Expression of the estrogen-inducible EGFP gene in aromatase-null mice reveals differential tissue responses to estrogenic compounds

Aromatase is an enzyme responsible for the conversion of androgen to estrogen. We genetically engineered an aromatase-deficient mouse (Ar−/− mouse) to express an enhanced green fluorescent protein (EGFP) gene in the uterus, ovary, adrenal and pituitary glands in a 17β-estradiol (E2)-inducible manner. In this study, we analyzed estrogenic activities of diethylstilbestrol, genistein, daidzein and E2 in the Ar−/− tissues by using the EGFP expression as an indicator. These analyses manifest differential responses of the tissues to the compounds and also allow to determine the relative estrogenic potency of the compounds to that of E2 in vivo. Furthermore, analyses of the EGFP expression in ERα-deficient mice suggested that the expression is ERα-dependent in the uterus and pituitary gland. In conclusion, the Ar−/− mouse carrying the E2-inducible EGFP gene is a valuable tool for quantitative analyses of natural and synthetic estrogenic compounds in vivo.