A Diaphanous and Enabled dependent asymmetric actin cable array repositions nuclei during Drosophila oogenesis

Abstract

Cells reposition their nuclei for a diversity of specialized functions through a wide variety of cytoskeletal mechanisms. To complete oogenesis, Drosophila nurse cells employ novel actin cable arrays to reposition their nuclei. During oogenesis, 15 nurse cells connected by ring canals contract to "dump" their cytoplasmic contents into the oocyte. Just prior to dumping, actin cables initiate from the nurse cell cortex and elongate toward their nuclei, pushing them away from the ring canals to prevent obstruction. How the actin cable arrays generate directional nuclear movement is not known. We found regional differences in the actin cable growth rate that are dependent on the differential localization of the actin assembly factors Enabled (Ena) and Diaphanous (Dia). Mislocalization of Ena resulted in actin cable arrays with a uniform growth rate. In the absence of growth rate asymmetry, nuclear relocation was significantly altered and cytoplasmic dumping was incomplete. This novel mechanism for nuclear repositioning relies on the regulated cortical localization of Dia and Ena producing asymmetric actin cable arrays that push the nuclei away from the ring canals, enabling successful oogenesis. Summary statementThis work demonstrates that an asymmetric actin cable array regulated by the differential localization of Diaphanous and Enabled is necessary to reposition nurse cell nuclei and complete oogenesis in Drosophila.