The contribution of follicle cells to non-apoptotic programmed cell death of nurse cells during late oogenesis. Allison Timmons, Claire Schenkel, Jon Iker Etchegaray, Jeffrey Taylor, Olivia Rudnicki, Kim McCall. Biology, Boston University, Boston, MA.

   Programmed cell death (PCD) is an essential process in animal development and tissue homeostasis which ensures that aged, damaged, or excess cells are eliminated. In the Drosophila ovary, PCD occurs as a normal part of development. During late oogenesis, germline derived nurse cells (NCs), which provide nutrients, proteins, mRNAs, and organelles for the developing oocyte, transfer their contents into the oocyte and undergo PCD. Interestingly, disruption of apoptosis or autophagy only partially inhibits PCD of the NCs, indicating that other mechanisms contribute to the process. One possibility is that the surrounding epithelial follicle cells (FCs) non-autonomously contribute to the death of the NCs during late oogenesis. We have found that disruption of the engulfment receptor draper, ced-12, or the JNK signaling pathway in the stretch FCs leads to a persisting nuclei phenotype, indicating that these genes are required for NC death and/or clearance. Overexpression of draper or a constitutively activated JNKK in the FCs is sufficient to kill the NCs. Furthermore, Draper staining is reduced in JNK pathway mutants, suggesting that they interact to eliminate the NCs. LysoTracker staining shows that the acidification of the NCs that normally occurs during late oogenesis is absent in draper mutants, suggesting that Draper may play a role in the death of the NCs. In order to identify other genes involved in PCD and/or clearance in late oogenesis, we are conducting a candidate RNAi screen. We also plan to perform epistasis experiments to determine the pathways that lead to NC death and clearance during late oogenesis. Further investigations are underway to distinguish the role of the FCs in the death vs. clearance of NCs. Developmental PCD of the NCs in the Drosophila ovary is a unique example of PCD that may lead to a greater understanding of the careful coordination between death and clearance, as well as forms of PCD that are non-apoptotic.