Choi, Pui Yee2014-09-052014-09-052014-06https://hdl.handle.net/11299/165430University of Minnesota M.S. thesis. June 2014. Major: Molecular, Cellular, Developmental Biology and Genetics. Advisor:Hiroshi Nakato. 1 computer file (PDF) vii, 30 pages.Adult stem cells reside in specialized microenvironments, niches, which provide signals for the stem cells to maintain their undifferentiated and self-renewing state. To maintain stem cell quality, stem cells are sometimes replaced by progenitor cells through niche competition. However, the cellular and molecular basis for stem cell competition for niche occupancy are largely unknown. Here, we used the epithelial follicle stem cells (FSCs) system in the Drosophila ovary to study how FSC maintenance and niche competitive behaviors are regulated by heparan sulfate proteoglycans (HSPGs) and their post-translational modification. We found that a class of HSPGs, glypicans, regulates FSC maintenance and FSC competitiveness for niche occupancy. Furthermore, Notum, a secreted hydrolase known to cleave glypicans from the cell surface, is also a regulator of FSC niche competitive behavior. Our work highlights the significance of glypcans in adult stem cell systems and will further propel the study of stem cell maintenance and stem cell competition for niche occupancy.en-USThesis or Dissertation