Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “gastrulation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed1977

A fine-structural study of embryonic and larval development in the gymnoblastic hydroid Pennaria tiarella.

1. The pregastrulation blastomers contain electron-dense granules which become localized after gastrulation in the apices of the developing epithelio-muscle cells and persist throughout larval development. The cytoplasm of the blastomeres is organized into anucleate, membrane-delimited lobules. The lobules, which persist until six hours of development, come to contain a single, peripherally located cisterna of granular endoplasmic reticulum. Microvilli are present at the earliest stages examined and persist throughout development. Cilia are first detected at four hours. 2. Gastrulation, marked by the appearance of the mesoglea, occurs between six and eight hours of development. Basal foot processes of epithelio-muscle cells are detected by eight hours, but myonemes cannot be detected until later in development. 3. Immediately following gastrulation, mucous cells begin their differentiation from dividing cells located near the apex of the ectoderm. During their differentiation, the cells elongate toward the mesoglea. 4. By 16 hours post-fertilization, a third cell type can be detected in the ectoderm. The cell, which contains no granules, has an unusual cytoplasmic organization in which fused membranes divide the cytoplasm into parallel compartments containing a single cisterna of granular endoplasmic reticulum. 5. The findings of the present study are correlated with those of previous studies of development in Pennaria and other hydroids. The possible functional roles of the Type I granules, the cytoplasmic lobules, and the nongranular cell are discussed.

Animals↗
PubMed1978

Cellular morphology and architecture during early morphogenesis of the ascidian egg: an SEM study.

1. Cellular morphology and architecture during early morphogenesis of the ascidian embryo were examined by SEM. 2. The outer surface of the embryo was essentially smooth. The blastocoel could be seen in the dissected blastula. On the cell surface bordering the blastocoel, numerous pseudopodia extended from cells onto adjacent cells. These pseudopodia were suggested to contribute to cell-to-cell adhesion. 3. Before the initiation of gastrulation, a layer of the cells of the animal (ventral) hemisphere and that of the cells of the vegetal (dorsal) hemisphere adhered closely together. The blastocoel could no longer be observed. 4. The gastrulation began during the seventh cleavage. The gastrocoel was formed by a folding of the two layers of the cells. Examinations of the dissected gastrulae suggested two cooperative forces for the gastrulation: first, the epibolic or enfolding movement of the ventral ectoderm cells and secondly, the change in shape of the constituent cells. 5. The neural tube formation progressed in a similar fashion to that of vertebrates.

Animals↗
PubMed1975

[Protein synthesis in loach embryos isolated from the yolk and cultivated in vitro].

Changes in protein synthesis in the loach (Misgurnus fossilis) blastoderms cultivated in vitro in the Holtfreter solution after their separation from the yolk at the early and late-blastula stages were assessed by biochemical and autoradiographic methods. The embryos incubated in vitro at the from blastula stage are characterized by the sharp activation of protein synthesis and the vegetal-animal gradient of protein synthesis, as well as in the control embryos; such embryos gastrulate and proceed to primary differentiation. On the contrary, in the embryos incubated from the early blastula stage the protein synthesis is inhibited and no regional differences in its intensity are noted; such embryos do not proceed to gastrulation. Possible causes of the protein synthesis activation in differentiating blastoderms and interrelationship between the character of protein synthesis and the ability of embryos for differentiation are discussed. The protein synthesis activation and the vegetal-animal gradient appearance are considered as a biochemical criterion of primary differentiation during gastrulation in fish embryos.

Animals↗
PubMed1979

Somitogenesis in amphibia. II. Origins in early embryogenesis of two factors involved in somite specification.

A somite pre-pattern is established shortly before visible segmentation. The pre-pattern results from the interaction of two components: a wave of cell behavioural change that passes along the axis, and, an underlying co-ordination of the cells that is the basis for their association into large somite-sized groupings. The evidence is derived from studies of the zones of abnormal segmentation that follow temperature shocks delivered between the neurula and tail-bud stages (Pearson & Elsdale, 1979). Temperature shock given earlier at the mid-gastrula stage is however ineffective in inducing abnormalities in somitogenesis. Shocks given before the mid-gastrula stage reveal a prior period of sensitivity stretching back into the blastula. Thus early and late sensitive periods can be defined separated by a short refactory period. Quite different patterns in the distribution of somite abnormalities characterize the results of shock during the two sensitive periods, suggesting different aetiologies. It is concluded that the wave of rapid cell change is set up early in embryogenesis during the blastula stage, and each cell of the prospective paraxial mesoderm carries a determination to change after a specific length of time, i.e. a countdown is set in each cell. As a result of the movements of gastrulation, the prospective paraxial mesoderm cells become laid out along the axis of the neurula in the order (antero-posterior sequence) in which they will change. The achievement of the correct redistribution of the cells depends crucially on the conservation of the sequence in the blastula by the maintenance of topological integrity throughout gastrulation. It is suggested that early shock disturbs gastrulation movements, causing some mixing up of the cells resulting in incoherence of the wavefront. Whereas early shocks are thus assumed to affect the wave, the evidence suggests that late shock undergoes co-ordination. It is concluded therefore that co-ordination is established later, after the refractory period, around the late gastrula stage.

Animals↗
PubMed2025

Glycolytic activity instructs germ layer proportions through regulation of Nodal and Wnt signaling.

Metabolic pathways can influence cell fate decisions, yet their regulative role during embryonic development remains poorly understood. Here, we demonstrate an instructive role of glycolytic activity in regulating signaling pathways involved in mesoderm and endoderm specification. Using a mouse embryonic stem cell (mESC)-based in vitro model for gastrulation, we found that glycolysis inhibition increases ectodermal cell fates at the expense of mesodermal and endodermal lineages. We demonstrate that this relationship is dose dependent, enabling metabolic control of germ layer proportions through exogenous glucose levels. We further show that glycolysis acts as an upstream regulator of Nodal and Wnt signaling and that its influence on cell fate specification can be decoupled from its effects on growth. Finally, we confirm the generality of our findings using a human gastrulation model. Our work underscores the dependence of signaling pathways on metabolic conditions and provides mechanistic insight into the nutritional regulation of cell fate decision-making.

Glycolysis↗
PubMed2025

Cell fate specification modes shape transcriptome evolution in the highly conserved spiral cleavage.

Early animal development can be remarkably variable, influenced by lineage-specific reproductive strategies and adaptations. Yet, early embryogenesis is also strikingly conserved in certain groups, such as Spiralia. In this clade, a shared cleavage program (i.e., spiral cleavage) and similar cell lineages are ancestral to at least seven phyla. Why early development is so conserved in specific groups and plastic in others is not fully understood. Here, we investigated two annelid species (Owenia fusiformis and Capitella teleta) with spiral cleavage but different modes of specifying their primary progenitor cells. By generating high-resolution transcriptomic time courses from the oocyte to gastrulation, we demonstrate that transcriptional dynamics differ markedly between these species during spiral cleavage and instead reflect their distinct timings of embryonic organiser specification. However, the end of cleavage and gastrulation exhibit high transcriptomic similarity, when orthologous transcription factors share gene expression domains, suggesting this period is a previously overlooked mid-developmental transition in annelid embryogenesis. Together, our data reveal hidden transcriptomic plasticity during spiral cleavage, indicating an evolutionary decoupling of morphological and transcriptomic conservation during early embryogenesis.

Animals↗
PubMed2025

Genomic evolution of EGF-CFC genes in deuterostomes.

BACKGROUND: EGF-CFC proteins are a bilaterian innovation, but they are best known for their roles in Nodal signaling during gastrulation and left-right patterning in vertebrates. Species with multiple family members show evidence of functional specialization. For example, in mouse, Cripto is required for gastrulation, whereas CFC1 is involved in left-right patterning. However, members of the EGF-CFC family across model organisms exhibit limited sequence conservation beyond the EGF-CFC domain, posing challenges for determining their evolutionary history and functional conservation. RESULTS: In this study, we describe the evolutionary history of the EGF-CFC family of proteins across several branches of deuterostomes, with a particular focus on vertebrates. We trace the EGF-CFC gene family from a single gene in the deuterostome ancestor through its expansion and functional specialization in tetrapods, and subsequent gene loss and translocation in eutherian mammals. Mouse Cripto and CFC1, zebrafish Tdgf1, and each Xenopus EGF-CFC gene (Tdgf1, Tdgf1.2 and Cripto.3) are all descendants of the ancestral deuterostome Tdgf1 gene. CONCLUSIONS: We propose that subsequent to EGF-CFC family expansion in tetrapods, Tdgf1B (Xenopus Tdgf1.2) acquired specialization in the left-right patterning cascade, and then after its translocation in eutherians to a different chromosomal location, CFC1 has maintained that specialization.

Animals↗
PubMed1978

Possible involvement of putrescine in nucleolar formation in early embryos.

Continuous treatment of developing eggs of the polychete Ophryotrocha labronica with alpha-methylornithine, which inhibits synthesis of putrescine, led to arrest of development at gastrulation. The present ultrastructural analysis suggests that the arrest of development is due to failure to form nuclei, and thus reveals a possible role for putrescine in nucleolar formation. Further support for this contention was provided by means of electron-microscopical autoradiography. It was found that newly synthesized putrescine, derived from administered 3H-ornithine, labeled the nucleoli intensely at the time of their normal appearance during gastrulation, the time at which the rate of endogenous putrescine synthesis is maximal. These observations have led to the conclusion that putrescine synthesis may be directly involved in formation of nucleoli.

Animals↗
PubMed1976

The fine structure of the embryo during the gastrula stage of Comanthus japonica (Echinodermata: Crinoidea).

The fine structure of the embryo of Comanthus has been described by scanning and transmission electron microscopy at two-hourly intervals throughout the gastrula stage (from the fifth through the fifteenth hours of development). At 5 hr, gastrulation has occurred in the absence of any structure comparable to the echinoid hyaline layer; therefore, at least one important mechanism proposed for echinoid gastrulation cannot occur in this crinoid. At 7 hr, the blastocoelic basal lamina has formed, and all ectodermal and entodermal nuclei contain dense aggregates, which are probably perichromatin fibrils. At 9 hr, the blastocoel contains mesenchyme cells, presumably of entodermal origin. At 11 hr, ciliogenesis has started at the apical surfaces of the ectoderm cells and at the archenteral surfaces of the entoderm cells; many of the newly formed cilia are swollen subterminally. At 13 hr, a conspicuous glycocalyx is beginning to cover the apical ends of the ectoderm cells, and the fertilization membrane is beginning to dissolve from its inner surface. Between 5 and 13 hr, there is a gradual development of a junctional complex associating the apicolateral margins of the ectoderm cells; the zonula adherens part of the complex appears at 5 hr and is well developed by 7 hr, and then the septate junction part of the complex appears at 9 hr and is well developed by 13 hr. At 15 hr, the blastopore has closed, the ectodermal glycocalyx is fully developed, some mesenchyme cells appear to be differentiating into skeleton forming cells, and the fertilization membrane is in the last stages of dissolution.

Animals↗
PubMed2025

NANOG is repurposed after implantation to repress Sox2 and begin pluripotency extinction.

Loss of pluripotency is an essential step in post-implantation development that facilitates the emergence of somatic cell identities essential for gastrulation. Before implantation, pluripotent cell identity is governed by a gene regulatory network that includes the key transcription factors SOX2 and NANOG. However, it is unclear how the pluripotency gene regulatory network is dissolved to enable lineage restriction. Here, we show that SOX2 is required for post-implantation pluripotent identity in the mouse, and cells that lose SOX2 expression in the posterior epiblast are no longer pluripotent. Using in vitro and in vivo analyses, we demonstrate anticorrelated expression of NANOG and SOX2 preceding gastrulation, culminating in an early disappearance of pluripotent identity from posterior NANOGhigh/SOX2low epiblast. Surprisingly, Sox2 expression is repressed by NANOG and embryos with post-implantation deletion of Nanog maintain posterior SOX2 expression. Our results demonstrate that the distinctive features of post-implantation pluripotency are underpinned by altered functionality of pluripotency transcription factors, ensuring correct spatio-temporal loss of embryonic pluripotency.

Animals↗
PubMed1979

Inhibition of polyisoprenoid and glycoprotein biosynthesis causes abnormal embryonic development.

Compactin, a potent inhibitor of polyisoprenoid biosynthesis, induces abnormal gastrulation during sea urchin development at concentrations that have no effect on earlier embryonic development or on macromolecular synthesis. Three lines of evidence suggest that the developmental lesion caused by compactin results from inhibition of dolichol biosynthesis and a concomitant inhibition in the biosynthesis of the oligosaccharide chains of N-linked glycoproteins. (i) Embryos cultured in the presence of compactin gastrulate normally when supplemented with dolichol alone, whereas supplementation with cholesterol or coenzyme Q or both does not prevent the compactin-induced developmental lesion. (ii) Exogenously supplemented [3H]dolichol is incorporated into a compound with the chromatographic properties of oligosaccharide-pyrophosphoryldolichol. (iii) Embryos cultured in the presence of compactin exhibit a decreased capacity to synthesize mannose-labeled glycolipids and N-linked glycoproteins. This decrease in synthesis is abolished if the embryos are cultured in the presence of dolichol along with compactin.

Animals↗
PubMed2026

Maternal redd1 mRNA decline triggers mTORC1 activation during the blastula-gastrula transition in zebrafish embryos.

During early metazoan development, maternal mRNAs and proteins stored in the egg sustain initial cellular functions. After the blastula stage, developmental control shifts to zygotic gene expression, and maternal transcripts are progressively degraded. Although mTORC1 is a central regulator of global mRNA translation and cell growth, its role in controlling maternal mRNA translation prior to gastrulation remains poorly understood. In zebrafish embryos, the mTORC1 inhibitor redd1 is abundantly expressed after fertilization but decreases following the maternal-to-zygotic transition (MZT), inversely correlating with mTORC1 activity. Overexpression of redd1 suppresses mTORC1, impairs gastrulation, and reduces translation of 5'TOP mRNAs and key regulatory genes, underscoring the necessity of relieving mTORC1 inhibition after the blastula stage. To investigate redd1 translation under conditions of low mTORC1 activity, we injected reporter mRNAs containing its 5' and 3' UTRs. The 3'UTR promoted polyadenylation and enhanced translation, while both UTRs enabled efficient reporter expression despite mTORC1 suppression, indicating that redd1 mRNA is translated independently of canonical mTORC1 pathways. Similarly, maternal mRNAs such as nanog, myca, pou5f3, and ccnb1, as well as the early zygotic transcript dharma, are translated through mTORC1-independent mechanisms. Together, these findings reveal a transient phase of mTORC1 suppression in early zebrafish embryos and demonstrate that select maternal and zygotic mRNAs bypass this regulation to ensure proper developmental progression.

Animals↗
PubMed1977

[Scanning electron microscopy study of membrane modification of blastomeres in the first stages of ovum development in trout (Salmo irideus Gibb.)].

Our study relates to the development of the membrane relief of the blastomeres of the trout egg from the stage before their division up to gastrulation. The surface of the blastoderm shows first a more or less dense system of crests which by the time of gastrulation are replaced by microvilli distributed over the whole surface of the enveloping layer. The deep blastomeres, loosely connected to each other by lamellipodes and filopodes produce only a few projections of their membranes and these are only semispherical bodies. Possible roles of the microvillosities in the respiratory exchange of the egg and in the motility of the enveloping layer, are considered.

Animals↗
PubMed1979

Changes in protein synthesis during the development of Xenopus laevis.

Patterns of protein synthesis during the development of Xenopus were studied by two-dimensional gel electrophoresis. Up to the end of the blastula stage we find no newly synthesized proteins which are not already made in the oocyte. The first new proteins are seen during gastrulation, and they increase in number during neurulation. Some of these are restricted to the 'ectodermal' region, and some to the 'endodermal' region of embryos divided into two parts. These new, region-specific proteins include alpha-actin. When the oocyte matures the number of detectable newly synthesized proteins decreases, reaching a minimum in the unfertilized egg. Some, such as beta- and gamma-actin, re-appear at the end of cleavage. This could not be shown to be a recovery artifact. The relation of the total mRNA to these changes in protein synthesis was studied by translation in the lysed reticulocyte cell-free system. The mRNAs that code for oocyte proteins that cease synthesis in the unfertilized egg and re-appear in blastulae are nevertheless detectable in total RNA made from eggs. These proteins therefore seem to cease and resume synthesis through translational control. mRNAs for new proteins first appear after gastrulation, just when these proteins are first detected in vivo. This strongly suggests, though it does not prove, that new gene activity is involved. It is therefore likely that region-specific gene activity is already present by the gastrula stage of development, and has an impact on the most abundant kinds of proteins made in the embryo.

Actins↗
PubMed1978

Studies on dwarf larvae developed from isolated blastomeres of the starfish. Asterina pectinifera.

Not only a whole denuded egg, but also blastomeres isolated from 2-, 4- and 8-cell starfish embryos developed into morphologically normal, but dwarf bipinnariae, the sizes of which were roughly proportionate to that of the respective original blastomeres. Some of the blastomeres isolated from the 16-cell stage were also capable of developing into the larval stage. All isolated blastomeres divided in good synchrony with the control embryos. Blastulae of all groups gastrulated within quite a short range of time, around 14-5 h after insemination at 20+/-1 degrees C, although one-third of the 1/8-blastula missed this chance but gastrulated by 19.5 h. The number of constituent cells of the 1/8-gastrula was counted to be about 560, which corresponds roughly to one-half that of the 1/4-, one-fourth of the 1/2- and one-eight of the 1/1-gastrula. This ratio also fitted roughly for the total cell volume. The results are compared with those of other invertebrate species, as well as of some vertebrates, and are discussed in connexion not only with the concepts of 'regulative' and 'mosaic' eggs, but also with a criterion that does not fit into either of these; the developmental system of the mammals.

Animals↗
PubMed1977

[Dynamics of the regional metabolic differences in the early development of the sea urchin].

The regional differences in Strongylocentrotus intermedius from the stage of 32 blastomeres till the middlelate gastrula stage were studied by the vital and supravital staining (intensity of oxidative-reductive processes), the incorporation of 3H-leucine (intensity of protein synthesis) and 14C-acrilamide (intensity of free radical processes). Two periods of rapid switches of metabolic intensity correlated within the same embryo were established. The beginning of the first period coincides with the onset of blastula epithelization and that of the second one with the onset of gastrulation. The metabolic "patterns" are multivariant up to the second switch although, in the most cases, the metabolic activity of the equatorial area is the lowest. From the onset of gastrulation the metabolic patterns become uniform: the vegetative area dominates by the intensity of precursors' incorporation and by the sensitivity of its respiratory systems to the oxygen deficiency. The relationships between the metabolic and morphological rearrangements are discussed.

Acrylamides↗
PubMed1976

[Transport RNA in early embryogenesis of fish. 3. Certain problems of regulation of RNA synthesis at the early stages of development of the loach (Misgurnus fossilis (1)].

tRNA synthesis in the early loach embryos of different ploidy and factors of the activation of synthesis and the maturation of tRNA molecules at the mid-blastula stage have been studied. tRNA synthesis is activated at the early- and mid-blastula and in the beginning of gastrulation. The normal activation of synthesis and maturation of tRNA molecules require the embryo to be maintained in the contact with the yolk at the earlier developmental stages. The methionine starvation may be one of the factors limiting the rate of tRNA maturation. The activity of tRNA synthesis during blastulation was shown to depend on gene dosage. At this stage the paternal and maternal tRNA genes are transcribed independently. In the beginning of gastrulation, the type of tRNA synthesis control markedly changes and the effect of gene dose compensation manifests itself, that is typical for the control of rRNA synthesis as well. The data obtained are discussed with respect to the state of protein synthesizing system at the moment of activation of specific protein syntheses with the onset of morphogenesis.

Animals↗