FOXL2 endometrial expression is impacted by P4 and not IFNT in cattle
Résumé
In mammals, implantation is critical for the outcome of pregnancy and involves a tightly regulated communication between the endometrium and the embryo. Using bovine endometrium, our recent transcriptome analyses listed several families of transcription factors, including several Forkhead box (FOX) tran- scription factors at day 20 post-oestrus. Among them, a member of the FOXL sub-class -FOXL2- appeared as differentially regulated between the caruncles and the intercaruncular areas. FOXL2 is a key gene for ovarian differentiation and until now its expression was thought to be restricted to pituitary, ovary and foetal eyelid. In order to gain new insights into FOXL2 biological functions in the endometrium, we characterized the expression and the regulation of this factor during the estrous cycle and establishment of pregnancy in cattle. Both FOXL2 transcript and protein were expressed from day 5 to day 20 of the estrous cycle, and their levels showed a significant increase (3-fold, P < 0.01) during the luteolytic phase The endometrial expression of FOXL2 mRNA did not vary during maternal recognition of pregnancy (16 to 20 days post-estrus) and FOXL2 did not appear to be an interferon-tau target gene. A two-day progesterone sup- plementation in heifers led to a clear down-regulation of FOXL2 protein levels (2.5-fold, P < 0.05). In addition, ovariectomized cows treated with progesterone exhibit a significant inhibition of FOXL2 expression compared to control ovariec- tomized cows (2.4-fold, P < 0.05). Altogether our results indicate that FOXL2 expression is negatively regulated by progesterone in the endometrium. At the cellular level, FOXL2 was detected in endometrial stromal and glandular cells and its sub-cellular localization was shown to be nuclear in endometrial samples collected during the luteolytic phase while it was not detected in the nuclei during the luteal phase and at implantation. Our findings provide the first evidence that FOXL2 is part of the physiology of endometrial tissue in mammals.