Fig. 1. mio is required for oocyte development. (A) The cell types and stages of Drosophila oogenesis. In region 1 of the germarium (R1), a germline stem cell divides to give rise to a cyst of 16 interconnected cystocytes. In region 2a (R2a), the two pro-oocytes (dark grey), as well as the two adjacent cells with three ring canals (light grey), construct SC. The meiotic gradient is restricted to the single oocyte by region 3 (stage 1). In region 3, the nurse cells enter the endocycle. (B) Microtubule-based directional transport to the oocyte (black). (C) A wild-type stage 5 egg chamber. Note that the oocyte DNA has condensed into a compact karyosome (arrow). (D) A mio² egg chamber that contains 16-polyploid nurse cells. (E,F) Ovarioles from wild-type (E) and mio² homozygous female (F). Ovarioles were stained with Hoechst to visualize nuclei. O, oocyte.