Investigating the Role of Ecdysone Receptor in Germline to Somatic Cell Communication

Abstract

Oogenesis requires complex coordination between both somatic and germ cell populations, relying on systemic signals such as hormones for proper oocyte production and formation. Drosophila melanogaster is an excellent model organism to explore how signaling from germ to somatic cells is required for viable egg production. Drosophila oogenesis utilizes steroid hormones such as ecdysone to facilitate many aspects of germ cell development such as ovariole formation, germline stem cell proliferation, and cyst formation. Ecdysone function relies on reception by the heterodimeric complex, Ecdysone Receptor (EcR) and Ultaspiracle (Usp), that in turn activates transcriptional targets. EcR and Usp are expressed in both germline and somatic cell populations, but the role that ecdysone signaling plays in germ cells to control somatic cell processes is unclear. To allow germline compatibility, three EcR RNAi lines and three dominant negative lines were developed in Drosophila to deplete or block EcR function in the germline. Using various germline specific drivers, we found that loss of EcR results in significant somatic cell focused phenotypes. Irregularities such as non-ascending egg chambers where egg chambers stall in repeating stages were observed. Upon further phenotypic analysis, we also discovered cyst collision phenotypes where 16-cell cysts were not properly encapsulated by somatic follicle cells. There was also a significant decrease in follicle cell proliferation, suggesting that EcR is needed to stimulate proliferation of overlying somatic cells. Overall, this suggests that EcR is needed in the germline for follicle assembly. We plan to further investigate germ to somatic cell communication using live imaging to visualize both follicle cell migration. This will inform us if EcR non-autonomously promotes follicle cell migration through centripetal movements.