Sox13 is a novel early marker for hair follicle development

Abstract Sox13, a group D member of the S ry-related high-mobility groupb ox ( Sox) transcription factor family, is expressed in various tissues including the hair follicle. However, its spatiotemporal expression patterns in the hair follicleand its role in hair development remain to be elucidated. To address these questions, we generated Sox13- LacZ -knock-in mice (Sox13 LacZ/+ ), in which the LacZ reporter gene was inserted in-frame into exon 2, which contains the translation initiation codon. X-galstaining in Sox13 LacZ/+ embryos revealed that Sox13 is initially expressed in the epithelial portion of the placode, and subsequently in the hair germ and the hair peg during early hair follicledevelopment. In postnatal catagen and anagen, Sox13 was detected in the epithelial sheath, whereas in telogen, Sox13 was localized in the bulge region, where hair folliclestem cells reside. Immunohistochemistry with an anti-β-galactosidase antibody and anti- hair keratinantibodies that specifically mark the different layers of the hair folliclerevealed that Sox13 was predominantly expressed in the outer root sheathin anagen. However, the integumentary structures of Sox13 LacZ / LacZ mice were grossly and histologically indistinguishable from those of wild type mice. These results suggest that although Sox13 is dispensable for epidermal and adnexal development, Sox13 is a useful marker for early hair follicledevelopment.