Expression analysis ofjagged genes in zebrafish embryos (original) (raw)
Related papers
The role of Suppressor of Hairless in Notch mediated signalling during zebrafish somitogenesis
Mechanisms of Development, 2003
Suppressor of Hairless (Su(H)) codes for a protein that interacts with the intracellular domain of Notch to activate the target genes of the Delta -Notch signalling pathway. We have cloned the zebrafish homologue of Su(H) and have analysed its function by morpholino mediated knockdown. While there are at least four notch and four delta homologues in zebrafish, there appears to be only one complete Su(H) homologue. We have analysed the function of Su(H) in the somitogenesis process and its influence on the expression of notch pathway genes, in particular her1, her7, deltaC and deltaD. The cyclic expression of her1, her7 and deltaC in the presomitic mesoderm is disrupted by the Su(H) knockdown mimicking the expression of these genes in the notch1a mutant deadly seven. deltaD expression is similarly affected by Su(H) knockdown like deltaC but shows in addition an ectopic expression in the developing neural tube. The inactivation of Su(H) in a fss/tbx24 mutant background leads furthermore to a clear breakdown of cyclic her1 and her7 expression, indicating that the Delta -Notch pathway is required for the creation of oscillation and not only for the synchronisation between neighbouring cells. The strongest phenotypes in the Su(H) knockdown embryos show a loss of all somites posterior to the first five to seven ones. This phenotype is stronger than the known amorphic phenotypes for notch1 (des) or deltaD (aei) in zebrafish, but mimicks the knockout phenotype of RBP-Jk gene in the mouse, which is the homologue of Su(H). This suggests that there is some functional redundancy among the Notch and Delta genes. This fact that the first five to seven somites are only weakly affected by Su(H) knockdown indicates that additional genetic pathways may be active in the specification of the most anterior somites. q
Journal of Neuroscience, 2011
Sensory systems are specialized to recognize environmental changes. Sensory organs are complex structures composed of different cell types, including neurons and sensory receptor cells, and how these organs are generated is an important question in developmental neurobiology. The posterior lateral line (pLL) is a simple sensory system in fish and amphibians that detects changes in water motion. It consists of neurons and sensory receptor hair cells, both of which are derived from the cranial ectoderm preplacodal region. However, it is not clearly understood how neurons and the sensory epithelium develop separately from the same preplacodal progenitors. We found that the numbers of posterior lateral line ganglion (pLLG) neurons, which are marked by neurod expression, increased in embryos with reduced Notch activity, but the forced activation of Notch reduced their number, suggesting that Notch-mediated lateral inhibition regulates the pLLG cell fate in zebrafish. By fate-mapping analysis, we found that cells adjacent to the pLLG neurons in the pre-pLL placodal region gave rise to the anterior part of the pLL primordium (i.e., sensory epithelial progenitor cells), and that the choice of cell fate between pLLG neuron or pLL primordium was regulated by Notch signaling. Since Notch signaling also affects hair cell fate determination at a later stage, our study suggests that Notch signaling has dual, time-dependent roles in specifying multiple cell types during pLL development.
Development, 2004
Alterations of the Delta/Notch signalling pathway cause multiple morphogenetic abnormalities in somitogenesis, including defects in intersomitic boundary formation and failure in maintenance of somite regularity. Notch signalling has been implicated in establishing the anteroposterior polarity within maturing somites and in regulating the activity of a molecular segmentation clock operating in the presomitic mesoderm. The pleiotropy of Notch signalling obscures the roles of this pathway in different steps of somitogenesis. One possibility is that distinct Notch effectors mediate different aspects of Notch signalling. In this study,we focus on two zebrafish Notch-dependent hairy/Enhancer-of-split-related transcription factors, Her6 and Her4, which are expressed at the transition zone between presomitic mesoderm and the segmented somites. The results of overexpression/gain-of-function and of morpholino-mediated loss-of-function experiments show that Her6 and Her4 are Notch signalling ...
Developmental Biology, 2005
The Tü bingen large-scale zebrafish genetic screen completed in 1996 identified a set of five genes required for orderly somite segmentation. Four of them have been molecularly identified and three were found to code for components of the Notch pathway, which are required for the coordinated oscillation of gene expression, known as the segmentation clock, in the presomitic mesoderm (PSM). Here, we show that the final member of the group, beamter (bea), codes for the Notch ligand DeltaC, and we present and characterize two new alleles, including one allele encoding for a protein truncated in the 7th EGF repeat and an allele deleting only the DSL domain which was previously shown to be necessary for ligand function. Interestingly however, when we over-express any of the mutant deltaC mRNAs, we observe antimorphic effects on both hindbrain neurogenesis and hypochord formation. Expression of bea/deltaC oscillates in the PSM, and a triple fluorescent in situ analysis of its oscillation in relation to that of other oscillating genes in the PSM reveals differences in subcellular localization of the oscillating mRNAs in individual cells in different oscillation phases. Mutations in aei/deltaD and bea/deltaC differ in the way they disrupt the oscillating expression of her1 and deltaC. Furthermore, we find that the double mutants have significantly stronger defects in hypochord formation but not in somitogenesis or hindbrain neurogenesis, indicating genetically that the two delta's may function either semi-redundantly or distinctly, depending upon context. D
Developmental Biology, 2007
The different cell types of the vertebrate pancreas arise asynchronously during organogenesis. Beta-cells producing insulin, alpha-cells producing glucagon, and exocrine cells secreting digestive enzymes differentiate sequentially from a common primordium. Notch signaling has been shown to be a major mechanism controlling these cell-fate choices. So far, the pleiotropy of Delta and Jagged/Serrate genes has hindered the evaluation of the roles of specific Notch ligands, as the phenotypes of knock-out mice are lethal before complete pancreas differentiation. Analyses of gene expression and experimental manipulations of zebrafish embryos allowed us to determine individual contributions of Notch ligands to pancreas development. We have found that temporally distinct phases of both endocrine and exocrine cell type specification are controlled by different delta and jagged genes. Specifically, deltaA knock-down embryos lack alpha cells, similarly to mib (Delta ubiquitin ligase) mutants and embryos treated with DAPT, a gamma secretase inhibitor able to block Notch signaling. Conversely, jagged1b morphants develop an excess of alpha-cells. Moreover, the pancreas of jagged2 knock-down embryos has a decreased ratio of exocrine-to-endocrine compartments. Finally, overexpression of Notch1a-intracellular-domain in the whole pancreas primordium or specifically in beta-cells helped us to refine a model of pancreas differentiation in which cells exit the precursor state at defined stages to form the pancreatic cell lineages, and, by a feedback mediated by different Notch ligands, limit the number of other cells that can leave the precursor state.
Su(H) mediated Notch signalling and the role of different her genes during zebrafish somitogenesis
2006
4.2 her11 is involved in the somitogenesis clock in zebrafish 4.2.1 her11 is synexpressed with her1 and her7 stripes in the intermediate and anterior PSM 4.2.2 Delta-Notch signalling is required to regulate her11 expression in the PSM 4.2.3 Striped expression of her11 in the PSM is cooperatively regulated by Her1 and Her7 4.2.4 The regulation of cyclic hey1 expression in the PSM 4.2.5 A role for her11 and hey1 in her1 and her7 stripe regulation? 4.3 her12 and its role during zebrafish somitogenesis 4.3.1 her12 is dynamically expressed during zebrafish somitogenesis 4.3.2 her12 is differentially regulated by Delta-Notch signalling, her7 and her11 4.3.3 The function of her12 during somitogenesis 4.3.3.1 her12 misexpression 4.3.3.2 her12 morpholino knockdowns 4.4 her1 and her13.2 play a combinatorial role in anterior somite formation in zebrafish 4.4.1 Anterior somites require her1 and her13.2 function 4.4.2 Anterior somites and the breakdown of the oscillator 4.4.3 Cyclic her gene expression is crucial for anterior somites 5. Discussion 5.1 The role of Suppressor of Hairless in Notch mediated signalling during zebrafish somitogenesis 5.1.1 Danio Su(H) is essential for zebrafish development 5.1.2 Notch signalling in the PSM 5.1.3 Cyclic gene expression during early somitogenesis and the formation of the first somites 5.2 her11 is involved in the somitogenesis clock in zebrafish 5.2.1 Expression compartments of mouse hes7 homologues in zebrafish 5.2.2 Differences in the regulation of her/hey genes through the D-N pathway 5.2.3 The involvement of her11 in cyclic gene expression 5.3 her12 and its role during zebrafish somitogenesis 5.3.1 A complex her12 expression during somitogenesis and its regulation though Delta-Notch Table of Contents 5.3.2 A role for her12 in cyclic gene expression and somite border formation? 5.4 her1 and her13.2 play a combinatorial role in anterior somite formation in zebrafish 5.4.1 Combined "clock and wavefront" signalling for anterior somites? 5.4.2 Early oscillation and anterior borders 5.4.3 A function for mHes6 homologues during somitogenesis only in lower vertebrates? 5.5 Zebrafish somitogenesis-a rather derived mode? 6. References 88
Sequence and embryonic expression of deltaC in the zebrafish
Mechanisms of Development, 2000
Four genes ± deltaA, deltaB, deltaC and deltaD ± coding for homologues of the Notch ligand Delta have been discovered in zebra®sh . We report here the cDNA sequence and expression pattern of deltaC. Its closest relatives are deltaB and Xenopus X-Delta-2. Unlike deltaA, deltaB, and deltaD, deltaC is not expressed in the majority of nascent primary neurons; but it is strongly expressed in the early retina, where it precedes other delta genes. It is also expressed in cranial ganglia, in sensory epithelia including ear and lateral line, and in scattered epidermal cells. In the mesoderm, expression is visible by 50% epiboly; it is seen subsequently in the tail bud, in stripes in the presomitic mesoderm and in the posterior half of each somite. There is expression also in notochord, blood vessels and pronephros. q
Notch signaling can regulate endoderm formation in zebrafish
Developmental Dynamics, 2004
Early in vertebrate development, the processes of gastrulation lead to the formation of the three germ layers: ectoderm, mesoderm, and endoderm. The mechanisms leading to the segregation of the endoderm and mesoderm are not well understood. In mid-blastula stage zebrafish embryos, single marginal cells can give rise to both endoderm and mesoderm (reviewed by Warga and Stainier [2002] The guts of endoderm formation. In: Solnica-Krezel L, editor. Pattern formation in zebrafish. Berlin: Springer-Verlag. p 28–47). By the late blastula stage, however, single marginal cells generally give rise to either endoderm or mesoderm. To investigate this segregation of the blastoderm into cells with either endodermal or mesodermal fates, we analyzed the role of Notch signaling in this process. We show that deltaC, deltaD, and notch1 are expressed in the marginal domain of blastula stage embryos and that this expression is dependent on Nodal signaling. Activation of Notch signaling from an early stage leads to a reduction of endodermal cells, as assessed by sox17 and foxA2 expression. We further find that this reduction in endoderm formation by the activation of Notch signaling is preceded by a reduction in the expression of bonnie and clyde (bon) and faust/gata5, two genes necessary for endoderm formation (Reiter et al. [1999] Genes Dev 13:2983–2995; Reiter et al. [2001] Development 128:125–135; Kikuchi et al. [2001] Genes Dev 14:1279–1289). However, activation of Notch signaling in bon mutant embryos leads to a further reduction in endodermal cells, also arguing for a bon-independent role for Notch signaling in endoderm formation. Altogether, these results suggest that Notch signaling plays a role in the formation of the endoderm, possibly in its segregation from the mesoderm. Developmental Dynamics 229:756–762, 2004. © 2004 Wiley-Liss, Inc.
Jagged2: A Serrate-like Gene Expressed during Rat Embryogenesis
Developmental Biology, 1996
DSL (Delta, Serrate, Lag-2) ligands activate Notch signaling and thereby regulate the differentiation of many different cell types during development. We have isolated a novel Serrate-like gene, Jagged2, whose amino acid sequence and expression pattern during rat embryogenesis suggest that it functions as a ligand for Notch. In contrast to previously described DSL ligands for Notch, Jagged2 is not widely expressed in the developing central nervous system. However, Jagged2 and Notch1 are coexpressed in the apical ectodermal ridge (AER), suggesting a role for this ligand-receptor pair in limb development. Furthermore, unlike Jagged1, Jagged2 is coexpressed with Notch in the developing thymus, where it may induce Notch signaling to direct T-cell fate. Our data are consistent with the idea that the diversity of cell types regulated by Notch signaling is a consequence of activation of unique Notch isoforms by different DSL ligands.