Differential expression and regulation of Runx1 in mouse uterus during the peri-implantation period.

Runx1 transcription factor is a key developmental regulator. However, little is known about the effects of Runx1 on embryo implantation and decidualization. The aim of this study is to examine the expression and regulation of Runx1 in mouse uterus during the peri-implantation period. There was no evident Runx1 mRNA signal on days 1-4 of pregnancy. On day 5 of pregnancy, Runx1 mRNA was mainly localized in the subluminal stroma surrounding the implanting blastocyst. A similar result was observed in the estrogen-activated implantation uterus. Simultaneously, a high level of Runx1 mRNA expression was detected on days 6-8 of pregnancy and under artificial decidualization. 8-Br-cAMP could induce the expression of Runx1 mRNA in the uterine stromal cells. Moreover, the induction was obviously blocked by PKA inhibitor H89. Inhibition of Runx1 with specific siRNA could decrease the proliferation of stromal cells and expression of decidual markers Prl8a2 and Prl3c1 in the uterine stromal cells. Further study found that inhibition of Runx1 could also suppress the expression of Cox-2, mPGES-1 and Mmp2 genes in uterine stromal cells. Estrogen and progesterone could induce the expression of Runx1 mRNA in ovariectomized mouse uterus and uterine stromal cells. Taken together, these data suggest that Runx1 may play an important role during mouse decidualization.