Induction and patterning of the neural plate

The development of the vertebrate nervous system begins when ectoderm on the dorsal surface of the embryo is induced by the organizer to form the neural plate. During neural induction, the organizer appears to specify a region of ectoderm that forms neural tissue, to induce morphogenesis within a region of ectoderm called the notoplate, and to pattern the neural plate to form different parts of the nervous system along the dorsal-ventral (D- V) and anterior-posterior axis (A-P). Recent studies have shown that all of these events can proceed at least partially via signals that pass from the organizer into ectoderm by so-called planar induction. Recent studies have also addressed the molecular signals that potential underlie the generation of the neural A-P axis. Although there is good evidence that polypeptide growth factors can induce different mesodermal cell types, it is not clear as yet whether these molecules provide A-P positional information for dorsal tissues, including the nervous system. Retinoic acid has also been shown to have the properties of a patterning signal and may act via homeobox genes, but the role of endogenous retinoic acid has not been established. In addition, we discuss the induction of the most anterior end of the neural plate, which is perhaps the least understood aspect of neural induction. With the recent isolation of vertebrate forebrain specific markers, the induction of this part of the nervous system can be explored in future experiments. © 1992.