The Characterization of Drosophila Shroom

Many complex mechanisms regulate cytoskeletal-dependant changes in cell morphology and behavior embryonic and adult life. The actin-binding protein Shroom 3 (Shrm3) appears to interact with Rho kinase (Rok) to direct the assembly of a contractile actomyosin network in neuroepithelial cells, causing apical constriction during neural tube formation. An ortholog of Shrm3 was identified, Drosophila Shroom (dShrm), that contains homology to the Shrm3 domain responsible for constriction. When properly targeted, the invertebrate domain also exhibits the ability to cause apical constriction, suggesting that the pathway is conserved in invertebrates. Drosophila melanogaster will likely provide a powerful model system to study the localization and function of Shrm during tissue morphogenesis. The project has three goals: to classify the endogenous expression of dShrm, to investigate the effects of over expressing dShrm in various tissues, and to determine a potential interaction between dShrm and dRok. There are two isoforms of dShrm we have primarily studied, dShrmA and dShrmB. Using in situ hybridization and immunohistochemistry, we have shown that endogenous dShrm proteins localizes to adherens junctions (dShrmA) and the apical plasma membranes (dShrmB) of cells in the ectoderm, trachea system, and other cell populations during embryogenesis. Over expression of dShrm in the ectoderm, as well as the eye and wing imaginal discs, causes dramatic defects in tissue architecture. Over expression of dShrmA with dRok has shown that there is an interaction between these two proteins. Further work will focus on defining the mechanism by which dShrm functions and which tissues require its activity during embyogenesis