Transcriptional control of pituitary gonadotropin genes

描述(由申请人提供)： 项目摘要/摘要生育力取决于下丘脑-垂体-性腺轴的适当神经内分泌调节。代谢紊乱，包括肥胖，通常以高胰岛素血症为特征，并与女性生育力下降有关。在这些疾病中，对类固醇、配子发生和排卵至关重要的促性腺激素的产生也受到干扰。这项应用的总体目标是确定促性腺激素基因的表达是否受垂体促性腺激素细胞中叉头转录因子的调节。FOXO蛋白受胰岛素信号的调节，因此，可能是代谢状态和生育能力之间的重要调节纽带。FOXO调节多种细胞功能，如细胞凋亡、应激抵抗和新陈代谢，但它们在神经内分泌调节生殖中的作用尚未被广泛研究。我们的初步结果表明，FoxO1在垂体促性腺激素细胞中表达，并且在这些细胞中，FoxO1的磷酸化和细胞定位受到胰岛素的调节。我们的初步研究还表明，FoxO1抑制基础和GnRH对黄体生成素和卵泡刺激素的诱导。我们的假设是，FoxO1转录因子抑制垂体促性腺激素细胞中促性腺激素的合成，而胰岛素信号通过使FoxO1转录失活来缓解这种抑制。在这项提案中，我们将利用新的方法来研究FOXO1在体外和体内转录调节促性腺激素合成的机制。在具体目标1中，将使用脑垂体特异性基因敲除小鼠模型来确定促性腺激素中FoxO1的表达是否对生育是必要的，以及FoxO1是否在肥胖相关的不育症中发挥作用。在具体目标2中，将使用生化和组织细胞培养模型来表征FoxO1调节促性腺激素产生的机制。具体目标3将阐述促性腺激素细胞中通过FoxO1进行胰岛素信号转导的机制，并使用条件活跃的FoxO1转基因小鼠模型确定中断FoxO1的胰岛素调节是否会影响生育。这一建议的结果有可能回答有关FoxO1在促性腺激素产生中的作用的基本问题，并为激素控制生育的广泛机制提供洞察。了解这些机制可能对开发新的避孕方法或不孕症治疗具有重要意义。潜在的应用还可能在治疗一系列疾病方面带来新的方向，这些疾病可能是由于促性腺激素产生故障而导致的，如闭经、性早熟、理想性性腺功能减退和多囊卵巢综合征。这项提议的资金还将使作为早期调查者的PI能够在生殖内分泌学领域建立一个完全独立的研究方案。

DESCRIPTION (provided by applicant): Project Summary/Abstract Fertility depends on proper neuroendocrine regulation of the hypothalamic-pituitary-gonadal axis. Metabolic disorders, including obesity, are often characterized by hyperinsulinemia and associated with reduced fertility in women. Production of gonadotropin hormones critical for steroidogenesis, gametogenesis and ovulation is also disturbed in these disorders. The overall goal of this application is to determine whether gonadotropin gene expression is regulated by forkhead transcription factors in pituitary gonadotrope cells. FoxO proteins are regulated by insulin signaling and thus, may be an important regulatory link between metabolic status and fertility. FoxOs regulate diverse cellular functions, such as apoptosis, stress resistance and metabolism, but their role in the neuroendocrine regulation of reproduction has not been extensively explored. Our preliminary results indicate that FoxO1 is expressed in pituitary gonadotrope cells and that FoxO1 phosphorylation and cellular localization is regulated by insulin in these cells. Our preliminary studies also show that FoxO1 suppresses basal and GnRH induction of luteinizing hormone and follicle-stimulating hormone. Our hypothesis is that the FoxO1 transcription factor suppresses gonadotropin synthesis in pituitary gonadotrope cells and that insulin signaling relieves this suppression by rendering FoxO1 transcriptionally inactive. In this proposal, we will utilize novel approaches to study mechanisms of FoxO1 transcriptional regulation of gonadotropin synthesis in vitro and in vivo. In Specific Aim 1, a pituitary-specific knockout mouse model will be used to determine whether FoxO1 expression in the gonadotrope is necessary for fertility and whether FoxO1 plays a role in obesity-related infertility. In Specific Aim 2, biochemical and tissue cell culture models will be used to characterize mechanisms of FoxO1 regulation of gonadotropin production. Specific Aim 3 will address mechanisms of insulin signal transduction via FoxO1 in gonadotrope cells and determine if disruption of insulin regulation of FoxO1 impacts fertility using a conditionally active FoxO1 transgenic mouse model. Results from this proposal have the potential to answer fundamental questions regarding the role of FoxO1 in gonadotropin production and provide insight into broad mechanisms of hormonal control of fertility. Understanding these mechanisms may be relevant for the development of novel contraceptive methods or infertility treatments. Potential applications could also lead to new directions in treating a range of disorders that can result from malfunction in gonadotropin production, such as amenorrhea, precocious puberty, ideopathic hypogonadism, and polycystic ovarian syndrome. Funding of this proposal will also allow the PI, as an Early-Stage Investigator, to establish a fully-independent research program in the field of reproductive endocrinology.