Decoding the epigenetic networks that orchestrate endometrial function

PROJECT SUMMARY Infertility and subfertility are pervasive problems in women worldwide, with approximately half of conceptions ending in early pregnancy loss. Recurrent implantation failure (RIF) remains a major clinical barrier in women undergoing assisted reproductive technologies, even in women of reproductive age with high quality embryos. Among those who achieve pregnancy, recurrent pregnancy loss (RPL) poses an additional challenge. These failures underscore the critical importance of the uterine environment, particularly the endometrium, in mediating successful implantation and pregnancy maintenance. However, the molecular mechanisms underlying uterine dysfunction in RIF, RPL, and related disorders remain poorly understood. Emerging evidences suggest that epigenetic mechanisms—including DNA methylation, histone modification, and non-coding RNAs—play essential roles in orchestrating transcriptional networks that regulate uterine function during pregnancy (e.g., implantation and decidualization) and disease (e.g., endometriosis and endometrial cancer). This proposal focuses on Ten-Eleven Translocation (TET) family proteins—TET1, TET2, and TET3—which mediate active DNA demethylation by oxidizing 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC). Beyond their catalytic activity, TET proteins also interact with transcription factors (e.g., WT1) and epigenetic modifiers (e.g., SIN3A), suggesting additional regulatory roles. TET expression in both human and mouse endometrial cells peaks during the window of receptivity and is reduced in endometriosis. Using Pgr-Cre, we have generated uterine-specific conditional knockout models for Tet1, Tet2, and Tet3. While all three lines of female mice show subfertility, Tet2d/d and Tet3d/d females display pronounced reductions in fertility. Strikingly, Tet2-Tet3 double knockout females are completely infertile due to implantation failure. The goal of this proposal is to define the in vivo roles of TET2 and TET3 in uterine receptivity to implantation of blastocyst and stromal decidual transformation using multi-omics approaches in genetically engineered mouse models (Aim 1), and to translate these findings to human biology using primary human endometrial stromal cells and epithelial organoids (Aim 2). Deciphering the TET2/TET3-dependent regulatory networks will identify novel molecular targets for improving implantation outcomes and treating RIF, RPL, endometriosis, and endometrial cancer.