Gene expression profiling of Smad1/5 cKO and Acvr2a cKO mice
We generated mice with single or double conditional inactivation of SMAD1 and SMAD5 using progesterone receptor (PR) cre (Smad1flox/flox;Smad5flox/flox;Pgr-cre+/-, or “Smad1/5 cKO”). Female mice with single SMAD1 or SMAD5 deletion were subfertile, whereas Smad1/5 cKO were infertile and had no visible implantation sites at 4.5 days post-coitum (dpc), indicating functional redundancy of SMAD1 and SMAD5. Histological and molecular analyses of the Smad1/5 cKO uteri during pregnancy determined that the infertility was the result of impaired uterine receptivity. During the window of implantation, uteri of Smad1/5 cKO mice responded abnormally to estradiol (E2) and to progesterone (P4), retained luminal PR expression, and displayed cytoplasmic FOXO1 mis-localization. Furthermore, uteri of Smad1/5 cKO mice did not respond to an artificial decidual stimulus and the stroma failed to differentiate. To determine the cell surface receptor complex that controls BMP signaling during implantation, we generated mice with conditional deletion of Acvr2a and Acvr2b using Pgr-cre+/-. We determined that Acvr2b cKO females were subfertile, while Acvr2a cKOs were infertile and displayed a range of ovarian and uterine abnormalities, including endometrial and implantation defects that phenocopied those of Smad1/5 cKO mice. Transcriptomic profiling of the Smad1/5 cKO and Acvr2a cKO uterus showed that genes involved in epithelial cell remodeling and microvilli/ciliated cell function were overrepresented in both genotypes. These results demonstrate that BMP signals mediated via ACVR2A and SMAD1/5 control endometrial receptivity and embryo implantation by remodeling the apicobasal polarity of the epithelium during the window of implantation. Overall design: Multiple group comparison