This study analyzes the expression and the function of Xenopus msx-1 (Xmsx-1) in embryos, in relation to the ventralizing activity of bone morphogenetic protein-4 (BMP-4). Expression of Xmsx-1 was increased in UV-treated ventralized embryos and decreased in LiCl-treated dorsalized embryos at the neurula stage (stage 14). Whole-mount in situ hybridization analysis showed that Xmsx-1 is expressed in marginal zone and animal pole areas, laterally and ventrally, but not dorsally, at mid-gastrula (stage 11) and late-gastrula (stage 13) stages. Injection of BMP-4 RNA, but not activin RNA, induced Xmsx-1 expression in the dorsal marginal zone at the early gastrula stage (stage 10+), and introduction of a dominant negative form of BMP-4 receptor RNA suppressed Xmsx-1 expression in animal cap and ventral marginal zone explants at stage 14. Thus, Xmsx-1 is a target gene specifically regulated by BMP-4 signaling. Embryos injected with Xmsx-1 RNA in dorsal blastomeres at the 4-cell stage exhibited a ...

A Xenopus laevis homeobox gene, Xhox3, has been isolated using the homeobox of the Drosophila pair-rule gene even skipped as a hybridization probe. Xhox3 is first transcribed at the midblastula transition; RNA levels peak at the early neurula stage and decrease thereafter. During the early period of Xhox3 expression, the gastrula and neurula stages, transcripts are found in a graded fashion along the anteroposterior (A-P) axis in the mesoderm and are most concentrated at the posterior pole. In the late period of expression, the tailbud and tadpole stage, transcripts are concentrated at the two ends of the embryo: in the anterior nervous system and posterior tail bud. Analysis of Xhox3 expression in experimentally perturbed embryos shows that different A-P fates in the mesoderm are correlated with different levels of Xhox3 expression. Based on these results and those with other frog homeobox genes, we propose a role for homeobox genes in the patterning of the A-P embryonic axis.. ...

The zebrafish DVR-1 (zDVR-1) gene, like Xenopus Vg1, is present maternally as an unprocessed precursor protein which is distributed ubiquitously along the future dorsoventral axis. Also, like Vg1, overexpression of zDVR-1 in zebrafish directs synthesis of more precursor, but no processed protein. Ho …

Free Online Library: Twin Xenopus laevis embryos appearing from flattened eggs.(Report) by Japan Academy Proceedings Series B: Physical and Biological Sciences; Agricultural industry Engineering and manufacturing Biological sciences Common plantanna Genetic aspects Research Embryonic development Analysis Gene expression

The common laboratory frog Xenopus laevis has puzzled researchers because it has twice the normal number of genes. A newly published genome sequence shows why: between 15 and 20 million years ago, two different species interbred and produced a hybrid, which then mated with its parent species to eventually form a new organism with a doubled genome. The frog has since adapted to the excess by losing or disabling many of these genes.

Fig. 8. Additive effects of Xvent genes in gainand loss-of-function. (A) Xvent genes ventralize mesoderm in an additive fashion. Embryos were either non-injected (Co) or microinjected radially at the 4- to 8-cell stage with Xvent-1 (range 0.125-0.25 ng/blastomere) or Xvent-2 mRNA (range 0.37-075 ng/blastomere), or injected with a mixture (same range of both). The average dorsoanterior index (Kao and Elinson, 1988) of embryos was 4.8 (uninjected control, n=22), 4.4 (Xvent-1, n=34), 3.0 (Xvent- 2, n=47) and 2.6 (Xvent-1 + Xvent-2, n=33). (B) Xvent genes function in an additive fashion in downregulation of dorsal and upregulation of ventral marker genes in DMZ. Embryos were either non-injected (Co), or microinjected radially at the 4- and 8-cell stage with the doses indicated in ng/blastomere with Xvent-1 or Xvent-2 mRNAs, or injected with a mixture. Control (Co) VMZ and DMZs were explanted at early gastrula stage and fixed immediately for total RNA preparation. Expression of marker genes indicated ...

To gain insight into the mechanisms involved in the formation of maternally stored mRNPs during Xenopus laevis development, we searched for soluble cytoplasmic proteins of the oocyte that are able to selectively bind mRNAs, using as substrate radiolabeled mRNA. In vitro mRNP assembly in solution was followed by UV-cross-linking and RNase digestion, resulting in covalent tagging of polypeptides by nucleotide transfer. Five polypeptides of approximately 54, 56 60, 70, and 100 kD (p54, p56, p60, p70, and p100) have been found to selectively bind mRNA and assemble into mRNPs. These polypeptides, which correspond to previously described native mRNP components, occur in three different particle classes of approximately 4.5S, approximately 6S, and approximately 15S, as also determined by their reactions with antibodies against p54 and p56. Whereas the approximately 4.5S class contains p42, p60, and p70, probably each in the form of individual molecules or small complexes, the approximately 6S particles ...

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The primary patterning event in early vertebrate development is the formation of the mesoderm and its subsequent induction of the neural tube. Classic experiments suggest that the vegetal region signals the animal hemisphere to diverge from the pathway of forming ectoderm to form mesoderm such as mu …

Description: The library was made from dT primed cDNA and cloned into vector pCS107. PolyA RNA were primed with an oligo dT primer (5-GACTAGTTCTAGATCGCGAGCGGCCGCCCTTTTTTTTTTTTTTT -3), ligated to a SalI adapter (5-TCGACCCACGCGTCCG-3 and 5-CGGACGCGTGGG-3) and digested with NotI. cDNA was size selected using 1.1% agarose gel electrophoresis (>0.6kb) then ligated into NotI and SalI digested pCS107 vector. Primary library, non-amplified. Library constructed at the DOE Joint Genome Institute (Walnut Creek, CA) as part of the Xenopus Gene Collection project. ...

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Transcriptional regulation of tissue separation during gastrulation of Xenopus laevis [Elektronische Ressource] / presented by Isabelle Köster : Transcriptional regulation of tissue separation during gastrulation of Xenopus laevis Dissertation submitted to the Combined Faculties of the Natural Sciences and for Mathematics of the Ruperto-Carola University of Heidelberg, Germany for the degree of Doctor of Natural Sciences presented by Dipl.-Biol. Isabelle Köster Dissertation submitted to the Combined Faculties of the

TY - JOUR. T1 - Spatially and temporally regulated α6 integrin cleavage during Xenopus laevis development. AU - Demetriou, Manolis C.. AU - Stylianou, Panayiota. AU - Andreou, Maria. AU - Yiannikouri, Olga. AU - Tsaprailis, George. AU - Cress, Anne E. AU - Skourides, Paris. PY - 2008/2/15. Y1 - 2008/2/15. N2 - The α6 integrin is essential for early nervous system development in Xenopus laevis. We have previously reported a uPA cleaved form of integrin α6 (α6p), in invasive human prostate cancer tissue, whose presence correlates with increased migration and invasive capacity. We now report that α6 is cleaved during the normal development of Xenopus in a spatially and temporally controlled manner. In addition, unlike normal mammalian tissues, which lack α6p, the major form of the α6 integrin present in adult Xenopus is α6p. The protease responsible for the cleavage in mammals, uPA, is not involved in the cleavage of Xenopus α6. Finally, overexpression of a mammalian α6 mutant which ...

Author: Schmidt, A. et al.; Genre: Journal Article; Published in Print: 2005-02-15; Keywords: cell cycle; anaphase-promoting complex/cyclosome; Xenopus; polo-like kinase; cytostatic factor; mitotic exit; Title: Xenopus polo-like kinase Plx1 regulates XErp1, a novel inhibitor of APC/C activity

The caudal-related (Cdx) homeodomain transcription factors have a conserved role in the development of posterior structures in both vertebrates and invertebrates. A particularly interesting finding is that Cdx proteins have an important function in the regulation of expression from a subset of Hox genes. In this study, we report the cloning of cDNAs from the Cdx genes of the amphibian Xenopus tropicalis. Xenopus tropicalis is a diploid species, related to the commonly used laboratory animal Xenopus laevis, and has attracted attention recently as a potential genetic model for animal development. The Xenopus tropicalis cDNAs, Xtcad1, Xtcad2, and Xtcad3, show between 88 and 94% sequence identity with their Xenopus laevis orthologues. This finding corresponds to between 90 and 95% identity at the level of derived amino acid sequence. We also present a detailed description of Xtcad1, Xtcad2, and Xtcad3 expression during normal development. In common with the Cdx genes of other vertebrates, the ...

Fibroblast growth factors (FGFs) mediate many cell-to-cell signaling events during early development. Nou-darake (ndk), a gene encoding an FGF receptor (FGFR)-like molecule, was found to be highly and specifically expressed in the head region of the planarian Dugesia japonica, and its functional analyses provided strong molecular evidence for the existence of a brain-inducing circuit based on the FGF signaling pathway. To analyze the role of ndk during vertebrate development, we isolated the Xenopus ortholog of ndk, the vertebrate FGFR-like 1 gene (XFGFRL1). Expression of XFGFRL1/Xndk was first detected in the anterior region at the late gastrula stage and dramatically increased at the early neurula stage in an overall anterior mesendodermal region, including the prechordal plate, paraxial mesoderm, anterior endoderm, and archenteron roof. This anterior expression pattern resembles that of ndk in planarians, suggesting that the expression of FGFRL1/ndk is conserved in evolution between these two

In our laboratory, we use Xenopus laevis, commonly known as the African clawed frog (learn more on wikipedia). Xenopus laevis is a great model system for dissecting the molecular pathways in DNA replication and the maintenance of genomic stability. Cell-free extracts made from Xenopus eggs contain all the proteins necessary to undergo 12 rounds of cell-cycle regulated, semi-conservative DNA replication in the absence of transcription. Events in these extracts are highly synchronous, allowing the analysis of short-lived intermediates and the dissection of signal transduction cascades. Particularly, the function of essential proteins can be addressed by immunodepletion or neutralization of these proteins, coupled to rescue with recombinant proteins. Xenopus cell-free extracts are generated by centrifuging unfertilized Xenopus eggs and isolating the cytoplasmic layer. Female Xenopus can be induced to lay an abundance of eggs after hormone injection. In fact, Xenopus laevis were used as a pregnancy ...

The frog genus Xenopus is widely used as a model system for studying developmental biology and fundamental cell biological processes. The advantages that Xenopus offer as an experimental system include (1) the availability of large abundant eggs that are easily manipulated, (2) ready accessibility to any developmental stage, and (3) conservation of cellular pathways between Xenopus and mammals. Over the past 50 years, pioneering studies on Xenopus have been crucial towards our understanding of nuclear reprogramming, embryonic patterning, membrane channels and receptors, and the cell cycle.. Despite its popularity for biomedical research, genomic resources for Xenopus have been lagging behind other model organisms. A major reason for this is that early developmental and molecular studies have relied on a particular species known as Xenopus laevis, which is pseudotetraploid as a result of genome duplication around 30 million years ago. The presence of four copies of every gene complicates genetic ...

Rödder, D., Ihlow, F., Courant, J., Secondi, J., Herrel, A., Rebelo, R., Measey, G. J., et al. (2017): Global realized niche divergence in the African clawed frog Xenopus laevis. - Ecology and Evolution 2017: 1-15; DOI: 10.1002/ece3.3010

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MASTL (microtubule-associated serine/threonine kinase-like), more commonly known as Greatwall (GWL), has been proposed as a novel cancer therapy target. GWL plays a crucial role in mitotic progression, via its known substrates ENSA/ARPP19, which when phosphorylated inactivate PP2A/B55 phosphatase. When over-expressed in breast cancer, GWL induces oncogenic properties such as transformation and invasiveness. Conversely, down-regulation of GWL selectively sensitises tumour cells to chemotherapy. Here we describe the rst structure of the GWL minimal kinase domain and development of a small-molecule inhibitor GKI-1 (Greatwall Kinase Inhibitor-1). In vitro, GKI-1 inhibits full-length human GWL, and shows cellular e cacy. Treatment of HeLa cells with GKI-1 reduces ENSA/ARPP19 phosphorylation levels, such that they are comparable to those obtained by siRNA depletion of GWL; resulting in a decrease in mitotic events, mitotic arrest/cell death and cytokinesis failure. Furthermore, GKI-1 will be a useful ...

Delineation of apical and basolateral membrane domains is a critical step in the epithelialization of the outer layer of cells in the embryo. We have examined the initiation of polarized membrane traffic in Xenopus and show that membrane traffic is not polarized in oocytes but polarized membrane domains appear at first cleavage. The following proteins encoded by injected RNA transcripts were used as markers to monitor membrane traffic: (a) VSV G, a transmembrane glycoprotein preferentially inserted into the basolateral surface of polarized epithelial cells; (b) GThy-1, a fusion protein of VSV G and Thy-1 that is localized to the apical domains of polarized epithelial cells; and (c) prolactin, a peptide hormone that is not polarly secreted. In immature oocytes, there is no polarity in the expression of VSV G or GThy-1, as shown by the constitutive expression of both proteins at the surface in the animal and vegetal hemispheres. At meiotic maturation, membrane traffic to the surface is blocked; ...

Domain architectures containing both Cysteine-rich domain and PH domain-like in Xenopus tropicalis 76_4.2. Links to architectures containing these domain pairs in other groups of genomes are provided. Domain pairs which are not adjacent can be added/removed.

In zebrafish embryos, factors involved in both axis induction and primordial germ cell (PGC) development are localized to the vegetal pole of the egg. However, upon egg activation axis induction factors experience an asymmetric off-center shift whereas PGC factors undergo symmetric animally-directed movement. We examined the spatial relationship between the proposed dorsal genes wnt8a and grip2a and the PGC factor dazl at the vegetal cortex. We find that RNAs for these genes localize to different cortical depths, with the RNA for the PGC factor dazl at a deeper cortical level than those for axis-inducing factors. In addition, and in contrast to the role of microtubules in the long-range transport of dorsal determinants, we find that germ line determinant transport depends on the actin cytoskeleton. Our results support a model in which vegetal cortex differential RNA transport behavior is facilitated by RNA localization along cortical depth and differential coupling to cortical transport ...

Domain architectures containing the following SCOP superfamilies 57424,57424,57424,57424,57424,57424,57424,57424,57424,57424,57424,57184,63825,_gap_,57196,57196,57196,_gap_,57196,_gap_ in Xenopus tropicalis 76_4.2. Domain architectures illustrate each occurrence of 57424,57424,57424,57424,57424,57424,57424,57424,57424,57424,57424,57184,63825,_gap_,57196,57196,57196,_gap_,57196,_gap_.

UNSPECIFIED. (1987) THE DEVELOPMENT OF ANIMAL CAP CELLS IN XENOPUS - A MEASURE OF THE START OF ANIMAL CAP COMPETENCE TO FORM MESODERM. DEVELOPMENT, 101 (3). pp. 557-563. ISSN 0950-1991 ...

GenEZ™ ORF cDNA clones makes it easy to order customized expression-ready ORF clones from the worlds largest commercial ORF clone database. You can Browse ORF cDNA clones by species Xenopus tropicalis, page 1

GenEZ™ ORF cDNA clones makes it easy to order customized expression-ready ORF clones from the worlds largest commercial ORF clone database. You can Browse ORF cDNA clones by species Xenopus tropicalis, page 196

Xenopus laloo protein: involved in induction of mesoderm by fibroblast growth factor; isolated from Xenopus laevis; amino acid sequence in first source; GenBank AF081803

Embryonic Stage **[[Stage 1]] **Cleavage ***[[Stage 2]] ***[[Stage 3]] ***[[Stage 4]] ***[[Stage 5]] ***[[Stage 6]] **Blastula ***[[Stage 7]] ***[[Stage 8]] ***[[Stage 9]] **Gastrula ***[[Stage 10]] ***[[Stage 11]] ***[[Stage 12]] **Neurula ***[[Stage 13]] ***[[Stage 14]] ***[[Stage 15]] ***[[Stage 16]] ***[[Stage 17]] ***[[Stage 18]] ***[[Stage 19]] ***[[Stage 20]] ***[[Stage 21]] **Tailbud ***Early tailbud ****[[Stage 22]] ****[[Stage 23]] ****[[Stage 24]] ****[[Stage 25]] ****[[Stage 26]] ****[[Stage 27]] ****[[Stage 28]] ***Late tailbud ****[[Stage 29/30,Stage 29 and 30]] ****[[Stage 31]] ****[[Stage 32]] ****[[Stage 33/34,Stage 33 and 34]] ****[[Stage 35/36,Stage 35 and 36]] ****[[Stage 37/38,Stage 37 and 38]] ****[[Stage 39]] ****[[Stage 40]] ****[[Stage 41]] ****[[Stage 42]] ****[[Stage 43]] ****[[Stage 44]] **Tadpole ***Premetamorphosis ****[[Stage 45]] ****[[Stage 46]] ****[[Stage 47]] ****[[Stage 48]] ****[[Stage 49]] ****[[Stage 50]] Digitized images and developmental data from ...

A novel role of TCF family in body axis formation. Revolutionary high impact discoveries are described, elucidating the missing link in the Wnt pathway and protein-TCF combinations with dual functions. By studying the primary axis formation of Xenopus laevis, it was firstly shown that, in combination with beta-catenin, TCF acts as a potent activator of proto-oncogenes. Secondly, it was discovered that in combination with the Groucho family of proteins, TCF acts as suppressor of oncogene transcription. Stronlgy suggesting that TCF controls oncogene transcription in a dual fashion. These discoveries contributed to the origination of a major area of cancer research and opened multiple angles for cancer therapy development ...

Xenbase would like to thank Mustafa Khokha for making his data for these charts available to us. ,br/>,br/>Original reference:,br/> Khokha, M. K., Chung, C., Bustamante, E. L., Gaw, L. W., Trott, K. A., Yeh, J., Lim, N., Lin, J. C., Taverner, N., Amaya, E., Papalopulu, N., Smith, J. C., Zorn, A. M., Harland, R. M. and Grammer, T. C. (2002), Techniques and probes for the study of Xenopus tropicalis development. Developmental Dynamics, 225: 499-510. doi: 10.1002/dvdy.10184 [http://www.ncbi.nlm.nih.gov/pubmed/12454926?dopt=Abstract] ===Xenopus tropicalis=== {, border=1 class=tableizer-table class=tableizer-firstrow ! ! colspan=3 align=center , 16°C ! colspan=3 align=center , 18°C ! colspan=3 align=center , 22°C ! colspan=3 align=center , 25°C ! colspan=3 align=center , 28°C ! colspan=3 align=center , 30°C ,- , ,b>NF Stage,/b> , ,b>Average,/b> , ,b>Minimum,/b> , ,b>Maximum,/b> , ,b>Average,/b> , ,b>Minimum,/b> , ,b>Maximum,/b> , ,b>Average,/b> , ,b>Minimum,/b> , ...

Induces expression of a number of neural crest marker genes as part of a heterodimer with isoform b of pbx1, to specify neural crest cell fate. Binds to a highly conserved region in the promoter of the neural crest marker gene zic3.

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Xenopus Blimp1 protein: controls anterior endomesodermal cell fate in Spemanns organizer in Xenopus; amino acid sequence in first source; GenBank AF182280

Sonic Hedgehog (Shh) and Indian Hedgehog (Ihh) are members of the Hedgehog (Hh) family of signaling molecules known to be involved in embryonic patterning and morphogenesis. The Hh proteins undergo an autocatalytic cleavage to yield an N- terminal and a C-terminal peptide, with the signaling capacities confined to the N peptide. Drosophila Hh-N has been shown to act via both short- and long-range signaling. In vertebrates, however, attempts to directly demonstrate Shh (SHH) or Ihh (IHH) proteins at a distance from producing cells have been largely unsuccessful. Furthermore, the fact that the Hh N peptides occur in a cholesterol-modified, membrane-tethered form is not easily reconciled with long-range signaling. This study used optimized immunohistochemistry combined with tissue separation and biochemical analyses in vivo and in vitro to determine the range of action of SHH and IHH in the mouse embryo. In all embryonic structures studied, we detect signaling peptides in producing cells, but we ...

Xkid es una cromoquinesina del sistema de Xenopus, necesaria para el alineamiento de los cromosomas en la placa metafásica y para la transición entre la meiosis I y meiosis II en los oócitos. El objectivo de este trabajo era estudiar la regulación de Xkid por fosforilación en los oócitos y en el extracto de huevos de Xenopus. Para poder cumplirlo se estableció un método para la expresión de proteínas añadiendo al extracto de huevos ARN mensajeros sintetizados in vitro. Los resultados obtenidos sugieren que Xkid es eficientemente fosforilada en el sitio cdk1 durante la meiosis y la mitosis. Aunque la forma de Xkid fosforilada se localiza eficientemente a nivel de los cromosomas mitóticos, esta fosforilación no parece tener ningún papel regulador sobre esta localización. En cambio, parece interferir con la localización de Xkid sobre los microtúbulos mitóticos. El efecto dominante negativo de la forma de Xkid que mimetiza la fosforilación durante la formación del huso mitótico, ...

Fujifilms 3D mammography creates 3D images by using two high resolution images taken from different angles. One of these images is a conventional 2D image. The images are presented on a special viewer. 3D images enable the internal anatomical breast structures to be identified more clearly than in a 2D image due to tissue separation and microcalcifications stratification. With this system, it is expected that image interpretation is as quick or even quicker than 2D mammography and false positives are reduced.. ...

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Domain architecture and assignment details (superfamily, family, region, evalue) for gi|139635|sp|P19009| from Xenopus laevis . Plus protein sequence and external database links.

Recombinant Prkr Interacting Protein 1 (IL11 Inducible) (PRKRIP1) Protein (His tag). Species: Xenopus laevis. Source: Yeast. Order product ABIN1674163.

हम इन विट्रो में स्व-निरंतर mitotic दोलनों की पीढ़ी के लिए एक विधि वर्तमान में Xenopus laevis के अंडे के अर्क...

The first 12 cell divisions of Xenopus laevis embryos do not require gene transcription. This means that the regulation of gene expression during this period is controlled at post transcriptional levels and makes Xenopus early development a potentially interesting biological system with which to study the mechanisms involved. We describe here the stability characteristics of several maternal Xenopus mRNAs which are deadenylated soon after fertilisation (J. Paris and M. Philippe, Dev. Biol., in press). We show that these mRNAs were only degraded in the embryo after the midblastula transition (MBT), when gene transcription was initiated. The kinetics with which the deadenylated maternal mRNAs decreased in the post-MBT embryos showed sequence specificity. The degradation of these mRNAs after the MBT was inhibited by cycloheximide but was not affected by dactinomycin. Therefore, the destabilization of these mRNAs does not appear to be initiated by new embryonic gene transcripts. Sequence comparisons ...

The African clawed frogs Xenopus laevis and Xenopus tropicalis are prominent animal model organisms. Xenopus research contributes to the understanding of genetic, developmental and molecular mechanisms underlying human disease. The Xenopus Anatomy Ontology (XAO) reflects the anatomy and embryological development of Xenopus. The XAO provides consistent terminology that can be applied to anatomical feature descriptions along with a set of relationships that indicate how each anatomical entity is related to others in the embryo, tadpole, or adult frog. The XAO is integral to the functionality of Xenbase ( http://www.xenbase.org ), the Xenopus model organism database. We significantly expanded the XAO in the last five years by adding 612 anatomical terms, 2934 relationships between them, 640 synonyms, and 547 ontology cross-references. Each term now has a definition, so database users and curators can be certain they are selecting the correct term

The vertebrate Otx gene family is related to otd, a gene contributing to head development in Drosophila. We previously reported on the expression of Xotx2 gene, homologous to the murine Otx2 gene, during early Xenopus development. In the present paper we report an extensive analysis of the expression pattern of Xotx2 during later stages of development and also the cloning and developmental expression of two additional Otx Xenopus genes, Xotx1 and Xotx4. These latter two genes bear a good degree of homology to murine Otx1, higher for Xotx1 than for Xorx4. Both these genes are expressed in the forebrain and midbrain regions and their developmental patterns of expression are very similar, although not perfectly superimposable. Spatial and temporal expression patterns of the three Xotx genes suggest that they may be involved in the early subdivision of the rostral brain, providing antero-posterior positional information within the most anterior districts of the neuraxis. The three Xotx genes are ...

We have examined the timing of specification of the pronephric tubules and duct in Xenopus laevis by explanting the presumptive pronephric rudiments into blastula ectodermal wraps. We have established I-he time point of specification using the monoclonal antibody markers 3G8 and 4A6 which recognize antigens in pronephric tubule and duct, respectively. We show that, by experimental analysis in explants, kidney tubules are specified by stage 12.5 in the pronephric anlagen whereas pronephric duct is specified later between stages 13 and 14. Furthermore we show that signals involved in tubulogenesis of the pronephric tubules are normally received between stage 12.5 and 13. These experiments unambiguously pinpoint the timing of pronephros specification analyzed by explant experimentation to a developmental stage prior to that demonstrated for urodele amphibia, and provide an essential biological backdrop to a search for the molecular nature of pronephric inducers. (C) 1998 Elsevier Science Ireland ...

The goal of this laboratory course is to introduce vertebrate developmental biology to undergraduate students, emphasizing both classical and contemporary aspects of this field. During the course, the students combine the use of living Xenopus laevis material with active tutorial participation, with the aim of illustrating how the fertilized egg can generate the diversity of cell types and complexity of pattern seen only a few days later in the embryo. Special emphasis is given to the observation and manipulation of living material. The laboratory course includes a comprehensive analysis of both oogenesis and early development and is divided into two overlapping parts that combine tutorial and practical approaches. The first part is devoted to oogenesis; oocytes are sorted out, allowed to mature in vitro and observed in histological section. In the second part, students perform an in vitro fertilization of Xenopus eggs and a mesoderm and neural induction assay of animal cap explants. Successful

In vertebrate species, induction of the embryonic axis is initiated by the transport of maternally supplied determinants, initially localized to the vegetal pole of the egg, toward the prospective organizer in the animal region. This transport process remains incompletely understood. Here, we review studies involving embryonic manipulations, visualization, and functional analysis of the cytoskeleton and loss- and gain-of-function conditions, which provide insights in this process. Transport of dorsal determinants requires cytoskeletal reorganization of a vegetal array of microtubules, microtubule motors, and an off-center movement of the vegetal cortex with respect to the inner egg core, a so-called cortical rotation. Additional mechanisms may be used in specific systems, such as a more general animally directed movement found in the teleost embryo. Initial polarity of the microtubule movement depends on early asymmetries, which are amplified by the movement of the outermost cortex. An interplay between

Part I of the dissertation focused on (1) the identification of maternal dorsalizing RNAs that are localized within the animal hemisphere along the dorsal-ventral axis at the 16-cell stage and (2) the determination of their post-transcriptional activation mechanism. An RT-PCR screen to investigate the differential expression of known maternal dorsalizing factors revealed the localized accumulation of XWnt8b transcripts in ventral animal midline blastomeres. This finding is interesting since XWnts have been shown to induce secondary axis formation when ectopically expressed on the ventral side before the onset of zygotic transcription (MBT). Overexpression of XWnt8b in dorsal animal midline blastomeres inhibited their ability to autonomously elongate, implicating that XWnt8b counteracts an intrinsic dorsal program of these blastomeres. However, the mere localization of XWnt8b transcripts does not predict protein distribution and therefore, the time point at which these transcripts are in the ...

Zebrafish paraxial protocadherin (papc) encodes a transmembrane cell adhesion molecule (PAPC) expressed in trunk mesoderm undergoing morphogenesis. Microinjection studies with a dominant-negative secreted construct suggest that papc is required for proper dorsal convergence movement s during gastrulation. Genetic studies show that papc is a close downstream target of spadetail, gene encoding a transcription factor required for mesodermal morphogenetic movements. Further, we show that the floating head homeobox gene is required in axial mesoderm to repress the expression of both spadetail and papc, promoting notochord and blocking differentiation of paraxial mesoderm. The PAPC structural cell-surface transcription factors and the actual cell biological behaviors that execute morphogenesis during gastrulation ...

In most organisms, control of the developmental program involves a regulated transition from maternally supplied mRNAs and proteins to newly synthesized zygotically encoded factors. This phenomena, known as the maternal to zygotic transition (MZT), is observed in a wide range of embryos in the animal and plant kingdoms; in chordates, the MZT typically occurs during midblastula stages, and therefore is often referred to as the midblastula transition (MBT). Early development of most organisms is exclusively maternally controlled, and the zygotic genome of the embryo remains transcriptionally silent until after the MBT, when the transition to zygotic control culminates. Recent work in a number of organisms has identified several genes that are activated prior to the MBT, but whether precocious expression of specific mRNAs is important for later development has not been examined in detail. In this work, I characterize the role of a maternal transcription factor in preMBT transcription, and identify a