LAUSR

Embryonic diapause is a reproductive strategy in which embryo development and growth is temporarily arrested within the uterus to ensure the survival of neonates and mothers during unfavorable conditions. Pregnancy is reinitiated when conditions become favorable for neonatal survival. The mechanism of how the uterus enters diapause remains unclear. Mice with uterine deletion of Foxa2, a transcription factor, are infertile. In this study, we show that dormant blastocysts are recovered from these mice on day 8 of pregnancy with persistent uterine Msx1 expression, a gene critical to maintaining the uterine quiescent state, suggesting that these mice enter embryonic diapause. Leukemia inhibitory factor (LIF) can resume implantation in these mice. Although estrogen is critical for implantation in progesterone (P4)-primed uterus, our current model reveals that FOXA2-independent estrogenic effects are detrimental to sustaining uterine quiescence. Interestingly, P4 and anti-estrogen can prolong uterine quiescence in the absence of FOXA2. While we find that Msx1 expression persists in the uterus deficient in Foxa2, the complex relationship of FOXA2 with Msx genes and estrogen receptors remains to be explored.