Gene expression analyses of PR action in the uteri of SRC-2 mutant mice

Ovarian estrogen (E2) and progesterone (P4) are indispensable for embryo-implantation and endometrial stromal decidualization; however, the molecular mechanisms that underpin these reproductive processes are unclear. Steroid receptor coregulator-2 (SRC-2) belongs to the multifunctional SRC/p160 family which also includes SRC-1 and SRC-3. Sharing strong sequence homology, all three SRCs exert diverse regulatory effects by modulating the transcriptional potency of nuclear receptor family members, including the estrogen and progesterone receptor (ER and PR respectively). Importantly, absence of SRC-2 in PR positive cells in the epithelial, stromal, and myometrial compartments of the murine uterus results in a striking infertility defect. This reproductive phenotype highlights a key role for SRC-2 in uterine function which is not shared with other coregulators. Intriguingly, abrogation of uterine SRC-2 does not block embryo apposition or attachment to the apical surface of luminal epithelial cells of the endometrium but rather prevents P4-dependent local decidualization of the sub-epithelial stroma. Remarkably, epithelial-specific ablation of SRC-2 in the murine uterus does not compromise endometrial functionality, again underscoring the unique importance of stromal derived SRC-2 in uterine function. The stromal decidualization defect resulting from SRC-2 ablation is reflected at the molecular level by a marked attenuation in P4 responsive target genes known to be critical for P4 dependent decidualization (i.e. ERBB receptor feedback inhibitor 1, Follistatin and Fkbp5). Conversely, the induction of E2 or P4 target genes involved in embryo implantation (i.e. leukemia inhibitory factor (LIF) and Indian hedgehog (Ihh) respectively) is not affected by SRC-2s absence. As with mouse studies, decidualization of primary human stromal cells (HESCs) in culture is blocked by SRC-2 knockdown; however, HESC decidualization is unaffected by knockdown of SRC-1 or SRC-3. As a consequence of SRC-2 knockdown, molecular studies disclose a striking decrease in the induction of a subset of P4 target genes (i.e. WNT4 and FKBP5) which are essential for the stromal-epithelioid transformation step, the cellular hallmark of endometrial decidualization. Collectively, these studies not only showcase the evolutionary importance of SRC-2 in endometrial biology but also suggest that deregulation of this coregulator may underpin a spectrum of hormone-dependent uterine pathologies such as endometriosis and endometrial cancer.

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Kommagani R, Szwarc MM, Kovanci E, Creighton CJ, O'Malley BW, Demayo FJ, Lydon JP