Upregulation of FOXA2 in uterine luminal epithelium and vaginal basal epithelium of epiERα-/- (Esr1fl/flWnt7aCre/+) mice†

Abstract

Forkhead box protein A2 (FOXA2) is a pioneer transcription factor important for epithelial budding and morphogenesis in different organs. It has been used as a specific marker for uterine glandular epithelial cells (GE). FOXA2 has close interactions with estrogen receptor α (ERα). ERα binding to Foxa2 gene in the uterus indicates its regulation of Foxa2. The intimate interactions between ERα and FOXA2 and their essential roles in early pregnancy led us to investigate the expression of FOXA2 in the female reproductive tract of pre-implantation epiERα-/- (Esr1fl/flWnt7aCre/+) mice, in which ERα is conditionally deleted in the epithelium of reproductive tract. In the oviduct, FOXA2 is detected in the ciliated epithelial cells of ampulla but absent in the isthmus of day 3.5 post-coitum (D3.5) Esr1fl/fl control and epiERα-/- mice. In the uterus, FOXA2 expression in the GE appears to be comparable between Esr1fl/fl and epiERα-/- mice. However, FOXA2 is upregulated in the D0.5 and D3.5 but not PND25-28 epiERα-/- uterine luminal epithelial cells (LE). In the vagina, FOXA2 expression is low in the basal layer and increases toward the superficial layer of the D3.5 Esr1fl/fl vaginal epithelium, but FOXA2 is detected in the basal, intermediate, and superficial layers, with the strongest FOXA2 expression in the intermediate layers of the D3.5 epiERα-/- vaginal epithelium. This study demonstrates that loss of ERα in LE and vaginal basal layer upregulates FOXA2 expression in these epithelial cells during early pregnancy. The mechanisms for epithelial cell-type specific regulation of FOXA2 by ERα remain to be elucidated.

Keywords: ERα; FOXA2; uterine glandular epithelium; uterine luminal epithelium; vaginal basal epithelium.

Graphical Abstract

Figure 1

Detection of FOXA2 in preimplantation epiERα^−/− FRT using immunohistochemistry. Brown: FOXA2 staining (except ERα staining in G0–H02); blue: hematoxylin counterstaining. (A) Day 0.5 post-coitum (D0.5) Esr1^fl/fl oviduct. (B) D0.5 epiERα^−/− oviduct. (A3) and (B3) are enlarged from the boxed area in A1 and B1, respectively; black arrow shows a secretory epithelial cell in the ampulla with blue hematoxylin counterstaining in the nucleus; red arrow shows a ciliated epithelial cell in the ampulla with brown FOXA2 staining in the nucleus. (C) D0.5 Esr1^fl/fl uterus. (D) D0.5 epiERα^−/− uterus. Red ^* shows neutrophil infiltration in uterine lumen. (E) D3.5 Esr1^fl/fl uterus. (F) D3.5 epiERα^−/− uterus. (G0) and (G) PND25 Esr1^fl/fl uterine sections for detecting ERα (G0) and FOXA2 (G), respectively. (H0) and (H) are PND25 epiERα^−/− uterine sections for detecting ERα (H0) and FOXA2 (H), respectively. (G0)–(H02) confirm the deletion of ERα in epiERα^−/− LE and GE; black arrow in (G01)–(H02) and (G1) – (H2) indicates GE. (A1)–(H2) are enlarged from the boxed areas in (A)–(H), respectively. (A)–(H): LE, uterine luminal epithelium; GE, uterine glandular epithelium; Str, stroma; red arrow in (D1)–(F2) indicates FOXA2 staining in the LE. (I) Coronal section of a D3.5 Esr1^fl/fl vagina. (I1)–(I3) are enlarged from the boxed areas in (I); (I1a)–(I3a) are enlarged from the boxed area in (I1)–(I3), respectively. (J) Coronal section of a D3.5 epiERα^−/− vagina. (J1)–(J3) are enlarged from the boxed areas in (J); (J1a)–(J3a) are enlarged from the boxed area in (J1)–(J3), respectively. (I1a)–(J3a): red dotted line separating vaginal stroma and basal epithelial layers; blue arrow: basal epithelial layer; black arrow in (J3a): infiltrated neutrophils. No specific staining in the negative control (data not shown).