On the roles of inscuteable in asymmetric cell divisions in Drosophila

Three processes requiring insc, protein localization, RNA localization, and mitotic spindle orientation, appear to be tightly correlated but nevertheless independent. The apical cortical localization of Insc protein occurs prior to mitosis and precedes the basal localization of Pros, Numb, and pros RNA. In insc null mutants, neuroblasts divide in more random orientations and fail to correctly localize Pros, Numb, and pros RNA to their correct position during mitosis. Our results suggest that asymmetric localization of Insc during interphase functions to establish positional information for spindle orientation and the basal localization of Numb, Pros, and pros RNA during mitosis. Insc probably interacts with a number of interacting partners in order to effect its various functions. One of its partners, Stau, is involved exclusively in the process of RNA localization.