Local regulation of signaling isoprenoids in gonad development - ABSTRACT Organ development requires precise spatiotemporal regulation of various signaling factors. While much is known about how genetically encoded signaling ligands are regulated, less is known about lipid and small molecule signaling ligands. One such class of signaling molecules critical for development across the animal kingdom is signaling isoprenoids, which include Retinoic acids and Juvenile hormones (JHs). Our lab overcomes challenges in detection, redundancy and pleiotropy prevalent for these developmentally essential isoprenoids by harnessing the wealth of tools to identify and manipulate individual cells in Drosophila melanogaster. We generated various mutants lacking JH-related factors including a JH synthesis enzyme, two classes of degradation enzymes, and transcription factors, as well as fluorescent JH reporters to investigate JH signaling dynamics. Here, I will leverage these tools to understand how local and dynamic regulation of signaling isoprenoids facilitates the development of two organs: the ovary and testis. The Drosophila embryonic gonads provide an ideal model due to a wealth of validated gonadal markers and drivers. Preliminary data by us and others suggest JH ligand availability is differentially regulated in the embryonic ovary and testis, though this has not been experimentally verified, nor are JH functions in gonad development known. I recently found that both JH synthesis and degradation enzymes are required for female and male fertility. Using our JH reporter, we found that JH signaling is dynamic during juvenile ovary development yet highly restricted in the male germline stem cell (GSC) niche throughout juvenile and adult stages. During this F31 training fellowship, I will test the hypothesis that precise, local and sex-specific JH signaling in the embryonic gonads is achieved through active JH degradation in non-niche testicular cell types to facilitate male GSC niche development and male fertility. Through successful completion of experiments outlined in this proposal, I will determine a) when and how JH signaling first becomes differentially regulated in the gonad, b) the function of JH signaling in testis niche development, and c) which genes are regulated by JH signaling in embryonic gonads. To accomplish these goals, I will combine our lab’s genetic tools to detect and manipulate JH in individual cell types with immunohistochemistry, RNA FISH, confocal microscopy, fluorescence-activated cell sorting, CRISPR- mediated homologous repair, qPCR, and single-cell RNA sequencing. Thus, this F31 fellowship will not only provide a rich training platform to prepare me for my ultimate goal of becoming an independent researcher in the field of reproductive development, but it will also reveal fundamental insights into how local regulation of signaling isoprenoids facilitate organ development.
