Unipolar membrane association of dishevelled mediates frizzled planar cellpolarity signaling

Drosophila epithelia acquire a planar cell polarity (PCP) orthogonal to the ir apical-basal axes. Frizzled (Fz) is the receptor for the PCP signal, and Dishevelled (Dsh) transduces the signal. Here, I demonstrate that unipolar relocalization of Dsh to the membrane is required to mediate PCP, but not Wingless (Wg) signaling. Dsh membrane localization reflects the activation of Fz/PCP signaling, revealing that the initially symmetric signal evolves to one that displays unipolar asymmetry, specifying the cells' ultimate pol arity. This transition from symmetric to asymmetric Dsh localization requir es Dsh function, and reflects an amplification process that generates a ste ep intracellular activity gradient necessary to determine PCP.