Drosophila Ovarian Stem Cell Establishment is Regulated by Nuclear Hormone Receptor ftz-f1

Stem cells are a fundamental underpinning of tissue biology. Loss of the self-renewing function of stem cells leads to conditions such as infertility and tissue wasting. Stem cells integrate a variety of signals to maintain their fate and proliferative capacity. Although intrinsic and local cues are well studied , less is known about how extrinsic signals , such as hormones , affect stem cell fate and function. The highly characterized Drosophila melanogaster steroid hormone ecdysone regulates germline stem cell (GSC) proliferation and self-renewal , as well as oogenesis and metamorphosis. Though many genes , including nuclear hormone receptor ftz transcription factor 1 (ftz-f1) , are thought to be targets of ecdysone signaling , it is unclear how these targets impact GSC fate and function. To explore the role of ftz-f1 in ovarian stem cells , we used the UAS-GAL4 system and RNA interference (RNAi) to reduce ftz-f1 function specifically in germ cells or surrounding somatic cells. We demonstrate that ftz-f1 is intrinsically required for the establishment of the proper number of GSCs during development. Reduced ftz-f1 function in germ cells leads to a significant decrease in average number of GSCs. During larval stages , ftz-f1 depleted ovaries contain a number of PGCs located significantly further away from the terminal filament stacks. Our results also suggest that ftz-f1 is required in ovarian somatic cells during development for proper movement of germ cells out of the germarium in adult stages. Taken together , we suggest ftz-f1 function during juvenile stages is critical for the establishment of GSCs and development of their progeny