Cell autonomous polarization by the planar cell polarity signaling pathway.

Planar Cell Polarity (PCP) signaling polarizes epithelial cells in a plane orthogonal to their apical-basal axis. A core PCP signaling module both generates molecular asymmetry within cells and coordinates the direction of polarization between neighboring cells. Two subcomplexes of core proteins segregate to opposite sides of the cell, defining a polarity axis. Homodimers of the atypical cadherin Flamingo are thought to be the scaffold upon which these subcomplexes assemble and are required for intercellular polarity signaling. The central role for Flamingo homodimers in scaffolding and intercellular communication suggests that cells in which intercellular signaling via Flamingo is disabled should fail to polarize. We show that cells lacking Flamingo, or bearing a truncated Flamingo that cannot homodimerize do in fact polarize. Cell polarization requires both positive and negative feedback, and in a multicellular tissue, feedback might involve both intracellular and intercellular pathways. We identify positive and negative feedback pathways that operate cell autonomously to drive polarization.