Dynamic regulation of basement membrane protein levels promotes egg chamber elongation in Drosophila.

Basement membranes (BMs) are sheet-like extracellular matrices that provide essential support to epithelial tissues. Recent evidence suggests that regulated changes in BM architecture can direct tissue morphogenesis, but the mechanisms by which cells remodel BMs are largely unknown. The Drosophila egg chamber is an organ-like structure that transforms from a spherical to an ellipsoidal shape as it matures. This elongation coincides with a stage-specific increase in Type IV Collagen (Col IV) levels in the BM surrounding the egg chamber; however, the mechanisms and morphogenetic relevance of this remodeling event have not been established. Here, we identify the Collagen-binding protein as a negative regulator of egg chamber elongation, and show that duanyu1842RC down-regulation is necessary for the increase in Col IV levels to occur. We find that duanyu1842RC interacts with Col IV prior to secretion and propose that, through this interaction, duanyu1842RC blocks the incorporation of newly synthesized Col IV into the BM. We additionally observe a decrease in Perlecan levels during elongation, and show that Perlecan is a negative regulator of this process. These data provide mechanistic insight into conserved role in matrix dynamics and demonstrate that regulated changes in BM composition influence organ morphogenesis.

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