Basement Membrane Manipulation in Drosophila Wing Discs Affects Dpp Retention but Not Growth Mechanoregulation.

Basement membranes (BMs) are extracellular matrix polymers basally underlying epithelia, where they regulate cell signaling and tissue mechanics. Constriction by the BM shapes Drosophila wing discs, a well-characterized model of tissue growth. Recently, the hypothesis that mechanical factors govern wing growth has received much attention, but it has not been definitively tested. In this study, we manipulated BM composition to cause dramatic changes in tissue tension. We found that increased tissue compression when perlecan was knocked down did not affect adult wing size. BM elimination, decreasing compression, reduced wing size but did not visibly affect Hippo signaling, widely postulated to mediate growth mechanoregulation. BM elimination, in contrast, attenuated signaling by bone morphogenetic protein/transforming growth factor β ligand Dpp, which was not efficiently retained within the tissue and escaped to the body cavity. Our results challenge mechanoregulation of wing growth, while uncovering a function of BMs in preserving a growth-promoting tissue environment.