Drosophila Glypicans Regulate Follicle Stem Cell Maintenance and Niche Competition

University of Minnesota M.S. thesis. December 2017. Major: Molecular, Cellular, Developmental Biology and Genetics. Advisor: Hiroshi Nakato. 1 computer file (PDF); 56 pages.Several types of stem cells are regularly replaced by progenitor cells through competition to ensure the maintenance of a healthy stem cell population in the niche. However, the molecular basis underlying this maintenance and competition for niche occupancy is poorly understood. Here, it is demonstrated that two members of the heparan sulfate proteoglycan proteins in Drosophila, Dally and Dally-like (Dlp), differentially regulate follicle stem cell (FSC) maintenance and FSC competitiveness for niche occupancy. We find that dally is essential for normal FSC maintenance while dlp mutant FSC progenitors outcompete normal FSCs and eventually occupy the entire epithelial sheet. In addition, Dally and Dlp have both partially redundant and distinct roles in regulating JAK/STAT, Wg and Hh signaling in FSCs. This suggest that glypicans regulate the HS-dependent signaling pathway, and therefore influence FSC competitive behavior that was observed