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Wolfgang Driever - One of the best experts on this subject based on the ideXlab platform.
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functional interactions of genes mediating convergent extension knypek and trilobite during the partitioning of the eye primordium in zebrafish
Developmental Biology, 1998Co-Authors: Florence L Marlow, Fried Zwartkruis, Jarema Malicki, Stephan C F Neuhauss, Leila Abbas, Molly Weaver, Wolfgang Driever, Lilianna SolnicakrezelAbstract:Vertebrate eye development in the anterior region of the neural Plate involves a series of inductive interactions dependent on the underlying Prechordal Plate and signals from the midline of the neural Plate, including Hedgehog. The mechanisms controlling the spatiotemporal expression pattern of hedgehog genes are currently not understood. Cyclopia is observed in trilobite (tri) and knypek (kny) mutants with affected convergent extension of the embryonic axis during gastrulation. Here, we demonstrate that tri mutants show a high frequency of partial or complete cyclopia, kny mutants exhibit cyclopia infrequently, while kny m119 tri m209 double-mutant embryos have dramatically reduced convergent extension and are completely cyclopic. We analyzed the relationships between the convergent extension defect, the expression of hedgehog and Prechordal Plate genes, and the formation of cyclopia in kny m119 and tri m209 mutants. Our results correlate the cyclopia phenotype with the abnormal location of hh-expressing cells with respect to the optic primordium. We show that cyclopia in these mutants is not due to an incompetence of tri and kny cells to respond to Hedgehog signaling. Rather, it is a consequence of exceeding a critical distance (>40 ‐50 mm) between hedgehog-expressing cells and the prospective eye field. We hypothesize that at this distance, midline cells are not in an appropriate position to physically separate the eye field and that HH and other signals do not reach the appropriate target cells. Furthermore, tri and kny have overlapping functions in establishing proper alignment of the anterior neural Plate and midline cells expressing shh and twhh genes when the partitioning of the eye primordium takes place. © 1998 Academic Press
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the one eyed pinhead gene functions in mesoderm and endoderm formation in zebrafish and interacts with no tail
Development, 1997Co-Authors: Alexander F. Schier, Stephan C F Neuhauss, Wolfgang Driever, William S. Talbot, Kathryn Ann HeldeAbstract:The zebrafish locus one-eyed pinhead (oep) is essential for the formation of anterior axial mesoderm, endoderm and ventral neuroectoderm. At the beginning of gastrulation anterior axial mesoderm cells form the Prechordal Plate and express goosecoid (gsc) in wild-type embryos. In oep mutants the Prechordal Plate does not form and gsc expression is not maintained. Exposure to lithium, a dorsalizing agent, leads to the ectopic induction and maintenance of gsc expression in wild-type embryos. Lithium treatment of oep mutants still leads to ectopic gsc induction but not maintenance, suggesting that oep acts downstream of inducers of dorsal mesoderm. In genetic mosaics, wild-type cells are capable of forming anterior axial mesoderm in oep embryos, suggesting that oep is required in prospective anterior axial mesoderm cells before gastrulation. The oep gene is also essential for endoderm formation and the early development of ventral neuroectoderm, including the floor Plate. The loss of endoderm is already manifest during gastrulation by the absence of axial-expressing cells in the hypoblast of oep mutants. These findings suggest that oep is also required in lateral and ventral regions of the gastrula margin. The sonic hedgehog (shh).gene is expressed in the notochord of oep animals. Therefore, the impaired floor Plate development in oep mutants is not caused by the absence of the floor Plate inducer shh. This suggests that oep is required downstream or in parallel to shh signaling. The ventral region of the forebrain is also absent in oep mutants, leading to severe cyclopia. In contrast, anterior-posterior brain patterning appears largely unaffected, suggesting that underlying Prechordal Plate is not required for anterior-posterior pattern formation but might be involved in dorsoventral brain patterning. To test if oep has a wider, partially redundant role, we constructed double mutants with two other zebrafish loci essential for patterning during gastrulation. Double mutants with floating head, the zebrafish Xnot homologue, display enhanced floor Plate and adaxial muscle phenotypes. Double mutants with no tail (ntl), the zebrafish homologue of the mouse Brachyury locus, display severe defects in midline and mesoderm formation including absence of most of the somitic mesoderm. These results reveal a redundant function of oep and ntl in mesoderm formation. Our data suggest that both oep and ntl act in the blastoderm margin to specify mesendodermal cell fates.
Kathleen A Mahon - One of the best experts on this subject based on the ideXlab platform.
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a novel inducible element activated by contact with rathke s pouch is present in the regulatory region of the rpx hesx1 homeobox gene
Developmental Biology, 2003Co-Authors: Edit Hermesz, Lisa Williamssimons, Kathleen A MahonAbstract:Abstract Reciprocal inductive interactions are postulated to play a role in the determination and differentiation of the pituitary gland and the ventral hypothalamus. The homeobox gene Rpx/Hesxl is expressed during gastrulation in the anterior endoderm, Prechordal Plate, and the prospective cephalic neural Plate, and at later stages of development in Rathke’s pouch, the primordium of the pituitary. We have defined the regulatory elements necessary for proper spatial and temporal expression during development in transgenic mice using lacZ reporter genes. Proper spatial and temporal expression in the anterior endoderm Prechordal Plate and anterior neural Plate can be recapitulated with as little as 568 bp of upstream sequence and intragenic sequence containing the first exon and intron. Late-stage expression in Rathke’s pouch requires additional negative and positive regulatory elements. Interestingly, deletion analysis uncovered an element that directs transgene expression to a region of the hypothalamus that lies in direct contact with Rathke’s pouch. In vitro tissue recombination experiments have established that this expression is induced by contact with the pouch. We propose that this element may be present in other genes that normally respond to signals emanating from the pouch during the development of the hypothalamic–pituitary axis. The Rpx–lacZ transgenic mice provide a novel model system for the molecular dissection of inductive cell signaling during pituitary development.
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rpx a novel anterior restricted homeobox gene progressively activated in the Prechordal Plate anterior neural Plate and rathke s pouch of the mouse embryo
Development, 1996Co-Authors: Edit Hermesz, Susan Mackem, Kathleen A MahonAbstract:We have isolated a new murine homeobox gene, Rpx (for Rathke's pouch homeobox), that is dynamically expressed in the prospective cephalic region of the embryo during gastrulation. Early expression is seen in the anterior midline endoderm and Prechordal Plate precursor. Expression is subsequently activated in the overlying ectoderm of the cephalic neural Plate, suggesting that inductive contact with Rpx-expressing mesendoderm is required for this expression. Subsequently, Rpx expression is extinguished in the mesendoderm while remaining in the prospective prosencephalic region of the neural Plate ectoderm. Ultimately, transcripts become restricted to Rathke's pouch, the primordium of the pituitary, which is known to be derived from the most anterior ectoderm of the early embryo. Down regulation of Rpx in the pouch coincides with the differentiation of pituitary-specific cell types. Rpx is the earliest known marker for the pituitary primordium, suggestive of a role in the early determination or differentiation of the pituitary. Since Rpx is expressed so dynamically and so early in the anterior region of the embryo, and since its early expression domain is much more extensive than the region fated to form the pituitary, it is likely that Rpx is involved in the initial determination of the anterior (Prechordal) region of the embryo.
Lilianna Solnicakrezel - One of the best experts on this subject based on the ideXlab platform.
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targeted gene expression in the zebrafish Prechordal Plate
Genesis, 2006Co-Authors: Adi Inbal, Jacek Topczewski, Lilianna SolnicakrezelAbstract:Targeted gene expression is a powerful tool for understanding gene function in vivo. In zebrafish, overexpression of gene products is typically accomplished ubiquitously, without temporal and spatial specificity. However, the yeast Gal4/UAS system can be used for targeted gene expression in zebrafish. Here we describe the generation and characterization of Tg[gsc: Gal4-VP16] transgenic zebrafish lines that harbor a construct encoding Gal4-VP16 transcriptional activator under the control of a fragment of the goosecoid gene promoter. Tg[gsc:Gal4-VP16] embryos express Gal4-VP16 RNA in presumptive Prechordal Plate mesendoderm during late blastula and throughout gastrulation. By crossing these fish to Tg[UAS-GFP] transgenic fish, we show that the gsc:Gal4-VP16 transgene is capable of driving strong expression of a target gene in the Prechordal Plate and its derivatives during gastrulation and segmentation. Thus, the use of Tg[gsc:Gal4-VP16] fish can help in understanding gene function in the Prechordal Plate, an embryonic structure that is crucial for normal neural patterning. genesis 44:584–588, 2006. Published 2006 Wiley-Liss, Inc.
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functional interactions of genes mediating convergent extension knypek and trilobite during the partitioning of the eye primordium in zebrafish
Developmental Biology, 1998Co-Authors: Florence L Marlow, Fried Zwartkruis, Jarema Malicki, Stephan C F Neuhauss, Leila Abbas, Molly Weaver, Wolfgang Driever, Lilianna SolnicakrezelAbstract:Vertebrate eye development in the anterior region of the neural Plate involves a series of inductive interactions dependent on the underlying Prechordal Plate and signals from the midline of the neural Plate, including Hedgehog. The mechanisms controlling the spatiotemporal expression pattern of hedgehog genes are currently not understood. Cyclopia is observed in trilobite (tri) and knypek (kny) mutants with affected convergent extension of the embryonic axis during gastrulation. Here, we demonstrate that tri mutants show a high frequency of partial or complete cyclopia, kny mutants exhibit cyclopia infrequently, while kny m119 tri m209 double-mutant embryos have dramatically reduced convergent extension and are completely cyclopic. We analyzed the relationships between the convergent extension defect, the expression of hedgehog and Prechordal Plate genes, and the formation of cyclopia in kny m119 and tri m209 mutants. Our results correlate the cyclopia phenotype with the abnormal location of hh-expressing cells with respect to the optic primordium. We show that cyclopia in these mutants is not due to an incompetence of tri and kny cells to respond to Hedgehog signaling. Rather, it is a consequence of exceeding a critical distance (>40 ‐50 mm) between hedgehog-expressing cells and the prospective eye field. We hypothesize that at this distance, midline cells are not in an appropriate position to physically separate the eye field and that HH and other signals do not reach the appropriate target cells. Furthermore, tri and kny have overlapping functions in establishing proper alignment of the anterior neural Plate and midline cells expressing shh and twhh genes when the partitioning of the eye primordium takes place. © 1998 Academic Press
Thomas M Roberts - One of the best experts on this subject based on the ideXlab platform.
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morphogenesis of Prechordal Plate and notochord requires intact eph ephrin b signaling
Developmental Biology, 2001Co-Authors: Joanne Chan, John D Mably, Fabrizio C Serluca, Jaunian Chen, Nathaniel B Goldstein, Matthew C Thomas, Jennifer A Cleary, Caroline H Brennan, Mark C Fishman, Thomas M RobertsAbstract:Eph receptors and their ligands, the ephrins, mediate cell-to-cell signals implicated in the regulation of cell migration processes during development. We report the molecular cloning and tissue distribution of zebrafish transmembrane ephrins that represent all known members of the mammalian class B ephrin family. The degree of homology among predicted ephrin B sequences suggests that, similar to their mammalian counterparts, zebrafish B-ephrins can also bind promiscuously to several Eph receptors. The dynamic expression patterns for each zebrafish B-ephrin support the idea that these ligands are confined to interact with their receptors at the borders of their complementary expression domains. Zebrafish B-ephrins are expressed as early as 30% epiboly and during gastrula stages: in the germ ring, shield, Prechordal Plate, and notochord. Ectopic overexpression of dominant-negative soluble ephrin B constructs yields reproducible defects in the morphology of the notochord and Prechordal Plate by the end of gastrulation. Notably disruption of Eph/ephrin B signaling does not completely destroy structures examined, suggesting that cell fate specification is not altered. Thus abnormal morphogenesis of the Prechordal Plate and the notochord is likely a consequence of a cell movement defect. Our observations suggest Eph/ephrin B signaling plays an essential role in regulating cell movements during gastrulation.
Edit Hermesz - One of the best experts on this subject based on the ideXlab platform.
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a novel inducible element activated by contact with rathke s pouch is present in the regulatory region of the rpx hesx1 homeobox gene
Developmental Biology, 2003Co-Authors: Edit Hermesz, Lisa Williamssimons, Kathleen A MahonAbstract:Abstract Reciprocal inductive interactions are postulated to play a role in the determination and differentiation of the pituitary gland and the ventral hypothalamus. The homeobox gene Rpx/Hesxl is expressed during gastrulation in the anterior endoderm, Prechordal Plate, and the prospective cephalic neural Plate, and at later stages of development in Rathke’s pouch, the primordium of the pituitary. We have defined the regulatory elements necessary for proper spatial and temporal expression during development in transgenic mice using lacZ reporter genes. Proper spatial and temporal expression in the anterior endoderm Prechordal Plate and anterior neural Plate can be recapitulated with as little as 568 bp of upstream sequence and intragenic sequence containing the first exon and intron. Late-stage expression in Rathke’s pouch requires additional negative and positive regulatory elements. Interestingly, deletion analysis uncovered an element that directs transgene expression to a region of the hypothalamus that lies in direct contact with Rathke’s pouch. In vitro tissue recombination experiments have established that this expression is induced by contact with the pouch. We propose that this element may be present in other genes that normally respond to signals emanating from the pouch during the development of the hypothalamic–pituitary axis. The Rpx–lacZ transgenic mice provide a novel model system for the molecular dissection of inductive cell signaling during pituitary development.
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rpx a novel anterior restricted homeobox gene progressively activated in the Prechordal Plate anterior neural Plate and rathke s pouch of the mouse embryo
Development, 1996Co-Authors: Edit Hermesz, Susan Mackem, Kathleen A MahonAbstract:We have isolated a new murine homeobox gene, Rpx (for Rathke's pouch homeobox), that is dynamically expressed in the prospective cephalic region of the embryo during gastrulation. Early expression is seen in the anterior midline endoderm and Prechordal Plate precursor. Expression is subsequently activated in the overlying ectoderm of the cephalic neural Plate, suggesting that inductive contact with Rpx-expressing mesendoderm is required for this expression. Subsequently, Rpx expression is extinguished in the mesendoderm while remaining in the prospective prosencephalic region of the neural Plate ectoderm. Ultimately, transcripts become restricted to Rathke's pouch, the primordium of the pituitary, which is known to be derived from the most anterior ectoderm of the early embryo. Down regulation of Rpx in the pouch coincides with the differentiation of pituitary-specific cell types. Rpx is the earliest known marker for the pituitary primordium, suggestive of a role in the early determination or differentiation of the pituitary. Since Rpx is expressed so dynamically and so early in the anterior region of the embryo, and since its early expression domain is much more extensive than the region fated to form the pituitary, it is likely that Rpx is involved in the initial determination of the anterior (Prechordal) region of the embryo.