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Updated: Aug 6, 2026
Determination of Reproductive Competence by Confirming Pubertal Onset and Performing a Fertility Assay in Mice and Rats
Published on: October 13, 2018
Early onset of puberty and early ovarian failure in CYP7B1 knockout mice
Yoko Omoto1, Richard Lathe, Margaret Warner
1Department of Medical Nutrition, Karolinska Institute, 141 86 Huddinge, Sweden.
Abstract:
CYP7B1 is the enzyme responsible for hydroxylation and termination of the estrogenic actions of the androgen metabolite, 5alpha-androstane-3beta, 17beta-diol (3betaAdiol). 3betaAdiol is estrogenic in ERalpha or ERbeta positive cells only if they do not express CYP7B1. In this study we show that female CYP7B1(-/-) mice experience early onset of growth of the uterus and mammary glands and commence estrus cycles 2 days earlier than their wild-type littermates. Adult mammary glands and uteri appear to be under continuous estrogenic stimulation. We conclude that, by cell-specific regulation of the estrogenicity of 3betaAdiol, CYP7B1 performs two major tasks: (i) it allows 3betaAdiol to have growth inhibitory effects through ERbeta and (ii) it permits estradiol-specific activation of estrogen receptors by protection of certain cells from the estrogenic effects of 3betaAdiol. When CYP7B1 is inactivated, 3betaAdiol activates estrogen receptors indiscriminately, and the overall effect is prolonged and inappropriate exposure to estrogen.
Insights
The enzyme CYP7B1 regulates estrogenic effects of androgen metabolites. Its absence in mice leads to early reproductive organ development and continuous estrogenic stimulation.
Area of Science:
- Endocrinology
- Molecular Biology
- Biochemistry
Background:
- The enzyme Cytochrome P450 7B1 (CYP7B1) metabolizes androgen metabolites.
- 5alpha-androstane-3beta, 17beta-diol (3betaAdiol) is an androgen metabolite with estrogenic activity.
- CYP7B1 regulates the estrogenicity of 3betaAdiol, particularly in cells expressing estrogen receptors (ERalpha or ERbeta).
Purpose of the Study:
- To investigate the physiological role of CYP7B1 in regulating estrogenic actions.
- To determine the consequences of CYP7B1 deficiency on reproductive development and function.
Main Methods:
- Utilized CYP7B1 knockout (CYP7B1-/-) mouse models.
- Compared reproductive organ development and estrus cyclicity between CYP7B1-/- mice and wild-type littermates.
Main Results:
- Female CYP7B1-/- mice exhibited precocious growth of the uterus and mammary glands.
- Estrus cycles initiated 2 days earlier in CYP7B1-/- mice compared to controls.
- Adult mammary glands and uteri in CYP7B1-/- mice showed signs of continuous estrogenic stimulation.
Conclusions:
- CYP7B1 plays a critical role in cell-specific regulation of 3betaAdiol's estrogenicity.
- CYP7B1 enables 3betaAdiol to exert growth-inhibitory effects via ERbeta.
- CYP7B1 protects specific cells from 3betaAdiol's estrogenic effects, allowing estradiol-specific ER activation.
- Inactivation of CYP7B1 leads to indiscriminate 3betaAdiol activation of estrogen receptors, resulting in prolonged estrogen exposure.
