Functional characterisation of novel crumbs complex interactors in the context of epithelial morphogenesis

Abstract

The Crumbs (CRB) complex is critical for the establishment of epithelial polarity and occupies a distinct domain above the tight junction (TJ), the Vertebrate Marginal Zone (VMZ). Many novel VMZ components were identified, but their functions are unclear. Moreover, when and how the VMZ separates from TJ is unknown. The goal of this project is to elucidate the function and spatio-temporal regulation of the VMZ, especially in the context of epithelial lumen morphogenesis. To address this, I applied a combination of loss-of-function approaches in 2D and 3D MDCK cell culture models, biochemical methods, and light and electron microscopy. I demonstrate that the VMZ separates from TJ during early stages of lumen formation, and that apical membrane trafficking to the nascent lumen is mediated by Vacuolar Apical Compartments (VACs). I also show that CRB and its novel interactors are essential for normal epithelial polarity development and lumen formation.