Decoding Mechanisms and Lineages of Germline Stem Cells in the Zebrafish Ovary

Oogenesis is the process of producing oocytes and mature eggs from germline stem cells (GSCs) and it is essential for fertility, reproduction, and embryonic development. Mammalian GSCs are not maintained in post-fetal ovaries, and their oocyte production in the fetus determines the number and quality of eggs for the entire female lifespan. Zebrafish oogenesis is well conserved with mammalian oogenesis. However, unlike mammals, zebrafish GSCs are maintained and produce oocytes throughout life, making zebrafish an ideal model for studying development and regeneration. How zebrafish GSCs are regulated in producing oocytes is poorly understood. We hypothesize that dynamic spatial regulation of GSCs is essential for their maintenance and their production of oocytes, and that uncovering these regulatory differences between zebrafish and mammalian GSCs will be important for better studying women reproduction and reproductive health therapies. Using RNA in situ hybridization against a universal GSCs marker, nanos2, we identified GSCs’ distribution to understand their spatial organization and potential interactions with other cells. To study their division dynamics we are generating a transgenic line Tg(nos2:mKate2-PEST) for live time-lapse imaging. Tracking GSCs in a live manner will not only reveal divisions, but also dynamic interactions with other cells. Finally, to track the origin of oocytes, we will conduct cre/lox-based lineage tracing using zebrabow, giving each GSCs clone a unique color code. These experiments will provide insights into mechanisms underlying GSC biology in the vertebrate ovary. Understanding how the female ovary develops and regenerates will improve therapeutic solutions for women reproduction and health.