This protein is essential for differentiation. It may play a role in localizing of Nanos (a maternal determinant) activity in oocytes. During oogenesis, plays a specific role, together with Rab6 but independently of Sec5, in the polarization of the oocyte microtubule cytoskeleton, in oskar mRNA localization and in the anterodorsal secretion of grk. Plays a role in the biogenesis of annulate lamellae containing nuclear pore complex components (PubMed:31626769). Interacts (via C-terminal domain) with Rab6. In ovaries, expressed in oocyte and nurse cells. Expressed maternally and zygotically (PubMed:2576013). Expressed during oogenesis and throughout development (PubMed:2576013, PubMed:11546740). Mutant embryos show Nanos mislocalization and thus bicaudal development (PubMed:2590944). RNAi-mediated knockdown results in sterility and egg chamber defects including loss of annulate lamellae (PubMed:31626769). Belongs to the BicD family.