Rasputin affects actin dynamics in developing egg chambers. C. Pazman , S.R. Haynes. Department of Biochemistry, USUHS, Bethesda, MD.

   The Drosophila homolog of the RasGAP binding protein G3BP is encoded by rasputin (rin). Mutations in rin genetically interact with components of the Ras signaling pathway at the level of Ras and above, but not with Raf/MAPK pathway components. rin mutants are viable and display defects in the developing egg chambers and in the eye. Egg chambers from null mutant females have multiple defects. These abnormalities include partitioning defects of the cysts, multinucleate nurse cells, and disorganization of the actin-based cytoskeleton. The formation of the actin bundles is disrupted, and the ring canals disintegrate during later stages of oogenesis, suggesting a defect in the function of a cytoskeletal protein. These defects cause an abnormal cytoplasm transport, which leads to the formation of "dumpless" eggs. Our current studies are focusing on the role of rin in the maintenance of the actin cytoskeleton during oogenesis.