ALPHA-SPECTRIN IS REQUIRED FOR GERMLINE CELL-DIVISION AND DIFFERENTIATION IN THE DROSOPHILA OVARY

During Drosophila oogenesis, developing germline cysts are spanned by a large cytoplasmic structure called a fusome, containing alpha-spectr in and the adducin-like product of the hu-li tai shao (hts) gene. We f ound that fusomes contain two additional membrane skeletal proteins: b eta-spectrin and ankyrin, hts was shown previously to be required for cyst formation and oocyte differentiation; the role of the fusome itse lf, however, and the organization and function of its other components , remains unclear. Using the FRT/FLP recombinase system to generate cl ones of alpha-spectrin-deficient cells in the ovary, we have shown tha t alpha-spectrin is also required for cyst formation and oocyte differ entiation, but that its role in each process is distinct from that of Hts protein. Furthermore, alpha-spectrin is required for these process es in germline cells, but not in the follicle cells that surround each cyst, We have also found that the organization of membrane skeletal p roteins is more dependent on alpha-spectrin in the fusome than at the plasma membrane in other cells. Our results suggest that the fusome an d its associated membrane skeleton play a central role in regulating t he divisions and differentiation of cyst cells.