Estrogen Receptor-Dependent Genomic Responses in the Uterus Mirror the Biphasic Physiological Response to Estrogen

Abstract

The physiological responses of the rodent uterus to acute estrogen (E) dosing can be divided into early and late events. Examples of early responses include increased RNA transcription, hyperemia, and water imbibition 2 and 6 h following E administration respectively, whereas later responses include cycles of DNA synthesis and mitosis of epithelial cells beginning 10 and 16 h after E. The development of estrogen receptor (ER) knockout (ERKO) mice, combined with microarray technology, has allowed us to design a genomic approach to study the acute response of the rodent reproductive tract to E. To determine whether early and late biological responses are correlated with altered regulation of a single set of genes or distinct sets of genes characteristic of early and late responses, uterine RNA was obtained from ovariectomized mice that were treated with vehicle or with estradiol for 2 h (early) or 24 h (late). Samples were also prepared from identically treated mice that lacked either ERalpha (alphaERKO) or ERbeta (betaERKO) to address the relative contributions of the ERs in the uterine responses. Microarray analysis of the relative expression of 8700 mouse cDNAs indicated distinct clusters of genes that were regulated both positively and negatively by E in the early or late phases as well as clusters of genes regulated at both times. Both early and late responses by the betaERKO samples were indistinguishable from those of WT samples, whereas the alphaERKO showed little change in gene expression in response to E, indicating the predominant role for ERalpha in the genomic response. Further studies indicated that the genomic responses in samples from intermediate time points (6 h, 12 h) fall within the early or late clusters, rather than showing unique clusters regulated in the intermediary period. The use of this genomic approach has illustrated how physiological responses are reflected in genomic patterns. Furthermore, the identification of functional gene families that are regulated by E in the uterus combined with the utilization of genetically altered experimental animal models can help to uncover and define novel mechanisms of E action.

Control of Uterine Cell Proliferation and Differentiation by C/EBPb: Functional Implications for Establishment of Early Pregnancy

“…Numerous earlier studies focused on the role of pubertal E in the growth and function of the female reproductive tract. 21,22 These studies documented that the uterine epithelial cells undergo mitotic divisions in response to E. The development of ER null mice confirmed that the proliferative effects of E in the uterus are indeed mediated by the ERα isoform. 23 It is widely postulated that ER, a ligand inducible transcription factor, generates downstream signaling molecules that impact on the cell cycle to trigger mitosis.…”

“…7 It is well documented that E stimulates epithelial cell proliferation in rodent uterus. 21,22 In the uteri of C/EBPβ null mice, however, epithelial proliferation in response to E is markedly reduced. Following E treatment, the Ki67 staining in the uterine epithelium of the null mice was found to be much weaker compared to that seen in the wild-type mice.…”

Uterine epithelial estrogen receptor α is dispensable for proliferation but essential for complete biological and biochemical responses

“…Lactoferrin (Ltf) is a protein regulated by E 2 in mammalian uterine epithelium (3,25). After 3 d, E 2 significantly induced Ltf mRNA in WT uteri (Fig.…”

Tools to evaluate estrogenic potency of dietary phytoestrogens:A consensus paper from the EU Thematic Network “Phytohealth” (QLKI-2002-2453)

“…This view is further supported by findings in gene array studies in uterus and bone of ERα-KO and ERβ-KO mice. Both studies report that the expression of the vast majority of genes is triggered through the ERα, whereas ERβ has to be regarded as a modulator of the magnitude of the ERα response (Hewitt et al, 2003;Lindberg et al, 2003) The classical in vivo models most commonly used for testing estrogenicity of compounds are summarized in section 5 respective section later. INT INT INT INTAKE OF DIET AKE OF DIET AKE OF DIET AKE OF DIET AKE OF DIETAR AR AR AR ARY Y Y Y Y PHYTOESTROGENS IN EUROPE PHYTOESTROGENS IN EUROPE PHYTOESTROGENS IN EUROPE PHYTOESTROGENS IN EUROPE PHYTOESTROGENS IN EUROPE The limited information on phytoestrogen intake among Europeans has increased during this century (Tables 1 and 2).…”