The villin-like protein encoded by the Drosophila quail gene is required for actin bundle assembly during oogenesis

Mutations in the Drosophila quail gene result in female sterility due to the disruption of cytoplasmic transport from the nurse cells into the oocyte late in oogenesis. Nurse cells from quail mutant egg chambers fail to assemble cytoplasmic actin filament bundles correctly. We have cloned the quail gene and found that it encodes a protein with homology to the vertebrate actin-regulating protein villin. Unlike vertebrate villin, which is restricted to specialized absorptive epithelial cells, the villin-like protein encoded by quail is germline specific in adult flies. Antibodies directed against the quail protein show a striking colocalization with filamentous actin in the nurse cells and the oocyte. Our results demonstrate that the villin-like product of quail is required for the formation of cytoplasmic actin filament bundles in nurse cells, possibly by regulating both the polymerization and organization of actin filaments as demonstrated for vertebrate villin in vitro.