Figure 1. Sox2 ablation in DP precursors does not affect hair follicle formation.

(A) Schematic of the three major hair follicle formation waves during embryonic morphogenesis.

(B) Sox2 expression analysis (green) in postnatal day P5 skin of Sox2^GFP knock-in reporter mice. Lamb1 stained the basement membrane (red). Nuclei are highlighted with DAPI (blue). Asterisk marks autofluorescence of hair shafts. Note GFP is expressed in DPs of 1^st wave guard (1) and 2^nd wave awl/auchene (2) hair follicles. DPs of 3^rd wave zigzag follicles (3) do not express Sox2.

(C) High magnification examples of hair follicle types with Sox2^GFP positive and negative DPs.

(D) Quantification of Sox2^GFP positive DPs in P5 follicles of all 3 waves. n=130 hairs per mouse. Data are mean ± SD from 3 mice.

(E)Targeting of DP precursor cells with Tbx18^Cre. Top: Schematic of Tbx18^Cre crossed with R26R^LacZ reporter line. Bottom: Whole-mount X-Gal stained Tbx18^Cre/R26R^LacZ embryo showed robust Cre activity in a hair follicle distribution at E14.5. Histological analyses of sectioned embryos with Cre reporter activity in DP precursors.

(F)Efficient ablation of Sox2 protein in Tbx18^Cre/Sox2^fl/fl conditional knockout (cKO) embryo. Sox2 immunofluorescence was absent in cKO dermal condensates (arrows) at E14.5. Syndecan-1 (Sdc1) labeled dermal condensates and Lamb1 marked the basement membrane.

(G) Immunofluorescence staining for Sox2 at P5. Sox2 is absent in null DPs (arrow) in a Sox2^GFP reporter background.

(H) Hematoxylin/eosin staining of Sox2 heterozygous (HET; Tbx18^Cre/Sox2^GFP/+) and conditional knockout (cKO; Tbx18^Cre/Sox2^GFP/fl) skins at P5.

(I) Quantification of total hair follicles and of follicles from the 3 waves at P5. n=75 hairs per mouse. Data are mean ± SD from 2 mice. Scale bars are 25 μm in A-F and 250 μm in G. See also Figure S1 and S2.