Wild-type estrogen receptor (ERbeta1) and the splice variant (ERbetacx/beta2) are both expressed within the human endometrium throughout the normal menstrual cycle.

Estrogen action is mediated via two subtypes of the estrogen receptor (ER), usually referred to as ERalpha and ERbeta. We have previously compared the spatial and temporal expressions of ERalpha and ERbeta proteins in human endometrium and reported that endothelial cells exclusively express ERbeta. In the present study we have extended our investigations to compare the pattern of expression of wild-type (ERbeta1) and a newly identified ERbeta variant isoform (ERbetacx/beta2) that lacks the ability to bind steroids. mRNAs encoding both ERbeta1 and ERbetacx/beta2 receptors were identified in human endometrial extracts by RT-PCR. Quantitative TaqMan R-TPCR demonstrated that levels of total mRNAs were increased significantly premenstrually as circulating progesterone levels declined. ERbeta1 and ERbetacx/beta2 proteins were identified within multiple cell types within the endometrium using isotype-specific monoclonal antibodies; immunoexpression of ERbetacx/beta2 appeared less intense than that of ERbeta1 in endometrial glandular epithelium and endothelial cells. Immunoexpression of ERbeta1 appeared unchanged throughout the menstrual cycle. In contrast, levels of ERbetacx/beta2-specific immunoreactivity were specifically reduced in gland cells within the functional layer, but not in those of the basal layer, in the midsecretory phase. It is possible that coexpression of ERbetacx/beta2 in cells containing ERbeta1 and/or ERalpha may modulate the effects of estrogens on the endometrium.

ERbeta1 and the ERbeta2 splice variant (ERbetacx/beta2) are expressed in distinct cell populations in the adult human testis.

Estrogens can regulate germ cell function. Estrogen action is mediated via high affinity ERs; two subtypes (ERalpha and ERbeta) have been identified. We have shown previously that ERbeta is expressed in nuclei of multiple human testicular cells. A variant isoform of human (h) ERbeta (hERbetacx/2), formed by alternative splicing, has been identified in testicular cDNA libraries by two laboratories. The present study examined the expression of wild-type (ERbeta1) and variant (ERbeta2) beta receptors in human testes by 1) RT-PCR with isoform specific primers, and 2) single and double immunohistochemistry using monoclonal antibodies raised against peptides unique to the C termini of hERbeta1 and hERbeta2. PCR products specific for ERbeta1 and ERbeta2 were amplified from cDNA pools prepared from human testes and granulosa cells. On Western blots, the anti-ERbeta1 monoclonal antibody bound to recombinant ERbeta1 and the anti-ERbeta2 monoclonal to recombinant hERbeta2. Neither bound to the other ERbeta isoform nor to recombinant ERalpha. ERbeta1 and ERbeta2 proteins were both detected in human testis. Immunoexpression of ERbeta1 was most intense in pachytene spermatocytes and round spermatids, whereas low levels of expression were detected in Sertoli cells, spermatogonia, preleptotene, leptotene, zygotene, and diplotene spermatocytes. Highest levels of expression of ERbeta2 protein were detected in Sertoli cells and spermatogonia with low/variable expression in preleptotene, pachytene, and diplotene spermatocytes. No immunostaining was detected in elongating spermatids. Most interstitial cells expressed more ERbeta2 than ERbeta1. It is speculated that the cells most susceptible to modulation by estrogenic ligands are round spermatids in which levels of expression of ERbeta1 are high. In contrast, expression of ERbeta2, an isoform that may act as a dominant negative inhibitor of ER action, in Sertoli cells and spermatogonia, could protect these cells from adverse effects of estrogens.