THE DROSOPHILA FUSOME, A GERMLINE-SPECIFIC ORGANELLE, CONTAINS MEMBRANE SKELETAL PROTEINS AND FUNCTIONS IN CYST FORMATION

Oogenesis in Drosophila takes place within germline cysts that support polarized transport through ring canals interconnecting their 15 nurs e cells and single oocyte. Developing cystocytes are spanned by a larg e cytoplasmic structureknown as the fusome that has been postulated to help form ring canals and determine the pattern of nurse cell-oocyte interconnections. We identified the adducin-like hts product and alpha -spectrin as molecular components of fusomes, discovered a related str ucture in germline stem cells and documented regular associations betw een fusomes and cystocyte centrosomes. hts mutations completely elimin ated fusomes, causing abnormal cysts containing a reduced number of ce lls to form. Our results imply that Drosophila fusomes are required fo r ovarian cyst formation and suggest that membrane skeletal proteins r egulate cystocyte divisions.