A non-cell-autonomous contribution of somatic cells to programmed cell death of the germline in Drosophila. Claire E. Schenkel, Jon Iker Etchegaray, Kim McCall. Biology, Boston University, Boston, MA.

   Programmed cell death is an important process in human development and disease. Apoptosis, autophagic cell death, and necrosis are the most well-known forms of cell death, but recent research has begun to characterize other forms of cell death, including phagoptosiscell death initiated by a phagocytic mechanism. Our laboratory investigates the genetic control of cell death using the ovary of Drosophila melanogaster as a model. Each egg chamber includes germline-derived nurse cells and an oocyte, surrounded by somatic follicle cells. During normal egg chamber development, the nurse cells transfer their cytoplasmic contents to the oocyte as they initiate programmed cell death, and by time the egg chamber is mature, the nurse cell nuclei are completely gone. The mechanisms controlling this developmental cell death are mysterious; it occurs independently of the major cell death pathways. Research in the lab has shown that the phagocytic receptor Draper is required non-cell-autonomously for the removal of nurse cell nuclei. When draper was knocked out or knocked down in the follicle cells, persisting nurse cell nuclei were highly visible in all stage 14 egg chambers. To determine which cells required Draper activity, we knocked down draper in subsets of follicle cells, and found that a group called the stretch follicle cells are the most crucial in this process. Further experiments have aimed to identify whether draper-mediated engulfment mechanisms play an active role in the nurse cell death process or affect clearance only. We first aimed to determine if the nurse cells were able to transfer their nuclear contents in draper mutants. This release of contents does occur, but noticeably later in development in draper mutant flies than in controls, indicating that follicle cell mechanisms are involved in the death process. Future experiments will examine acidification patterns and nuclear lamin morphology to further characterize the role of the follicle cells in nurse cell death. These studies will reveal the contribution of follicle cells to the death and clearance of nurse cells.