PRIMARY NEUROGENESIS IN XENOPUS EMBRYOS REGULATED BY A HOMOLOG OF THEDROSOPHILA NEUROGENIC GENE-DELTA

X-Delta-1, a Xenopus homologue of the Drosophila Delta gene, is expres sed in the early embryonic nervous system in scattered cells that appe ar to be the prospective primary neurons. Ectopic X-Delta-1 activity i nhibits production of primary neurons and interference with endogenous X-Delta-1 activity results in overproduction of primary neurons. Thes e results indicate that the X-Delta-1 protein mediates lateral inhibit ion delivered by prospective neurons to adjacent cells, and that commi tment to a neural fate in vertebrates is regulated by Delta-Notch sign alling as in Drosophila.