共查询到20条相似文献,搜索用时 31 毫秒
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Regulation of proneural gene expression and cell fate during neuroblast segregation in the Drosophila embryo. 总被引:9,自引:0,他引:9
The Drosophila embryonic central nervous system develops from sets of progenitor neuroblasts which segregate from the neuroectoderm during early embryogenesis. Cells within this region can follow either the neural or epidermal developmental pathway, a decision guided by two opposing classes of genes. The proneural genes, including the members of the achaete-scute complex (AS-C), promote neurogenesis, while the neurogenic genes prevent neurogenesis and facilitate epidermal development. To understand the role that proneural gene expression and regulation play in the choice between neurogenesis and epidermogenesis, we examined the temporal and spatial expression pattern of the achaete (ac) regulatory protein in normal and neurogenic mutant embryos. The ac protein is first expressed in a repeating pattern of four ectodermal cell clusters per hemisegment. Even though 5-7 cells initially express ac in each cluster, only one, the neuroblast, continues to express ac. The repression of ac in the remaining cells of the cluster requires zygotic neurogenic gene function. In embryos lacking any one of five genes, the restriction of ac expression to single cells does not occur; instead, all cells of each cluster continue to express ac, enlarge, delaminate and become neuroblasts. It appears that one key function of the neurogenic genes is to silence proneural gene expression within the nonsegregating cells of the initial ectodermal clusters, thereby permitting epidermal development. 相似文献
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Pierre Kerner Elena Simionato Martine Le Gouar Michel Vervoort 《Evolution & development》2009,11(5):513-524
SUMMARY The molecular mechanisms underlying the formation and patterning of the nervous system are relatively poorly understood for lophotrochozoans (like annelids) as compared with ecdysozoans (especially Drosophila ) and deuterostomes (especially vertebrates). Therefore, we have undertaken a candidate gene approach to study aspects of neurogenesis in a polychaete annelid Platynereis dumerilii . We determined the spatiotemporal expression for Platynereis orthologs of four genes ( SoxB, Churchill, prospero / Prox , and SoxC) known to play key roles in vertebrate neurogenesis. During Platynereis development, SoxB is expressed in the neuroectoderm and its expression switches off when committed neural precursors are formed. Subsequently, Prox is expressed in all differentiating neural precursors in the central and peripheral nervous systems. Finally, SoxC and Churchill are transcribed in patterns consistent with their involvement in neural differentiation. The expression patterns of Platynereis SoxB and Prox closely resemble those in Drosophila and vertebrates—this suggests that orthologs of these genes play similar neurogenic roles in all bilaterians. Whereas Platynereis SoxC , like its vertebrate orthologs, plays a role in neural cell differentiation, related genes in Drosophila do not appear to be involved in neurogenesis. Finally, conversely to Churchill in Platynereis , vertebrate orthologs of this gene are expressed during neuroectoderm formation, but not later during nerve cell differentiation; in the insect lineage, homologs of these genes have been secondarily lost. In spite of such instances of functional divergence or loss, the present study shows conspicuous similarities in the genetic control of neurogenesis among bilaterians. These commonalities suggest that key features of the genetic program for neurogenesis are ancestral to bilaterians. 相似文献
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The notch signaling pathway is required to specify muscle progenitor cells in Drosophila. 总被引:7,自引:0,他引:7
B Giebel 《Mechanisms of development》1999,86(1-2):137-145
Organization and function of the Notch signaling pathway in Drosophila are best understood with respect to its role in the process of selection of neural progenitor cells. However, there is evidence that, besides neurogenesis, the Notch signaling pathway is involved in several other developmental processes, one of which is the selection of muscle progenitor cells. Thus, the number of these cells is increased in neurogenic mutants, and it has been proposed that muscle progenitor cells are selected from clusters of equivalent cells expressing genes of the achaete-scute gene complex (AS-C). Here, I present evidence for the participation of additional elements of the Notch signaling pathway in myogenesis. Gal4 mediated expression of a Notch variant, E(spl) and Hairless shows that the selection of muscle progenitor cells obeys principles apparently identical to those acting at the selection of neural progenitor cells. 相似文献
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Wheeler SR Carrico ML Wilson BA Brown SJ Skeath JB 《Development (Cambridge, England)》2003,130(18):4373-4381
The study of achaete-scute (ac/sc) genes has recently become a paradigm to understand the evolution and development of the arthropod nervous system. We describe the identification and characterization of the ac/sc genes in the coleopteran insect species Tribolium castaneum. We have identified two Tribolium ac/sc genes - achaete-scute homolog (Tc-ASH) a proneural gene and asense (Tc-ase) a neural precursor gene that reside in a gene complex. Focusing on the embryonic central nervous system we find that Tc-ASH is expressed in all neural precursors and the proneural clusters from which they segregate. Through RNAi and misexpression studies we show that Tc-ASH is necessary for neural precursor formation in Tribolium and sufficient for neural precursor formation in Drosophila. Comparison of the function of the Drosophila and Tribolium proneural ac/sc genes suggests that in the Drosophila lineage these genes have maintained their ancestral function in neural precursor formation and have acquired a new role in the fate specification of individual neural precursors. Furthermore, we find that Tc-ase is expressed in all neural precursors suggesting an important and conserved role for asense genes in insect nervous system development. Our analysis of the Tribolium ac/sc genes indicates significant plasticity in gene number, expression and function, and implicates these modifications in the evolution of arthropod neural development. 相似文献
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Comparative analysis of neurogenesis in the myriapod Glomeris marginata (Diplopoda) suggests more similarities to chelicerates than to insects 总被引:1,自引:0,他引:1
Molecular data suggest that myriapods are a basal arthropod group and may even be the sister group of chelicerates. To find morphological indications for this relationship we have analysed neurogenesis in the myriapod Glomeris marginata (Diplopoda). We show here that groups of neural precursors, rather than single cells as in insects, invaginate from the ventral neuroectoderm in a manner similar to that in the spider: invaginating cell groups arise sequentially and at stereotyped positions in the ventral neuroectoderm of Glomeris, and all cells of the neurogenic region seem to enter the neural pathway. Furthermore, we have identified an achaete-scute, a Delta and a Notch homologue in GLOMERIS: The genes are expressed in a pattern similar to the spider homologues and show more sequence similarity to the chelicerates than to the insects. We conclude that the myriapod pattern of neural precursor formation is compatible with the possibility of a chelicerate-myriapod sister group relationship. 相似文献
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Jose A. Campos-Ortega 《Molecular neurobiology》1995,10(2-3):75-89
The neurogenic ectoderm ofDrosophila melanogaster consists of the ventral neuroectoderm and the procephalic neuroectoderm. It is hypothesized that epidermal and central neural
progenitor cells separate from each other in three steps: conference on the neuroectodermal cells the capability of producing
neural or epidermal progenies, separation of the two classes of progenitor cells, and specification of particular types of
neuroblasts and epidermoblasts. Separation of neuroblasts and epidermoblasts in controlled by proneural and neurogenic genes.Delta andNotch serve as mediators of direct protein-protein interactions. E(spl)-C inhibits neurogenesis, creating epidermal cells. The achaete-scute complex (AS-C) controls the commitment of nonoverlapping
populations of neuroblasts and leads the development of neuroectodermal cells as neuroblasts. 相似文献
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Wang L Zhang ZG Gregg SR Zhang RL Jiao Z LeTourneau Y Liu X Feng Y Gerwien J Torup L Leist M Noguchi CT Chen ZY Chopp M 《The Journal of biological chemistry》2007,282(44):32462-32470
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Cau E Gradwohl G Casarosa S Kageyama R Guillemot F 《Development (Cambridge, England)》2000,127(11):2323-2332
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During neurogenesis in Drosophila, ectodermal cells are endowed with the capacity to become neuronal precursors. Following their selection, these cells initiate neuronal lineage development and differentiation. The processes of neuronal precursor specification and neuronal lineage development require the activities of several groups of genes functioning in a complex, hierarchical regulatory network. Whereas the proneural genes promote neurogenic potential, neurogenic genes restrict the acquisition of this identity to a subset of ectodermal cells. Following their selection, these cells express the pan neural neuronal precursor genes and a set of neuronal lineage identity genes. While lineage identity genes allow the various lineages to acquire specific identities, neuronal precursor genes presumably regulate functional and developmental characteristics common to all neuronal precursor cells. © 1996 Wiley-Liss, Inc. 相似文献
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Gazave E Lapébie P Renard E Bézac C Boury-Esnault N Vacelet J Pérez T Manuel M Borchiellini C 《Development genes and evolution》2008,218(9):479-489
Data on nonbilaterian animals (sponges, cnidarians, and ctenophores) have suggested that Antennapedia (ANTP) class homeobox genes played a crucial role in the early diversification of animal body plans. Estimates of ancestral gene diversity within this important class of developmental regulators have been mostly based on recent analyses of the complete genome of a demosponge species, leading to the proposal that all ANTP families found in nonsponges animals (eumetazoans) derived from an ancestral "proto-NK" six-gene cluster. However, a single sponge species cannot reveal ancestral metazoan traits, in particular because lineage-specific gene duplications or losses are likely to have occurred during the long history of the Porifera. We thus looked for ANTP genes by degenerate polymerase chain reaction search in five species belonging to the Homoscleromorpha, a sponge lineage recently phylogenetically classified outside demosponges and characterized by unique histological features. We identified new genes of the ANTP class called HomoNK. Our phylogenetic analyses placed HomoNK (without significant support) close to the NK6 and NK7 families of cnidarian and bilaterian ANTP genes and did not recover the monophyly of the proposed "proto-NK" cluster. Our expression analyses of the HomoNK gene OlobNK in adult Oscarella lobularis showed that this gene is a strict marker of choanocytes, the most typical sponge cell type characterized by an apical flagellum surrounded by a collar of microvilli. These results are discussed in the light of the predominant neurosensory expression of NK6 and NK7 genes in bilaterians and of the recent proposal that choanocytes could be the sponge homologs of sensory cells. 相似文献
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《Cell cycle (Georgetown, Tex.)》2013,12(7):1263-1264
EGFL7 drives the formation of neurons from neural stem cells. In the embryonic and adult brain this process is essential for neurogenesis and homeostasis of the nervous system. The function of adult neurogenesis is not fully understood but maybe it supports life-long learning and brain repair after injuries such as stroke. The transition of neural stem cells into mature neurons is tightly regulated. One of the essential signaling pathways governing this process is the Notch pathway, which controls metazoan development. In a recent publication, we identified a novel non-canonical Notch ligand, EGFL7, and described its impact on neural stem cells.1 We explored the molecular mechanisms, which this molecule affects to regulate the self-renewal capacity of neural stem cells and to promote their differentiation into neurons. In this review, we discuss the implications of our findings for adult neurogenesis and illustrate the potential of EGFL7 to serve as an agent to increase neurogenesis and the self-renewal potential of the brain. 相似文献
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