APOPTOSIS IN LATE-STAGE DROSOPHILA NURSE CELLS DOES NOT REQUIRE GENESWITHIN THE H99 DEFICIENCY

We have determined that nurse cells are cleared from the Drosophila eg g chamber by apoptosis, DNA fragmentation begins in nurse cells at sta ge 12, following the completion of cytoplasm transfer from the nurse c ells to the oocyte. During stage 13, nurse cells increasingly contain highly fragmented DNA and disappear from the egg chamber concomitantly with the formation of apoptotic vesicles containing highly fragmented nuclear material. In dumpless mutant egg chambers that fail to comple te cytoplasm transport from the nurse cells, DNA fragmentation is mark edly delayed and begins during stage 13, when the majority of cytoplas m is lost from the nurse cells. These data suggest the presence of cyt oplasmic factors in nurse cells that inhibit the initiation of DNA fra gmentation. Ln addition, we have examined the ovarian expression patte rns of regulatory genes implicated in Drosophila apoptosis, The positi ve regulators, reaper (rpr), head involution defective (hid) and grim, as well as the negative regulators, DIAP1 and DIAP2, are transcribed during oogenesis, However, germline clones homozygous for the deficien cy Df(3)H99, which deletes rpr, hid and grim, undergo oogenesis in a m anner morphologically indistinguishable from wild type, indicating tha t genes within this region are not necessary for apoptosis in nurse ce lls.