotic spindle apparatus. ... Brinkley is attempting to uncover the molecular basis of errors and defects in the nucleus and mitotic apparatus that cause ...
Tricellular junctions exert a pulling force on the spindle apparatus and serve as a geometrical clues to determine orientation ... In some Drosophila epithelia, during cell divisions tricellular junctions establish physical contact with spindle apparatus ...
... are properly aligned to the spindle apparatus. Only then, SAC releases its inhibition of the anaphase promoting complex (APC), ... The spindle assembly checkpoint (SAC) is a molecular safe-guarding mechanism that governs proper chromosome segregation in ... Sun, S.-C.; Kim, N.-H. (14 November 2011). "Spindle assembly checkpoint and its regulators in meiosis". Human Reproduction ... The cohesin complex is responsible for keeping together sister chromatids and provides binding sites for spindle attachment. ...
Yoshio Masui cell cycle Cdk1 cyclin DNA replication nuclear transport spindle apparatus condensin cohesin Lohka MJ, Masui Y ( ... 1985). "Induction of nuclear envelope breakdown, chromosome condensation, and spindle formation in cell-free extracts". J. Cell ... it undergoes a series of structural changes and is eventually converted into a set of M phase chromosomes with bipolar spindles ... other than cyclin B is necessary for initiating chromosome segregation Discovery of a mechanism of spindle assembly that ...
In several site excavations ancient instruments were found, mainly spindle whorls apparatus (malacates), in the remains of some ... On the one hand, they have often been associated with spindle whorls, although there is little ethnographic documentation to ... Its most definite function, more than any of the remaining ceramic artifacts, always considered as spindle whorls. However, as ...
The mechanism of polyploidy induction by noscapine is suggested to involve either chromosome spindle apparatus damage or cell ... Schuler, M.; Muehlbauer, P.; Guzzie, P.; Eastmond, D.A. (1999). "Noscapine hydrochloride disrupts the mitotic spindle in ...
TCJ provide mechanical and geometrical clues for the spindle apparatus to ensure that cell divide along its long axis. Several ...
This contact between the asbestos fiber and the chromosomes or structural proteins of the spindle apparatus can induce complex ...
... which face in opposite directions and attach to opposite poles of the mitotic spindle apparatus. Following the transition from ... The spindle checkpoint, or SAC (for spindle assembly checkpoint), also known as the mitotic checkpoint, is a cellular mechanism ... As mitosis progresses, both centrosomes separate to establish the mitotic spindle. In this way, the spindle in a mitotic cell ... Whereas the spindle checkpoint protein levels present in the outer plate diminish as MTs anchor, other components such as EB1, ...
A major function of the peroxisome is the breakdown of very long chain fatty acids through beta oxidation. In animal cells, the long fatty acids are converted to medium chain fatty acids, which are subsequently shuttled to mitochondria where they are eventually broken down to carbon dioxide and water. In yeast and plant cells, this process is carried out exclusively in peroxisomes.[8] The first reactions in the formation of plasmalogen in animal cells also occur in peroxisomes. Plasmalogen is the most abundant phospholipid in myelin. Deficiency of plasmalogens causes profound abnormalities in the myelination of nerve cells, which is one reason why many peroxisomal disorders affect the nervous system.[8] Peroxisomes also play a role in the production of bile acids important for the absorption of fats and fat-soluble vitamins, such as vitamins A and K. Skin disorders are features of genetic disorders affecting peroxisome function as a result. Peroxisomes contain oxidative enzymes, such as D-amino ...
Orgel LE (Dec 1968). "Evolution of the genetic apparatus". Journal of Molecular Biology. 38 (3): 381-93. doi:10.1016/0022-2836( ... Diener TO (Aug 1971). "Potato spindle tuber "virus". IV. A replicating, low molecular weight RNA". Virology. 45 (2): 411-28. ...
... was first observed by Keith R. Porter and his student Thomas Ashford at the Rockefeller Institute. In January 1962 they reported an increased number of lysosomes in rat liver cells after the addition of glucagon, and that some displaced lysosomes towards the centre of the cell contained other cell organelles such as mitochondria. They called this autolysis after Christian de Duve and Alex B. Novikoff. However Porter and Ashford wrongly interpreted their data as lysosome formation (ignoring the pre-existing organelles). Lysosomes could not be cell organelles, but part of cytoplasm such as mitochondria, and that hydrolytic enzymes were produced by microbodies.[14] In 1963 researchers published a detailed ultrastructural description of "focal cytoplasmic degradation," which referenced a 1955 German study of injury-induced sequestration. The study recognized three continuous stages of maturation of the sequestered cytoplasm to lysosomes, and that the process was not limited to injury ...
In the muscles, the muscle spindles convey information about the degree of muscle length and stretch to the central nervous ... In contrast with the high level of gene family apparatuses structure, Andrikou and Arnone found that the cis regulatory ... Scattered throughout the muscles are muscle spindles that provide sensory feedback information to the central nervous system. ( ...
When this happens on a deck where both supply and take-up spindles are powered, the tape continues to feed, creating a fold. It ... von Szalay conducted a number of recording sessions with a custom-made apparatus, consisting of a microphone in an insulated ...
... with a deeply forked tail and a smooth body shaped like a spindle tapered at both ends. They are countershaded with silvery ...
For example, they have to ensure that lysosomal enzymes are transferred specifically to the golgi apparatus and not to another ... In this manner, microtubules assist the transport of chromosomes towards the spindle poles by utilizing the dynein motor ...
Spindle diagram for the evolution of fish and other vertebrate classes.[52] The earliest classes that developed jaws were the ... The pharyngeal jaw apparatus consists of two upper and one single lower plate, all of which have dentations that differ in size ... "Functional morphology of the pharyngeal jaw apparatus in moray eels" (PDF). Journal of Morphology. 269 (5): 604-619. doi ... "Independent evolution of the specialized pharyngeal jaw apparatus in cichlid and labrid fishes". BMC Evolutionary Biology. 7 ...
Stage II sleep is characterized by sleep spindles - transient runs of rhythmic activity in the 12-14 Hz range (sometimes ... US patent 7286871, Mark S. Cohen, "Method and apparatus for reducing contamination of an electrical signal", published 2004-05- ... Other transient features are normal: vertex waves and sleep spindles are seen in normal sleep. ... the thalamocortical resonance underlying sleep spindles), while many others are not (e.g., the system that generates the ...
A spindle of DVD-RW's.. Computer data storage is a technology consisting of computer components and recording media that are ... Vision Electronic Recording Apparatus. *Magnetic recording *Magnetic storage. *Magnetic tape. *Magnetic tape data storage ...
Because the glycocalyx is so prominent throughout the cardiovascular system, disruption to this structure has detrimental effects that can cause disease. Certain stimuli that cause atheroma may lead to enhanced sensitivity of vasculature. Initial dysfunction of the glycocalyx can be caused by hyperglycemia or oxidized low-density lipoproteins (LDLs), which then causes atherothrombosis. In microvasculature, dysfunction of the glycocalyx leads to internal fluid imbalance, and potentially edema. In arterial vascular tissue, glycocalyx disruption causes inflammation and atherothrombosis.[8] Experiments have been performed to test precisely how the glycocalyx can be altered or damaged. One particular study used an isolated perfused heart model designed to facilitate detection of the state of the vascular barrier portion, and sought to cause insult-induced shedding of the glycocalyx to ascertain the cause-and-effect relationship between glycocalyx shedding and vascular permeability. Hypoxic perfusion ...
... binary fission takes place without the formation of a spindle apparatus on the cell. Like in mitosis (and unlike in meiosis), ...
Golgi apparatus. • lamellipodium. • cytoplasmic side of plasma membrane. • endosome. • lateral plasma membrane. • catenin ... or P-cadherin is not sufficient to modify the morphology and the tumorigenic behavior of murine spindle carcinoma cells. ...
... dysfunctional spindle apparatus, or flawed anaphase checkpoint genes.[2] Many micronucleus assays have been developed to test ... defects in mitotic spindle assembly, mitosis check point defects, abnormal centrosome amplification, and telomeric end fusions ... that are not included in the daughter nuclei produced by mitosis because they fail to correctly attach to the spindle during ... that result in dicentric chromosomes that detach from the spindle during anaphase. Micronuclei originating from chromosome loss ...
The cycle begins with (1) a region of the golgi apparatus is pinched off to form the synaptic vesicle and this vesicle is ...
... spindle shaped electrode. The electrode confines the ions so that they both orbit around the central electrode and oscillate ...
a b c d Bill Spindle, Nicole Friedman & Benoît Faucon, "Iran Deal Raises Prospect of Fresh Oil Glut", The Wall Street Journal ( ... a backlash by political hard-liners began and the Revolutionary Guard intelligence apparatus "started rounding up journalists, ...
The mitotic apparatus is made up of a central spindle and polar asters made up of polymers of tubulin protein called ... One method involves asymmetric positioning of the cleavage spindle.[9] This occurs when the aster at one pole attaches to the ... Radial cleavage is characteristic of the deuterostomes, which include some vertebrates and echinoderms, in which the spindle ... Unequal cleavage occurs in two ways: asymmetric positioning of the mitotic spindle, or through the formation of a polar lobe ( ...
Method and apparatus for acid blast etching of metal plates 1900. Pencoyd Iron Works, Pencoyd Iron Works[4] Engenharia Bridge ... Spindle Support 1891. Bevington, James H.James H. Bevington[3] Engenharia Welding Metal and Spinning and Shaping Tube ... Clinical chemistry procedures and apparatus 1966. Blizard, Everitt P.Everitt P. Blizard[13] Física Development of the theory of ...
The intraligamentary syringe offers mechanical advantage by using a trigger-grasp or click apparatus to employ a gear or lever ...
Golgi apparatus: The primary function of the Golgi apparatus is to process and package the macromolecules such as proteins and ... which separate during cell division and help in the formation of the mitotic spindle. A single centrosome is present in the ... Some (such as the nucleus and golgi apparatus) are typically solitary, while others (such as mitochondria, chloroplasts, ... It directs the transport through the ER and the Golgi apparatus. Centrosomes are composed of two centrioles, ...
The ribosomes and associated molecules are also known as the translational apparatus. ...
The mitotic spindle can be seen, stained green, attached to the two sets of chromosomes, stained light blue. All chromosomes ... The daughter chromosomes then migrate to opposite poles of the mitotic spindle, and new nuclei reassemble around them. ... the so-called closed mitosis with extranuclear spindle). In many other protists (e.g., ciliates, sporozoans) and fungi, the ... Golgi apparatus (or "Golgi body"). *Cytoskeleton. *Smooth endoplasmic reticulum. *Mitochondrion. *Vacuole. *Cytosol (fluid that ...
The radial spoke is known to play a role in the mechanical movement of the flagellum/cilium. For example, mutant organisms lacking properly functioning radial spokes have flagella and cilia that are immotile. Radial spokes also influence the cilium "waveform"; that is, the exact bending pattern the cilium repeats. How the radial spoke carries out this function is poorly understood. Radial spokes are believed to interact with both the central pair microtubules and the dynein arms, perhaps in a way that maintains the rhythmic activation of the dynein motors. For example, one of the radial spoke subunits, RSP3, is an anchor protein predicted to hold another protein called protein kinase A (PKA). PKA would theoretically then be able to activate/inactivate the adjacent dynein arms via its kinase activity. However, the identities and functions of the many radial spoke subunits are just beginning to be elucidated. ...
In cell biology, microsomes are heterogenous vesicle-like artifacts (~20-200 nm diameter) re-formed from pieces of the endoplasmic reticulum (ER) when eukaryotic cells are broken-up in the laboratory; microsomes are not present in healthy, living cells.[1] Microsomes can be concentrated and separated from other cellular debris by differential centrifugation. Unbroken cells, nuclei, and mitochondria sediment out at 10,000 g, whereas soluble enzymes and fragmented ER, which contains cytochrome P450 (CYP), remain in solution (g is the Earth's gravitational acceleration). At 100,000 g, achieved by faster centrifuge rotation, ER sediments out of solution as a pellet but the soluble enzymes remain in the supernatant. In this way, cytochrome P450 in microsomes is concentrated and isolated. Microsomes have a reddish-brown color, due to the presence of the heme. Because of the need for a multi-part protein-system, microsomes are necessary to analyze the metabolic activity of CYPs. These CYPs are highly ...
... which may progress to destruction of the periodontal attachment apparatus.[7] The plaque accumulates in the small gaps between ... Spindle cell carcinoma. *Squamous cell carcinoma. *Verrucous carcinoma. *Oral florid papillomatosis. *Oral melanosis *Smoker's ...
"Method and apparatus for computer aided machining". 16 September 1997.. *^ Yong, Loong Tee; Moy, Peter K. (2008). " ... In order to reduce the lateral tool load, tool engagement is reduced, while feed rates and spindle speeds are generally ...
... while the other pulled the tray out from the test apparatus. Both would then feed. The birds were observed waiting for their ... Spindle neuron. References[edit]. *^ a b c d e f g h i The Cambridge Declaration on Consciousness (Archive) 7 July 2012. ...
1 25 x 1 3 x 1 4 m Beocrufys2 Condition ready for operation Condition good Electric 380 Volt Dividing apparatus with tailstock ... The grinding machine price should reflect the number of spindles machine size age and options for that machine. Discover. ... 1 25 x 1 3 x 1 4 m Beocrufys2 Condition ready for operation Condition good Electric 380 Volt Dividing apparatus with tailstock ... 1 25 x 1 3 x 1 4 m Beocrufys2 Condition ready for operation Condition good Electric 380 Volt Dividing apparatus with tailstock ...
The apparatus spins in a large cylinder, and thus, the more general name for this machine is a centrifugal casting machine. ... Sep 10, 2019· VERTICAL SPINDLE ROTARY TABLE GRINDER The machine is mostly suitable for small workpieces in large quantities. ... The surface grinding machines are further classified according to the position of the spindle and working table ... ...
... centers range from 3-axis benchtop CNC mills to 5 axis CNC mills short to long travels and fast to heavy-duty RPM spindle ... roller mills apparatus. *miller batching plant. *bowl mill raw al pulverisers. *tub grinding services ... on three sides simultaneously in conventional milling machines the milling head holds a vertical or horizontal main spindle and ...
Search in 260 mm grinding spindle head / power capacity 32 kW speeds of grinding spindle 377 U/min total power requirement 64 ... Compare prices now good Electric 380 Volt Dividing apparatus with tailstock Universal tool grinding machine with a NEW dividing ...
High Precision Internal Grinding machine Up to 4 grinding spindles on the rotating turret Motor controlled by CNC and The new ... in europe Leading grinding machine manufacturers around the world rely on Koyo grinding machine tools and apparatus for high ... product line of Doimak The latest CNC technology is implemented with built in drives and linear motors Wide range of spindle ...
A vertical underground stump grinding apparatus having an elongated stump grinding tool rotatable about a vertical axis with ... 1982 SMTW M7475B 1K RPM 33 HP VERTICAL SPINDLE ROTARY SURFACE GRINDER … ... the sled having skid means for guiding the apparatus over the surface of . ... 1982 SMTW M7475B 1K RPM 33 HP VERTICAL SPINDLE ROTARY SURFACE GRINDER … ...
Large mills built in the same configuration as planers except with a milling spindle instead of a planing head.Pietro Carnaghi ... apparatus for crushing mediions broyeures spciale matter for pc ...
  • It is referred to as the mitotic spindle during mitosis, a process that produces genetically identical daughter cells, or the meiotic spindle during meiosis, a process that produces gametes with half the number of chromosomes of the parent cell. (wikipedia.org)
  • Besides chromosomes, the spindle apparatus is composed of hundreds of proteins. (wikipedia.org)
  • Attachment of microtubules to chromosomes is mediated by kinetochores, which actively monitor spindle formation and prevent premature anaphase onset. (wikipedia.org)
  • The cellular spindle apparatus includes the spindle microtubules, associated proteins, which include kinesin and dynein molecular motors, condensed chromosomes, and any centrosomes or asters that may be present at the spindle poles depending on the cell type. (wikipedia.org)
  • The dynamic lengthening and shortening of spindle microtubules, through a process known as dynamic instability determines to a large extent the shape of the mitotic spindle and promotes the proper alignment of chromosomes at the spindle midzone. (wikipedia.org)
  • The immunofluorescence studies also showed that after release of the NuMA protein from chromosomes of metaphase or anaphase cells, the protein bound specifically to the polar region of the mitotic spindle. (nih.gov)
  • Results suggest that the NuMA protein has specific attachment sites on both metaphase chromosomes and mitotic spindle poles (the site where post-mitotic nuclear assembly occurs). (nih.gov)
  • We photobleached two large areas at the opposite sides of the metaphase plate in spindles of Drosophila S2 cells expressing Cherry-tagged tubulin, leaving unbleached only the area near the chromosomes. (nih.gov)
  • Also performs a similar stabilizing function at the kinetochore which is essential for the bipolar alignment of chromosomes on the mitotic spindle. (abcam.com)
  • Chromosomes are positioned along equator of cell by spindle fibres. (brainscape.com)
  • The mitotic checkpoint prevents a eukaryotic cell from commencing to separate its replicated genome into two daughter cells (anaphase) until all of its chromosomes are properly aligned on the metaphase plate, with the two copies of each chromosome attached to opposite poles of the mitotic spindle. (biomedsearch.com)
  • The mitotic checkpoint is also curious in the sense that, before metaphase alignment, chromosomes that are not being pulled in opposite directions by the mitotic spindle activate the checkpoint, but during anaphase, these same tensionless chromosomes can no longer activate the checkpoint. (biomedsearch.com)
  • The suppression of PP2Aα, but not PP2Aβ, is sufficient to induce metaphase arrest, during which time lagging chromosomes are observed moving between the spindle poles and the metaphase plate. (aacrjournals.org)
  • Before the division of the ovum, chromosomes that belong together (homologs) initially arrange themselves at the centre of the cell by means of so-called spindle fibres. (mpg.de)
  • She also discovered that chromosomes are often incorrectly bound to the spindle apparatus. (mpg.de)
  • The spindle fibers are used to control the movement and segregation of chromosomes in both the mitosis cell division and meiosis cell division. (reference.com)
  • These photos were taken with confocal fluorescence microscopy of eggs stained with special dyes to show the spindles and chromosomes. (advancedfertility.com)
  • When the chromosomes line up properly in a straight line on the spindle apparatus in the egg, the division process would be expected to proceed normally so that the egg would end up with its proper complement of 23 chromosomes. (advancedfertility.com)
  • Chromosomes are segregated by the spindle apparatus, which is made up of fibrous protein structures called microtubules. (uni-muenchen.de)
  • The chromosomes are separated and distributed to the daughter cells with the help of a spindle apparatus. (mpg.de)
  • They control the compaction of the chromosomes and regulate their attachment to the spindle apparatus. (mpg.de)
  • The Mitotic Spindle Assembly Checkpoint ((M)SAC) is an evolutionary conserved mechanism that ensures the correct segregation of chromosomes by restraining cell cycle progression from entering anaphase until all chromosomes have made proper bipolar attachments to the mitotic spindle. (nih.gov)
  • During mitosis, which occurs after chromosomes are duplicated during S phase, two sister chromatids are held together each with its own kinetochore which face in opposing directions and attach to opposite poles of the mitotic spindle. (phys.org)
  • During cell division, these spindles are organized by the chromosomes and microtubule-associated proteins. (genetics.org)
  • even though chromosomes are joined by chiasmata they fail to segregate at meiosis I. Cytological analyses have revealed that sub is required for bipolar spindle formation. (genetics.org)
  • There is a substantial body of evidence that the chromosomes have a significant role in organizing the microtubules of a female meiotic spindle ( M c K im and H awley 1995 ). (genetics.org)
  • In Drosophila oocytes, meiotic spindle formation begins with a mass of microtubules emanating from the chromosomes, suggesting that the chromosomes nucleate or capture microtubules that are later shaped into a bipolar spindle. (genetics.org)
  • In fact, individual chromosomes have been shown to form bipolar spindles in Drosophila oocytes ( T heurkauf and H awley 1992 ) and other organisms ( W aters and S almon 1995 ). (genetics.org)
  • The points where chromosomes attach to spindle fibers. (studystack.com)
  • Chromosomes condense, centrioles move to poles and the spindle apparatus forms. (studystack.com)
  • Kinetochore fibers interact with the spindle to align chromosomes at the metaphase plate. (studystack.com)
  • The spindle apparatus disappears, nuclear membrane and nucleoli reform, and the chromosomes uncoil. (studystack.com)
  • The duplicated chromatin condenses, spindle apparatus forms, nucleoli and nuclear membrane disappears, homologous chromosomes intertwine (synapsis) resulting in a tetrad of 4 chromatids which cross over. (studystack.com)
  • A look into the microscope shows how the spindle fibres "grab" the chromosomes at the kinetochore and position them at the cell's centre line during cell division. (uni-heidelberg.de)
  • A little later, the chromosomes have divided and are pulled apart by the spindle fibres. (uni-heidelberg.de)
  • One histone variant called "CENP-A" (centromere protein A) only occurs in the centromere region of chromosomes: "Without this specific histone", explains Sylvia Erhardt, "the kinetochore, the contact point for the spindle fibres, can't develop. (uni-heidelberg.de)
  • These connections, called chiasmata, ensure the proper alignment of chromosomes on the spindle apparatus at meiosis I. (genetics.org)
  • When cells divide, Lis1 controls orientation of the mitotic spindle, an apparatus of subcellular fibers that segregates chromosomes during cell division. (eurekalert.org)
  • Describe spindle fibers and state their role in the separation of chromosomes during eukaryotic cell division. (quizlet.com)
  • In order to segregate chromosomes into the two emerging cells, the spindle itself needs a bipolar structure, and so the microtubules must be sorted to align with the long pole-to-pole axis of the spindle. (eurekalert.org)
  • During the metaphase, the spindle apparatus becomes well-defined and the chromosomes get arranged at the equatorial plate. (syvum.com)
  • The nuclear membrane complex is disaggregated into vesicles as a result, exposing the condensed chromosomes to the expanding microtubular network of the mitotic spindle. (fsu.edu)
  • As the kinetochore microtubules attach to their receptors on the chromatid kinetochores, the chromosomes are brought into agitated motion and move rapidly back and forth as tension is exerted by the spindle. (fsu.edu)
  • Simultaneously, polar microtubules emanating from the centrosomes interact with each other to form an interconnecting network between the chromosomes and further establish the structure of the mitotic spindle. (fsu.edu)
  • Eventually, at anaphase, the kinetochore microtubules will pull the sister chromatids toward opposite poles of the mitotic spindle to ensure that each daughter cell receives a complete genetic complement of chromosomes. (fsu.edu)
  • The safety of FEB's freezing solutions was demonstrated by undertaking a study visualizing the DNA in the egg's chromosomes and the egg's meiotic spindle apparatus. (prweb.com)
  • During cell division, two main MT structures are important - the spindle apparatus , which makes sure the chromosomes line up and are moved apart correctly, and the central spindle , that allows the cell to cleave precisely in two. (exeter.ac.uk)
  • In fungi, spindles form between spindle pole bodies embedded in the nuclear envelope, which does not break down during mitosis. (wikipedia.org)
  • Spindle assembly required during mitosis depends on microtubule polymerization. (nih.gov)
  • In conclusion, KBTBD8 is a new member of the BTB-kelch superfamily that is located in the Golgi apparatus and translocates to the spindle apparatus during mitosis. (biomedcentral.com)
  • 2. Inhibiting metaphase stage of mitosis by interfering with spindle formation. (brainscape.com)
  • The centrosome duplicates and, during mitosis, separates to form the two poles of the mitotic spindle (MITOTIC SPINDLE APPARATUS). (bioportfolio.com)
  • Immunostaining indicates that cell cycle arrest occurs before the completion of mitosis and is associated with the appearance of aberrant mitotic spindles. (aacrjournals.org)
  • What Is the Role of Spindle Fibers in Mitosis? (reference.com)
  • During the portion of mitosis known as metaphase , spindle fibers (which attach to the centromeres) jostle the chromatid pairs to the middle of the cell. (encyclopedia.com)
  • The kinetochore forms in eukaryotes, assembles on the centromere and links the chromosome to microtubule polymers from the mitotic spindle during mitosis and meiosis. (phys.org)
  • they form a spindle apparatus that helps separate genetic material into two new cells during mitosis. (stanford.edu)
  • It was found that levels of phospho-TBK1 increases and localizes to centrosomes and the mitotic spindles during mitosis. (aacrjournals.org)
  • At the same time, it is not clear whether TBK1 regulates mitosis my modulating the Spindle Assembly Checkpoint (SAC). (aacrjournals.org)
  • During mitosis the nuclear membrane and the nucleolus remain intact with an intranuclear spindle apparatus (closed orthomitosis). (tolweb.org)
  • The spindle apparatus is formed from very thin protein threads called microtubules that stretch between opposite poles of the cell during mitosis. (icr.org)
  • Our data provide functional evidence that 4.1R makes crucial contributions to the structural integrity of centrosomes and mitotic spindles which normally enable mitosis and anaphase to proceed with the coordinated precision required to avoid pathological events. (asm.org)
  • At the pointed ends, known as spindle poles, microtubules are nucleated by the centrosomes in most animal cells. (wikipedia.org)
  • Acentrosomal or anastral spindles lack centrosomes or asters at the spindle poles, respectively, and occur for example during female meiosis in most animals. (wikipedia.org)
  • Localizes to centrosomes, kinetochores and the mitotic spindle from prometaphase. (abcam.com)
  • Centrosomes catalyse the formation of microtubules needed to assemble the mitotic spindle apparatus 1 . (nature.com)
  • On the basis of these phenotypes and the observation that sub mutations genetically interact with ncd, we propose that SUB is one member of a group of microtubule-associated proteins required for bipolar spindle assembly in the absence of the centrosomes. (genetics.org)
  • Describe the role of centrosomes in the formation of the spindle apparatus. (quizlet.com)
  • Centrosomes nucleate and organize interphase microtubules and are instrumental in mitotic bipolar spindle assembly, ensuring orderly cell cycle progression with accurate chromosome segregation. (asm.org)
  • Centrosomes nucleate and organize interphase microtubules and direct assembly of mitotic bipolar spindles responsible for accurate chromosome segregation in somatic vertebrate cells. (asm.org)
  • Phase transition of spindle-associated protein regulate spindle apparatus assembly. (nih.gov)
  • We demonstrate that the evolutionarily conserved low-complexity protein, BuGZ, undergoes phase transition or coacervation to promote assembly of both spindles and their associated components. (nih.gov)
  • The localization of Esp1 to the spindle apparatus, analyzed by live cell imaging, is regulated in a manner consistent with a function during anaphase B. The protein accumulates in the nucleus in G2 and is mobilized onto the spindle pole bodies and spindle midzone at anaphase onset, where it persists into midanaphase. (rupress.org)
  • Spindle association is not fully restored in pds1 mutants expressing an Esp1-nuclear localization sequence fusion protein, suggesting that Pds1 is also required to promote Esp1 spindle binding. (rupress.org)
  • We show that Pds1 interaction is required to obtain efficient transport of Esp1 to the nucleus and for subsequent binding of the protein to the mitotic spindle, which appears to be crucial for proper anaphase progression. (rupress.org)
  • We identified the Golgi apparatus as the subcellular localization of the KBTBD8 protein in non-dividing cells and could show that KBTBD8 co-localizes with α-tubulin on the spindle apparatus of mitotic cells suggesting a role in cell proliferation. (biomedcentral.com)
  • The ch-TOG/XMAP215 protein is essential for spindle pole organization in human somatic cells. (nih.gov)
  • Chromator, a novel and essential chromodomain protein interacts directly with the putative spindle matrix protein skeletor. (semanticscholar.org)
  • The spindle apparatus is anchored to the opposite poles of the cell and determines the position of the future cleavage site in the middle of the cell, where a contractile protein ring is assembled. (uni-muenchen.de)
  • Kinetochore- and microtubule-binding protein that plays a key role in spindle assembly (PubMed:24462186, PubMed:24462187, PubMed:26388440). (genecards.org)
  • The kinetochore ( /kɪˈnɛtəkɔər/) is the protein structure on chromatids where the spindle fibers attach during cell division to pull sister chromatids apart. (phys.org)
  • Previous studies in Drosophila melanogaster implicated at least one kinesin motor protein, NCD, in tapering the microtubules into a bipolar spindle. (genetics.org)
  • We have identified a second Drosophila kinesin-like protein, SUB, that is required for meiotic spindle function. (genetics.org)
  • TBK1 physically interacts and phosphorylates centrosomal protein CEP170 and mitotic apparatus protein NuMA. (aacrjournals.org)
  • The researchers found that the motor protein kinesin-5 (green) helps prepare the spindle by. (eurekalert.org)
  • The researchers described how a protein called kinesin-5 acts like a kind of molecular motor to help organize the mitotic spindle. (eurekalert.org)
  • For this study, the researchers took a detailed look at the physical forces generated by the motor protein as it helps organize the mitotic spindle. (eurekalert.org)
  • Notably, all types of defective spindles have mislocalized NuMA ( nu clear m itotic a pparatus protein), a 4.1R binding partner essential for spindle pole focusing. (asm.org)
  • This gene encodes a protein associated with the mitotic spindle apparatus. (bio-rad.com)
  • The encoded protein may be involved in the functional and dynamic regulation of mitotic spindles. (bio-rad.com)
  • During prometaphase, the mitotic spindle microtubules are now free to enter the nuclear region, and formation of specialized protein complexes known as kinetochores begins on each centromere. (fsu.edu)
  • These populations of MTs are organised by a multitude of MT associated proteins (MAPs), including protein motor complexes, to form a polarized and focused spindle capable of chromosome segregation. (exeter.ac.uk)
  • In cell biology, the spindle apparatus (or mitotic spindle) refers to the cytoskeletal structure of eukaryotic cells that forms during cell division to separate sister chromatids between daughter cells. (wikipedia.org)
  • This event presumably allows sister chromatids to separate when pulled by microtubules connecting their kinetochores to opposite poles of the mitotic spindle. (rupress.org)
  • It is not yet clear how the separation of duplicated sister chromatids (anaphase A) is coordinated with spindle elongation (anaphase B). (rupress.org)
  • Spindle fibres contract to pull sister chromatids apart at the centromere . (brainscape.com)
  • Following the transition from metaphase to anaphase, the sister chromatids separate from each other, and the individual kinetochores on each chromatid drive their movement to the spindle poles that will define the two new daughter cells. (phys.org)
  • The sister chromatids are pulled to the poles by the spindle fibers. (studystack.com)
  • In some cases, the two sister chromatids, although correctly assembled in the mitotic spindle apparatus, simply fail to separate at anaphase. (fsu.edu)
  • Following movement of sister chromatids to the spindle poles in anaphase, a bundle of MTs form between the separating DNA. (exeter.ac.uk)
  • Mitotic Spindle Assembly: Building the Bridge between Sister K-Fibers. (semanticscholar.org)
  • They move to opposite poles during prophase and form spindle fibers made of microtubules. (studystack.com)
  • Our results indicate that exposure to NNK leads to a significantly altered spindle orientation, centrosome amplification, and chromosome misalignment in COPD cells as compared with normal epithelial cells. (aacrjournals.org)
  • When PLK4 is chemically inhibited, cell division proceeds without centrosome duplication, generating centrosome-less cells that exhibit delayed, acentrosomal spindle assembly 4 . (nature.com)
  • The female meiotic spindle lacks a centrosome or microtubule-organizing center in many organisms. (genetics.org)
  • In 4.1R-depleted mitotic cells, efficient centrosome separation is reduced, resulting in monopolar spindle formation. (asm.org)
  • In most animal cells, the formation of the spindle apparatus is mediated by complex interactions between MTs nucleated by the centrosome, those organised by mitotic DNA, and those seeded by the growing spindle itself. (exeter.ac.uk)
  • Opposing the action of these microtubule-stabilizing proteins are a number of microtubule-depolymerizing factors which permit the dynamic remodeling of the mitotic spindle to promote chromosome congression and attainment of bipolarity. (wikipedia.org)
  • The complexity of the relationship between kinetochores and the mitotic spindle reflects the requirement for accurate distribution of the genetic material between dividing cells. (fsu.edu)
  • Centrioles move to opposite poles of cell and spindle fibres are released to form a spindle apparatus . (brainscape.com)
  • This is where the fibres of the spindle apparatus attach themselves. (uni-heidelberg.de)
  • Chiasmata hold the homologs together during spindle formation of meiosis I and are required for orientation of the homologs at metaphase until the kinetochores are pulled to their proper poles at anaphase. (genetics.org)
  • In addition to chiasmata, chromosome segregation at meiosis I requires a bipolar attachment of bivalents on the spindle apparatus ( N icklas 1997 ). (genetics.org)
  • Mutants with defects in chromosome segregation during Drosophila female meiosis potentially identify genes that have a role in spindle organization or function. (genetics.org)
  • The meiotic spindle is a critical component of eggs that is involved in organizing the chromosome pairs so that a proper division of the pairs can occur as the egg is developing. (advancedfertility.com)
  • An excellent study published in the medical journal "Human Reproduction" in October of 1996 investigated the influence of maternal age on meiotic spindle assembly in human eggs. (advancedfertility.com)
  • Late prophase, or prometaphase , begins with the disruption of the nuclear envelope, which is broken down into small membrane vesicles that closely resemble the endoplasmic reticulum and tend to remain visible around the mitotic spindle. (fsu.edu)
  • Microtubule-associated proteins (MAPs) associate with microtubules at the midzone and the spindle poles to regulate their dynamics. (wikipedia.org)
  • Since several previously identified spindle-associated components also contain low-complexity regions, we propose that coacervating proteins may be a hallmark of proteins that comprise a spindle matrix that functions to promote assembly of spindles by concentrating its building blocks. (nih.gov)
  • This work represents an important advance in our efforts to build, from the ground up, the dynamic spindle apparatus out of purified proteins," says Kapoor, the senior author. (eurekalert.org)
  • Part I presents approaches for visualizing and analyzing the dynamic behaviors of the spindle apparatus, the microtubule based machine that drives chromosome segregation. (springer.com)
  • These fibrillar aggregates, referred to as microtubule foci, form small asters and collectively perform the role of the spindle pole during the two meiotic divisions. (biologists.org)
  • The two asters are the poles of the spindle apparatus. (thefreedictionary.com)
  • BuGZ coacervation and its binding to microtubules and tubulin are required to promote assembly of spindle and spindle matrix in Xenopus egg extract and in mammalian cells. (nih.gov)
  • It was shown that exogenously added NuMA antigen/antibody complex bound only to the mitotic spindle poles of permeabilized primate cells and not to the spindle poles of other mammalian cells, thus demonstrating the specificity of the spindle-pole interaction. (nih.gov)
  • To test our hypothesis, we assessed the genotoxic effects of a potent tobacco-smoke carcinogen [4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, (NNK)] on bronchial epithelial cells from patients with COPD and normal bronchial epithelial cells and identified genes associated with mitotic spindle defects and chromosome missegregation that also overlap with lung cancer. (aacrjournals.org)
  • In agreement, Pds1 interacts with the spindle at the metaphase-anaphase transition and a fraction remains at the spindle pole bodies and the spindle midzone in anaphase cells. (rupress.org)
  • This is consistent with the localization of Esp1 to the spindle pole bodies (SPBs) and mitotic spindle observed in live cells and the kinetics of Esp1 spindle association. (rupress.org)
  • We report here the finding of abnormal Golgi apparatus morphology in motor neuron like cells depleted of SMN as well as Golgi apparatus morphology in SMA patient fibroblasts. (bioportfolio.com)
  • Fig. 3: Acentrosomal spindle assembly and coalescence of pericentriolar material is suppressed by elevated TRIM37 levels in PLK4-inhibited cells. (nature.com)
  • Here, working at the resolution limit of the method, we describe a correlative light-SBF-SEM workflow to resolve microtubules of the mitotic spindle in human cells. (biologists.org)
  • In readiness for cell division, eukaryotic cells build a mitotic spindle. (biologists.org)
  • In human cells, the mitotic spindle is a fusiform structure, which at metaphase is virtually spherical. (biologists.org)
  • Aurora A, which is also present in human cells, is known to play a crucial role in the control of spindle assembly, and is activated on the astral microtubules. (uni-muenchen.de)
  • a group of blind-ending SPINDLE MICROTUBULES radiating out from the CENTRIOLES of dividing cells in lower plants and all animals. (thefreedictionary.com)
  • During cell division, the mitotic spindle divides up duplicate DNA for the two future daughter cells. (eurekalert.org)
  • Many millions of times per day, football-shaped structures called mitotic spindles form within the body's cells as they prepare to divide. (eurekalert.org)
  • It helps coordinate and govern the speed and location of the microtubules in the spindle. (eurekalert.org)
  • Other microtubules in the spindle (not attached to centromeres) are termed polar microtubules, and these help form and maintain the spindle structure along with astral microtubules, which remain outside the spindle. (fsu.edu)
  • Thus, centrioles are not obligatory organelles of the spindle apparatus. (biologists.org)
  • MAD1L1 is a component of the mitotic spindle-assembly checkpoint that prevents the onset of anaphase until all chromosome are properly aligned at the metaphase plate. (cancerindex.org)
  • To date there is only one member of this family known that is located in the Golgi apparatus. (biomedcentral.com)
  • The overrun controller compares the currently counted result with overrun upper limit and lower limit values and generates first and second flag signals braking the rotation of the spindle motor according to the compared result. (google.se)
  • an overrun controller for (i) performing one of up-counting, down-counting and holding a previously counted result, according to the frame clock signal divided by the second predetermined number and the second status signals, (ii) comparing the currently counted result with overrun upper limit and lower limit values, and (iii) generating first and second flag signals to brake the rotation of the spindle motor according to the compared result. (google.se)
  • The speed of rotation of the spindle must be maintained at a constant r.p.m., which is typically 3600 r.p.m. (google.com)
  • In this instance, a Ran GTP gradient is the main regulator of spindle microtubule organization and assembly. (wikipedia.org)
  • in mammals, CLASP1 and CLASP2 both contribute to proper spindle assembly and microtubule dynamics in anaphase. (wikipedia.org)
  • Interaction of CK1δ with γTuSC ensures proper microtubule assembly and spindle positioning. (nextbio.com)
  • Here we show that acentrosomal spindle assembly following PLK4 inhibition depends on levels of the centrosomal ubiquitin ligase TRIM37. (nature.com)
  • Low TRIM37 levels accelerate acentrosomal spindle assembly and improve proliferation following PLK4 inhibition, whereas high TRIM37 levels inhibit acentrosomal spindle assembly, leading to mitotic failure and cessation of proliferation. (nature.com)
  • By contrast, elevated TRIM37 expression inhibits acentrosomal spindle assembly through a distinct mechanism that involves degradation of the centrosomal component CEP192. (nature.com)
  • Petry, S. Mechanisms of mitotic spindle assembly. (nature.com)
  • Coacervation promotes microtubule bundling and concentrates tubulin, promoting microtubule polymerization and assembly of spindle and spindle matrix by concentrating its building blocks (PubMed:26388440). (genecards.org)
  • In-silico modeling of the mitotic spindle assembly checkpoint. (nih.gov)
  • In the wide middle portion, known as the spindle midzone, antiparallel microtubules are bundled by kinesins. (wikipedia.org)
  • Subsequently localizes to the spindle midzone from anaphase and to the midbody from telophase. (abcam.com)
  • In this case report, we describe a case of isolated oculomotor nerve palsy associated with antibodies to mitotic spindle apparatus (anti-MSA). (dovepress.com)
  • Antinuclear mitotic spindle apparatus antibody (MSA) and anticentromere antibody (ACA) are related mitotic antibodies, playing roles in autoimmune diseases and carcinomas, but the expression of MAD2, MSA, and ACA in SCLC is unclear. (medscimonit.com)
  • Finally, they are arranged at the opposite poles of the spindle. (syvum.com)
  • We illustrate how Pitx2 activity directs asymmetrical gonad morphogenesis by controlling mitotic spindle orientation of the developing gonad cortex and how, by modulating cyclinD1 expression during asymmetric ovarian development, Pitx2 appears to control gonad organ size. (biomedsearch.com)
  • The MTs of the mitotic spindle are densely packed and so resolving their organization in 3D is challenging. (biologists.org)
  • Spindles containing fluorescently tagged tubulin are photobleached to generate a non-fluorescent stripe, which moves toward the spindle poles allowing a measure of the flux. (nih.gov)
  • Roles of polymerization dynamics, opposed motors, and a tensile element in governing the length of Xenopus extract meiotic spindles. (semanticscholar.org)
  • Cell division is orchestrated by two main microtubule (MT) based structures called the ' spindle apparatus ' and the ' central spindle ', which function at different times to co-ordinate this dynamic process. (exeter.ac.uk)
  • In sub mutations, we observed spindles that were unipolar, multipolar, or frayed with no defined poles. (genetics.org)
  • Multipolar spindles and bipolar spindles with misaligned chromatin are also induced by 4.1R depletion. (asm.org)
  • B-E. Representative images ( B ) show that xBuGZ depletion reduced astral MT length, bipolar spindle formation and length, which were all rescued by His-xBuGZ. (nih.gov)
  • F-H. xBuGZ depletion caused multiple sperm spindle defects ( F ), which was rescued by His-xBuGZ ( G , H ). ~500 ( G ) and ~50 ( H ) structures were analyzed in each experiment and condition. (nih.gov)
  • Depletion of TBK1 was shown to trigger defects in spindle apparatus and prevents mitotic progression (Pillai et al. (aacrjournals.org)
  • The chromatin is stained with a blue fluorescent probe (DAPI), while the microtubule network (mitotic spindle) is stained green (Alexa Fluor 488) and cellular mitochondria are stained with a red dye (MitoTracker Red CMXRos). (fsu.edu)
  • These complexes become attached to a subset of the spindle microtubules, which are then termed kinetochore microtubules. (fsu.edu)
  • A crucial early event in carcinogenesis is the induction of the genomic instability through alterations in the mitotic spindle apparatus. (aacrjournals.org)
  • We hypothesized that tobacco smoke carcinogens induce mitotic spindle apparatus abnormalities and alter expression of crucial genes leading to increased genomic instability and ultimately tumorigenesis. (aacrjournals.org)
  • Sister segregation is particularly mysterious since bacteria lack a eukaryotic-like spindle apparatus. (harvard.edu)
  • The aster function is uncertain, but does not seem to be concerned with spindle formation. (thefreedictionary.com)
  • In research published October 1 in Developmental Cell , scientists at The Rockefeller University reveal new insights into the mechanical forces that govern elements of the mitotic spindle formation. (eurekalert.org)
  • As many kinesin-5 molecules work together directing microtubules, they become the governing force of the spindle formation. (eurekalert.org)
  • This central spindle assists in the formation of the contractile ring, a transient actin and myosin-II based structure, which is then able to direct cytokinesis. (exeter.ac.uk)