OVEREXPRESSION OF RNRACGAP IN DROSOPHILA-MELANOGASTER DEREGULATES CYTOSKELETAL ORGANIZATION IN CELLULARISING EMBRYOS AND INDUCES DISCRETE IMAGINAL PHENOTYPES

RacGAP proteins have been shown to down-regulate members of the Rho/Ra c subfamily, small GTPases controlling actin network organisation. Onl y one RacGAP protein, RnRacGAP, has been identified in Drosophila. To examine RnRacGAP function, we generated transgenic strains expressing RnRacGAP under the control of the heat-shock promoter hsp70. In cellul arising embryos, ectopic RnRacGAP induces lethality, associated with r adical cell-shape changes, apical F-actin delocalisation, and inhibiti on of basal actin polymerisation. Overexpression of RnRacGAP in pupae induces a number of phenotypes with distinct critical periods of induc tion. These include wing shape and margin changes, wing vein defects, disorientation of wing hairs and thoracic bristles, and abdominal segm ent fusion. Thus, changes in cell shape/adhesion and reorganisation of the actin network are sensitive to overexpression of RnRacGAP through out development in Drosophila. (C) 1997 Elsevier Science Ireland Ltd.