Elsevier

Developmental Biology

Volume 406, Issue 2, 15 October 2015, Pages 212-221
Developmental Biology

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

https://doi.org/10.1016/j.ydbio.2015.08.018Get rights and content
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Highlights

  • Egg chamber elongation requires temporal down-regulation of SPARC.

  • SPARC negatively regulates Collagen IV levels in the basement membrane.

  • SPARC and Collagen IV interact within the secretory pathway of the follicle cells.

  • Increased Collagen IV and decreased Perlecan levels promote egg chamber elongation.

Abstract

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 SPARC as a negative regulator of egg chamber elongation, and show that SPARC down-regulation is necessary for the increase in Col IV levels to occur. We find that SPARC interacts with Col IV prior to secretion and propose that, through this interaction, SPARC 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 SPARC's conserved role in matrix dynamics and demonstrate that regulated changes in BM composition influence organ morphogenesis.

Keywords

Drosophila
Morphogenesis
Basement membrane
SPARC
Type IV Collagen
Perlecan

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