Identification and Characterization of Genes Implicated in Epithelial Cell Polarization and Basement Membrane Deposition in Drosophila melanogaster Oogenesis

Abstract

Epithelia exhibit apical-basal polarity that is manifested in the cytoplasmic and surface organization of individual cells. To achieve polarity, proteins are transported to specific domains in the cell through vesicle trafficking. This apical-basal polarity of epithelial cells is the driving force behind many developmental functions in organisms. In recent years, the basement membrane (BM) secreted basally by epithelial cells has been recognized as an initial cue for apical-basal polarity. However, little is known about how BM proteins first achieve a polarized distribution. The follicular epithelium present during Drosophila melanogaster oogenesis provides a powerful model system for studying epithelial morphogenesis. Crag was the first gene identified that specifically controls the polarized secretion of BM components. To further study BM deposition, we performed a genetic mosaic screen in the follicular epithelium. We identified 5 mutant fly lines, which exhibited defects in polarized BM deposition and epithelial integrity. In particular, we isolated a new mutant JH59A, whose follicle cells lead to aberrant accumulation of the BM component Perlecan on both sides of epithelial cells without affecting the distribution of apical or basolateral membrane proteins. Altogether, our results indicate a specific role for JH59A in the organization of epithelial architecture by regulating the polarized deposition of BM proteins.