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. The Notch genes are highly conserved both in invertebrates and in vertebrates, suggesting that Notch pathway regulates cell fate decisions during vertebrates development. Notch, Delta and Serrate homologs in chicken have been cloned (Henrique et al., Nature 375: 787-790, 1995; Myat et al., Dev. Biol. 174: 233-247, 1996). We isolated a novel chick homolog of Drosophila Serrate, named C-Serrate-2, and examined its expression 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 the regions where C-Serrate-2 was expressed, C-Notch-1 was also expressed. Our observations suggest that Serrate-2-Notch-1 signaling plays a role in a variety of morphogeneses during the chick development.