EXPRESSION OF A DELTA-HOMOLOG IN PROSPECTIVE NEURONS IN THE CHICK

THE product of the Delta gene, acting as ligand, and that of the Notch gene, acting as receptor, are key components in a lateral-inhibition signalling pathway that regulates the detailed patterning of many diff erent tissues in Drosophila(1-8). During neurogenesis in particular, n eural precursors, by expressing Delta, inhibit neighbouring Notch-expr essing cells from becoming committed to a neural fate(5,9,10). Vertebr ates are known to have several Notch genes(11-14), but their functions are unclear and their ligands hitherto unidentified. Here we identify and describe a chick Delta homologue, C-Delta-1. We show that C-Delta -1 is expressed in prospective neurons during neurogenesis, as new cel ls are being born and their fates decided. Our data from the chick, co mbined with parallel evidence from Xenopus(15), suggest that both the Delta/Notch signalling mechanism and its role in neurogenesis have bee n conserved in vertebrates.