A DROSOPHILA GENE WITH PREDICTED RHOGEF, PLECKSTRIN HOMOLOGY AND SH3 DOMAINS IS HIGHLY EXPRESSED IN MORPHOGENIC TISSUES

We have identified a Drosophila gene that has substantial sequence hom ology to a distinct class of proto-oncogenes that includes DBL, VAV, T iam-1, ost and ect-2. It has predicted Rho or Rac guanine exchange fac tor (Rho/RacGEF) and pleckstin homology (PH) domains with the PH immed iately downstream of the Rho/RacGEF. Rho/RacGEFs catalyze the dissocia tion of GDP from the Rho/Rac subfamily of Ras-like GTPases, thus activ ating the target Rho/Rac (Takai et al. (1995) Trends Biochem. Sci. 20, 227-231]. Members of the Rho/Rac subfamily regulate organization of t he actin cytoskeleton, which controls the morphology, adhesion and mot ility of cells (Nobes et al. (1995) J. Cell Sci. 108, 225-233; Ridley and Hall (1992) Cell 70, 389-399; Ridley et al. (1992) Cell 70, 401-41 0]. Message from this gene is found throughout oogenesis and embryogen esis. Of particular interest, message is most abundant in furrows and folds of the embryo where cell shapes are changing and the cytoskeleto n is likely to be undergoing reorganization.