Stem cell niche organization in the Drosophila ovary requires the ECM component Perlecan

Stem cells reside in specialized microenvironments or niches that balance stem cell proliferation and differentiation.1,2 The extracellular matrix (ECM) is an essential component of most niches, because it controls niche homeostasis, provides physical support, and conveys extracellular signals.3–11 Basement membranes (BMs) are thin ECM sheets that are constituted mainly by Laminins, Perlecan, Collagen IV, and Entactin/Nidogen and surround epithelia and other tissues.12 Perlecans are secreted proteoglycans that interact with ECM proteins, ligands, receptors, and growth factors such as FGF, PDGF, VEGF, Hedgehog, and Wingless.13–18 Thus, Perlecans have structural and signaling functions through the binding, storage, or sequestering of specific ligands. We have used the Drosophila ovary to assess the importance of Perlecan in the functioning of a stem cell niche. Ovarioles in the adult ovary are enveloped by an ECM sheath and possess a tapered structure at their anterior apex termed the germarium. The anterior tip of the germarium hosts the germline niche, where two to four germline stem cells (GSCs) reside together with a few somatic cells: terminal filament cells (TFCs), cap cells (CpCs), and escort cells (ECs).19 We report that niche architecture in the developing gonad requires trol, that niche cells secrete an isoform-specific Perlecan-rich interstitial matrix, and that DE-cadherin-dependent stem cell-niche adhesion necessitates trol. Hence, we provide evidence to support a structural role for Perlecan in germline niche establishment during larval stages and in the maintenance of a normal pool of stem cells in the adult niche. •The Drosophila ovarian niche contains a Perlecan-rich interstitial matrix•Niche cells express and secrete specific Perlecan isoforms•Absence of trol results in aberrant niches containing fewer niche and stem cells•trol regulates DE-cadherin levels in larval and adult niche cells Tissues host stem cells in niches that normally contain extracellular matrix (ECM). Díaz-Torres et al. identify the ECM molecule Perlecan as an essential component of the ovarian niche in Drosophila. Results reveal the importance of Perlecan for proper niche morphogenesis during pre-adult development and for tissue homeostasis in the adult female.