Tissue-level alignment of cells via Frizzled-Dishevelled-Vangl2 core complex
Planar cell polarity (PCP) is the coordinated alignment of cells within the plane of an epithelium, perpendicular to the apical-basal axis. The core PCP module — Frizzled (Fz), Dishevelled (Dsh), and Vangl2/Strabismus — forms asymmetric complexes across cell-cell junctions: Fz-Dsh accumulates at one face and Vangl2-Pk at the opposite face of each cell. Intercellular coupling then propagates this asymmetry across the tissue, aligning all cells in the same direction. Global cues (Wnt gradients, Fat-Dachsous protocadherins) provide the initial symmetry-breaking bias. PCP controls wing hair orientation in Drosophila (the classic readout), cochlear hair cell stereociliary bundles, neural tube closure via convergent extension, and left-right body asymmetry. Loss-of-function produces the whirlpool-like swirling patterns of Vangl2 mutant mouse coats.