Fig. 1. Ontogeny of p63 in mouse female reproductive tract. P63, K14 and PR proteins were detected by IHC in mouse female reproductive tract. At E18, the sinus vagina (SVG) was uniformly positive for p63 (A) and K14 (B). By contrast, p63 was detected only in a small subset of columnar epithelial cells in the Müllerian vagina (MVG) (A,C,D) and the cervix (CVX) (A). Uterus (UT) was negative for p63 and K14. Red arrows indicate p63-positive epithelial cells. The black arrow (C) indicates boundary between sinus and Müllerian vaginal epithelia. At postnatal day 1 (P1), although p63-positive epithelial cells increased (E, red arrows), K14 was still undetectable in CVX and MVG (F). In the P2 CVX, p63-positive squamous basal epithelial cells were detected (G, red arrows) and some basal epithelial cells were weakly positive for K14 (H, red arrow). Some luminal columnar epithelial cells were also positive for p63 (G, black arrows). Note change in nuclear polarity in the emerging basal cells (G). By P14, the SCJ (red arrowheads) was formed, and p63 (I), K14 (J) and PR (K) expression abruptly changed at the SCJ. To test the effect of steroid hormones, ovariectomized adult female BALB/c mice were treated with oil (L), E₂+P₄ (M) or E₂ alone (N). Hormone treatments did not change the boundary of p63 expression at the SCJ. E₂ induced stratification but not p63 expression in UtE (N, blue arrows).