PHYSIOLOGICAL REGULATION OF GONADOTROPIN GENE EXPRESSION

这项建议的目的是阐明 促性腺激素释放激素脉冲信号及其周围环境 卵巢激素环境对促性腺激素3表达的调节 雌性大鼠的亚单位基因。我们还计划探索一种可能的 类固醇调节亚单位基因转录的机制，即 转录持续时间的调节。 哺乳动物的生殖由脑下垂体激素控制， 黄体生成素(LH)和卵泡刺激素(FSH)。Lh和 FSH由一个共同的α亚基和特定的β亚基组成， 依次由促性腺激素细胞中的3个基因编码。只有一张 已知下丘脑GnRH调节亚单位基因表达和 激素分泌，通过对促黄体生成素和卵泡刺激素合成的不同调节 而已知的分泌物在正常生理学中也会发生。因此，差异化 合成和分泌似乎受到不同模式的调节。 GnRH脉动性分泌的(幅度和频率)，以及 性腺激素和多肽对垂体的直接反馈效应 促性腺激素细胞。我们建议验证一只GnRH缺陷雌性大鼠 模型；评估不同模式的外源性促性腺激素释放激素脉冲对 亚单位mRNA的表达；确定是否需要其他神经肽 快速增加促黄体生成素βmRNA；并确定反应是否 受雌二醇(E_2)、孕酮(P)、抑制素和卵泡抑素的调节； 探讨基因表达调控的生理机制 大鼠的发情周期。第二个目标是测试我们的假设 亚基基因转录增加的持续时间 搏动性Gn RH信号受性腺类固醇激素的调节。我们 有初步证据表明，对Gn RH脉冲的反应，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 诚然，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作用 基因转录和维持荷尔蒙分泌是有充分证据的。 已知促性腺激素释放激素脉冲的模式在排卵周期和 促性腺激素释放激素频率和幅度调节机制的异常 似乎是导致女性无排卵综合征的重要组成部分。 GnRH脉冲在下丘脑闭经(HA)和 多囊卵巢高催乳素血症和高频率发生 疾病(PCO)。我们先前在大鼠身上的数据显示，慢频率GnRH 刺激促进FSHβmRNA表达和FSH分泌(如在HA中所见 和高催乳素血症)，并且快频GnRH脉冲有利于α和 黄体生成素β基因的表达和黄体生成素的分泌(与多囊卵巢相同)。这 为我们的论点提供了强有力的支持，即 促性腺激素释放激素调节大鼠基因表达的机制 允许深入了解正常的生理机制，并最终得到改善 治疗人类无排卵所致不孕症的方法。

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.