View Program - 63rd Annual Drosophila Research Conference

Most adult tissues have multiple specialized stem cell populations residing within a single microenvironment, or niche, that repopulate and regenerate the tissue over time. While much is known about how the niche controls a single stem cell line, not much is known regarding the interaction and coordination between the different stem cell types contained by a single niche. The Drosophila testis niche contains two populations of stem cells: Cyst Stem Cells (CySC) and Germline Stem Cells (GSC) that must be precisely coordinated for proper tissue function. It is known that two CySC daughter cells envelope a single GSC daughter cell, insulating the GSC daughter from niche signals. Our lab has identified that somatic control of GSC cytokinesis helps coordinate daughter cell release from the niche, resulting in this 2:1 ratio. Further, we determined that the 2:1 ratio is required for complete and proper GSC daughter cytokinesis. Inhibition of CySC encystment leads to failure of abscission, or membrane severing, between GSC-daughter pairs and results in failure of release of a differentiating germ cell from the niche. Therefore, we hypothesize that a signal from CySCs is necessary to trigger proper abscission of the GSCs. We have additionally found that Wnt pathway activation within CySCs is required for successful completion of GSC abscission. Surprisingly, we find that somatic Wnt pathway activation does not directly regulate GSC abscission. Instead, we have discovered that Wnt activity in CySCs is necessary to dampen GSC cycling rate. Inhibition of the Wnt pathway in somatic stem cells results in a significant increase in GSC cycling rate and a consequent failure of these cells to successfully complete cytokinesis prior to mitotic entry. Further understanding how somatic stem cells regulate the cycling rate of adjacent GSCs will elucidate the collaborative mechanisms in place within the niche to ensure tissue homeostasis.

Investigating the Regulation of Germline Stem Cell Cytokinesis by Somatic Stem Cells