DIVERSE ROLES FOR THE NOTCH RECEPTOR IN THE DEVELOPMENT OF DROSOPHILA-MELANOGASTER

Notch proteins appear to be involved in cell fate commitments with dee p evolutionary roots. Homologues have been shown to play key roles in the development of nematodes, insects, amphibia, and mammals. Activity of the Notch receptor has been observed in the patterning of ectoderm , mesoderm, and endoderm, indicating an origin prior to the functional differentiation of these germ layers. To understand how a single rece ptor can participate so widely in development, we have been examining the role of specific extracellular segments of Notch. Early studies of mutations affecting widely separated EGF-like elements of Notch first raised the possibility for interaction with multiple ligands. Biochem ical approaches, and exhaustive structure function studies in transgen ic Drosophila are beginning to reveal how this receptor is activated, and point to a range of physical interactions with other proteins.