Fig. 7. Stratification and differential cytokeratin expression in the UPE and sinus epithelium in E12.5 Hoxa13^GFP male embryos. (A,B) Sonic hedgehog (Shh) expression in the UPE is unaffected by loss of Hoxa13 function. Arrows denote a shift in epithelial morphology and stratification from a multilayered cuboidal shape (A) to rounded simple epithelium (B) in homozygous mutants. (C) Cytokeratin 14 (K-14) is highly expressed in the stratified epithelium of heterozygous embryos. (D) K-14 expression is severely reduced in the UPE of Hoxa13^GFP-homozygous mutants, whereas both control and homozygous-mutant embryos exhibit normal levels of cytokeratin 8/18 expression in the same epithelial tissues (E,F). Scale bars: 50 µm.