An estrogen receptor-alpha knock-in mutation provides evidence of ligand-independent signaling and allows modulation of ligand-induced pathways in vivo.
Estrogen-nonresponsive estrogen receptor-alpha (ERalpha) knock-in (ENERKI) mice were generated to distinguish between ligand-induced and ligand-independent ER-alpha actions in vivo. These mice have a mutation [glycine 525 to leucine (G525L)] in the ligand-binding domain of ERalpha, which significantly reduces ERalpha interaction with and response to endogenous estrogens, whereas not affecting growth factor activation of ligand-independent pathways. ENERKI mice had hypoplastic uterine tissues and rudimentary mammary gland ductal trees. Females were infertile due to anovulation, and their ovaries contained hemorrhagic cystic follicles because of chronically elevated levels of LH. The ENERKI phenotype confirmed that ligand-induced activation of ERalpha is crucial in the female reproductive tract and mammary gland development. Growth factor treatments induced uterine epithelial proliferation in ovariectomized ENERKI females, directly demonstrating that ERalpha ligand-independent pathways were active. In addition, the synthetic ERalpha selective agonist propyl pyrazole triol (PPT) and ER agonist diethylstilbestrol (DES) were still able to activate ligand-induced G525L ERalpha pathways in vitro. PPT treatments initiated at puberty stimulated ENERKI uterine development, whereas neonatal treatments were needed to restore mammary gland ductal elongation, indicating that neonatal ligand-induced ERalpha activation may prime mammary ducts to become more responsive to estrogens in adult tissues. This is a useful model for in vivo evaluation of ligand-induced ERalpha pathways and temporal patterns of response. DES did not stimulate an ENERKI uterotrophic response. Because ERbeta may modulate ERalpha activation and have an antiproliferative function in the uterus, we hypothesize that ENERKI animals were particularly sensitive to DES-induced inhibition of ERalpha due to up-regulated uterine ERbeta levels.
Sinkevicius
Kerstin W
KW
The Ben May Department for Cancer Research, The University of Chicago, Chicago, Illinois 60637, USA.
Burdette
Joanna E
JE
Woloszyn
Karolina
K
Hewitt
Sylvia C
SC
Hamilton
Katherine
K
Sugg
Sonia L
SL
Temple
Karla A
KA
Wondisford
Fredric E
FE
Korach
Kenneth S
KS
Woodruff
Teresa K
TK
Greene
Geoffrey L
GL
D000230:Adenocarcinoma; D000273:Adipose Tissue / Q000502:physiology; D019943:Amino Acid Substitution; D000818:Animals; D045744:Cell Line, Tumor; D003001:Cloning, Molecular; D004054:Diethylstilbestrol / Q000494:pharmacology; D016889:Endometrial Neoplasms; D004958:Estradiol / Q000502:physiology; D047628:Estrogen Receptor alpha / Q000235:genetics*; D047629:Estrogen Receptor beta / Q000235:genetics; D005260:Female; D005640:Follicle Stimulating Hormone / Q000502:physiology; D005838:Genotype; D006801:Humans; D008024:Ligands; D007986:Luteinizing Hormone / Q000502:physiology; D008321:Mammary Glands, Animal / Q000166:cytology / Q000502:physiology; D051379:Mice; D009154:Mutation; D016133:Polymerase Chain Reaction; D015398:Signal Transduction; D014599:Uterus / Q000187:drug effects / Q000502:physiology
D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D008024:Ligands; D004958:Estradiol; D004054:Diethylstilbestrol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone