The Drosophila centrosomal protein Nuf is required for recruiting Dah, a membrane associated protein, to furrows in the early embryo

During mitosis of the Drosophila cortical syncytial divisions, actin-based membrane furrows separate adjacent spindles. Our genetic analysis indicates that the centrosomal protein Nuf is specifically required for recruitment of components to the furrows and the membrane-associated protein Dah is pri marily required for the inward imagination of the furrow membrane. Recruitm ent of actin, anillin and peanut to the furrows occurs normally in dah-deri ved embryos. However, subsequent imagination of the furrows fails in dah-de rived embryos and the septins become dispersed throughout the cytoplasm, Th is indicates that stable septin localization requires Dah-mediated furrow i nvagination. Close examination of actin and Dah localization in wild-type e mbryos reveals that they associate in adjacent particles during interphase and co-localize in the invaginating furrows during prophase and metaphase. We show that the Nuf centrosomal protein is required for recruiting the mem brane-associated protein Dah to the furrows, In nuf-mutant embryos, much of the Dah does not reach the furrows and remains in a punctate distribution. This suggests that Dah is recruited to the furrows in vesicles and that th e recruiting step is disrupted in nuf mutants. These studies lead to a mode l in which the centrosomes play an important role in the transport of membr ane-associated proteins and other components to the developing furrows.