ISOLATION OF A NOVEL CHICK HOMOLOG OF SERRATE AND ITS COEXPRESSION WITH C-NOTCH-1 IN CHICK DEVELOPMENT

Intercellular signaling mediated by the transmembrane proteins, Notch as receptor and its ligands, Delta and Serrate, plays essential roles in the developmental fate decision of many cell types in Drosophila. T he Notch genes are highly conserved both in invertebrates and in verte brates, suggesting that Notch pathway regulates cell fate decisions du ring vertebrates development. Notch, Delta and Serrate homologs in chi cken have been cloned (Henrique et al., Nature 375: 787-790, 1995; Mya t ef al., Dev. Biol. 174: 233-247, 1996). We isolated a novel chick ho molog of Drosophila Serrate, named C-Serrate-2, and examined its expre ssion patterns during the early chick development using whole-mount in situ hybridization. C-Serrate-2 transcripts were detected in several tissues including the forebrain, the myotome and the apical ectodermal ridge (AER) of the limb bud of a 4-day-old chick embryo. In most of t he regions where C-Serrate-2 was expressed, C-Notch-1 was also express ed. Our observations suggest that Serrate-2-Notch-1 signaling plays a role in a variety of morphogeneses during the chick development.