Rho affects cadherin localization during Drosophila development. S.M. Parkhurst , C.R. Magie , D. Pinto-Santini. Div Basic Sci, Fred Hutchinson Cancer Res Ctr, Seattle, WA.

   Rho GTPases are important regulators of cellular behavior through their effects on a wide variety of processes, including actin cytoskeletal rearrangement, transcriptional activation, and regulation of cell adhesion. Mutations in the Drosophila RhoA homolog, Rho1, results in a number of maternal and zygotic morphogenetic defects. These phenotypes are consistent with a role for Rho1 in regulating cytoskeletal dynamics and cell shape changes, as well as in signal transduction leading to transcriptional activation. While the mechanisms that underlie Rho GTPase effects are just beginning to be defined, subcellular localization of Rho proteins has been shown to be an important aspect of their function. Some Rho functions are compromised by mutations that prevent their recruitment to the plasma membrane. We are using a monoclonal antibody that specifically recognizes Drosophila Rho1 to investigate the relationship of Rho1 subcellular localization to Rho1 function during development. Rho1 protein is expressed at a low level in the cytoplasm of all cells, but accumulates apically, particularly at sites of cadherin-based adherens junction formation in both the embryo and ovary. We find cadherin distribution is aberrant in Rho1 mutants, suggesting a role for Rho in regulating cadherin localization during development. We are currently investigating the mechanistic basis for these observations.