REQUIREMENT FOR DYNAMIN DURING NOTCH SIGNALING IN DROSOPHILA NEUROGENESIS

Singling out of a unique neural precursor from a group of equivalent c ells, during Drosophila neurogenesis, involves Notch-mediated lateral signaling. During this process, activation of the Notch signaling path way leads to repression of neural development. Disruption of this sign aling pathway results in the development of an excess of neural cells. The loss of activity of dynamin, which is encoded by the gene shibire and is required for endocytosis, results in a similar phenotype. Here we have investigated the requirement of shibire function for Notch si gnaling during the segregation of sensory bristles on the notum of the ny. Overexpression of different constitutively active forms of Notch in shibire mutant flies indicates that shibire function is not necessa ry for transduction of the signal downstream of Notch, even when the r eceptor is integrated in the plasma membrane. However, when wild-type Notch is activated by its ligand Delta, dynamin is required in both si gnaling and receiving cells for normal singling out of precursors. Thi s suggests an active role of the signaling cell for ligand-mediated re ceptor endocytosis in the case of transmembrane ligands. We discuss th e possible implications of these results for normal functioning of Not ch-mediated lateral signaling. (C) 1997 Academic Press.