THU569 Steroid Receptor Coactivator 3 Is Required To Prevent Early Pregnancy Loss In The Mouse

Disclosure: V. Maurya: None. L. Hai: None. M.M. Szwarc: None. W. San-Pin: None. F.J. DeMayo: None. J.P. Lydon: None. Members of the Steroid Receptor Coactivator (SRC) family enact distinct transcriptional coregulator functions within a broad spectrum of physiologies and pathologies. We previously demonstrated that endometrial SRC-3 is critical for in vitro human endometrial stromal cell decidualization, a critical cellular process in the establishment of the maternofetal interface. To address SRC-3’s in vivo role in endometrial periimplantation biology, we recently generated a SRC-3 conditional knockout mouse model (SRC-3(d/d)) in which SRC-3 is selectively ablated in cells that express the progesterone receptor. A six-month breeding trial with wild type proven stud males demonstrated that the SRC-3(d/d) female fails to produce litters (n>10 per genotype). Unlike the SRC-2(d/d) female, however, both embryo attachment and implantation into the stromal compartment of the SRC-3(d/d) endometrium are not impaired at gestation day (GD) 5 or 6. While endometrial stromal decidualization initiates with embryo invasion, pregnant SRC-3(d/d) mice exhibit early pregnancy loss (EPL) by GD-7.5 (before placentation). At GD-6, the SRC-3(d/d) decidua is significantly smaller than those of sibling controls. Histological analyses reveal extensive decidual cell death in the SRC-3(d/d) decidua by GD-7, which results in the sudden demise of the embryo. These histological findings are supported by recent genome-wide RNA profiling studies that show a pro-survival role for SRC-3 in this tissue. Based on these results, we conclude that endometrial SRC-3 is critical for maintaining the functionality and survival of the decidual stromal cell and embryo developmental progression to placentation. Therefore, endometrial SRC-3 (and its downstream signaling networks) are predicted to represent new molecular determinants of non-aneuploid EPL, a poorly understood pregnancy complication for which diagnostic and treatment options are limited. Presentation Date: Thursday, June 15, 2023