Expression of a Delta homologue 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 different tissues in Drosophila 1–8 . During neurogenesis in particular, neural precursors, by expressing Delta , inhibit neighbouring Notch -expressing cells from becoming committed to a neural fate 5,9,10 . Vertebrates 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 cells are being born and their fates decided. Our data from the chick, combined with parallel evidence from Xenopus 15 , suggest that both the Delta/ Notch signalling mechanism and its role in neurogenesis have been conserved in vertebrates.