CHARACTERIZING FM60, A NEW MUTANT AFFECTING BASEMENT MEMBRANE DEPOSITION AND EPITHELIAL ARCHITECTURE IN DROSOPHILA

Abstract

Apical-basal polarity is pivotal to the function and integrity of epithelia and is sustained by the integration of environmental cues and intracellular trafficking. Epithelial cells secrete a specialized extracellular matrix (ECM) called the basement membrane (BM) that serves as a mechanical anchor as well a basal cue to instruct apical-basal polarity in the overlying cells. Yet, the factors that lead to the exclusively basal deposition of BM components in the first place are not well understood. The Rab GTPase Rab10 and the GEF protein Crag have been implicated in this process, but their regulators and exact roles remain unknown. Using the follicular epithelium (FCE) of the Drosophila melanogaster egg chamber as a model system, we investigate the mechanisms underlying BM polarity. In this thesis, I present FM60, a new mutant isolated by the Schüpbach lab that is associated with a polarity defect in BM deposition. FM60 mutant epithelial cells aberrantly accumulate BM proteins such as Collagen IV and Perlecan on their apical surface. Despite this, the mutant cells correctly localize other polarity markers, suggesting that rather than regulating global polarity, the gene affected by FM60 is primarily involved in the BM deposition pathway. In analyzing candidate genes, I found strong evidence that FM60 is an allele of Receptor component protein (Rcp) and that Rcp is involved in polarized BM deposition. Since Rcp is known to facilitate G protein-coupled receptor (GPCR) signaling, I propose future studies focusing on Rcp’s interactions with GPCRs and the downstream pathways in the FCE.