Estrogen-induced proliferation of uterine epithelial cells is independent of estrogen receptor alpha binding to classical estrogen response elements.
Acting via the estrogen receptor (ER), estradiol exerts pleomorphic effects on the uterus, producing cyclical waves of cellular proliferation and differentiation in preparation for embryo implantation. In the classical pathway, the ER binds directly to an estrogen response element to activate or repress gene expression. However, emerging evidence supports the existence of nonclassical pathways in which the activated ER alters gene expression through protein-protein tethering with transcription factors such as c-Fos/c-Jun B (AP-1) and Sp1. In this report, we examined the relative roles of classical and nonclassical ER signaling in vivo by comparing the estrogen-dependent uterine response in mice that express wild-type ERalpha, a mutant ERalpha (E207A/G208A) that selectively lacks ERE binding, or ERalpha null. In the compound heterozygote (AA/-) female, the nonclassical allele (AA) was insufficient to mediate an acute uterotrophic response to 17beta-estradiol (E2). The uterine epithelial proliferative response to E2 and 4-hydroxytamoxifen was retained in the AA/-females, and uterine luminal epithelial height increased commensurate with the extent of ERalpha signaling. This proliferative response was confirmed by 5-bromo-2'-deoxyuridine incorporation. Microarray experiments identified cyclin-dependent kinase inhibitor 1A as a nonclassical pathway-responsive gene, and transient expression experiments using the cyclin-dependent kinase inhibitor 1A promoter confirmed transcriptional responses to the ERalpha (E207A/G208A) mutant. These results indicate that nonclassical ERalpha signaling is sufficient to restore luminal epithelial proliferation but not other estrogen-responsive events, such as fluid accumulation and hyperemia. We conclude that nonclassical pathway signaling via ERalpha plays a critical physiologic role in the uterine response to estrogen.
O'Brien
Jeanne E
JE
Division of Reproductive Endocrinology and Infertility, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA.
Peterson
Theresa J
TJ
Tong
Ming Han
MH
Lee
Eun-Jig
EJ
Pfaff
Liza E
LE
Hewitt
Sylvia C
SC
Korach
Kenneth S
KS
Weiss
Jeffrey
J
Jameson
J Larry
JL
D000818:Animals; D051402:Aquaporin 5 / Q000378:metabolism; D002460:Cell Line; D049109:Cell Proliferation; D056742:Cyclin D2; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism; D004717:Endometrium / Q000166:cytology*; D004847:Epithelial Cells / Q000166:cytology*; D004965:Estrogen Antagonists / Q000378:metabolism; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism*; D004967:Estrogens / Q000378:metabolism*; D005260:Female; D005838:Genotype; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009929:Organ Size; D011374:Progesterone / Q000097:blood; D011485:Protein Binding; D011980:Receptors, Progesterone / Q000378:metabolism; D020218:Response Elements; D015398:Signal Transduction / Q000502:physiology; D013629:Tamoxifen / Q000031:analogs & derivatives / Q000378:metabolism; D014599:Uterus / Q000033:anatomy & histology*
C496038:Aqp5 protein, mouse; D051402:Aquaporin 5; C486196:Ccnd2 protein, mouse; C493957:Cdkn1a protein, mouse; D056742:Cyclin D2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004965:Estrogen Antagonists; D047628:Estrogen Receptor alpha; D004967:Estrogens; D011980:Receptors, Progesterone; D013629:Tamoxifen; C016601:afimoxifene; D011374:Progesterone