The team of Maximilian Fürthauer at the Institut de Biologie Valrose in Nice is looking for a highly motivated doctoral or postdoctoral research fellow to study the role of MyosinI proteins in establishing zebrafish Left/Right asymmetry.. While well conserved molecular pathways govern antero-posterior and dorso-ventral patterning in different phyla, highly divergent mechanisms have been proposed to be responsible for the specification of Left/Right asymmetry in different organisms. A cilia-driven, directional fluid flow is important for symmetry breaking in numerous vertebrates, including zebrafish. Alternatively, cilia-independent mechanisms have been suggested to involve localized ion flows or directional cellular rearrangements dependent on cytoskeletal polarity. This raises the question whether a unifying mechanism controlling Left/Right asymmetry still remains to be identified? An attractive hypothesis is that cytoskeletal chirality may provide a template for organismal laterality.. In ...
The mammalian sonic hedgehog (Shh) signalling pathway is essential for embryonic development and the patterning of multiple organs. Disruption or activation of Shh signalling leads to multiple birth defects, including holoprosencephaly, neural tube defects and polydactyly, and in adults results in tumours of the skin or central nervous system. Genetic approaches with model organisms continue to identify novel components of the pathway, including key molecules that function as positive or negative regulators of Shh signalling. Data presented here define Tulp3 as a novel negative regulator of the Shh pathway. We have identified a new mouse mutant that is a strongly hypomorphic allele of Tulp3 and which exhibits expansion of ventral markers in the caudal spinal cord, as well as neural tube defects and preaxial polydactyly, consistent with increased Shh signalling. We demonstrate that Tulp3 acts genetically downstream of Shh and Smoothened (Smo) in neural tube patterning and exhibits a genetic ...
Vertebrates, including humans, typically appear symmetrical from the outside; however, internally, there is clear left-right (LR) asymmetry: the heart, stomach, and spleen are on the left, while the liver and gall bladder are on the right; the right side of the lungs has more lobes than the left, and the intestines coil counterclockwise. This patterning is set up very early during development and requires the asymmetric expression of nodal in the left lateral plate mesoderm. This is a conserved aspect of normal LR patterning in all vertebrates studied; however, distinct mechanisms have been found to regulate left-sided nodal expression in different species (reviewed in Raya and Belmonte, 2006). In addition, many vertebrates have a ciliated laterality organ. In mouse and chick, it is the node, in zebrafish it is Kupffers vesicle (KV), and in frog it is the gastrocoel roof plate (GRP). The cilia in these laterality organs are motile and create a directional fluid flow. This directional flow is essential
Developmental patterning requires juxtacrine signaling in order to tightly coordinate the fates of neighboring cells. Recent work has shown that Notch and Delta, the canonical metazoan juxtacrine signaling receptor and ligand, mutually inactivate each other in the same cell. This cis-interaction generates mutually exclusive sending and receiving states in individual cells. It generally remains unclear, however, how this mutual inactivation and the resulting switching behavior can impact developmental patterning circuits. Here we address this question using mathematical modeling in the context of two canonical pattern formation processes: boundary formation and lateral inhibition. For boundary formation, in a model motivated by Drosophila wing vein patterning, we find that mutual inactivation allows sharp boundary formation across a broader range of parameters than models lacking mutual inactivation. This model with mutual inactivation also exhibits robustness to correlated gene expression ...
article{8516871, abstract = {The root vascular tissues provide an excellent system for studying organ patterning, as the specification of these tissues signals a transition from radial symmetry to bisymmetric patterns. The patterning process is controlled by the combined action of hormonal signaling/transport pathways, transcription factors, and miRNA that operate through a series of non-linear pathways to drive pattern formation collectively. With the discovery of multiple components and feedback loops controlling patterning, it has become increasingly difficult to understand how these interactions act in unison to determine pattern formation in multicellular tissues. Three independent mathematical models of root vascular patterning have been formulated in the last few years, providing an excellent example of how theoretical approaches can complement experimental studies to provide new insights into complex systems. In many aspects these models support each other; however, each study also ...
Pan-embryonic Ca2+ waves during epiboly/gastrula stages are believed to coordinate convergent extension (CE), the lengthening and narrowing of groups of cells, as well as their directed migration to the future dorsal side (Wallingford et al., 2001; Wallingford et al., 2002). Genetic data supports this idea, in that zebrafish homozygous zygotic Wnt-5 mutants (pipetail) display CE defects and have reduced Ca2+ release frequency (Westfall et al., 2003a). In fact, thapsigargin treatment during 30-50% epiboly resulted in cell movement defects and a shortened anterior-posterior axis (data not shown), consistent with previously described thapsigargin-induced phenotypes (Creton, 2004). However, brief thapsigargin treatment of epiboly/gastrula stage zebrafish and Xenopus disrupts laterality without perturbing normal cell movement. Similar laterality defects are generated with additional inhibitors (valproate, to disrupt inositol levels, XeC, to inhibit IP3-induced Ca2+ release and cyclopiazonic acid, to ...
A patterning system with a photoresist overhang allows material to be deposited onto a substrate in various positions by varying the angle from which the material is deposited, and by rotating the substrate. The patterning system can be used to fabricate a stack of organic light emitting devices on a substrate using the same patterning system and without removing the substrate from vacuum.
Various different kinases have been identified that phosphorylate Dishevelled proteins (Bernatik et al., 2011; Cong et al., 2004a; Gentzel et al., 2015; Kishida et al., 2001; Klein et al., 2006; Kühl et al., 2001; Ossipova et al., 2005; Peters et al., 1999; Shimizu et al., 2014; Sun et al., 2001; Willert et al., 1997). As counterparts, to date only the rather universal phosphatases PP1 and PP2 have been described (Carmen Figueroa-Aldariz et al., 2015; Shimizu et al., 2014). Here, we have identified the phosphatase Pgam5 as an interactor of Dvl2-Arrb2 protein complexes and negative regulator of Wnt/β-Catenin signaling.. In gastrula and post-gastrula stage Xenopus laevis embryos, pgam5 was expressed throughout the ectoderm but biased towards the anterior-dorsal ectoderm and the anterior neural tube. Consistent with this expression pattern, we showed that Pgam5 plays a role in head formation and a-p patterning. Low anterior Wnt/β-Catenin activity is required for the induction of anterior fates ...
With headphone listening, the naturally occurring left/right asymmetry in head and ear shapes can produce frequency-dependent variations in the perceived location of a sound source. In this paper, this phenomenon is studied by determining the interaural level differences required to center a set of narrow-band stimuli with different center frequencies. It is shown that the perceived asymmetry varies from one listener to another. Some of the asymmetry can be explained with asymmetry in...
How did gastropods evolve torsion? I have looked all over. There doesnt seem to be any clear idea of what torsion does now, let alone what purpose it...
The formation of the spot-like Spemann-type organizer (dark green/yellow) responsible for the dorso-ventral pattern is restricted to the blastopore. Thus, since the blastopore became a large ring , the dorsal organizer has automatically a pronounced off-axis position as required. The Spemann-type organizer with its spot-like extension is by itself insufficient to generate a dorsoventral pattern along the long-extended anteroposterior axis. An important step is, therefore, the generation of a midline organizer. It is the marginal ring and not the Spemann-Organizer that provide the positional information for the AP patterning. Evidence exists that WNT signals, generated in the ring, are involved in the posterior transformation of the more anteriorely located cells that form the future brain [1,2]. Also the activation of more posterior HOX genes takes place in the ring except of the organizing region [3]. For the zebra fish it has been shown that AP-markers appear in the correct order even in the ...
Electrohydrodynamic (EHD) patterning provides an alternative to fabricate the controllable polymeric micro/nano-structures, which have wide applications in industry. Both steady state and dynamic development of EHD patterning structures are discussed in this paper. For the steady state modeling, a discontinuous boundary element coupled with finite element method is applied. Numerical results reveal that a critical voltage exists, below which a small amplitude structure is obtained and above which polymer evolves into patterns with a large height/width ratio. The transient process of EHD patterning is represented by the numerical solution of the phase field equation coupled with the electric field and Navier-Stokes equation. The computer model is capable of describing the dynamic development of the electrically-induced transport and surface deformation phenomena during EHD patterning. The coupled multi-field equations are discretized in finite difference with an enhancement by parallel computing. ...
The present invention includes a conforming template for patterning liquids disposed on substrates. The template includes a body having opposed first and second surfaces. The first surface includes a plurality of recessed regions with a patterning region being disposed between adjacent recessed regions. Specifically, the recessed regions define flexure regions about which each patterning region may move independent of the remaining patterning regions of the template. In one embodiment the template is mounted to a fluid chamber having an inlet and a throughway. The template is connected to the throughway and the inlet is connected to a fluid source to facilitate deformation of the template to conform to a profile of a surface adjacent thereto.
Our findings suggest an inherent, cryptic chirality in VMCs that is revealed by an unbiased extracellular mechanical transition and mediated by cytoskeletal reorganization, analogous to chemically induced chirality seen in neutrophil-like cells.31 To our knowledge, this is the first demonstration of an association between LR asymmetry and cytoskeletal reorganization, triggered by an unbiased mechanical interface, and the first demonstration that a microscale dynamic asymmetry unfolds into a de novo, consistently oriented and periodic macroscale pattern resembling tissue architecture. In VMCs, the rightward-biased turning required stress-fiber accumulation at the FN/PEG interface, suggesting that chirality may be in the architecture of the actin filament assembly at the macroscale level, say as clockwise or counterclockwise orientation. Alternatively, it may arise from chirality at the micro- or nanoscale, such as helicity of microfilaments, or chiral rotagen molecules, such as dynein or myosin, ...
Coordinated spacing and patterning of stomata allow efficient gas exchange between plants and the atmosphere. Here we report that three ERECTA (ER)-family leucine-rich repeat-receptor-like kinases (LRR-RLKs) together control stomatal patterning, with specific family members regulating the specification of stomatal stem cell fate and the differentiation of guard cells. Loss-of-function mutations in all three ER-family genes cause stomatal clustering. Genetic interactions with a known stomatal patterning mutant too many mouths (tmm) revealed stoichiometric epistasis and combination-specific neomorphism. Our findings suggest that the negative regulation of ER-family RLKs by TMM, which is an LRR receptor-like protein, is critical for proper stomatal differentiation.. ...
The eye imaginal disc displays dorsal-ventral (D-V) and anterior-posterior polarity prior to the onset of differentiation, which initiates where the D-V midline intersects the posterior margin. As the wave of differentiation progresses anteriorly, additional asymmetry develops as ommatidial clusters rotate coordinately in opposite directions in the dorsal and ventral halves of the disc; this forms the equator, a line of mirror-image symmetry that coincides with the D-V midline of the disc. The currently unanswered question of how D-V pattern is established and how it relates to ommatidial rotation was addressed by assaying the expression of various asymmetric markers under conditions that lead to ectopic differentiation, such as removal of patched or wingless function. D-V patterning is found to develop gradually. wingless plays an important role in setting up this pattern. To determine if positional information associated with equatorial formation is present along the D-V axis of the disc ahead ...
In the minds of many, Hox gene null mutant phenotypes have confirmed the direct role that these genes play in specifying the pattern of vertebrate embryos. The genes are envisaged as defining discrete spatial domains and, subsequently, conferring specific segmental identities on cells undergoing differentiation along the antero-posterior axis. However, several aspects of the observed mutant phenotypes are inconsistent with this view. These include: the appearance of other, unexpected transformations along the dorsal axis; the occurrence of mirror-image duplications; and the development of anomalies outside the established domains of normal Hox gene expression. In this paper, Hox gene disruptions are shown to elicit regeneration-like responses in tissues confronted with discontinuities in axial identity. The polarities and orientations of transformed segments which emerge as a consequence of this response obey the rules of distal transformation and intercalary regeneration. In addition, the incidence of
A different patterning mechanism must generate the domains of expression of rn and bab and must lead to tarsal growth and differentiation. The presumptive tarsus is included within the Dll-expression domain (Fig. 2B), and Dllfunction is required for bab and rn activation and tarsal development at 84 hours AEL, as shown by Dllmutants and Dll - clones [Fig. 2, E and F; (7)]. However, neither theDll-expressing cells in the center of the disc (the presumptive distal tip), nor the most peripheralDll-expressing cells, express rn orbab (Fig. 2B). These peripheral cells appear to be medial cells expressing both Dll and dac (compare B and C of Fig. 2), and double-staining reveals that indeed the early rings of rn and bab expression are abutted bydac (Fig. 2D). These observations suggest that rnand bab expression, promoted by Dll, is repressed in medial Dll-expressing cells by dac and in the central cells by another factor. In clones ofdac- cells induced at 80 hours AEL, we observe ectopic outgrowths and ...
J:58465 Donoviel DB, Hadjantonakis AK, Ikeda M, Zheng H, Hyslop PS, Bernstein A, Mice lacking both presenilin genes exhibit early embryonic patterning defects. Genes Dev. 1999 Nov 1;13(21):2801-10 ...
Bryant, P. J. (1975) Regeneration and Duplication in Imaginal Discs, in Ciba Foundation Symposium 29 - Cell Patterning (eds R. Porter and J. Rivers), John Wiley & Sons, Ltd., Chichester, UK. doi: 10.1002/9780470720110.ch5 ...
These data are consistent with previous reports of intronic miRNA function, in which the miRNA regulates the same biological process as the protein encoded by the host gene.29 miR-218 may contribute to "fine-tuning" of Slit-Robo pathway genes or generate negative feedback in response to Slit gene activation. It is interesting to speculate that miR-218 may serve to repress the expression of the Robo1/2 receptors in the Slit ligand-expressing cells, thereby spatially separating ligand from receptor. Because Robo4 is not a target of miR-218 regulation, it also is possible that miR-218 affects the ratio of Robo1/2 and Robo4 proteins, thereby influencing vascular patterning.. It is currently debated whether the Robo1 and -2 receptors provide a positive or negative influence on EC migration, although Robo4 is generally thought of as a repulsive or stabilizing cue during vascular pathfinding.9,37 In our hands, it appears that repression of Robo1/2 and HSPG biosynthetic molecules by miR-218 negatively ...
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Graduate students register for 255) This course focusses on how animals form their basic body plans; from the formation of their germ layers; ectoderm, endoderm and mesoderm, to how they are organized along the main developmental axes; the anteroposterior and dorsoventral axes. The course will focus in part on the molecular mechanisms that underlie these developmental decisions from work carried out in established developmental model species. However, we will also explore the current understanding of how these mechanisms evolved from new insights from emerging models representing a broad range of animal phyla. The setting at Hopkins Marine Station will allow us to carry out experiments from animals collected in the field, and the course will involve a substantial lab component to complement concepts and approaches presented in lecture. nPre-requisites : Biocore or by permission of ...
Grafts of ShhC25II-soaked beads reproduce the stage-dependent effects of PMP treatments on eye DV patterning. (A) Lateral views of heads of st. 33 embryos that
What does Brad Pitt have in common with a fruit fly? They both have cowlicks-a swirl of hair caused by a patterning mechanism. Now, researchers have discovered the genes that cause cowlicks are regulated by a tumor suppressor protein.
J:186907 DAndrea D, Liguori GL, Le Good JA, Lonardo E, Andersson O, Constam DB, Persico MG, Minchiotti G, Cripto promotes A-P axis specification independently of its stimulatory effect on Nodal autoinduction. J Cell Biol. 2008 Feb 11;180(3):597-605 ...
How is Anterior and Posterior abbreviated? A-P stands for Anterior and Posterior. A-P is defined as Anterior and Posterior very frequently.
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CPR 100-120 compressions per minute and at a depth of no less than 1/3 of anterior/posterior diameter of chest with interruptions less than 5 seconds ...
TY - JOUR. T1 - Linking early determinants and cilia-driven leftward flow in left-right axis specification of Xenopus laevis. T2 - A theoretical approach. AU - Schweickert, Axel. AU - Walentek, Peter. AU - Thumberger, Thomas. AU - Danilchik, Mike. PY - 2012/2/1. Y1 - 2012/2/1. N2 - In vertebrates, laterality - the asymmetric placement of the viscera including organs of the gastrointestinal system, heart and lungs - is under the genetic control of a conserved signaling pathway in the left lateral plate mesoderm (LPM). A key feature of this pathway, shared by embryos of all non-avian vertebrate classes analyzed to date (e.g. fish, amphibia and mammals) is the formation of a transitory midline epithelial structure. Remarkably, the motility of cilia projecting from this epithelium produce a leftward-directed movement of extracellular liquid. This leftward flow precedes any sign of asymmetry in gene expression. Numerous analyses have shown that this leftward flow is not only necessary, but indeed ...
TY - JOUR. T1 - Wnt3a links left-right determination with segmentation and anteroposterior axis elongation. AU - Nakaya, Masa Aki. AU - Biris, Kristin. AU - Tsukiyama, Tadasuke. AU - Jaime, Shaulan. AU - Rawls, J. Alan. AU - Yamaguchi, Terry P.. PY - 2005/12. Y1 - 2005/12. N2 - The alignment of the left-right (LR) body axis relative to the anteroposterior (AP) and dorsoventral (DV) axes is central to the organization of the vertebrate body plan and is controlled by the node/organizer. Somitogenesis plays a key role in embryo morphogenesis as a principal component of AP elongation. How morphogenesis is coupled to axis specification is not well understood. We demonstrate that Wnt3a is required for LR asymmetry. Wnt3a activates the Delta/Notch pathway to regulate perinodal expression of the left determinant Nodal, while simultaneously controlling the segmentation clock and the molecular oscillations of the Wnt/β-catenin and Notch pathways. We provide evidence that Wnt3a, expressed in the primitive ...
Inversin is a protein that in humans is encoded by the INVS gene. This gene encodes a protein containing multiple ankyrin domains and two IQ calmodulin-binding domains. The encoded protein may function in renal tubular development and function, and in left-right axis determination. This protein interacts with nephrocystin and infers a connection between primary cilia function and left-right axis determination. A similar protein in mice interacts with calmodulin. Mutations in this gene have been associated with nephronophthisis type 2. Two transcript variants encoding distinct isoforms have been identified for this gene. INVS has been shown to interact with NPHP1. GRCh38: Ensembl release 89: ENSG00000119509 - Ensembl, May 2017 GRCm38: Ensembl release 89: ENSMUSG00000028344 - Ensembl, May 2017 "Human PubMed Reference:". "Mouse PubMed Reference:". Otto EA, Schermer B, Obara T, OToole JF, Hiller KS, Mueller AM, Ruf RG, Hoefele J, Beekmann F, Landau D, Foreman JW, Goodship JA, Strachan T, Kispert A, ...
Cranial placodes are evolutionary innovations of vertebrates. However, they most likely evolved by redeployment, rewiring and diversification of preexisting cell types and patterning mechanisms. In the second part of this review we compare vertebrates with other animal groups to elucidate the evolutionary history of ectodermal patterning. We show that several transcription factors have ancient bilaterian roles in dorsoventral and anteroposterior regionalisation of the ectoderm. Evidence from amphioxus suggests that ancestral chordates then concentrated neurosecretory cells in the anteriormost non-neural ectoderm. This anterior proto-placodal domain subsequently gave rise to the oral siphon primordia in tunicates (with neurosecretory cells being lost) and anterior (adenohypophyseal, olfactory, and lens) placodes of vertebrates. Likewise, tunicate atrial siphon primordia and posterior (otic, lateral line, and epibranchial) placodes of vertebrates probably evolved from a posterior proto-placodal region in
Blimp1, a zinc-finger containing DNA-binding transcriptional repressor, functions as a master regulator of B cell terminal differentiation. Considerable evidence suggests that Blimp1 is required for the establishment of anteroposterior axis formation and the formation of head structures during early vertebrate development. In mouse embryos, Blimp1 is strongly expressed in axial mesendoderm, the tissue known to provide anterior patterning signals during gastrulation. Here, we describe for the first time the defects caused by loss of Blimp1 function in the mouse. Blimp1 deficient embryos die at mid-gestation, but surprisingly early axis formation, anterior patterning and neural crest formation proceed normally. Rather, loss of Blimp1 expression disrupts morphogenesis of the caudal branchial arches and leads to a failure to correctly elaborate the labyrinthine layer of the placenta. Blimp1 mutant embryos also show widespread blood leakage and tissue apoptosis, and, strikingly, Blimp1 homozygous mutants
Developmental Biology. Research Categories: Developmental Biology Research Description: We ask how the embryo works. Prior to morphogenesis the embryo specifies each cell through transcriptional regulation and signaling. Our research builds gene regulatory networks to understand how that early specification works. We then ask how this specification programs cells for their morphogenetic movements at gastrulation, and how the cells deploy patterning information. Current projects examine 1) novel signal transduction mechanisms that establish and maintain embryonic boundaries mold the embryo at gastrulation; 2) specification of primary mesenchyme cells in such a way that they are prepared to execute an epithelial-mesenchymal transition, and then study mechanistically the regulation of that transition; 3) the specification of endoderm necessary for invagination of the archenteron; 4) formation of the oral/aboral ectoderm and the means by which patterning information is distributed three ...
Brueckner Lab:. Research Interests: Development of vertebrate left-right asymmetry Cilia in development Cardiac morphogenesis The development of non-random asymmetry along the left-right axis is a unique feature of vertebrate development. Defects in this process in mouse and man commonly affect the development of the heart and result in severe congenital cardiac anomalies. The goal of my laboratory is to understand the mechanism by which embryonic cilia create and signal left-right positional information, and to investigate whether cilia have essential roles in other developmental processes. We have previously shown that the vertebrate LR axis is initiated at the mammalian node late in gastrulation. Dynein-driven motility of monocilia found on node cells generates directional flow of extraembryonic fluid, termed "nodal flow". The direction of nodal flow is determined by the inherent chirality of the cilium itself, and artificial reversal of nodal flow is able to reverse the LR axis. Nodal flow ...
Graded Hedgehog (Hh) signaling governs the balance of Gli transcriptional activators and repressors to specify diverse ventral cell fates in the spinal cord. It remains unclear how distinct intracellular Gli activity is generated. Here, we demonstrate that Sufu acts universally as a negative regulator of Hh signaling, whereas Kif7 inhibits Gli activity in cooperation with, and independent of, Sufu. Together, they deter naïve precursors from acquiring increasingly ventral identity. We show that Kif7 is also required to establish high intracellular Gli activity by antagonizing the Sufu-inhibition of Gli2. Strikingly, by abolishing the negative regulatory action of Sufu, diverse ventral cell fates can be specified in the absence of extracellular Hh signaling. These data suggest that Sufu is the primary regulator of graded Hh signaling and establish that the antagonistic and cooperative actions of Kif7 and Sufu are responsible for setting up distinct Gli activity in ventral cell fate specification.
Gli-type zinc finger proteins play important regulatory roles in vertebrate and invertebrate embryogenesis. In Xenopus, the Gli-type proteins XGli-3 and XGli-4 are first expressed in earliest stages of mesoderm and neural development. Transient transfection assays reveal that XGli-3 and XGli-4 can f …
Predicted to have RNA polymerase II proximal promoter sequence-specific DNA binding activity. Involved in determination of heart left/right asymmetry; somite rostral/caudal axis specification; and somite specification. Predicted to localize to the nucleus. Human ortholog(s) of this gene implicated in spondylocostal dysostosis. Is expressed in margin; mesoderm; post-vent region; and somite. Orthologous to human MESP2 (mesoderm posterior bHLH transcription factor 2 ...
The dorsal gastrula organizer plays a fundamental role in establishment of the vertebrate axis. We demonstrate that the zebrafish bozozok (boz) locus is required at the blastula stages for formation of the embryonic shield, the equivalent of the gastrula organizer and expression of multiple organizer-specific genes. Furthermore, boz is essential for specification of dorsoanterior embryonic structures, including notochord, prechordal mesendoderm, floor plate and forebrain. We report that boz mutations disrupt the homeobox gene dharma. Overexpression of boz in the extraembryonic yolk syncytial layer of boz mutant embryos is sufficient for normal development of the overlying blastoderm, revealing an involvement of extraembryonic structures in anterior patterning in fish similarly to murine embryos. Epistatic analyses indicate that boz acts downstream of ß-catenin and upstream to TGF-ß signaling or in a parallel pathway. These studies provide genetic evidence for an essential function of a ...
Author Summary Multicellular development requires tightly regulated spatial pattern formation, frequently including the generation of sharp differences over short length scales. Classic examples include boundary formation in the Drosophila wing veins and lateral inhibition patterning in the differentiation of sensory cells. These processes and a diverse variety of others are mediated by the Notch signaling system which allows neighboring cells to exchange information, via interaction between the Notch receptor on one cell and its ligands such as Delta, on another. Interestingly, recent evidence has shown that Notch and Delta within the same cell (in cis) also interact, mutually inactivating each other. However, the significance of this interaction for pattern formation has remained unclear. Here we show, by analytical and computational modeling, how this cis interaction intrinsically generates a difference-promoting logic that optimizes the system for use in fine-grained pattern formation. Specifically,
In developmental biology, an embryo is divided into two hemispheres: the animal pole and the vegetal pole within a blastula. The animal pole consists of small cells that divide rapidly, in contrast with the vegetal pole below it. In some cases, the animal pole is thought to differentiate into the later embryo itself, forming the three primary germ layers and participating in gastrulation. The animal pole is heavily pigmented while the vegetal pole remains unpigmented.[1] The vegetal pole contains large yolky cells that divide very slowly, in contrast with the animal pole above it. In some cases, the vegetal pole is thought to differentiate into the extraembryonic membranes that protect and nourish the developing embryo, such as the placenta in mammals and the chorion in birds. The development of the animal-vegetal axis occurs prior to fertilization.[2] Sperm entry can occur anywhere in the animal hemisphere.[3] The point of sperm entry defines the dorso-ventral axis - cells opposite the region ...
0050] The prosthesis according to the present invention comprises osseous anchoring means ensuring good stability of the elements of the prosthesis between one another during implantation of the prosthesis between the vertebrae. For this, the prosthesis according to the present invention comprises at least first osseous anchoring means (42) and at least second osseous anchoring means (41). The first osseous anchoring means (42) extend to near the periphery of the plate on which it is situated and the second osseous anchoring means (41) is offset according to the antero-posterior axis relative to the first osseous anchoring means (42). Therefore, the first osseous anchoring means (42) could consist, in an embodiment not illustrated here, of a winglet oriented perpendicularly to the antero-posterior axis of the spinal column and located near the leading edge or posterior edge of the plate on which they are located. The second osseous anchoring means (41) will thus be located in the vicinity of the ...
Somite polarity and segmental patterning of the peripheral nervous system.: The analysis of the outgrowth pattern of spinal axons in the chick embryo has shown
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The use of DNA as a structural material has been intensively developed since its inception in the early 1980s. The potential of DNA structures in the field of materials science is hampered by current approaches to augmentation. It is not currently possible to alter the targeting of heterogenous additional elements to structures once they have been made. The post hoc patterning of DNA architectures is therefore of great importance. The bacterial protein Recombinase A (RecA) may be able to provide this function. This thesis will discuss the patterning of DNA structures with RecA. RecA has been shown to pattern linear dsDNA strands with high levels of efficiency. To test the potential of RecA to pattern more complex DNA, novel strategies for creating DNA topologies have been explored. This work has produced DNA strands containing regions of base pair mismatching and with terminal three-way junctions. A method has also been developed for the creation of a 200 base product with unpaired branched ...
The floorplate (FP) is located at the ventral midline of the developing neural tube, and is involved in patterning and specification of ventral and dorsal cell fates. The FP has long been known to pattern ventral cell fates ...
An essential question of morphogenesis is how patterns arise without preexisting positional information, as inspired by Turing. In the past few years, cytoskeletal flows in the cell cortex have been identified as a key mechanism of molecular patterning at the subcellular level. Theoretical and in vitro studies have suggested that biological polymers such as actomyosin gels have the property to self-organize, but the applicability of this concept in an in vivo setting remains unclear. Here, we report that the regular spacing pattern of supracellular actin rings in the Drosophila tracheal tubule is governed by a self-organizing principle. We propose a simple biophysical model where pattern formation arises from the interplay of myosin contractility and actin turnover. We validate the hypotheses of the model using photobleaching experiments and report that the formation of actin rings is contractility dependent. Moreover, genetic and pharmacological perturbations of the physical properties of the ...
Why have certain features of animal body plans, such as bilateral symmetry, been conserved since the early Cambrian period, whereas at the species level, there has been a continuous accumulation of changes? Davidson and Erwin propose that the genetic regulatory networks associated with development contain three components that differ in their evolutionary conservation. Evolutionarily inflexible subcircuits ("kernels") perform essential upstream functions in building given body parts, while other small subcircuits ("plug-ins") have been repeatedly coopted to diverse developmental purposes, leaving highly flexible, individual cis-regulatory linkages to regulate detailed phenotypic variation.. E. H. Davidson, D. H. Erwin, Gene regulatory networks and the evolution of animal body plans. Science 311, 796-800 (2006). [Abstract] [Full Text]. ...
Cardiac pacemaker cells of the sinoatrial node initiate and maintain the rhythmic beating of the heart. This function requires that pacemaker cells be insulated...