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Claudio D. Stern - One of the best experts on this subject based on the ideXlab platform.

  • Molecular anatomy of the pre-Primitive-Streak chick embryo.
    Open biology, 2020
    Co-Authors: Hyung Chul Lee, Mark Turmaine, Nidia M. M. Oliveira, Youwen Yang, Irene De Almeida, Claudio D. Stern
    Abstract:

    The early stages of development of the chick embryo, leading to Primitive Streak formation (the start of gastrulation), have received renewed attention recently, especially for studies of the mecha...

  • Operations on Primitive Streak stage avian embryos.
    Methods in cell biology, 2008
    Co-Authors: Andrea Streit, Claudio D. Stern
    Abstract:

    Publisher Summary This chapter presents the basic techniques necessary for transplantation of cells between regions of the Primitive Streak stage embryo. It describes transplantation of Hensen's node between quail and chick embryos as a prototype example and present variations of this technique for obtaining other tissues for grafting and guidelines for homotopic or heterotopic grafting. In amniotes (reptiles, birds, and mammals), gastrulation occurs through a midline structure, the Primitive Streak. At the tip of the Primitive Streak lies the amniote organizer, Hensen's node. The acquisition of different fates is largely reliant on inductive processes, by which some cells emit signals that influence the fate of their neighbors. The mesoderm, endoderm, and neural plate are all thought to arise from the epiblast as a result of such inductive interactions. To study these events, it is essential to manipulate cells, either to map their normal fates in the embryo, or to challenge their developmental potential by placing cells in a new environment where they may be exposed to different signals, or to test the inducing properties of groups of cells by placing them adjacent to other putative responding tissues. This requires the embryo to be amenable to transplantation and culture to stages after these processes have taken place. The avian embryo lends itself perfectly to manipulations that at the time of laying, it is a large, flat, and translucent disc that can be cultured easily to early organogenesis stages outside the egg.

  • the amniote Primitive Streak is defined by epithelial cell intercalation before gastrulation
    Nature, 2007
    Co-Authors: Octavian Voiculescu, Lewis Wolpert, Federica Bertocchini, Ray Keller, Claudio D. Stern
    Abstract:

    Gastrulation is a key event in embryogenesis. The mechanisms controlling gastrulation movements in amniotes are not well known and are often extrapolated from studies in other species. Now Voiculescu et al. report the first time-lapse analysis of individual cell movements in living chick embryos during gastrulation. Multi-photon time-lapse microscopy reveals movements that differ from those described in fish and amphibians, with important implications for embryology and evolution of gastrulation in vertebrates. In particular the work reveals an early pregastrulation intercalation event that may hold the key to the classic question of how the amniote Primitive Streak evolved from the ancestral blastopore. The first time-lapse analysis of individual cell movements in living chick embryos during gastrulation are reported, and details that these movements differ from those described in fish and amphibians, with important implications for embryology and evolution of gastrulation in vertebrates. During gastrulation, a single epithelial cell layer, the ectoderm, generates two others: the mesoderm and the endoderm. In amniotes (birds and mammals), mesendoderm formation occurs through an axial midline structure, the Primitive Streak1, the formation of which is preceded by massive ‘polonaise’ movements2,3 of ectoderm cells. The mechanisms controlling these processes are unknown. Here, using multi-photon time-lapse microscopy of chick (Gallus gallus) embryos, we reveal a medio-lateral cell intercalation confined to the ectodermal subdomain where the Streak will later form. This intercalation event differs from the convergent extension movements of the mesoderm described in fish and amphibians (anamniotes)4,5,6,7,8: it occurs before gastrulation and within a tight columnar epithelium. Fibroblast growth factor from the extraembryonic endoderm (hypoblast, a cell layer unique to amniotes) directs the expression of Wnt planar-cell-polarity pathway components to the intercalation domain. Disruption of this Wnt pathway causes the mesendoderm to form peripherally, as in anamniotes1,9. We propose that the amniote Primitive Streak evolved from the ancestral blastopore by acquisition of an additional medio-lateral intercalation event, preceding gastrulation and acting independently of mesendoderm formation to position the Primitive Streak at the midline.

  • Formation of the chick Primitive Streak as studied in computer simulations.
    Journal of theoretical biology, 2005
    Co-Authors: Lawrence Bodenstein, Claudio D. Stern
    Abstract:

    We have used a computer simulation system to examine formation of the chick Primitive Streak and to test the proposal (Wei and Mikawa Development 127 (2000) 87) that oriented cell division could account for Primitive Streak elongation. We find that this proposal is inadequate to explain elongation of the Streak. In contrast, a correctly patterned model Streak can be generated if two putative mechanisms are operative. First, a subpopulation of precursor cells that is known to contribute to the Streak is assigned a specific, but simple, movement pattern. Second, additional cells within the epiblast are allowed to incorporate into the Streak based on near-neighbor relations. In this model, the Streak is cast as a steady-state system with continuous recruitment of neighboring epiblast cells, egress of cells into deeper layers and an internal pattern of cell movement. The model accurately portrays elongation and maintenance of a robust Streak, changes in the composition of the Streak and defects in the Streak after experimental manipulation.

  • determination of embryonic polarity in a regulative system evidence for endogenous inhibitors acting sequentially during Primitive Streak formation in the chick embryo
    Development, 2004
    Co-Authors: Federica Bertocchini, Isaac Skromne, Lewis Wolpert, Claudio D. Stern
    Abstract:

    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.

Andrea Münsterberg - One of the best experts on this subject based on the ideXlab platform.

  • fate mapping identifies the origin of shf ahf progenitors in the chick Primitive Streak
    PLOS ONE, 2012
    Co-Authors: Esther Camp, Susanne Dietrich, Andrea Münsterberg
    Abstract:

    Heart development depends on the spatio-temporally regulated contribution of progenitor cells from the primary, secondary and anterior heart fields. Primary heart field (PHF) cells are first recruited to form a linear heart tube; later, they contribute to the inflow myocardium of the four-chambered heart. Subsequently cells from the secondary (SHF) and anterior heart fields (AHF) are added to the heart tube and contribute to both the inflow and outflow myocardium. In amniotes, progenitors of the linear heart tube have been mapped to the anterior-middle region of the early Primitive Streak. After ingression, these cells are located within bilateral heart fields in the lateral plate mesoderm. On the other hand SHF/AHF field progenitors are situated anterior to the linear heart tube, however, the origin and location of these progenitors prior to the development of the heart tube remains elusive. Thus, an unresolved question in the process of cardiac development is where SHF/AHF progenitors originate from during gastrulation and whether they come from a region in the Primitive Streak distinct from that which generates the PHF. To determine the origin and location of SHF/AHF progenitors we used vital dye injection and tissue grafting experiments to map the location and ingression site of outflow myocardium progenitors in early Primitive Streak stage chicken embryos. Cells giving rise to the AHF ingressed from a rostral region of the Primitive Streak, termed region ‘A’. During development these cells were located in the cranial paraxial mesoderm and in the pharyngeal mesoderm. Furthermore we identified region ‘B’, located posterior to ‘A’, which gave rise to progenitors that contributed to the primary heart tube and the outflow tract. Our studies identify two regions in the early Primitive Streak, one which generates cells of the AHF and a second from which cardiac progenitors of the PHF and SHF emerge.

  • Fate mapping identifies the origin of SHF/AHF progenitors in the chick Primitive Streak
    PloS one, 2012
    Co-Authors: Esther Camp, Susanne Dietrich, Andrea Münsterberg
    Abstract:

    Heart development depends on the spatio-temporally regulated contribution of progenitor cells from the primary, secondary and anterior heart fields. Primary heart field (PHF) cells are first recruited to form a linear heart tube; later, they contribute to the inflow myocardium of the four-chambered heart. Subsequently cells from the secondary (SHF) and anterior heart fields (AHF) are added to the heart tube and contribute to both the inflow and outflow myocardium. In amniotes, progenitors of the linear heart tube have been mapped to the anterior-middle region of the early Primitive Streak. After ingression, these cells are located within bilateral heart fields in the lateral plate mesoderm. On the other hand SHF/AHF field progenitors are situated anterior to the linear heart tube, however, the origin and location of these progenitors prior to the development of the heart tube remains elusive. Thus, an unresolved question in the process of cardiac development is where SHF/AHF progenitors originate from during gastrulation and whether they come from a region in the Primitive Streak distinct from that which generates the PHF. To determine the origin and location of SHF/AHF progenitors we used vital dye injection and tissue grafting experiments to map the location and ingression site of outflow myocardium progenitors in early Primitive Streak stage chicken embryos. Cells giving rise to the AHF ingressed from a rostral region of the Primitive Streak, termed region ‘A’. During development these cells were located in the cranial paraxial mesoderm and in the pharyngeal mesoderm. Furthermore we identified region ‘B’, located posterior to ‘A’, which gave rise to progenitors that contributed to the primary heart tube and the outflow tract. Our studies identify two regions in the early Primitive Streak, one which generates cells of the AHF and a second from which cardiac progenitors of the PHF and SHF emerge.

  • Multicellular rosette formation during cell ingression in the avian Primitive Streak
    Developmental dynamics : an official publication of the American Association of Anatomists, 2008
    Co-Authors: Laura Wagstaff, Gemma Bellett, Mette M. Mogensen, Andrea Münsterberg
    Abstract:

    Cell movements are a fundamental feature during the development of multi-cellular organisms. In amniote gastrulation, cells ingress through the Primitive Streak, which identifies the anterior-posterior axis of the embryo. We investigated the cytoskeletal architecture during these morphogenetic processes and characterized microtubule organisation in whole chick embryos. This revealed the distribution of cells with polarized and radial microtubule (MT) arrays across different regions of the embryo. Cells in the epiblast usually displayed radial MT-arrays, while the majority of cells in the Primitive Streak had polarized MT-arrays. Within the Primitive Streak, many cells organized into groups and were arranged in rosette-like structures with a distinct centre characterized by an accumulation of actin. Extended confocal microscopy and three-dimensional image reconstruction identified tips of polarized cells that were protruding from the plane of rosettes, usually from the centre. We propose that organization into higher order structures facilitates cell ingression during gastrulation. Developmental Dynamics 237:91–96, 2008. © 2007 Wiley-Liss, Inc.

Gary C. Schoenwolf - One of the best experts on this subject based on the ideXlab platform.

  • Epiblast and Primitive-Streak origins of the endoderm in the gastrulating chick embryo.
    Development (Cambridge England), 2003
    Co-Authors: Aaron Lawson, Gary C. Schoenwolf
    Abstract:

    Gastrulation is characterized by the extensive movements of cells. Fate mapping is used to follow such cell movements as they occur over time, and prospective fate maps have been constructed for several stages of the model organisms used in modern studies in developmental biology. In chick embryos, detailed fate maps have been constructed for both prospective mesodermal and ectodermal cells. However, the origin and displacement of the prospective endodermal cells during crucial periods in gastrulation remain unclear. This study had three aims. First, we determined the Primitive-Streak origin of the endoderm using supravital fluorescent markers, and followed the movement of the prospective endodermal cells as they dispersed to generate the definitive endodermal layer. We show that between stages 3a/b and 4, the intraembryonic definitive endoderm receives contributions mainly from the rostral half of the Primitive Streak, and that endodermal movements parallel those of ingressing adjacent mesodermal subdivisions. Second, the question of the epiblast origin of the endodermal layer was addressed by precisely labeling epiblast cells in a region known to give rise to prospective somitic cells, and following their movement as they underwent ingression through the Primitive Streak. We show that the epiblast clearly contributes prospective endodermal cells to the Primitive Streak, and subsequently to definitive endoderm of the area pellucida. Finally, the relationship between the hypoblast and the definitive endoderm was defined by following labeled rostral Primitive-Streak cells over a short period of time as they contributed to the definitive endoderm, and combining this with in situ hybridization with a riboprobe for Crescent, a marker of the hypoblast. We show that as the definitive endodermal layer is laid down, there is cell-cell intercalation at its interface with the displaced hypoblast cells. These data were used to construct detailed prospective fate maps of the endoderm in the chick embryo, delineating the origins and migrations of endodermal cells in various rostrocaudal levels of the Primitive Streak during key periods in early development.

  • Localization of cells of the prospective neural plate, heart and somites within the Primitive Streak and epiblast of avian embryos at intermediate Primitive-Streak stages.
    Cells tissues organs, 2001
    Co-Authors: Carmen Lopez-sanchez, Virginio Garcia-martinez, Gary C. Schoenwolf
    Abstract:

    By constructing avian transplantation chimeras using fluorescently-labeled grafts and antibodies specific for grafted cells, we have generated a prospective fate map of the Primitive Streak and epiblast of the avian blastoderm at intermediate Primitive-Streak stages (stages 3a/3b). This high-resolution map confirms our previous study on the origin of the cardiovascular system from the Primitive Streak at these stages and provides new information on the epiblast origin of the neural plate, heart and somites. In addition, the origin of the rostral endoderm is now documented in more detail. The map shows that the prospective neural plate arises from the epiblast in close association with the rostral end of the Primitive Streak and lies within an area extending 250 µm rostral to the Streak, 250 µm lateral to the Streak and 125 µm caudal to the rostral border of the Streak. The future floor plate of the neural tube arises within the midline just rostral to the Streak, confirming our earlier study, but unlike at the late-Primitive Streak stages when both Hensen’s node and the midline area rostral to Hensen’s node contribute to the floor plate, only the area rostral to the Primitive Streak contributes to the floor plate at intermediate Primitive-Streak stages. Instead of contributing to the floor plate of the neural tube, the rostral end of the Primitive Streak at intermediate Primitive-Streak stages forms the notochord as well as the rostromedial endoderm, which lies beneath the prechordal plate mesoderm and extends caudolaterally on each side toward the cardiogenic areas. The epiblast lateral to the Primitive Streak and caudal to the neural plate contributes to the heart and it does so in rostrocaudal sequence (i.e., rostral grafts contribute to rostral levels of the straight heart tube, whereas progressively more caudal grafts contribute to progressively more caudal levels of the straight heart tube), and individual epiblast grafts contribute cells to both the myocardium and endocardium. The prospective somites (i.e., paraxial mesoderm) lie within the epiblast just lateral to the prospective heart mesoderm. Comparing this map with that constructed at late Primitive-Streak stages reveals that by the late Primitive-Streak stages, prospective heart mesoderm has moved from the epiblast through the Primitive Streak and into the mesodermal mantle, and that some of the prospective somitic mesoderm has entered the Primitive Streak and is undergoing ingression.

  • Classification scheme for genes expressed during formation and progression of the avian Primitive Streak
    The Anatomical record, 2001
    Co-Authors: Aaron Lawson, Jean François Colas, Gary C. Schoenwolf
    Abstract:

    We have systematically examined the expression patterns of thirteen genes by in situ hybridization during the formation and progression of the avian Primitive Streak. Based on common patterns of expression, we classify these genes into three distinct groups. Group 1 genes, subdivided into group 1A (Wnt8c, Slug, Vg1, and Nodal) and group 1B (Fgf8, Brachyury, and Cripto), were expressed first in the epiblast and then, throughout most of the length of the Primitive Streak. Group 2 genes, namely, cNot1, Sonic hedgehog (Shh), Hnf3β and Chordin, were confined to the rostral end of the Primitive Streak, and then, to Hensen's node. In contrast, Group 3 genes, comprising Goosecoid (GSC) and Crescent, were expressed in the hypoblast. This classification scheme provides a rational basis for categorizing genes expressed during avian gastrulation, and such systematization is likely to provide insight into the relationships among different genes and their potential roles in key events of gastrulation. Anat Rec 262:221–226, 2001. © 2001 Wiley-Liss, Inc.

  • Cell populations and morphogenetic movements underlying formation of the avian Primitive Streak and organizer.
    Genesis (New York N.Y. : 2000), 2001
    Co-Authors: Aaron Lawson, Gary C. Schoenwolf
    Abstract:

    Summary: The cell populations and morphogenetic movements that contribute to the formation of the avian Primitive Streak and organizer—Hensen's node—are poorly understood. We labeled selected groups of cells with fluorescent dyes and then followed them over time during formation and progression of the Primitive Streak and formation of Hensen's node. We show that (1) the Primitive Streak arises from a localized population of epiblast cells spanning the caudal midline of Koller's sickle, with the mid-dorsal cells of the Primitive Streak arising from the midline of the epiblast overlying Koller's sickle and the deeper and more lateral Primitive Streak cells arising more laterally within the epiblast overlying the sickle, from an arch subtending about 30°; (2) convergent extension movements of cells in the epiblast overlying Koller's sickle contribute to formation of the initial Primitive Streak; and (3) Hensen's node is derived from a mixture of cells originating both from the epiblast just rostral to the incipient (stage 2) Primitive Streak and later from the epiblast just rostral to the elongating (stage 3a/b) Primitive Streak, as well as from the rostral tip of the progressing Streak itself. Collectively, these results provide new information on the formation of the avian Primitive Streak and organizer, increasing our understanding of these important events of early development of amniotes. genesis 29:188–195, 2001. © 2001 Wiley-Liss, Inc.

  • Primitive-Streak origin and state of commitment of cells of the cardiovascular system in avian and mammalian embryos
    Cellular & molecular biology research, 1995
    Co-Authors: Gary C. Schoenwolf, Virginio Garcia-martinez
    Abstract:

    Early events of cardiovascular development have received renewed interest in recent years. The cardiovascular system is the first major organ system to become functional during early embryogenesis. Cells fated to form the cardiovascular system can be identified as early as during stages of gastrulation of avian and mammalian embryos. In the present brief summary, we describe the Primitive-Streak origin of the avian cardiovascular system and examine the state of commitment of prospective cardiogenic and vasculogenic areas of the Primitive Streak. In addition, we describe initial experiments aimed at elucidating the Primitive-Streak origin of the heart in mouse embryos. Finally, we consider the possible roles of Hensen's node and the "cardiac" endoderm in determination of cell fate and patterning of the avian developing heart tube. Although recent studies have shed considerable light on the origin, migration, and determination of the cardiovascular system, much still remains to be learned about mechanisms underlying cardiovascular patterning in the early embryo.

Daniel Dufort - One of the best experts on this subject based on the ideXlab platform.

  • Nuclear receptor NR5A2 is required for proper Primitive Streak morphogenesis
    Developmental dynamics : an official publication of the American Association of Anatomists, 2006
    Co-Authors: Cassandre Labelle-dumais, Mariève Jacob-wagner, Jean-françois Paré, Luc Bélanger, Daniel Dufort
    Abstract:

    NR5A2, also known as liver receptor homologue 1 (LRH-1) and fetoprotein transcription factor (FTF), is an orphan nuclear receptor involved in the regulation of cholesterol metabolism and steroidogenesis in the adult. NR5A2 was also shown to be expressed during early mouse embryogenesis. Consistent with its early expression pattern, a targeted disruption of this gene leads to embryonic lethality around the gastrulation period. To characterize the embryonic phenotype resulting from NR5A2 loss of function, we undertook morphological and marker gene analyses and showed that NR5A2-/- embryos display growth retardation, epiblast disorganization, a mild embryonic-extraembryonic constriction, as well as abnormal thickening of the proximo-posterior epiblast. We demonstrated that, although initial specification of the anterior-posterior axis occurred in the absence of NR5A2, Primitive Streak formation was impaired and neither embryonic nor extraembryonic mesoderm was generated. Moreover, although the visceral endoderm does not show major morphological abnormalities in NR5A2-/- embryos, a decrease in the expression level of HNF4 and GATA4 was observed. Aggregation experiments demonstrated that, in the presence of wild-type tetraploid cells, NR5A2 mutant cells in the epiblast are capable of undergoing normal gastrulation. Therefore, our results suggest a requirement for NR5A2 in extraembryonic tissues and identify a novel role of this gene in proper Primitive Streak morphogenesis.

  • β catenin signaling marks the prospective site of Primitive Streak formation in the mouse embryo
    Developmental Dynamics, 2004
    Co-Authors: Othman A. Mohamed, Hugh J. Clarke, Daniel Dufort
    Abstract:

    β-Catenin signaling has been shown to be involved in triggering axis formation in several organisms, including Xenopus and zebrafish. Genetic analysis has demonstrated that the Wnt/β-catenin signaling pathway is also involved in axis formation in the mouse, since a targeted deletion of β-catenin results in embryos that have a block in anterior–posterior axis formation, fail to initiate gastrulation, and do not form mesoderm. However, because β-catenin is ubiquitously expressed, the precise time and cell types in which this signaling pathway is active during early embryonic development remain unknown. Thus, to better understand the role of the Wnt/β-catenin signaling pathway in axis formation and mesoderm specification, we have examined both the distribution and signaling activity of β-catenin during early embryonic development in the mouse. We show that the N-terminally nonphosphorylated form of β-catenin as well as β-catenin signaling is first detectable in the extraembryonic visceral endoderm in day 5.5 embryos. Before the initiation of gastrulation at day 6.0, β-catenin signaling is asymmetrically distributed within the epiblast and is localized to a small group of cells adjacent to the embryonic–extraembryonic junction. At day 6.5 and onward, β-catenin signaling was detected in the Primitive Streak and mature node. Thus, β-catenin signaling precedes Primitive Streak formation and is present in epiblast cells that will go on to form the Primitive Streak. These results support a critical role for the Wnt/β-catenin pathway in specifying cells to form the Primitive Streak and node in the mammalian embryo as well as identify a novel domain of Wnt/β-catenin signaling activity during early embryogenesis. Developmental Dynamics 231:416–424, 2004. © 2004 Wiley-Liss, Inc.

  • β‐catenin signaling marks the prospective site of Primitive Streak formation in the mouse embryo
    Developmental dynamics : an official publication of the American Association of Anatomists, 2004
    Co-Authors: Othman A. Mohamed, Hugh J. Clarke, Daniel Dufort
    Abstract:

    β-Catenin signaling has been shown to be involved in triggering axis formation in several organisms, including Xenopus and zebrafish. Genetic analysis has demonstrated that the Wnt/β-catenin signaling pathway is also involved in axis formation in the mouse, since a targeted deletion of β-catenin results in embryos that have a block in anterior–posterior axis formation, fail to initiate gastrulation, and do not form mesoderm. However, because β-catenin is ubiquitously expressed, the precise time and cell types in which this signaling pathway is active during early embryonic development remain unknown. Thus, to better understand the role of the Wnt/β-catenin signaling pathway in axis formation and mesoderm specification, we have examined both the distribution and signaling activity of β-catenin during early embryonic development in the mouse. We show that the N-terminally nonphosphorylated form of β-catenin as well as β-catenin signaling is first detectable in the extraembryonic visceral endoderm in day 5.5 embryos. Before the initiation of gastrulation at day 6.0, β-catenin signaling is asymmetrically distributed within the epiblast and is localized to a small group of cells adjacent to the embryonic–extraembryonic junction. At day 6.5 and onward, β-catenin signaling was detected in the Primitive Streak and mature node. Thus, β-catenin signaling precedes Primitive Streak formation and is present in epiblast cells that will go on to form the Primitive Streak. These results support a critical role for the Wnt/β-catenin pathway in specifying cells to form the Primitive Streak and node in the mammalian embryo as well as identify a novel domain of Wnt/β-catenin signaling activity during early embryogenesis. Developmental Dynamics 231:416–424, 2004. © 2004 Wiley-Liss, Inc.

  • The transcription factor HNF3beta is required in visceral endoderm for normal Primitive Streak morphogenesis
    Development (Cambridge England), 1998
    Co-Authors: Daniel Dufort, Lois Schwartz, Kendraprasad Harpal, Janet Rossant
    Abstract:

    During early embryogenesis, the transcription factor HNF3beta is expressed in visceral and definitive endoderm, node, notochord and floorplate. A targeted mutation in the HNF3β gene results in the lack of a definitive node and notochord. Furthermore, lack of HNF3beta results in failure of proper Primitive Streak elongation. To address whether HNF3beta is required in visceral endoderm, we have used tetraploid embryo-ES cell aggregations to generate chimeric mouse embryos with wild-type visceral endoderm and homozygous mutant HNF3beta embryonic ectoderm or vice versa. Replacing the visceral endoderm of mutant HNF3beta embryos rescued proper Primitive Streak elongation and, conversely, mutant visceral endoderm imposed a severe embryonic-extraembryonic constriction on wild-type embryonic ectoderm. Restoration of normal Streak morphogenesis was not sufficient to allow formation of the node and notochord in HNF3beta mutant embryos. Thus, our results demonstrate that HNF3beta has two separate roles in Primitive Streak formation. One is to act within the visceral endoderm to promote proper Streak morphogenesis. The second is autonomous to the node and its precursors and involves specification of node and notochord cell fates. HNF3beta mutant embryos rescued for the embryonic-extraembryonic constriction developed further than mutant embryos, allowing examination of later roles for HNF3beta. We show that such mutant embryos lack foregut and midgut endoderm. In addition, left-right asymmetry is affected in the mutant embryos.

Joy Rathjen - One of the best experts on this subject based on the ideXlab platform.

  • a novel role for γ secretase in the formation of Primitive Streak like intermediates from es cells in culture
    Stem Cells, 2009
    Co-Authors: James N. Hughes, Natasha Dodge, Peter D. Rathjen, Joy Rathjen
    Abstract:

    γ-Secretase is a membrane-associated protease with multiple intracellular targets, a number of which have been shown to influence embryonic development and embryonic stem (ES) cell differentiation. This paper describes the use of the γ-secretase inhibitor N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT) to evaluate the role of γ-secretase in the differentiation of pluripotent stem cells to the germ lineages. The addition of DAPT did not prevent the formation of Primitive ectoderm-like cells from ES cells in culture. In contrast, the addition of DAPT during Primitive ectoderm-like cell differentiation interfered with the ability of both serum and BMP4 to induce a Primitive Streak-like intermediate and resulted in the preferential formation of neurectoderm. Similarly, DAPT reduced the formation of Primitive Streak-like intermediates from differentiating human ES cells; the culture conditions used resulted in a population enriched in human surface ectoderm. These data suggest that γ-secretase may form part of the general pathway by which mesoderm is specified within the Primitive Streak. The addition of an E-cadherin neutralizing antibody was able to partially reverse the effect of DAPT, suggesting that DAPT may be preventing the formation of Primitive Streak-like intermediates and promoting neurectoderm differentiation by stabilizing E-cadherin and preventing its proteolysis. STEM CELLS 2009;27:2941–2951

  • A Novel Role for γ‐Secretase in the Formation of Primitive Streak‐like Intermediates from ES Cells in Culture
    Stem cells (Dayton Ohio), 2009
    Co-Authors: James N. Hughes, Natasha Dodge, Peter D. Rathjen, Joy Rathjen
    Abstract:

    γ-Secretase is a membrane-associated protease with multiple intracellular targets, a number of which have been shown to influence embryonic development and embryonic stem (ES) cell differentiation. This paper describes the use of the γ-secretase inhibitor N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT) to evaluate the role of γ-secretase in the differentiation of pluripotent stem cells to the germ lineages. The addition of DAPT did not prevent the formation of Primitive ectoderm-like cells from ES cells in culture. In contrast, the addition of DAPT during Primitive ectoderm-like cell differentiation interfered with the ability of both serum and BMP4 to induce a Primitive Streak-like intermediate and resulted in the preferential formation of neurectoderm. Similarly, DAPT reduced the formation of Primitive Streak-like intermediates from differentiating human ES cells; the culture conditions used resulted in a population enriched in human surface ectoderm. These data suggest that γ-secretase may form part of the general pathway by which mesoderm is specified within the Primitive Streak. The addition of an E-cadherin neutralizing antibody was able to partially reverse the effect of DAPT, suggesting that DAPT may be preventing the formation of Primitive Streak-like intermediates and promoting neurectoderm differentiation by stabilizing E-cadherin and preventing its proteolysis. STEM CELLS 2009;27:2941–2951

  • A Novel Role for γ-Secretase in the Formation of Primitive Streak-like Intermediates from ES Cells in Culture
    Stem Cells, 2009
    Co-Authors: James N. Hughes, Natasha Dodge, Peter D. Rathjen, Joy Rathjen
    Abstract:

    Υ-Secretase is a membrane-associated protease with multiple intracellular targets, a number of which have been shown to influence embryonic development and embryonic stem (ES) cell differentiation. This paper describes the use of the Υ-secretase inhibitor N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT) to evaluate the role of Υ- secretase in the differentiation of pluripotent stem cells to the germ lineages. The addition of DAPT did not prevent the formation of Primitive ectoderm-like cells from ES cells in culture. In contrast, the addition of DAPT during Primitive ectoderm-like cell differentiation interfered with the ability of both serum and BMP4 to induce a Primitive Streak-like intermediate and resulted in the preferential formation of neurectoderm. Similarly, DAPT reduced the formation of Primitive Streak-like intermediates from differentiating human ES cells; the culture conditions used resulted in a population enriched in human surface ectoderm. These data suggest that Υ-secretase may form part of the general pathway by which mesoderm is specified within the Primitive Streak. The addition of an E-cadherin neutralizing antibody was able to partially reverse the effect of DAPT, suggesting that DAPT may be preventing the formation of Primitive Streak-like intermediates and promoting neurectoderm differentiation by stabilizing E-cadherin and preventing its proteolysis.James N. Hughes, Natasha Dodge, Peter D. Rathjen and Joy Rathje