1001 ROLES FOR THE DROSOPHILA EGF RECEPTOR

In the Drosophila genome there is a single member of the EGF receptor tyrosine kinase family. This receptor fulfills multiple roles during d evelopment, as reflected by the many designations given to mutant alle les in the locus (Egfr, DER, faint little ball, torpedo and Ellipse). The full scope of EGFR functions became apparent only in recent years: receptor activation was shown to have an instructive role in successi ve cell fate determination events during oogenesis, embryogenesis, and the proliferation and differentiation of imaginal discs. To ensure th e fidelity of these processes, the precise place and time of receptor activation are tightly regulated by the localized presentation of acti vating ligands, in conjunction with a negative-feedback loop generated by an inhibitory secreted factor. The cellular mechanisms that transl ate EGFR activation to discrete cell fates are now the focus of intens e studies.