Fig. 4. Hair cycle alteration in K14Cre⁺/Miz1^lox/lox mice. (A-H) Representative sections of comparable areas of back skin from P19 (A,B), P23 (C,D), P26 (E,F) and 1-year-old (G,H) control (A,C,E,G) and K14Cre⁺/Miz1^lox/lox mice (B,D,F,H). Note the sharp boundary between dermis and subcutis (arrow). Such sections were used to count the number of all hair follicle and those which are extending into the subcutis, representing hair follicle either in catagen or anagen, depending on the chosen time point and the hair follicle morphology. (I) Quantitative analysis of the percentage of subcutaneous follicles at different ages as indicated. The bars represent the medians. The differences of the medians for P18/19 and for one year were statistically significant (for both P<0.0001). (J) Proliferation of keratinocytes measured by the BrdU-labeling index. Mice received BrdU 1.5 hours before being sacrificed and sections were stained with an anti-BrdU antibody to count the percentage of S-phase cells, either in the interfollicular skin or in the hair follicle. The twofold difference found in the hair follicle epithelium was statistically significant (P<0.0001). The bars represent the medians. n, number of animals analyzed.