Fig. 2.

RAR signaling is required for maintaining uterine epithelial cell identity. (A–H) H&E staining of PD 80 uterine sections from control (A), Rara, Rarb, or Rarg sKO (B–D), Rara;Rarb, Rara;Rarg, or Rarb;Rarg dKO (E–G) and tKO (H) mice. Insets in A–H show lower-magnification images of the respective genotype. Arrows in D, F–H point to clusters of cells characterized by smaller and more densely staining nuclei, suggestive of immune cell infiltration. (I and J) IF staining for FOXA2 (red) and TRP63 (green) in control (I) and tKO (J) uteri. Epithelia outlined with dotted lines; l, lumen; g, glands. Arrows in I point to FOXA2-positive uterine glands of the control uterus. Arrow and arrowheads in J point to FOXA2-positive suprabasal cells and TRP63-positive basal cells in stratified epithelium of the tKO, respectively. The inset in J shows SIX1 staining (red) of tKO LE, which corresponds to epithelial metaplasia. (K and L) IF staining displays no KRT5 expression in control (K) but strong expression in the basal epithelium of the tKO uterus (L). (M and N) IF staining of FOXA2 displays normal gland development in the tKO at PD 15. (O) Quantification of FOXA2-positive glands at PD15. Six FOXA2-stained uterine sections were examined from each animal (CTRL 4.93E-05 ± 8.61E-06 glands/pxl² vs. tKO 5.16E-05 ± 2.96-E06 glands/pxl², P = 0.686, n = 3). (P) H&E staining at PD 21 reveals no apparent morphological changes in the tKO. (Q and R) IF staining reveals sporadic TRP63-positive or SIX1-positive cells (red, arrows in Q and R, respectively) within the simple-columnar tKO uterine epithelium (outlined by CDH1 staining, green). (S) Double IF staining reveals TRP63-positive cells (green, arrows) reside within the LE at the junctional zone between LE and GE as they transition into FOXA2-positive (red, arrowheads) GE cells. (Scale bars, 50 μm.)