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Kathryn V Anderson - One of the best experts on this subject based on the ideXlab platform.
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Dorsal-Ventral pattern formation in the Drosophila embryo: the role of zygotically active genes.
Current Topics in Developmental Biology, 2008Co-Authors: Edwin L. Ferguson, Kathryn V AndersonAbstract:Publisher Summary This chapter describes the zygotically active genes that specify the dorsal, the ventral pattern of the Drosophila embryo. These genes respond to a gradient of maternal positional information that defines their realms of activity, and they, in turn, fix these domains and may direct subsequent Patterning within these regions. Since these genes respond to and interpret maternal positional information, they are, in a sense, the dorsal–ventral counterparts of the anterior–posterior segmentation genes. Most of the zygotically expressed genes, known to be required for the dorsal–ventral Patterning in the embryo, are defined in the saturation mutagenesis experiments. From the cuticular phenotypes of the differentiated mutant embryos, genes that are required to allow the normal development of specific regions of the dorsal–ventral pattern are identified. The analysis of the mutant phenotypes and the molecular characterization of the regulation and activity of the zygotically required dorsal–ventral Patterning genes have provided important insights into the relationships between the cell position and differentiated fate. Three primary dorsal–ventral embryonic fields are defined in response to the maternal morphogen gradient. To establish these three fields, zygotically active dorsal–ventral Patterning genes are transcribed locally in response to define the thresholds of maternal morphogen, and, in addition, the activities of their gene products are also essential in defining the extents of the three fields.
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fusilli, an Essential Gene with a Maternal Role in Drosophila Embryonic Dorsal–Ventral Patterning
Developmental Biology, 2002Co-Authors: Noriko Wakabayashi-ito, Marcia P. Belvin, Dan A Bluestein, Kathryn V AndersonAbstract:Abstract The Drosophila fusilli (fus) gene was identified in a genetic screen for dominant maternal enhancers of an unusual dorsalizing mutation in the cactus gene, cactE10. While females that are heterozygous for the cactE10 allele produce embryos with wild-type dorsal–ventral Patterning, more than 90% of the embryos produced by females that are heterozygous for both cactE10 and the fus1 mutation are weakly dorsalized. Loss offusilli activity causes lethality during embryogenesis but not dorsal–ventral Patterning defects, indicating that fusilli is important in more than one developmental process. The fusilli gene encodes a protein with RNA binding motifs related to those in mammalian hnRNP F and H, which play roles in regulated RNA splicing. The fusilli RNA is not present in the oocyte or early embryo, and germ-line clones of fusilli mutations have no maternal effect on dorsal–ventral Patterning, indicating that the fusilli maternal effect does not depend on germ-line expression of the gene. Because the fusilli RNA is present in ovarian follicle cells, we propose that fusilli acts downstream of the Drosophila EGF receptor to control the biogenesis of follicle cell transcripts that control the initial dorsal–ventral asymmetry of the embryo.
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Positive and negative regulation of Easter, a member of the serine protease family that controls Dorsal-Ventral Patterning in the Drosophila embryo
Development, 1998Co-Authors: Sima Misra, Peter M. Hecht, Robert K. Maeda, Kathryn V AndersonAbstract:The sequential activities of four members of the trypsin family of extracellular serine proteases are required for the production of the ventrally localized ligand that organizes the Dorsal-Ventral pattern of the Drosophila embryo. The last protease in this sequence is encoded by easter, which is a candidate to activate proteolytically the ligand encoded by spatzle. Here, we demonstrate biochemically that the zymogen form of Easter is processed in vivo by a proteolytic cleavage event that requires the three upstream proteases. Processed Easter is present in extremely low amounts in the early embryo because it is rapidly converted into a high molecular mass complex, which may contain a protease inhibitor. Easter zymogen activation is also controlled by a negative feedback loop from Dorsal, the transcription factor at the end of the signaling pathway. Each of these regulated biochemical processes is likely to be important in generating the ventral-to-dorsal gradient of Dorsal protein that organizes cell fates in the early embryo.
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regulated nuclear import of rel proteins in the drosophila immune response
Nature, 1998Co-Authors: Louisa P Wu, Kathryn V AndersonAbstract:The Drosophila immune response uses many of the same components as the mammalian innate immune response, including signalling pathways that activate transcription factors of the Rel/NK-κB family1,2,3,4. In response to infection, two Rel proteins, Dif and Dorsal, translocate from the cytoplasm to the nuclei of larval fat-body cells1,2,5. The Toll signalling pathway, which controls dorsal–ventral Patterning during Drosophila embryogenesis6, regulates the nuclear import of Dorsal in the immune response2,7, but here we show that the Toll pathway is not required for nuclear import of Dif. Cytoplasmic retention of both Dorsal and Dif depends on Cactus protein; nuclear import of Dorsal and Dif is accompanied by degradation of Cactus. Therefore the two signalling pathways that target Cactus for degradation must discriminate between Cactus–Dorsal and Cactus–Dif complexes. We identified new genes that are required for normal induction of transcription of an antibacterial peptide during the immune response. Mutations in three of these genes prevent nuclear import of Dif in response to infection, and define new components of signalling pathways involving Rel. Mutations in three other genes cause constitutive nuclear localization of Dif; these mutations may block Rel protein activity by a novel mechanism.
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Genetic characterization of tube and pelle, genes required for signaling between Toll and dorsal in the specification of the Dorsal-Ventral pattern of the Drosophila embryo.
Genetics, 1993Co-Authors: Peter M. Hecht, Kathryn V AndersonAbstract:tube and pelle are two of the maternally transcribed genes required for Dorsal-Ventral Patterning of the Drosophila embryo. Females homozygous for strong alleles of tube or pelle produce embryos that lack all ventral and lateral embryonic pattern elements. By analyzing the phenotypes caused by 24 pelle and 9 tube alleles, we have defined characteristic features of the two genes, including the extremely variable phenotypes of a number of tube alleles and the antimorphic character of a number of pelle alleles. Double mutant females carrying dominant ventralizing alleles of Toll and dorsalizing alleles of tube or pelle produce dorsalized embryos, suggesting that tube and pelle act downstream of the membrane protein Toll in the signaling pathway that defines the embryonic Dorsal-Ventral pattern. Both tube and pelle are also important zygotically for survival: at least 30% of the zygotes lacking either tube or pelle die before adult stages, while 90-95% of tube(-) pelle(-) double mutant zygotes die. We discuss the phenotypes of tube-pelle double mutants in the context of whether the two proteins interact directly.
James Briscoe - One of the best experts on this subject based on the ideXlab platform.
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Homozygous Ft embryos are affected in floor plate maintenance and ventral neural tube Patterning.
Developmental Dynamics, 2005Co-Authors: Katrin Götz, James Briscoe, Ulrich RütherAbstract:Sonic hedgehog (Shh), produced by the notochord and floor plate cells of the neural tube, plays a critical role in organizing dorsal–ventral Patterning in the developing neural tube. We have investigated neural tube development in mouse embryos homozygous for the Fused toes (Ft) mutation, a deletion composed of genes of the Iroquois B (IrxB) cluster and of Fts, Ftm, and Fto. In Ft mutants starting from embryonic day 10.5, the floor plate appeared to degenerate and the notochord failed to undergo ventral displacement from the spinal cord. Consistent with the loss of Shh signalling from the floor plate, V3 neuron generation was reduced in Ft/Ft embryos and the domain of motor neuron generation expanded ventrally at the expense of V2 neurons. These data support the idea that Ft genes play an important role in dorsal–ventral Patterning of the neural tube acting to define the extent of motor neuron generation; moreover, the data reveal a previously unanticipated function for Ft genes in the maintenance of the floor plate. Developmental Dynamics 233:623–630, 2005. © 2005 Wiley-Liss, Inc.
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a gradient of gli activity mediates graded sonic hedgehog signaling in the neural tube
Genes & Development, 2005Co-Authors: Despina Stamataki, Fausto Ulloa, Stavroula V Tsoni, Anita Mynett, James BriscoeAbstract:During development, many signaling factors behave as morphogens, long-range signals eliciting different cellular responses according to their concentration. In ventral regions of the spinal cord, Sonic Hedgehog (Shh) is such a signal and controls the emergence, in precise spatial order, of distinct neuronal subtypes. The Gli family of transcription factors plays a central role in this process. Here we demonstrate that a gradient of Gli activity is sufficient to mediate, cell-autonomously, the full range of Shh responses in the neural tube. The incremental two- to threefold changes in Shh concentration, which determine alternative neuronal subtypes, are mimicked by similar small changes in the level of Gli activity, indicating that a gradient of Gli activity represents the intracellular correlate of graded Shh signaling. Moreover, our analysis suggests that cells integrate the level of signaling over time, consistent with the idea that signal duration, in addition to signal strength, is an important parameter controlling Dorsal-Ventral Patterning. Together, these data indicate that Shh signaling is transduced, without amplification, into a gradient of Gli activity that orchestrates Patterning of the ventral neural tube.
Despina Stamataki - One of the best experts on this subject based on the ideXlab platform.
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a gradient of gli activity mediates graded sonic hedgehog signaling in the neural tube
Genes & Development, 2005Co-Authors: Despina Stamataki, Fausto Ulloa, Stavroula V Tsoni, Anita Mynett, James BriscoeAbstract:During development, many signaling factors behave as morphogens, long-range signals eliciting different cellular responses according to their concentration. In ventral regions of the spinal cord, Sonic Hedgehog (Shh) is such a signal and controls the emergence, in precise spatial order, of distinct neuronal subtypes. The Gli family of transcription factors plays a central role in this process. Here we demonstrate that a gradient of Gli activity is sufficient to mediate, cell-autonomously, the full range of Shh responses in the neural tube. The incremental two- to threefold changes in Shh concentration, which determine alternative neuronal subtypes, are mimicked by similar small changes in the level of Gli activity, indicating that a gradient of Gli activity represents the intracellular correlate of graded Shh signaling. Moreover, our analysis suggests that cells integrate the level of signaling over time, consistent with the idea that signal duration, in addition to signal strength, is an important parameter controlling Dorsal-Ventral Patterning. Together, these data indicate that Shh signaling is transduced, without amplification, into a gradient of Gli activity that orchestrates Patterning of the ventral neural tube.
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dorsal ventral Patterning of the spinal cord requires gli3 transcriptional repressor activity
Genes & Development, 2002Co-Authors: Madelen Persson, Despina Stamataki, Elisabet Andersson, Johan Ericson, Jens Böse, Ulrich Rüther, Pascal Te Welscher, Josie BriscoeAbstract:Sonic hedgehog (Shh) plays a critical role in organizing cell pattern in the developing spinal cord. Gli proteins are thought to mediate Shh signaling, but their role in directing neural tube Patterning remains unclear. Here we identify a role for Gli3 transcriptional repressor activity in Patterning the intermediate region of the spinal cord that complements the requirement for Gli2 in ventral regions. Moreover, blocking all Gli responses results in a complete dorsalization of ventral spinal cord, indicating that in addition to the specific roles of Gli2 and Gli3 in the neural tube, there is functional redundancy between Gli proteins. Finally, analysis of Shh/Gli3 compound mutant mice substantiates the idea that ventral Patterning may involve a mechanism independent, or parallel, to graded Shh signaling. However, even in the absence of graded Shh signaling, Gli3 is required for the Dorsal-Ventral Patterning of the intermediate neural tube. Together these data raise the possibility that Gli proteins act as common mediators integrating Shh signals, and other sources of positional information, to control Patterning throughout the ventral neural tube.
Edwin L. Ferguson - One of the best experts on this subject based on the ideXlab platform.
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zen and the art of phenotypic maintenance: canalization of embryonic Dorsal-Ventral Patterning in Drosophila.
Fly, 2014Co-Authors: Jackie Gavin-smyth, Edwin L. FergusonAbstract:We recently uncovered a novel genetic mechanism that generates the phenotypic uniformity, or canalization, of BMP signaling and cell fate specification during Patterning of the Dorsal-Ventral (D/V) axis in D. melanogaster embryos. We went on to show that other wild-type Drosophila species lack this canalizing genetic circuitry and, consequently, have non-robust D/V Patterning. In this review, we propose molecular mechanisms that may give rise to stereotyped BMP signaling, and we identify an additional species that could have decanalized D/V Patterning. Extension of these analyses could in turn help explain why canalization is not a universal necessity for species survival.
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Dorsal-Ventral pattern formation in the Drosophila embryo: the role of zygotically active genes.
Current Topics in Developmental Biology, 2008Co-Authors: Edwin L. Ferguson, Kathryn V AndersonAbstract:Publisher Summary This chapter describes the zygotically active genes that specify the dorsal, the ventral pattern of the Drosophila embryo. These genes respond to a gradient of maternal positional information that defines their realms of activity, and they, in turn, fix these domains and may direct subsequent Patterning within these regions. Since these genes respond to and interpret maternal positional information, they are, in a sense, the dorsal–ventral counterparts of the anterior–posterior segmentation genes. Most of the zygotically expressed genes, known to be required for the dorsal–ventral Patterning in the embryo, are defined in the saturation mutagenesis experiments. From the cuticular phenotypes of the differentiated mutant embryos, genes that are required to allow the normal development of specific regions of the dorsal–ventral pattern are identified. The analysis of the mutant phenotypes and the molecular characterization of the regulation and activity of the zygotically required dorsal–ventral Patterning genes have provided important insights into the relationships between the cell position and differentiated fate. Three primary dorsal–ventral embryonic fields are defined in response to the maternal morphogen gradient. To establish these three fields, zygotically active dorsal–ventral Patterning genes are transcribed locally in response to define the thresholds of maternal morphogen, and, in addition, the activities of their gene products are also essential in defining the extents of the three fields.
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spatial bistability of dpp receptor interactions during drosophila dorsal ventral Patterning
Nature, 2005Co-Authors: Yuchiun Wang, Edwin L. FergusonAbstract:In many developmental contexts, a locally produced morphogen specifies positional information by forming a concentration gradient over a field of cells1. However, during embryonic dorsal–ventral Patterning in Drosophila, two members of the bone morphogenetic protein (BMP) family, Decapentaplegic (Dpp) and Screw (Scw), are broadly transcribed but promote receptor-mediated signalling in a restricted subset of expressing cells2,3,4. Here we use a novel immunostaining protocol to visualize receptor-bound BMPs and show that both proteins become localized to a sharp stripe of dorsal cells. We demonstrate that proper BMP localization involves two distinct processes. First, Dpp undergoes directed, long-range extracellular transport. Scw also undergoes long-range movement, but can do so independently of Dpp transport. Second, an intracellular positive feedback circuit promotes future ligand binding as a function of previous signalling strength. These data elicit a model in which extracellular Dpp transport initially creates a shallow gradient of BMP binding that is acted on by positive intracellular feedback to produce two stable states of BMP–receptor interactions, a spatial bistability in which BMP binding and signalling capabilities are high in dorsal-most cells and low in lateral cells.
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Spatial bistability of Dpp–receptor interactions during Drosophila dorsal–ventral Patterning
Nature, 2005Co-Authors: Yuchiun Wang, Edwin L. FergusonAbstract:In many developmental contexts, a locally produced morphogen specifies positional information by forming a concentration gradient over a field of cells1. However, during embryonic dorsal–ventral Patterning in Drosophila, two members of the bone morphogenetic protein (BMP) family, Decapentaplegic (Dpp) and Screw (Scw), are broadly transcribed but promote receptor-mediated signalling in a restricted subset of expressing cells2,3,4. Here we use a novel immunostaining protocol to visualize receptor-bound BMPs and show that both proteins become localized to a sharp stripe of dorsal cells. We demonstrate that proper BMP localization involves two distinct processes. First, Dpp undergoes directed, long-range extracellular transport. Scw also undergoes long-range movement, but can do so independently of Dpp transport. Second, an intracellular positive feedback circuit promotes future ligand binding as a function of previous signalling strength. These data elicit a model in which extracellular Dpp transport initially creates a shallow gradient of BMP binding that is acted on by positive intracellular feedback to produce two stable states of BMP–receptor interactions, a spatial bistability in which BMP binding and signalling capabilities are high in dorsal-most cells and low in lateral cells.
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Spatially Restricted Activation of the SAX Receptor by SCW Modulates DPP/TKV Signaling in Drosophila Dorsal–Ventral Patterning
Cell, 1998Co-Authors: Jeffrey L. Neul, Edwin L. FergusonAbstract:Abstract Dorsal–ventral Patterning within the embryonic ectoderm of Drosophila requires two TGFβ ligands, DPP and SCW, and two type I TGFβ receptors, TKV and SAX. In embryos lacking dpp signaling, increasing the level of TKV activity promotes progressively more dorsal cell types, while activation of SAX alone has no phenotypic consequences. However, SAX activity synergizes with TKV activity to promote dorsal development. Functional experiments suggest the two receptors have different ligands: DPP acts through TKV, and SCW acts through SAX. Furthermore, SOG, a negative regulator of this Patterning process, preferentially blocks SCW activity. We propose that spatial regulation of the SAX pathway modulates TKV signaling to create positional information over the embryonic ectoderm.
Xia Huang - One of the best experts on this subject based on the ideXlab platform.
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the cycloidea radialis module regulates petal shape and pigmentation leading to bilateral corolla symmetry in torenia fournieri linderniaceae
New Phytologist, 2017Co-Authors: Shihao Su, Junqing Xiao, Keyuan Jiao, Qincheng Peng, Xiaohe Hu, Ziqing Ye, Wei Xiao, Na Wang, Xia HuangAbstract:Summary The diverse pigmentation patterns of flower corollas probably result from pollinator-mediated selection. Previous studies demonstrated that R2R3-MYB factors may have been recruited in the regulation of corolla pigmentation. However, how R2R3-MYBs became so diverse in their regulation of different pigmentation patterns remains unclear. Here, we studied a Lamiales species, Torenia fournieri, which has elaborate zygomorphic flowers with dorsal–ventral asymmetries in corolla pigmentation. We found recent gene duplication events in CYCLOIDEA-like (CYC-like) and RADIALIS-like (RAD-like) genes, and functionally analyzed three dorsal-specific expression factors: TfCYC1, TfCYC2, and TfRAD1. We found that the CYC–RAD module coordinates petal shape and corolla pigmentation, as ectopic expression of TfCYC2 or TfRAD1 disrupted the asymmetric corolla pigmentation pattern and produced strongly dorsalized flowers. Dorsal petal identity was lost when TfCYC2 was down-regulated or when TfRAD1 was knocked out. In T. fournieri, the diversified CYC and RAD genes have evolved regulatory loops, and TfCYC2 binds directly to the regulatory regions of an R2R3-MYB factor gene, TfMYB1, which might lead to its asymmetric expression and ultimately establish the asymmetric pigmentation pattern. These findings support the existence of a regulatory module that integrates dorsal–ventral Patterning and asymmetric corolla pigmentation in T. fournieri.