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Mutation of the GnRHR Proximal Promoter AP-1 Element in Mice Results in Suboptimal GnRH Induction of LH and an Abnormal Reproductive Phenotype

Reproduction is regulated by the gonadotropins, LH and FSH, which are synthesized and secreted by pituitary gonadotrophs in response to hypothalamic GnRH in a pulse frequency dependent manner. The gonadotroph decodes GnRH pulsatility via the GnRH receptor (GnRHR), which increases in expression and c...

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Autores principales: Hausken, Krist N, Noel, Sekoni D, Kim, Han Kyeol, Carroll, Rona Stephanie, Kaiser, Ursula B
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Oxford University Press 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8090607/
http://dx.doi.org/10.1210/jendso/bvab048.1111
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author Hausken, Krist N
Noel, Sekoni D
Kim, Han Kyeol
Carroll, Rona Stephanie
Kaiser, Ursula B
author_facet Hausken, Krist N
Noel, Sekoni D
Kim, Han Kyeol
Carroll, Rona Stephanie
Kaiser, Ursula B
author_sort Hausken, Krist N
collection PubMed
description Reproduction is regulated by the gonadotropins, LH and FSH, which are synthesized and secreted by pituitary gonadotrophs in response to hypothalamic GnRH in a pulse frequency dependent manner. The gonadotroph decodes GnRH pulsatility via the GnRH receptor (GnRHR), which increases in expression and cell surface density before estrus and is responsible for downstream signaling cascades that differentially favor gonadotropin expression. The gonadotroph Gnrhr promoter contains a tripartite enhancer, including an AP-1 element that is necessary for full GnRH induction of Gnrhr expression in vitro. We previously generated an AP-1 knock-in (KI) mouse model with a single point mutation (C-269T) in the Gnrhr promoter AP-1 binding motif that resulted in an abnormal reproductive phenotype in female mice. Compared to wildtype (WT) littermates, female KI mice had a significant delay in first estrus, disrupted estrous cyclicity, fewer corpora lutea, and smaller litters. Males had no apparent reproductive phenotype. Basal serum gonadotropin levels were similar between WT and KI mice, but gonadectomy induced a significantly lower rise in serum LH levels of KI mice relative to WT mice, concomitant with significantly lower pituitary Gnrhr, Lhb, and Fshb mRNA levels in both sexes. We have now extended the characterization of these mice by measuring LH pulsatility and assessing GnRH induction of LH in vivo and in vitro. The frequency and amplitude of LH pulses over three hours were similar in ovariectomized WT and KI mice; however, KI mice had significantly reduced LH secretion, as measured by area under the curve. Similarly, GnRH treatment induced a diminished LH response in intact KI compared to WT males. In vitro cultures of hemi-pituitaries from gonadectomized WT and KI males were exposed to 0.01 nM GnRH and LH secretion into culture media was measured by ELISA at 0, 0.5, 1, 2, and 4 hours. There was no difference in basal LH secretion between WT and KI pituitaries but GnRH induction of LH was significantly lower in cultures from AP-1 mutant mice, indicating a direct impairment of GnRH action at the level of the pituitary. Taken together, these data indicate that the gonadotroph Gnrhr AP-1 promoter motif is critical for normal reproductive function. Prevention of AP-1 binding to the Gnrhr proximal promoter element decreases GnRH-induced Gnrhr, Lhb, and Fshb levels, impairs GnRH-stimulated LH secretion, and disrupts pubertal development and reproductive cyclicity in female mice.
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spelling pubmed-80906072021-05-05 Mutation of the GnRHR Proximal Promoter AP-1 Element in Mice Results in Suboptimal GnRH Induction of LH and an Abnormal Reproductive Phenotype Hausken, Krist N Noel, Sekoni D Kim, Han Kyeol Carroll, Rona Stephanie Kaiser, Ursula B J Endocr Soc Neuroendocrinology and Pituitary Reproduction is regulated by the gonadotropins, LH and FSH, which are synthesized and secreted by pituitary gonadotrophs in response to hypothalamic GnRH in a pulse frequency dependent manner. The gonadotroph decodes GnRH pulsatility via the GnRH receptor (GnRHR), which increases in expression and cell surface density before estrus and is responsible for downstream signaling cascades that differentially favor gonadotropin expression. The gonadotroph Gnrhr promoter contains a tripartite enhancer, including an AP-1 element that is necessary for full GnRH induction of Gnrhr expression in vitro. We previously generated an AP-1 knock-in (KI) mouse model with a single point mutation (C-269T) in the Gnrhr promoter AP-1 binding motif that resulted in an abnormal reproductive phenotype in female mice. Compared to wildtype (WT) littermates, female KI mice had a significant delay in first estrus, disrupted estrous cyclicity, fewer corpora lutea, and smaller litters. Males had no apparent reproductive phenotype. Basal serum gonadotropin levels were similar between WT and KI mice, but gonadectomy induced a significantly lower rise in serum LH levels of KI mice relative to WT mice, concomitant with significantly lower pituitary Gnrhr, Lhb, and Fshb mRNA levels in both sexes. We have now extended the characterization of these mice by measuring LH pulsatility and assessing GnRH induction of LH in vivo and in vitro. The frequency and amplitude of LH pulses over three hours were similar in ovariectomized WT and KI mice; however, KI mice had significantly reduced LH secretion, as measured by area under the curve. Similarly, GnRH treatment induced a diminished LH response in intact KI compared to WT males. In vitro cultures of hemi-pituitaries from gonadectomized WT and KI males were exposed to 0.01 nM GnRH and LH secretion into culture media was measured by ELISA at 0, 0.5, 1, 2, and 4 hours. There was no difference in basal LH secretion between WT and KI pituitaries but GnRH induction of LH was significantly lower in cultures from AP-1 mutant mice, indicating a direct impairment of GnRH action at the level of the pituitary. Taken together, these data indicate that the gonadotroph Gnrhr AP-1 promoter motif is critical for normal reproductive function. Prevention of AP-1 binding to the Gnrhr proximal promoter element decreases GnRH-induced Gnrhr, Lhb, and Fshb levels, impairs GnRH-stimulated LH secretion, and disrupts pubertal development and reproductive cyclicity in female mice. Oxford University Press 2021-05-03 /pmc/articles/PMC8090607/ http://dx.doi.org/10.1210/jendso/bvab048.1111 Text en © The Author(s) 2021. Published by Oxford University Press on behalf of the Endocrine Society. https://creativecommons.org/licenses/by-nc-nd/4.0/This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs licence (http://creativecommons.org/licenses/by-nc-nd/4.0/ (https://creativecommons.org/licenses/by-nc-nd/4.0/) ), which permits non-commercial reproduction and distribution of the work, in any medium, provided the original work is not altered or transformed in any way, and that the work is properly cited. For commercial re-use, please contact journals.permissions@oup.com
spellingShingle Neuroendocrinology and Pituitary
Hausken, Krist N
Noel, Sekoni D
Kim, Han Kyeol
Carroll, Rona Stephanie
Kaiser, Ursula B
Mutation of the GnRHR Proximal Promoter AP-1 Element in Mice Results in Suboptimal GnRH Induction of LH and an Abnormal Reproductive Phenotype
title Mutation of the GnRHR Proximal Promoter AP-1 Element in Mice Results in Suboptimal GnRH Induction of LH and an Abnormal Reproductive Phenotype
title_full Mutation of the GnRHR Proximal Promoter AP-1 Element in Mice Results in Suboptimal GnRH Induction of LH and an Abnormal Reproductive Phenotype
title_fullStr Mutation of the GnRHR Proximal Promoter AP-1 Element in Mice Results in Suboptimal GnRH Induction of LH and an Abnormal Reproductive Phenotype
title_full_unstemmed Mutation of the GnRHR Proximal Promoter AP-1 Element in Mice Results in Suboptimal GnRH Induction of LH and an Abnormal Reproductive Phenotype
title_short Mutation of the GnRHR Proximal Promoter AP-1 Element in Mice Results in Suboptimal GnRH Induction of LH and an Abnormal Reproductive Phenotype
title_sort mutation of the gnrhr proximal promoter ap-1 element in mice results in suboptimal gnrh induction of lh and an abnormal reproductive phenotype
topic Neuroendocrinology and Pituitary
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8090607/
http://dx.doi.org/10.1210/jendso/bvab048.1111
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