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

Stem cells reside in specialised microenvironments or niches that balance stem cell proliferation and differentiation. The extracellular matrix (ECM) is an essential component of most niches, as it controls niche homeostasis, provides physical support and conveys extracellular signals. Basement membranes (BMs) are thin ECM sheets constituted mainly by Laminins, Perlecan, Collagen IV and Entactin/Nidogen and that surround epithelia and other tissues. Perlecans are secreted proteoglycans that interact with ECM proteins, ligands, receptors and growth factors such as FGF, PDGF, VEGF, Hedgehog and Wingless. Thus, Perlecans have structural and signalling 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 few somatic cells: terminal filament (TF) cells, cap cells (CpCs) and escort cells (ECs). 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. Overall design: Targeted DamID. Two biological replicates for tj-GAL4, one replicate each of en-GAL4 and Bab1-GAL4 driving TaDa-RpII215 in Drosophila ovaries.