“ Tissue ” or “ planar ” polarity is a characteristic of many epithelial tissues and is not only required for proper cell alignment, but in many instances is absolutely essential for normal function. Planar cell polarity (PCP) is the polarization of cells within the plane of an epithelium in a direction perpendicular to the axis of the apico-basal polarity. The oriented hair alignment in mammalian skin (feather in birds or scales in fish) and highly organized stereocilia bundles in the vertebrate inner ear are examples of such tissue organization. PCP was first described inDrosophila, with non-canonical Wnt signaling (also called PCP signaling, seeChapter 10, Volume 1) shown to be critical for its establishment. Two of the best characterized PCP models inDrosophilaare the developing wing and the eye, where the graded activity of the Frizzled (Fz) receptor determines proximo-distal orientation of the wing hairs and mirror-imaged patterning of ommatidia, respectively. In this chapter, we describe simple methods to visualize PCP defects in theDrosophilaeye and wing, in both developing and adult tissues. These methods include confocal immunofluorescent analysis of larval or pupal tissues, stained with antibodies specific to PCP components or cytoskeleton markers, and light microscopy of the adult eye and wing.
