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The calcium (Ca2+) signaling pathways have crucial roles in development from fertilization through differentiation to organogenesis. In the nervous system, Ca2+ signals are important regulators for various neuronal functions, including formation and maturation of neuronal circuits and long-term memory. However, Ca2+ signals are also involved in the earliest steps of neurogenesis including neural induction, differentiation of neural progenitors into neurons, and the neuro-glial switch. This review examines when and how Ca2+ signals are generated during each of these steps with examples taken from in vivo studies in vertebrate embryos and from in vitro assays using embryonic and neural stem cells (NSCs). During the early phases of neurogenesis few investigations have been performed to study the downstream targets of Ca2+ which posses EF-hand in their structure. This opens an entire field of research. We also discuss the highly specific nature of the Ca2+ signaling pathway and its interaction with the other signaling pathways involved in early neural development.

We have previously shown that an increase in intracellular Ca 2؉ is both necessary and sufficient to commit ectoderm to a neural fate in Xenopus embryos. However, the relationship between this Ca 2؉ increase and the expression of early neural genes has yet to be defined. Using a subtractive cDNA library between untreated and caffeine-treated animal caps, i.e., control ectoderm and ectoderm induced toward a neural fate by a release of Ca 2؉ , we have isolated the arginine N-methyltransferase, xPRMT1b, a Ca 2؉ -induced target gene, which plays a pivotal role in this process. First, we show in embryo and in animal cap that xPRMT1b expression is Ca 2؉ -regulated. Second, overexpression of xPRMT1b induces the expression of early neural genes such as Zic3. Finally, in the whole embryo, antisense approach with morpholino oligonucleotide against xPRMT1b impairs neural development and in animal caps blocks the expression of neural markers induced by a release of internal Ca 2؉ . Our results implicate an instructive role of an enzyme, an arginine methyltransferase protein, in the embryonic choice of determination between epidermal and neural fate. The results presented provide insights by which a Ca 2؉ increase induces neural fate.calcium ͉ neural induction ͉ protein methyltransferase ͉ Xenopus