Region-specific reversal of epidermal planar polarity in the fancyrosettemouse

Abstract

AbstractThe planar cell polarity (PCP) pathway collectively orients thousands of cells with respect to a body axis to direct cellular behaviors that are essential for embryonic morphogenesis. Hair follicles of the murine epidermis provide a striking readout of PCP activity in their uniform alignment along the entire skin surface. Here, we characterize, from the molecular to tissue-scale, PCP establishment in therosettefancy mouse, a natural variant with posterior-specific whorls in its fur, to understand how epidermal polarity is coordinated across the tissue. We find that embryonic hair follicles ofrosettemutants emerge with reversed orientations specifically in the posterior region, creating a mirror image of epidermal polarity. Therosettetrait is associated with a missense mutation in the core PCP geneFzd6, which alters a consensus site for N-linked glycosylation and inhibits its membrane localization. Unexpectedly, this defect in Fzd6 trafficking, observed across the entire dorsal epidermis, does not interfere with the ability of other core PCP proteins to localize asymmetrically. Rather, the normally uniform axis of PCP asymmetry is disrupted and rotated in the posterior region such that polarity is reflected on either side of a transition zone. The result is a reversal of polarized cell movements that orient nascent follicles, specifically in the posterior of the embryo. Collectively, our multiscale analysis of epidermal polarity reveals PCP patterning can be regionally decoupled to produce the unique posterior whorls of the fancyrosettemouse.SummaryRegion-specific rotation of the Planar Cell Polarity axis reverses posterior hair follicles in the fancyrosettemouse.