Fig. 3. Phenotype of p63^–/–cervicovaginal epithelium (CVE). I. Epithelial morphology. The p63^–/– CVE was columnar and developed deep inclusions or glands (black arrows). The p63^–/–cervicovaginal grafts in the ovariectomized hosts showed uterine-like epithelial morphology (A). When the hosts were treated with E₂, the glandular p63^–/– CVE remained columnar but became hyperplastic (B). II. Cervicovaginal epithelial markers. Markers for squamous differentiation [p63 (C,D) and K14 (E,F)] and keratinization [K10 (G,H) and involucrin (I,J)] were assessed in p63⁺ (C,E,G,I) and p63^–/– (D,F,H,J) cervicovaginal grafts by IHC. The p63^–/– CVE failed to express squamous and keratinization markers. III. Common markers for uterine and cervicovaginal epithelia. Markers common for UtE and CVE [ER (K,L) and p130 (M,N)] were examined in p63⁺ (K,M) and p63^–/– (L,N) cervicovaginal grafts by IHC. Both p63⁺ and p63^–/– CVE strongly expressed ER and p130. IV. Regulation of PR by E₂. Expression of PR was assessed by IHC in p63⁺ (O,Q) and p63^–/– (P,R) cervicovaginal grafts in the ovariectomized (–E₂, O and P) or E₂-treated ovariectomized (+E₂, Q and R) hosts. In the p63⁺ CVE, PR was detectable only when the host was treated with E₂ (compare O with Q). By contrast, p63^–/– CVE expressed a high level of PR in the absence of E₂ (P), which is a unique phenotype of uterine epithelium. V. VgM/UtE tissue recombination. Tissue recombinants were made with UtE and VgM from E17 p63^–/– and p63⁺ embryos. Expression of p63 was examined in the tissue recombinants. The p63⁺ UtE developed into normal vaginal epithelium and expressed p63 when it was recombined with p63^–/– VgM (S). By contrast, p63^–/– UtE recombined p63⁺ VgM failed to undergo squamous differentiation (T). Scale bar: 50 µm.