The planar cell polarity (PCP) pathway regulates the orientation of cells and their appendages, such as hairs, along the body axis. The alignment of hairs in the murine epidermis offers a useful model to study PCP signalling, where mutations in PCP components present easily observable phenotypes. One such example is the rosette ‘fancy’ mouse, which has distinctive whorls of misoriented hairs, specifically in the posterior region. In this study, Maureen Cetera, Danelle Devenport and colleagues characterise the rosette trait, which they find is attributed to a missense mutation in Frizzled 6 (Fzd6), a core PCP receptor, at a consensus site for N-linked glycosylation, which is required for its correct trafficking to the plasma membrane. The authors show that, although other core PCP components still display polarised localisations within cells, they are not uniformly coordinated across the tissue. This loss of tissue-level coordination, which emerges during the earliest stages of hair follicle polarisation, results in reversed collective cell movements that drive hair follicle orientation, causing up to a 180° rotation of hairs in the posterior region. Together, these findings demonstrate that regional PCP patterning can be decoupled from the global PCP axis to generate the posterior whorls of the rosette fancy mouse.
