Maintenance of Proper Germline Stem Cell Number Requires Adipocyte Collagen in Adult Drosophila Females

Stem cells reside in specialized niches and are regulated by a variety of physiological inputs. Adipocytes influence whole-body physiology and stem cell lineages; however, the molecular mechanisms linking adipocytes to stem cells are poorly understood. Here, we report that collagen IV produced in adipocytes is transported to the ovary to maintain proper germline stem cell (GSC) number in adult Drosophila females. Adipocyte-derived collagen IV acts through -integrin signaling to maintain normal levels of E-cadherin at the niche, thereby ensuring proper adhesion to GSCs. These findings demonstrate that extracellular matrix components produced in adipocytes can be transported to and incorporated into an established adult tissue to influence stem cell number.