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Determination of Reproductive Competence by Confirming Pubertal Onset and Performing a Fertility Assay in Mice and Rats
Published on: October 13, 2018
ERα in Tac2 Neurons Regulates Puberty Onset in Female Mice
Megan L Greenwald-Yarnell1, Courtney Marsh1, Margaret B Allison1
1Neuroscience Graduate Program (M.L.G.-Y., S.M.M., M.G.M.); Division of Metabolism, Endocrinology and Diabetes (M.L.G.-Y., M.B.A., C.M.P., C.K., A.M., S.M.M., M.G.M.), Department of Internal Medicine; and Departments of Obstetrics and Gynecology (C.M., C.F.E., S.M.M.) and Molecular and Integrative Physiology (M.B.A., R.C., C.F.E., S.M.M., M.G.M.), University of Michigan, Ann Arbor, Michigan 48109.
Abstract:
A variety of data suggest that estrogen action on kisspeptin (Kiss1)-containing arcuate nucleus neurons (which coexpress Kiss1, neurokinin B (the product of Tac2) and dynorphin (KNDy) neurons restrains reproductive onset and function, but roles for estrogen action in these Kiss1 neurons relative to a distinct population of rostral hypothalamic Kiss1 neurons (which does not express Tac2 or dynorphin) have not been directly tested. To test the role for estrogen receptor (ER)α in KNDy cells, we thus generated Tac2(Cre) and Kiss1(Cre) knock-in mice and bred them onto the Esr1(flox) background to ablate ERα specifically in Tac2-expressing cells (ERα(Tac2)KO mice) or all Kiss1 cells (ERα(Kiss1)KO mice), respectively. Most ERα-expressing Tac2 neurons represent KNDy cells. Arcuate nucleus Kiss1 expression was elevated in ERα(Tac2)KO and ERα(Kiss1)KO females independent of gonadal hormones, whereas rostral hypothalamic Kiss1 expression was normal in ERα(Tac2)KO but decreased in ERα(Kiss1)KO females; this suggests that ERα in rostral Kiss1 cells is crucial for control of Kiss1 expression in these cells. Both ERα(Kiss1)KO and ERα(Tac2)KO females displayed early vaginal opening, early and persistent vaginal cornification, increased gonadotropins, uterine hypertrophy, and other evidence of estrogen excess. Thus, deletion of ERα in Tac2 neurons suffices to drive precocious gonadal hyperstimulation, demonstrating that ERα in Tac2 neurons typically restrains pubertal onset and hypothalamic reproductive drive.
Insights
Estrogen receptor alpha in kisspeptin neurons restrains reproductive onset. Ablating this receptor in Tac2 neurons triggers precocious puberty and estrogen excess, highlighting its role in controlling pubertal timing.
Area of Science:
- Neuroendocrinology
- Reproductive Biology
- Molecular Endocrinology
Background:
- Estrogen action on kisspeptin (Kiss1) neurons is implicated in reproductive regulation.
- The specific roles of estrogen receptor alpha (ERα) in different Kiss1 neuronal populations remain unclear.
Purpose of the Study:
- To investigate the function of ERα in kisspeptin neurons, particularly in arcuate nucleus KNDy (Kiss1, neurokinin B, dynorphin) neurons versus rostral hypothalamic Kiss1 neurons.
- To determine if ERα in Tac2-expressing neurons restrains reproductive onset and function.
Main Methods:
- Generated Tac2(Cre) and Kiss1(Cre) knock-in mice crossed with Esr1(flox) mice to create ERα(Tac2)KO and ERα(Kiss1)KO models.
- Analyzed Kiss1 expression in the arcuate nucleus and rostral hypothalamus.
- Assessed reproductive parameters including vaginal opening, vaginal cornification, gonadotropin levels, and uterine hypertrophy.
Main Results:
- Deletion of ERα in Tac2 neurons (ERα(Tac2)KO) and all Kiss1 neurons (ERα(Kiss1)KO) elevated arcuate nucleus Kiss1 expression.
- ERα in rostral Kiss1 neurons is crucial for controlling Kiss1 expression in that region.
- Both ERα(Kiss1)KO and ERα(Tac2)KO females exhibited precocious puberty and signs of estrogen excess.
Conclusions:
- Estrogen receptor alpha in Tac2-expressing neurons is essential for restraining pubertal onset.
- Deletion of ERα in these neurons leads to hypergonadotropic hyperestrogenism and precocious puberty.
- These findings demonstrate a critical role for ERα in Tac2 neurons in regulating the timing of puberty and hypothalamic reproductive drive.
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