%0 Journal Article %T Identification of Astrotactin2 as a Genetic Modifier That Regulates the Global Orientation of Mammalian Hair Follicles %A Hao Chang  %A Hugh Cahill  %A Philip M. Smallwood  %A Yanshu Wang  %A Jeremy Nathans %J PLOS Genetics %D 2015 %I Public Library of Science (PLoS) %R 10.1371/journal.pgen.1005532 %X Planar cell polarity (PCP) signaling controls the global orientation of surface structures, such as hairs and bristles, in both vertebrates and invertebrates. In Frizzled6-/- (Fz6-/-) mice, hair follicle orientations on the head and back are nearly random at birth, but reorient during early postnatal development to eventually generate a nearly parallel anterior-to-posterior array. We report the identification of a naturally occurring exon 5 deletion in Astrotactin2 (Astn2) that acts as a recessive genetic modifier of the Fz6-/- hair patterning phenotype. A genetically engineered Astn2 exon 5 deletion recapitulates the modifier phenotype. In Fz6-/-;Astn2ex5del/del mice, hair orientation on the back is subtly biased from posterior-to-anterior, leading to a 180-degree orientation reversal in mature mice. These experiments suggest that Astn2, an endosomal membrane protein, modulates PCP signaling. %U http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.1005532