Enabled plays roles in epithelial morphogenesis and nurse cell cytoplasmic transport. J. Gates¹, J.P. Mahaffey¹, F.B. Gertler², M. Peifer¹. 1) Lineberger Cancer Center, UNC-CH, Chapel Hill, NC; 2) Dept of Biology, MIT, Cambridge, MA.

   Intercellular adhesion and the actin cytoskeleton must be regulated to accommodate changes in cell shape and cell migrations that occur during development. If they are not regulated, morphogenesis is disrupted and normal development fails. Defects in dorsal closure and head involution are observed in embryos carrying mutations in integral components of the adherens junction, DE-cadherin and Armadillo (Arm) as well as the nonreceptor tyrosine kinase Abelson (Abl). Enabled (Ena) is a substrate of Abl and a member of the Ena/VASP family. Mammalian Ena/VASP proteins have been shown to promote cell adhesion and limit cell motility by regulating localized actin polymerization. We have found that ena genetically interacts with abl and arm in the epidermis and colocalizes with Arm at adherens junctions. This suggests that Ena may function at adherens junctions during morphogenesis to regulate adhesion by regulating actin polymerization. We are utilizing both genetic loss of function and mislocalization techniques to examine Enas role during morphogenesis. These experiments suggest that Ena is required during the late stages of dorsal closure. We are currently examining the actin cytoskeleton of the leading edge cells. Since it is possible that Enas maternal contribution is masking additional roles, we are using similar techniques to remove or mislocalize maternal Ena and have found that Ena may be required during germ band retraction and head involution. These experiments also reveal a role during oogenesis. Ena must be localized at the nurse cell cortex in order for the cytoplasmic actin bundles to form and/or be stabilized. When these actin bundles are not present, the nuclei are pushed into the ring canals during the rapid stage of cytoplasmic transport, preventing efficient transport. We are currently examining if cortical Ena is required for the formation or stabilization of the actin bundles and are also examining the consequences of generating germ line clones.