The apical polarity network in C. elegans larval epithelia

Cell polarity is a fundamental and universal property of cells. Epithelial cells, one of the major polarized animal cell types, polarize along an apical-basal axis and establish molecularly and functionally distinct apical, lateral and basal membrane domains. The boundary between the apical and lateral domains is marked by the presence of cell–cell junctions that provide adhesion between cells and prevent unwanted passage of molecules between cells. The establishment of polarity is mediated by mutually antagonistic interactions between apical and basal polarity regulators, including the apical Par and Crumbs complex and the basolateral Scribble module. Although canonical polarity regulators, such as members of the Par complex, have crucial roles in most studied tissues, there is a high degree of diversity among cell types: some cells can polarize in the absence of some these factors, their partners and functions are context-dependent, and they have roles that are independent on polarization. In order to understand the process of cell polarization, it is key to study how cell polarization varies between cell-types and whether alternative pathways operate in specific contexts. Here, we have studied in detail the apical Par and Crb complexes in C. elegans epithelia, uncovering new functions for both complexes and increasing our understanding of the apical polarity network. Moreover, we have gained new insights on the interaction between cell polarity and other cellular processes. As more becomes clear about the mechanisms that promote cell polarity, it becomes apparent that the organization of cell polarity is not the same in all tissues and organisms. The model system C. elegans, with its advanced genetic tools and characterized development, provides an attractive system to study cell polarity and its interaction with other processes, as well as how cell polarity is intertwined with tissue homeostasis and the development of an organism.