Neuroendocrine control of female germline stem cell increase in the fruit fly Drosophila melanogaster

The development and maintenance of many tissues are fueled by stem cells. Many studies have addressed how intrinsic factors and local signals from neighboring niche cells maintain stem cell identity and proliferative potential. In contrast, it is poorly understood how stem cell activity is controlled by systemic, tissue-extrinsic signals in response to environmental cues and changes in physiological status. Our laboratory has been focusing on female germline stem cells (fGSCs) in the fruit fly Drosophila melanogaster as a model system and studying neuroendocrine control of fGSC increase. The increase of fGSCs is induced by mating stimuli. We have previously reported that mating-induced fGSC increase is regulated by the ovarian steroid hormone and the enteroendocrine peptide hormone [Ameku & Niwa, PLOS Genetics 2016; Ameku et al. PLOS Biology 2018]. In this presentation, we report our recent finding showing a neuronal mechanism of mating-induced fGSC increase. We first found that the ovarian somatic cell-specific RNAi for Oamb, a G protein-coupled receptor for the neurotransmitter octopamine, failed to induce fGSC proliferation after mating. Both ex vivo and in vivo experiments revealed that octopamine and Oamb positively regulated mating-induced fGSC increase via intracellular Ca 2+ signaling. We also found that a small subset of octopaminergic neurons directly projected to the ovary, and neuronal activity of these neurons was required for mating-induced fGSC increase. This study provides a mechanism describing how the neuronal system controls stem cell behavior through stem cell niche signaling [Yoshinari et al. eLife 2020]. Here I will also present our recent data showing how the neuroendocrine system couples fGSC behavior to multiple environmental cues, such as mating and nutrition.