Analyses of skin phenotype in epidermis-specific CerS4 knockout mice. (A) Representative images and quantification of hair follicle stage of H/E-stained back skin sections of control (Ctr) and CerS4^epi−/− back skin at P4, 9, and 14 (scale bars 100 µm; n = 4–6 mice/genotype). (B) Representative images and quantification of P16 back skin sections stained for Lhx2 (grey) and keratin-14 (magenta) show reduced expression of Lhx2 in bulge stem cells (scale bars 50 µm; n = 3–4 mice/genotype; mean ± SD; unpaired t test). (C) Representative images and quantification of P16 Ctr and CerS4^epi−/− back skin sections stained for keratin-6 (grey), keratin-14 (magenta) show ectopic keratin-6 expression in the uHF of CerS4^epi−/− mice (scale bars 25 µm; n = 4 mice/genotype; mean ± SD; unpaired t test). (D) Representative photographs of adult Ctr and CerS4^epi−/− littermates show hair loss in CerS4^epi−/− mice. (E) Quantification of P21 Ctr and CerS4^epi−/− back skin sections with BrdU labeling and CD34 staining to mark the bulge stem cell compartment (scale bars 25 µm; n = 5 mice/genotype; mean ± SD; unpaired t test). (F) Quantification of P47 Ctr and CerS4^epi−/− back skin sections labeled with BrdU show increased BrdU incorporation in CerS4^epi−/− stem cells (scale bars 25 µm; n = 10 mice/genotype; mean ± SD; unpaired t test).