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The cellular and molecular basis of cnidarian neurogenesis
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International audience. Neurogenesis initiates during early development and it continues through laterdevelopmental stages and in adult animals to enable expansion, remodeling, andhomeostasis of the nervous system. The generation of nerve cells has been analyzedin detail in few bilaterian model organisms, leaving open many questionsabout the evolution of this process. As the sister group to bilaterians, cnidariansoccupy an informative phylogenetic position to address the early evolution ofcellular and molecular aspects of neurogenesis and to understand common principlesof neural development. Here we review studies in several cnidarian modelsystems that have revealed significant similarities and interesting differencescompared to neurogenesis in bilaterian species, and between different cnidariantaxa. Cnidarian neurogenesis is currently best understood in the sea anemoneNematostella vectensis, where it includes epithelial neural progenitor cells thatexpress transcription factors of the soxB and atonal families. Notch signaling regulatesthe number of these neural progenitor cells, achaete-scute and dmrt genesare required for their further development and Wnt and BMP signaling appearto be involved in the patterning of the nervous system. In contrast to many vertebratesand Drosophila, cnidarians have a high capacity to generate neuronsthroughout their lifetime and during regeneration. Utilizing this feature of cnidarianbiology will likely allow gaining new insights into the similarities and differencesof embryonic and regenerative neurogenesis. The use of differentcnidarian model systems and their expanding experimental toolkits will thuscontinue to provide a better understanding of evolutionary and developmentalaspects of nervous system formation.
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