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Claudio D. Stern - One of the best experts on this subject based on the ideXlab platform.
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neural induction by the node and placode induction by head mesoderm share an initial state resembling neural plate border and es cells
Proceedings of the National Academy of Sciences of the United States of America, 2018Co-Authors: Katherine E Trevers, Matthew J Stower, Ravindra Singh Prajapati, Mark Hintze, Anna Strobl, Monica Tambalo, Ramya Ranganathan, Natalia Moncaut, Mohsin A F Khan, Claudio D. SternAbstract:Around the time of gastrulation in higher vertebrate embryos, inductive interactions direct cells to form central nervous system (neural plate) or sensory placodes. Grafts of different tissues into the periphery of a chicken embryo elicit different responses: Hensen’s node induces a neural plate whereas the head mesoderm induces placodes. How different are these processes? Transcriptome analysis in time course reveals that both processes start by induction of a common set of genes, which later diverge. These genes are remarkably similar to those induced by an extraembryonic tissue, the Hypoblast, and are normally expressed in the pregastrulation stage epiblast. Explants of this epiblast grown in the absence of further signals develop as neural plate border derivatives and eventually express lens markers. We designate this state as “preborder”; its transcriptome resembles embryonic stem cells. Finally, using sequential transplantation experiments, we show that the node, head mesoderm, and Hypoblast are interchangeable to begin any of these inductions while the final outcome depends on the tissue emitting the later signals.
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a differential screen for genes expressed in the extraembryonic endodermal layer of pre primitive streak stage chick embryos reveals expression of apolipoprotein a1 in Hypoblast endoblast and endoderm
Gene Expression Patterns, 2008Co-Authors: Federica Bertocchini, Claudio D. SternAbstract:The lower layer of the pre-gastrulating chick embryo is an extra-embryonic tissue made up of two different cell populations, the Hypoblast and the endoblast. The Hypoblast is characterized by the expression of inhibitory signalling molecules (e.g. Cerberus, Dickkopf1, Crescent) and others (e.g. Otx2, goosecoid, Hex, Hesx1/RPX, FGF8). However, no genes expressed in the endoblast have yet been found. We designed a differential screen to identify markers differentially expressed in these two cell populations. This only revealed one novel gene, Apolipoprotein A1 (APO A1) with restricted endodermal layer expression. Expression of APO A1 begins very early throughout the lower layer (both Hypoblast and endoblast). At later stages it is also expressed in the endoderm and its derivatives, the anterior intestinal portal endoderm and the growing liver bud.
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a role for the Hypoblast ave in the initiation of neural induction independent of its ability to position the primitive streak
Developmental Biology, 2007Co-Authors: Amanda Albazerchi, Claudio D. SternAbstract:The mouse anterior visceral endoderm (AVE) has been implicated in embryonic polarity: it helps to position the primitive streak and some have suggested that it might act as a "head organizer", inducing forebrain directly. Here we explore the role of the Hypoblast (the chick equivalent of the AVE) in the early steps of neural induction and patterning. We report that the Hypoblast can induce a set of very early markers that are later expressed in the nervous system and in the forebrain, but only transiently. Different combinations of signals are responsible for different aspects of this early transient induction: FGF initiates expression of Sox3 and ERNI, retinoic acid can induce Cyp26A1 and only a combination of low levels of FGF8 together with Wnt- and BMP-antagonists can induce Otx2. BMP- and Wnt-antagonists and retinoic acid, in different combinations, can maintain the otherwise transient induction of these markers. However, neither the Hypoblast nor any of these factors or combinations thereof can induce the definitive neural marker Sox2 or the formation of a mature neural plate or a forebrain, suggesting that the Hypoblast is not a head organizer and that other signals remain to be identified. Interestingly, FGF and retinoids, generally considered as caudalizing factors, are shown here to play a role in the induction of a transient "pre-neural/pre-forebrain" state.
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BMC Developmental Biology BioMed Central Methodology article
2007Co-Authors: A Albazerchi, Olivier Cinquin, Claudio D. SternAbstract:A new method to transfect the Hypoblast of the chick embryo reveals conservation of the regulation of an Otx2 enhancer between mouse and chick extraembryonic endoder
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determination of embryonic polarity in a regulative system evidence for endogenous inhibitors acting sequentially during primitive streak formation in the chick embryo
Development, 2004Co-Authors: Federica Bertocchini, Isaac Skromne, Lewis Wolpert, Claudio D. SternAbstract:Avian embryos have a remarkable capacity to regulate: when a pre-primitive streak stage embryo is cut into fragments, each fragment can spontaneously initiate formation of a complete embryonic axis. We investigate the signalling pathways that initiate primitive streak formation and the mechanisms that ensure that only a single axis normally forms. As reported previously, an ectopic primitive streak can be induced by misexpression of Vg1 in the marginal zone. We now show that Vg1 induces an inhibitor that travels across the embryo (3 mm distance) in less than 6 hours. We provide evidence that this inhibitor acts early in the cascade of events downstream of Vg1. We also show that FGF signalling is required for primitive streak formation, in cooperation with Nodal and Chordin. We suggest that three sequential inhibitory steps ensure that a single axis develops in the normal embryo: an early inhibitor that spreads throughout the embryo (which can be induced by Vg1), a second inhibition by Cerberus from the underlying Hypoblast, and finally a late inhibition from Lefty emitted by the primitive streak itself.
Christoph Viebahn - One of the best experts on this subject based on the ideXlab platform.
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MOESM3 of Divergent axial morphogenesis and early shh expression in vertebrate prospective floor plate
2018Co-Authors: Stanislav Kremnyov, Christoph Viebahn, Kristine Henningfeld, Nikoloz TsikoliaAbstract:Additional file 3: Fig. 3. Schematic transversal view of a chicken embryo at the level of the posterior notochord. A: ventral to dorsal floor plate induction in the classical view—shh is first expressed in the notochord and induces shh in floor plate. Shh protein from both sources forms a gradient. B: modified model demonstrating early shh expression and shh gradient formation in the floor plate. Labeling: pink—notochord, blue—floor plate, green—Hypoblast/endoderm, brown—paraxial mesoderm, arrows—gradient formation and induction
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SEM reveals filopodia-like protrusions in the early embryonic disc of the chick
2017Co-Authors: L. Surchev, Christoph Viebahn, Hans-georg Sydow, Nikoloz TsikoliaAbstract:Embryonic development depends on an enormous amount of signaling events between a continuously growing number of cells. According to the classical view, signal transduction is based on either simple diffusion, transcytosis or migrating cells. Very recently the existence of filopodia-like protrusions has been proposed as a novel mechanism of long-range intercellular signaling during chick somite and limb development. Analogous thinner structures called cytonemes play a role in the development of Drosophila melanogaster , as well. The present study gives new insight into this problem by adding important information using scanning electron microscopy (SEM). Early chick embryos between stages 4 and 5 (representing late gastrulation and early neurulation) were dissected, fixed and critical-point dried and were then fractured in several steps, each step followed by platinum/palladium coating and analysis by SEM. Fracturing was carried out sequentially in the same specimens at different anterior-posterior levels anterior to the primitive node and the ultrastructure of the embryonic disc was analysed with special emphasis on cellular processes. We found cell protrusions of different shape and size in all three layers (mesoderm, epiblast, and Hypoblast) of the early embryonic discs. They were most abundant and prominent between the mesodermal cells but also seen in other layers as well as between layers. These protrusions can be roughly classified into cytoplasmic bridges with mid-bodies, cilia-like protrusions, as well as filopodia-like protrusions. As previously shown, cilia of different length are present on the apical surface of epiblast and Hypoblast cells. Similarly a plethora of variable protrusions with or without mid-bodies are seen between neighbouring cells within embryonic layers. Unexpectedly, we found that cells of the mesodermal layer form a dense net of filopodia-like contacts with the epithelial cells of the epiblast. Our data prove that filopodia-like protrusions are present at earlier developmental stages than previously shown. Their abundance indicates a major role in the intercellular communication during early chick embryonic development and may provide a structural basis of cell-to-cell communication during gastrulation and early neurulation in the chick.
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Dev Genes Evol (2011) 221:209–223 DOI 10.1007/s00427-011-0373-5 ORIGINAL ARTICLE
2011Co-Authors: Bmp Signals, Christoph Viebahn, Clas Hopf, Bernd PüschelAbstract:# The Author(s) 2011. This article is published with open access at Springerlink.com Abstract Molecular factors and tissue compartments involved in the foundation of the mammalian germline have been mainly described in the mouse so far. To find mechanisms applicable to mammals in general, we analyzed temporal and spatial expression patterns of the transcriptional repressor BLIMP1 (also known as PRDM1)andthesignaling molecules BMP2 and BMP4 in perigastrulation and early neurulation embryos of the rabbit using whole-mount in situ hybridization and high-resolution light microscopy. Both BMP2 and BMP4 are expressed in annular domains at the boundary of the embryonic disc, which—in contrast to the situation in the mouse—partly belong to intraembryonic tissues. While BMP2 expression begins at (pregastrulation) stage 1 in the Hypoblast, BMP4 expression commences— distinctly delayed compared to the mouse—diffusely at (pregastrulation) stage 2; from stage 3 onwards, BMP4 is expressed peripherally in Hypoblast and epiblast and in the mesoderm at the posterior pole of the embryonic disc. BLIMP1 expression begins throughout the Hypoblast at stage 1 and emerges in single primordial germ cell (PGC) precursors in the posterior epiblast at stage 2 and then in single mesoderm cells at positions identical to those identified by PGC-specific antibodies. These expression patterns suggest that function and chronology of factors involved in germline segregation are similar in mouse and rabbit, but higher temporal and spatial resolution offered by the rabbit demonstrates a variable role of bone morphogeneti
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Hypoblast controls mesoderm generation and axial patterning in the gastrulating rabbit embryo
Development Genes and Evolution, 2004Co-Authors: Jan Idkowiak, Juliane Plitzner, Gunnar Weisheit, Christoph ViebahnAbstract:Gastrulation in higher vertebrate species classically commences with the generation of mesoderm cells in the primitive streak by epithelio-mesenchymal transformation of epiblast cells. However, the primitive streak also marks, with its longitudinal orientation in the posterior part of the conceptus, the anterior-posterior (or head-tail) axis of the embryo. Results obtained in chick and mouse suggest that signals secreted by the Hypoblast (or visceral endoderm), the extraembryonic tissue covering the epiblast ventrally, antagonise the mesoderm induction cascade in the anterior part of the epiblast and thereby restrict streak development to the posterior pole (and possibly initiate head development anteriorly). In this paper we took advantage of the disc-shape morphology of the rabbit gastrula for defining the expression compartments of the signalling molecules Cerberus and Dickkopf at pre-gastrulation and early gastrulation stages in a mammal other than the mouse. The two molecules are expressed in novel expression compartments in a complementary fashion both in the Hypoblast and in the emerging primitive streak. In loss-of-function experiments, carried out in a New-type culturing system, Hypoblast was removed prior to culture at defined stages before and at the beginning of gastrulation. The epiblast shows a stage-dependent and topographically restricted susceptibility to express Brachyury , a T-box gene pivotal for mesoderm formation, and to transform into (histologically proven) mesoderm. These results confirm for the mammalian embryo that the anterior-posterior axis of the conceptus is formed first as a molecular prepattern in the Hypoblast and then irrevocably fixed, under the control of signals secreted from the Hypoblast, by epithelio-mesenchymal transformation (primitive streak formation) in the epiblast.
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polarity in the rabbit embryo
Seminars in Cell & Developmental Biology, 2004Co-Authors: Jan Idkowiak, Gunnar Weisheit, Christoph ViebahnAbstract:The main aim of the gastrulation process is commonly regarded to be the generation of the definitive germ layers known as mesoderm, endoderm and ectoderm. Here we discuss how the topography of gene expression, cellular migration and proliferative activity in the preliminary germ layers (Hypoblast and epiblast) of the rabbit embryo reveal the sequence of events that establishes the three major body axes. We present a testable model in which a combination of cellular movement in the Hypoblast with a morphogen gradient created by the (extraembryonic) trophoblast creates morphological polarity in the embryo and, hence, the co-ordinates for germ layer formation.
Peter L. Pfeffer - One of the best experts on this subject based on the ideXlab platform.
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building principles for constructing a mammalian blastocyst embryo
Biology, 2018Co-Authors: Peter L. PfefferAbstract:The self-organisation of a fertilised egg to form a blastocyst structure, which consists of three distinct cell lineages (trophoblast, epiblast and Hypoblast) arranged around an off-centre cavity, is unique to mammals. While the starting point (the zygote) and endpoint (the blastocyst) are similar in all mammals, the intervening events have diverged. This review examines and compares the descriptive and functional data surrounding embryonic gene activation, symmetry-breaking, first and second lineage establishment, and fate commitment in a wide range of mammalian orders. The exquisite detail known from mouse embryogenesis, embryonic stem cell studies and the wealth of recent single cell transcriptomic experiments are used to highlight the building principles underlying early mammalian embryonic development.
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Specific epiblast loss and Hypoblast impairment in cattle embryos sensitized to survival signalling by ubiquitous overexpression of the proapoptotic gene BAD. PloS one. 2014; 9(5):e96843. doi
2016Co-Authors: Jessica Van Leeuwen, Debra K. Berg, Craig S. Smith, David N. Wells, Peter L. PfefferAbstract:Early embryonic lethality is common, particularly in dairy cattle. We made cattle embryos more sensitive to environmental stressors by raising the threshold of embryo survival signaling required to overcome the deleterious effects of overexpressing the proapoptotic protein BAD. Two primary fibroblast cell lines expressing BAD and exhibiting increased sensitivity to stress-induced apoptosis were used to generate transgenic Day13/14 BAD embryos. Transgenic embryos were normal in terms of retrieval rates, average embryo length or expression levels of the trophectoderm marker ASCL2. However both lines of BAD-tg embryos lost the embryonic disc and thus the entire epiblast lineage at significantly greater frequencies than either co-transferrred IVP controls or LacZ-tg embryos. Embryos without epiblast still contained the second ICM-derived lineage, the hypopblast, albeit frequently in an impaired state, as shown by reduced expression of the Hypoblast markers GATA4 and FIBRONECTIN. This indicates a gradient of sensitivity (epiblast. Hypoblast. TE) to BAD overexpression. We postulate that the greater sensitivity of specifically the epiblast lineage that we have seen in our transgenic model, reflects an inherent greater susceptibility of this lineage to environmental stress and may underlie the epiblast-specific death seen in phantom pregnancies
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RESEARCH ARTICLE Morphological and Gene Expression Changes in Cattle Embryos from Hatched Blastocyst to Early Gastrulation Stages after Transfer of In Vitro Produced Embryos
2016Co-Authors: Jessica Van Leeuwen, Debra K. Berg, Peter L. PfefferAbstract:A detailed morphological staging system for cattle embryos at stages following blastocyst hatching and preceding gastrulation is presented here together with spatiotemporal mapping of gene expression for BMP4, BRACHYURY, CERBERUS1 (CER1), CRIPTO, EOMESODERMIN, FURIN and NODAL. Five stages are defined based on distinct develop-mental events. The first of these is the differentiation of the visceral Hypoblast underlying the epiblast, from the parietal Hypoblast underlying the mural trophoblast. The second con-cerns the formation of an asymmetrically positioned, morphologically recognisable region within the visceral Hypoblast that is marked by the presence of CER1 and absence of BMP4 expression. We have termed this the anterior visceral Hypoblast or AVH. Intra-epiblast cavi-ty formation and the disappearance of the polar trophoblast overlying the epiblast (Rauber’s layer) have been mapped in relation to AVH formation. The third chronological event in-volves the transition of the epiblast into the embryonic ectoderm with concomitant onset of posterior NODAL, EOMES and BRACHYURY expression. Lastly, gastrulation commences as the posterior medial embryonic ectoderm layer thickens to form the primitive streak and cells ingress between the embryonic ectoderm and Hypoblast. At this stage a novel domain of CER1 expression is seen whereas the AVH disappears. Comparison with the mouse re-veals that while gene expression patterns at the onset of gastrulation are well conserved, asymmetry establishment, which relies on extraembryonic tissues such as the Hypoblast and trophoblast, has diverged in terms of both gene expression and morphology
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Cattle embryo staging system from post-hatching to the start of gastrulation.
2015Co-Authors: Jessica Van Leeuwen, Debra K. Berg, Peter L. PfefferAbstract:Criteria for, and diagrammatic representation and typical sections (H&E or CER1 stained) of, cattle embryos at the five stages of development between hatching and the start of gastrulation, based on data from sectioning 32 embryos. All bars are 100 μm. AVH, anterior VH; EmE, embryonic ectoderm; Endo, endoderm; Epi, epiblast; H, undifferentiated Hypoblast; Meso, mesoderm; mTB, mural trophoblast; PH, parietal (mural) Hypoblast; PS, primitive streak; RL, Rauber’s Layer (polar TB); VH, (embryonic) visceral Hypoblast.
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Morphological and Gene Expression Changes in Cattle Embryos from Hatched Blastocyst to Early Gastrulation Stages after Transfer of In Vitro Produced Embryos
2015Co-Authors: Jessica Van Leeuwen, Debra K. Berg, Peter L. PfefferAbstract:A detailed morphological staging system for cattle embryos at stages following blastocyst hatching and preceding gastrulation is presented here together with spatiotemporal mapping of gene expression for BMP4, BRACHYURY, CERBERUS1 (CER1), CRIPTO, EOMESODERMIN, FURIN and NODAL. Five stages are defined based on distinct developmental events. The first of these is the differentiation of the visceral Hypoblast underlying the epiblast, from the parietal Hypoblast underlying the mural trophoblast. The second concerns the formation of an asymmetrically positioned, morphologically recognisable region within the visceral Hypoblast that is marked by the presence of CER1 and absence of BMP4 expression. We have termed this the anterior visceral Hypoblast or AVH. Intra-epiblast cavity formation and the disappearance of the polar trophoblast overlying the epiblast (Rauber’s layer) have been mapped in relation to AVH formation. The third chronological event involves the transition of the epiblast into the embryonic ectoderm with concomitant onset of posterior NODAL, EOMES and BRACHYURY expression. Lastly, gastrulation commences as the posterior medial embryonic ectoderm layer thickens to form the primitive streak and cells ingress between the embryonic ectoderm and Hypoblast. At this stage a novel domain of CER1 expression is seen whereas the AVH disappears. Comparison with the mouse reveals that while gene expression patterns at the onset of gastrulation are well conserved, asymmetry establishment, which relies on extraembryonic tissues such as the Hypoblast and trophoblast, has diverged in terms of both gene expression and morphology.
Federica Bertocchini - One of the best experts on this subject based on the ideXlab platform.
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a differential screen for genes expressed in the extraembryonic endodermal layer of pre primitive streak stage chick embryos reveals expression of apolipoprotein a1 in Hypoblast endoblast and endoderm
Gene Expression Patterns, 2008Co-Authors: Federica Bertocchini, Claudio D. SternAbstract:The lower layer of the pre-gastrulating chick embryo is an extra-embryonic tissue made up of two different cell populations, the Hypoblast and the endoblast. The Hypoblast is characterized by the expression of inhibitory signalling molecules (e.g. Cerberus, Dickkopf1, Crescent) and others (e.g. Otx2, goosecoid, Hex, Hesx1/RPX, FGF8). However, no genes expressed in the endoblast have yet been found. We designed a differential screen to identify markers differentially expressed in these two cell populations. This only revealed one novel gene, Apolipoprotein A1 (APO A1) with restricted endodermal layer expression. Expression of APO A1 begins very early throughout the lower layer (both Hypoblast and endoblast). At later stages it is also expressed in the endoderm and its derivatives, the anterior intestinal portal endoderm and the growing liver bud.
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determination of embryonic polarity in a regulative system evidence for endogenous inhibitors acting sequentially during primitive streak formation in the chick embryo
Development, 2004Co-Authors: Federica Bertocchini, Isaac Skromne, Lewis Wolpert, Claudio D. SternAbstract:Avian embryos have a remarkable capacity to regulate: when a pre-primitive streak stage embryo is cut into fragments, each fragment can spontaneously initiate formation of a complete embryonic axis. We investigate the signalling pathways that initiate primitive streak formation and the mechanisms that ensure that only a single axis normally forms. As reported previously, an ectopic primitive streak can be induced by misexpression of Vg1 in the marginal zone. We now show that Vg1 induces an inhibitor that travels across the embryo (3 mm distance) in less than 6 hours. We provide evidence that this inhibitor acts early in the cascade of events downstream of Vg1. We also show that FGF signalling is required for primitive streak formation, in cooperation with Nodal and Chordin. We suggest that three sequential inhibitory steps ensure that a single axis develops in the normal embryo: an early inhibitor that spreads throughout the embryo (which can be induced by Vg1), a second inhibition by Cerberus from the underlying Hypoblast, and finally a late inhibition from Lefty emitted by the primitive streak itself.
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The Hypoblast of the Chick Embryo Positions the Primitive Streak by Antagonizing Nodal Signaling
Developmental cell, 2002Co-Authors: Federica Bertocchini, Claudio D. SternAbstract:The Hypoblast (equivalent to the mouse anterior visceral endoderm) of the chick embryo plays a role in regulating embryonic polarity. Surprisingly, Hypoblast removal causes multiple embryonic axes to form, suggesting that it emits an inhibitor of axis formation. We show that Cerberus (a multifunctional antagonist of Nodal, Wnt, and BMP signaling) is produced by the Hypoblast and inhibits primitive streak formation. This activity is mimicked by Cerberus-Short (CerS), which only inhibits Nodal. Nodal misexpression can initiate an ectopic primitive streak, but only when the Hypoblast is removed. We propose that, during normal development, the primitive streak forms only when the Hypoblast is displaced away from the posterior margin by the endoblast, which lacks Cerberus.
Jessica Van Leeuwen - One of the best experts on this subject based on the ideXlab platform.
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Specific epiblast loss and Hypoblast impairment in cattle embryos sensitized to survival signalling by ubiquitous overexpression of the proapoptotic gene BAD. PloS one. 2014; 9(5):e96843. doi
2016Co-Authors: Jessica Van Leeuwen, Debra K. Berg, Craig S. Smith, David N. Wells, Peter L. PfefferAbstract:Early embryonic lethality is common, particularly in dairy cattle. We made cattle embryos more sensitive to environmental stressors by raising the threshold of embryo survival signaling required to overcome the deleterious effects of overexpressing the proapoptotic protein BAD. Two primary fibroblast cell lines expressing BAD and exhibiting increased sensitivity to stress-induced apoptosis were used to generate transgenic Day13/14 BAD embryos. Transgenic embryos were normal in terms of retrieval rates, average embryo length or expression levels of the trophectoderm marker ASCL2. However both lines of BAD-tg embryos lost the embryonic disc and thus the entire epiblast lineage at significantly greater frequencies than either co-transferrred IVP controls or LacZ-tg embryos. Embryos without epiblast still contained the second ICM-derived lineage, the hypopblast, albeit frequently in an impaired state, as shown by reduced expression of the Hypoblast markers GATA4 and FIBRONECTIN. This indicates a gradient of sensitivity (epiblast. Hypoblast. TE) to BAD overexpression. We postulate that the greater sensitivity of specifically the epiblast lineage that we have seen in our transgenic model, reflects an inherent greater susceptibility of this lineage to environmental stress and may underlie the epiblast-specific death seen in phantom pregnancies
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RESEARCH ARTICLE Morphological and Gene Expression Changes in Cattle Embryos from Hatched Blastocyst to Early Gastrulation Stages after Transfer of In Vitro Produced Embryos
2016Co-Authors: Jessica Van Leeuwen, Debra K. Berg, Peter L. PfefferAbstract:A detailed morphological staging system for cattle embryos at stages following blastocyst hatching and preceding gastrulation is presented here together with spatiotemporal mapping of gene expression for BMP4, BRACHYURY, CERBERUS1 (CER1), CRIPTO, EOMESODERMIN, FURIN and NODAL. Five stages are defined based on distinct develop-mental events. The first of these is the differentiation of the visceral Hypoblast underlying the epiblast, from the parietal Hypoblast underlying the mural trophoblast. The second con-cerns the formation of an asymmetrically positioned, morphologically recognisable region within the visceral Hypoblast that is marked by the presence of CER1 and absence of BMP4 expression. We have termed this the anterior visceral Hypoblast or AVH. Intra-epiblast cavi-ty formation and the disappearance of the polar trophoblast overlying the epiblast (Rauber’s layer) have been mapped in relation to AVH formation. The third chronological event in-volves the transition of the epiblast into the embryonic ectoderm with concomitant onset of posterior NODAL, EOMES and BRACHYURY expression. Lastly, gastrulation commences as the posterior medial embryonic ectoderm layer thickens to form the primitive streak and cells ingress between the embryonic ectoderm and Hypoblast. At this stage a novel domain of CER1 expression is seen whereas the AVH disappears. Comparison with the mouse re-veals that while gene expression patterns at the onset of gastrulation are well conserved, asymmetry establishment, which relies on extraembryonic tissues such as the Hypoblast and trophoblast, has diverged in terms of both gene expression and morphology
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Cattle embryo staging system from post-hatching to the start of gastrulation.
2015Co-Authors: Jessica Van Leeuwen, Debra K. Berg, Peter L. PfefferAbstract:Criteria for, and diagrammatic representation and typical sections (H&E or CER1 stained) of, cattle embryos at the five stages of development between hatching and the start of gastrulation, based on data from sectioning 32 embryos. All bars are 100 μm. AVH, anterior VH; EmE, embryonic ectoderm; Endo, endoderm; Epi, epiblast; H, undifferentiated Hypoblast; Meso, mesoderm; mTB, mural trophoblast; PH, parietal (mural) Hypoblast; PS, primitive streak; RL, Rauber’s Layer (polar TB); VH, (embryonic) visceral Hypoblast.
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Morphological and Gene Expression Changes in Cattle Embryos from Hatched Blastocyst to Early Gastrulation Stages after Transfer of In Vitro Produced Embryos
2015Co-Authors: Jessica Van Leeuwen, Debra K. Berg, Peter L. PfefferAbstract:A detailed morphological staging system for cattle embryos at stages following blastocyst hatching and preceding gastrulation is presented here together with spatiotemporal mapping of gene expression for BMP4, BRACHYURY, CERBERUS1 (CER1), CRIPTO, EOMESODERMIN, FURIN and NODAL. Five stages are defined based on distinct developmental events. The first of these is the differentiation of the visceral Hypoblast underlying the epiblast, from the parietal Hypoblast underlying the mural trophoblast. The second concerns the formation of an asymmetrically positioned, morphologically recognisable region within the visceral Hypoblast that is marked by the presence of CER1 and absence of BMP4 expression. We have termed this the anterior visceral Hypoblast or AVH. Intra-epiblast cavity formation and the disappearance of the polar trophoblast overlying the epiblast (Rauber’s layer) have been mapped in relation to AVH formation. The third chronological event involves the transition of the epiblast into the embryonic ectoderm with concomitant onset of posterior NODAL, EOMES and BRACHYURY expression. Lastly, gastrulation commences as the posterior medial embryonic ectoderm layer thickens to form the primitive streak and cells ingress between the embryonic ectoderm and Hypoblast. At this stage a novel domain of CER1 expression is seen whereas the AVH disappears. Comparison with the mouse reveals that while gene expression patterns at the onset of gastrulation are well conserved, asymmetry establishment, which relies on extraembryonic tissues such as the Hypoblast and trophoblast, has diverged in terms of both gene expression and morphology.
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NODAL expression.
2015Co-Authors: Jessica Van Leeuwen, Debra K. Berg, Peter L. PfefferAbstract:A, B. Adjacent sections of stage 1-RL embryo after WMISH for NODAL, stained with H&E (A) or not (B). NODAL is restricted to the epiblast and not expressed in the Hypoblast underlying the epiblast, which is indistinguishable from that underlying the mural TB. C, D. Adjacent H&E and Nodal sections of stage 2-VH embryo. Only the visceral Hypoblast (VH) and inner (ventral) epiblast are NODAL-positive. Rauber’s layer (RL) is starting to disintegrate. E, F, G. By stage 3-AVH, NODAL expression levels are weaker. NODAL is seen in the AVH (section F) and in the epiblast is confined to posterior region (section G). H, I. By stage 4-EmE, NODAL is still restricted to the AVH in the Hypoblast tissue and is expressed only in the posterior EmE. J-M. Overstained stage 4-EmE embryo indicating expression throughout VH but only presumptive posterior EmE expression (arrow in M., anterior EmE). Bar, 100 μm.