Post-transcriptional Pathways that Signal Leptin Regulation of Gonadotropes

瘦素对促性腺激素调节的转录后信号通路

• 批准号: 9195823
• 负责人: GWEN V CHILDS
• 金额: $ 47.04万
• 依托单位: UNIV OF ARKANSAS FOR MED SCIS
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-15 至 2021-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9195823
• 关键词: Ablation; Address; Binding; Clinical Protocols; Clomiphene; Data; Development; Diestrus; Equilibrium; Exons; Fasting; Female; Fertility; Food deprivation (experimental); Frequencies; Genetic; Genetic Translation; Goals; Gonadal structure; Gonadotropin Hormone Releasing Hormone; Gonadotropin-Releasing Hormone Receptor; Gonadotropins; Human; In Vitro; Infertility; Knowledge; Lead; Leptin; Leptin deficiency; Link; Lipodystrophy; Luteinizing Hormone; Mediating; Membrane; Menarche; Messenger RNA; Metabolic; Metabolism; MicroRNAs; Mission; Modeling; Molecular; Mus; Mutant Strains Mice; Neurons; Nutritional; Nutritional status; Ovulation; Periodicity; Physiologic pulse; Pituitary Gland; Portal System; Prevention; Process; Protein Isoforms; Proteins; Public Health; RNA-Binding Proteins; Receptor Gene; Regulation; Reporter; Repression; Reproduction; Reproductive Process; Research; Resources; Role; Serum; Signal Pathway; Signal Transduction; Site; Staging; Testing; Time; Translations; Untranslated RNA; Up-Regulation; genetic regulatory protein; hypothalamic pituitary gonadal axis; improved; in vivo; infertility treatment; innovation; knock-down; knockout gene; leptin receptor; mouse model; mutant; novel; novel diagnostics; novel therapeutic intervention; prevent; receptor; receptor expression; recombinase; reproductive; reproductive success; response; restoration; success

PROJECT SUMMARY/ABSTRACT The expression of GnRHRs is a critical, rate-limiting step in the reproductive process, however little is known about the mechanism behind the regulation of translation of GnRHR proteins. Gonadotrope functions may be limited in times of food deprivation, which is signaled by leptin deficiency, however there is a fundamental gap in understanding how leptin regulates gonadotropes. Leptin's importance to gonadotropes is highlighted by the infertile mouse model in which all isoforms of leptin receptors (LEPR) on gonadotropes are ablated, and the fact that the mutant gonadotropes have severely reduced GnRHR protein, but not mRNA levels. These findings provide important clues as to how leptin links fertility to metabolic status, however the molecular mechanisms underlying leptin control of gonadotropes are unknown. Our long-term goal is to fill this knowledge gap by identifying underlying mechanisms behind the infertility in the gonadotrope Lepr-null mutant mice. The central hypothesis to be tested is that loss of leptin signaling in gonadotropes prevents the normal diestrous upregulation of GnRH receptors causing a blunted or absent LH surge and infertility. A secondary hypothesis that leptin acts through posttranscriptional mechanisms to optimize gonadotrope function. The proposed studies will focus on three specific aims. Specific Aim 1 will determine if loss of leptin signaling in gonadotropes reduces fertility through prevention of the diestrous upregulation of GnRHR protein levels. These studies will ascertain if the Lepr-null gonadotropes are held in persistent diestrus because of low GnRHR proteins and if the normal surge in serum gonadotropins is absent. The efficacy of exogenous GnRH in the rescue of GnRHR levels in mutants and restoration of cyclicity and fertility will be tested. Specific Aim 2 studies will determine if leptin signaling to mRNA translational control mechanisms is required for gonadotrope function. These studies will globally assess leptin regulation of gonadotrope mRNA translation and specifically address control of Gnrhr mRNA translation. Genetic knockdown of identified candidate translational repressors will be used to restore GnRHR expression in mutant gonadotropes. Specific Aim 3 studies will determine if food deprivation recapitulates the effect of loss of leptin signaling to gonadotropes, including repression of Gnrhr mRNA translation. These in vivo studies will test the hypothesis that loss of leptin signaling during food deprivation also prevents diestrous upregulation of GnRHR. The studies will also determine if the in vitro deletion of identified translational control mechanisms (e.g. MSI, miRNAs) alleviates the fasting-induced repression of Gnrhr mRNA translation. Our research is innovative because it investigates the novel concept that leptin may regulate gonadotrope function at post-transcriptional levels. These findings are significant because clinical protocols used in infertility treatments (e.g. clomiphene) depend on normal responses to endogenous GnRH, which we have shown depends on normal leptin signaling.

项目概要/摘要 GnRHR 的表达是生殖过程中关键的限速步骤，但目前对其的研究很少。 了解 GnRHR 蛋白翻译调节背后的机制。促性腺激素功能 在食物匮乏时可能会受到限制，这是瘦素缺乏的信号，但是有一个 在理解瘦素如何调节促性腺激素方面存在根本差距。瘦素对促性腺激素的重要性是 不育小鼠模型强调了这一点，其中促性腺激素上的瘦素受体（LEPR）的所有亚型都是 消融，并且突变促性腺激素严重减少了 GnRHR 蛋白，但没有减少 mRNA 水平。这些发现为瘦素如何将生育能力与代谢状态联系起来提供了重要线索，然而 瘦素控制促性腺激素的分子机制尚不清楚。我们的长期目标是填补 通过确定促性腺激素 Lepr-null 不孕背后的潜在机制来弥补这一知识差距 突变小鼠。要测试的中心假设是促性腺激素中瘦素信号的丧失 防止 GnRH 受体正常的间情上调，导致 LH 减弱或缺失 激增和不孕。瘦素通过转录后作用发挥作用的次要假设 优化促性腺激素功能的机制。拟议的研究将集中于三个具体目标。 具体目标 1 将确定促性腺激素中瘦素信号传导的丧失是否会通过预防 GnRHR 蛋白水平的间情上调。这些研究将确定 Lepr-null 是否 由于 GnRHR 蛋白水平低且血清中的正常激增，促性腺激素处于持续的发情间期 促性腺激素不存在。外源 GnRH 在挽救突变体和 GnRHR 水平中的功效 周期性和生育力的恢复将受到考验。具体目标 2 研究将确定瘦素信号传导是否 mRNA 翻译控制机制是促性腺激素功能所必需的。这些研究将在全球范围内 评估瘦素对促性腺激素 mRNA 翻译的调节并专门解决 Gnrhr mRNA 的控制 翻译。已确定的候选翻译抑制因子的基因敲除将用于恢复 GnRHR 突变促性腺激素的表达。具体目标 3 研究将确定食物匮乏是否会重现 瘦素信号传导丧失对促性腺激素的影响，包括抑制 Gnrhr mRNA 翻译。这些在 体内研究将检验这样的假设：食物匮乏期间瘦素信号传导的丧失也可以防止景深 GnRHR 的上调。这些研究还将确定是否在体外删除已识别的翻译 控制机制（例如 MSI、miRNA）减轻禁食诱导的 Gnrhr mRNA 翻译抑制。 我们的研究具有创新性，因为它研究了瘦素可能调节促性腺激素的新概念 在转录后水平发挥作用。这些发现意义重大，因为临床方案用于 不孕不育治疗（例如克罗米芬）取决于对内源性 GnRH 的正常反应，我们有 显示取决于正常的瘦素信号传导。