Isolation and molecular characterization of a gene from Drosophila melanogaster encoding a predicted Rho guanine nucleotide exchange factor

Abstract

I conducted a chromosomal walk in the 38C region on the second chromosome to execute the molecular analysis of spire, (spir), a Drosophila maternal effect locus required for establishment of both the dorsal-ventral and anterior-posterior axes during embryonic development. This analysis resulted in the isolation and mapping of approximately 300 kb of DNA from 38D1 to 38C2. I identified a gene in this region, which I named Drosophila Rho-type Guanine Nucleotide Exchange Factor (DrtGEF) that has substantial sequence homology to a distinct class of proto-oncogenes that includes DBL, VAV, Tiam-1, ost and ect-2. It has predicted Rho or Rac guanine exchange factor (Rho/RacGEF) and pleckstrin homology (PH) domains with the PH domain being immediately downstream of the Rho/RacGEF domain (Cerione and Zheng 1996). Rho/RacGEFs catalyze the dissociation of GDP from the Rho/Rac subfamily of ras-like GTPases, thus activating the target Rho/Rac. Members of the Rho/Rac subfamily regulate organization of the actin cytoskeleton, which controls the morphology, adhesion and motility of cells. DrtGEF mRNA is present throughout oogenesis and embryogenesis. Of particular interest, DrtGEF mRNA is most abundant in furrows and folds of the embryo where cell shapes are changing and the cytoskeleton is likely to be undergoing a reorganization.