PHYSIOLOGICAL REGULATION OF GONADOTROPIN GENE EXPRESSION

这一建议的目的是阐明模式的作用， 促性腺激素释放激素（GnRH）脉冲信号和环境 卵巢激素环境，调节3种促性腺激素的表达 雌性大鼠的亚单位基因。 我们还计划探索一种可能的 类固醇调节亚基基因转录的机制，即 调节转录的持续时间。 哺乳动物的生殖是由脑垂体激素控制的， 促黄体生成激素（LH）和促卵泡激素（FSH）。 LH和 FSH由一个共同的α亚基和特异性的β亚基组成， 依次由促性腺细胞中的3个基因编码。 仅单个 已知下丘脑GnRH调节亚单位基因表达， 激素分泌，尽管LH和FSH合成的差异调节 并且已知在正常生理学中发生分泌。 因此差异化 合成和分泌似乎受到不同模式的调节 （振幅和频率）的GnRH脉冲分泌，连同 性腺类固醇和肽对垂体的直接反馈作用 促性腺细胞 我们建议验证GnRH缺乏的雌性大鼠 模型;评估不同模式的外源性GnRH脉冲对 亚单位mRNA表达;确定是否需要其他神经肽 快速增加LH β mRNA;并确定反应是否 受雌二醇（E2）、孕酮（P）、卵泡抑素（follistatin）和雌二醇（E2）调节; 研究调节基因表达的生理机制， 大鼠的发情周期 第二个目标是检验我们的假设， 增加的亚基基因转录的持续时间， 脉冲GnRH信号由性腺类固醇激素调节。 我们 有初步证据表明，在响应Gn RH脉冲，转录 在类固醇存在的情况下发生的持续时间较短，我们将 评估性腺类固醇在这方面的作用。 如果被证明是 的确，这将是一种新的类固醇调节机制， 促性腺激素的合成和分泌。 脉冲性促性腺激素释放激素刺激对启动亚单位的重要性 基因转录和维持激素分泌是有据可查的。 已知GnRH脉冲的模式在排卵周期中发生变化， 调节GnRH频率和幅度的机制异常 似乎是引起女性不排卵综合征的重要组成部分。 下丘脑性闭经（HA）的GnRH脉冲缓慢， 多囊卵巢综合征患者高催乳素血症发生率高 疾病（PCO）。 我们先前在大鼠中的数据表明，慢频率GnRH 刺激有利于FSH β mRNA表达和FSH分泌（如HA中所见 和高催乳素血症），快频率GnRH脉冲有利于α和 LH β mRNA表达和LH分泌（如PCO中发生的）。 这 提供了强有力的支持，我们的论点，拟议的研究， GnRH在调节大鼠基因表达中的作用机制将 允许洞察正常的生理机制，并最终改善 治疗由于不排卵引起的人类不育症的方法。

The aim of this proposal is to elucidate the roles of the pattern of the gonadotropin-releasing hormone (GnRH) pulse signal and the ambient ovarian hormonal milieu, in regulating expression of the 3 gonadotropin subunit genes in female rats. We also plan to explore a possible mechanism of steroidal regulation of subunit gene transcription, namely regulation of the duration of transcription. Reproduction in mammals is controlled by the pituitary hormones, luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH and FSH consist of a common alpha subunit and specific beta subunits, which in turn are coded by 3 genes in the gonadotrope cell. Only a single hypothalamic GnRH is known to regulate subunit gene expression and hormone secretion, though differential regulation of LH and FSH synthesis and secretion is known to occur in normal physiology. Thus differential synthesis and secretion appear to be regulated by different patterns (amplitude and frequency) of GnRH pulsatile secretion, together with the direct feedback effects of gonadal steroids and peptides on the pituitary gonadotrope cell. We propose to validate a GnRH deficient female rat model; assess effects of different patterns of exogenous GnRH pulses on subunit mRNA expression; establish if other neuropeptides are required to rapidly increase LH beta mRNA; and determine if responses are modulated by estradiol (E2), progesterone (P), inhibin, and follistatin; investigate the physiologic mechanisms regulating gene expression during the rat estrous cycle. The second goal is to test our hypothesis that the duration of increased subunit gene transcription in response to pulsatile Gn RH signals is regulated by gonadal steroid hormones. We have preliminary evidence that in response to Gn RH pulses, transcription occurs for a shorter duration in the presence of steroids and we will evaluate the roles of gonadal steroids in this respect. If proven to be true, this would be a novel mechanism of steroid regulation of gonadotropin synthesis and secretion. The critical importance of pulsatile GnRH stimulus to initiate subunit gene transcription and to maintain hormonal secretion is well documented. The pattern of GnRH pulses is known to change during ovulatory cycles and abnormalities of the mechanisms regulating GnRH frequency and amplitude appear to be an important part of syndromes causing anovulation in women. GnRH pulses are slow in hypothalamic amenorrhea (HA) and hyperprolactinemia and occur at fast frequency in polycystic ovarian disease (PCO). Our prior data in rats showed that slow frequency GnRH stimuli favor FSH beta mRNA expression and FSH secretion (as seen in HA and hyperprolactinemia), and fast frequency GnRH pulses favor alpha and LH beta mRNA expression and LH secretion (as occurs in PCO). This provides strong support to our contention that the proposed studies of the mechanisms of GnRH action in regulating gene expression in rats will allow insight into normal physiologic mechanisms, and ultimately improved methods of treating human infertility due to anovulation.