Cyst Cells Control Germ Cell Progenitor Numbers Via the Phagocytic Receptor Draper

Abstract

Rapid and constant proliferation generates a pool of germ cell (GC) progenitors for spermatogenesis. In an evolutionarily conserved process, almost a quarter of the nascent progenitors are removed by GC death, although the mechanisms that provoke this phenomenon remain largely unknown. Here, we report that in the Drosophila testis, support cyst cells, the functional orthologues of mammalian Sertoli cells, eliminate live GC progenitors. Cyst cells rely on the phagocytic receptor Draper (Drpr) and dJNK signaling to engulf live GCs and then clear the resulting debris. We show that unlike the fine-tuned phagocytosis of dead cells, only pro-phagocytic Drpr isoforms regulate the removal of live cells. We further show that Drpr levels decline with age, resulting in reduced elimination of progenitors and prolonged spermatogenesis. Since GC death is dictated by neighboring cyst cells, inhibition of paracrine signaling between the two cell types may provide a means for prolonging fertility.