Background:Endocrine-disrupting chemicals (EDCs) are suspected of altering estrogenic signaling through estrogen receptor (ER) α or β (mERβ1 in mice). Several EDC effects have been reported in animal studies and extrapolated to human studies. Unlike humans, rodents express a novel isoform of ERβ (mERβ2) with a modified ligand-binding domain sequence. EDC activity through this isoform remains uncharacterized.Objectives:We identified the expression pattern of mERβ2 in mouse tissues and assessed the estrogenic activity of EDCs through mERβ2.Methods:mERβ2 mRNA expression was measured in mouse tissues. HepG2 cells were used to assess the transactivation activity of mERβ isoforms with EDCs and ER co-activators. 293A cells transiently transfected with mER isoforms were used to detect EDC-mediated changes in endogenous ER target gene expression.Results:Expression of mERβ2 mRNA was detected in mouse reproductive tissues (ovary, testis, and prostate) and lung and colon tissues from both female and male mice. Five (E2, DES, DPN, BPAF, Coum, 1-BP) of 16 compounds tested by reporter assay had estrogenic activity through mERβ2. mERβ2 had a compound-specific negative effect on ERβ/ligand-mediated activity and ER target genes when co-expressed with mERβ1. mERβ2 recruited coactivators SRC2 or SRC3 in the presence of EDCs, but showed less recruitment than mERβ1.Conclusion:mERβ2 showed weaker estrogenic activity than mERβ1 in our in vitro system, and can dampen mERβ1 activity. In vivo models of EDC activity and ER-mediated toxicity should consider the role of mERβ2, as rodent tissue responses involving mERβ2 may not be reproduced in human biology.Citation:Donoghue LJ, Neufeld TI, Li Y, Arao Y, Coons LA, Korach KS. 2017. Differential activation of a mouse estrogen receptor β isoform (mERβ2) with endocrine-disrupting chemicals (EDCs). Environ Health Perspect 125:634–642; http://dx.doi.org/10.1289/EHP396

Non-genomic effects of estrogen receptor α (ERα) signaling have been described for decades. Several distinct animal models have been generated previously to analyze the non-genomic ERα signaling (e.g., MOER, ERαC451A). However, the mechanisms and physiological processes resulting solely from non-genomic signaling are still poorly understood. Herein, we describe a novel mouse model for analyzing non-genomic ERα actions named H2NES knock-in (KI). H2NES ERα possesses a nuclear export signal (NES) in the hinge region of ERα protein resulting in exclusive cytoplasmic localization that involves only the non-genomic action but not nuclear genomic actions. We generated H2NESKI mice by homologous recombination method and have characterized the phenotypes. H2NESKI homozygote mice possess almost identical phenotypes with ERα null mice except for the vascular activity on reendothelialization. We conclude that ERα mediated non-genomic estrogenic signaling alone is insufficient to control most estrogen-mediated endocrine physiological responses; however, there could be some physiological responses that are non-genomic action dominant. H2NESKI mice have been deposited in the repository at Jax (Stock No: 032176). These mice should be useful for analyzing non-genomic estrogenic responses and could expand analysis along with other ERα mutant mice lacking membrane-bound ERα. We expect the H2NESKI mouse model to aid our understanding of ERα-mediated non-genomic physiological responses. Additionally, as an in vivo model for evaluating the non-genomic action of various estrogenic agents.

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