Multiple roles of the Dcdc42 GTPase during wing development in Drosophila melanogaster

The Rho sub-family of GTPases. comprising Rho. Rac and Cdc42, regulates man y biological processes. including morphogenesis, cell polarity, migration, the cell cycle and gene expression. It is important to develop genetic appr oaches to allow the dissection, in vivo, of the mechanisms of GTPase regula tion and signal transmission, and their biological consequences. In this re gard, wing development in Drosophila melanogaster is an excellent model sys tem. To investigate the functions of the Drosophila Cdc42 GTPase (Dcdc42), we generated phenotypes during wing development, by expression of the domin ant-negative N17 and L89 mutants of Dcdc42. We have identified roles for Dc dc42 in wing growth, and in cell fate choice during the development of the wing veins and the peripheral nervous system. Reduction of Dcdc42 signallin g following over-expression of Dcdc42(N17) resulted in a broader but more d iffuse domain characterised by wing-margin sensory bristles. This was corre lated with a broadened stripe of Il wingless expression along the dorsal-ve ntral boundary of third-instar wing imaginal discs. Together with genetic i nteractions with loss- and gain-of-function Notch alleles, these data suppo rt a role for wild-type Dcdc42 as a negative regulator of Notch signalling.