REPRODUCTIVE PHYSIOLOGY OF GONADOTROPIN SYNTHESIS

描述（由申请方提供）：下丘脑十肽促性腺激素释放激素（GnRH）是哺乳动物生殖发育和功能的关键神经内分泌调节因子。GnRH与其靶点--垂体促性腺激素上的GnRH受体（GnRHR）结合，影响促性腺激素、促黄体生成素（LH）和促卵泡激素（FSH）的合成和间歇性释放。因此，GnRH通过GnRHR在生殖事件的协调中起着关键作用。促性腺激素受体在促性腺激素细胞中的水平受到严格调节，促性腺激素细胞对GnRH的反应与细胞表面的GnRH受体浓度直接相关。几种激素，最值得注意的是GnRH本身和雌激素是GnRHR基因转录激活的关键调节因子。本申请的总体目标是详细了解体外和体内GnRHR基因的激素调节的分子机制和生理后果。我们最近已经确定和表征了几个C/S元件，和它们的同源DMA结合的反式因子，参与促性腺激素特异性和调节GnRHR基因的表达在体外。本申请的目的是：（1）了解这些因子整合信号以决定GnRHR表达水平的分子机制;（2）表征这些因子在体内GnRHR基因转录调控中的作用。具体目标是：（1）进一步明确Pitx-1和AP-1（Jun/Fos）蛋白在小鼠GnRH受体（mGnRH HR）基因的促性腺激素特异性表达和GnRH刺激表达中的作用;（2）充分鉴定与SURG-1结合的反式因子，并明确它们对GnRH反应性的贡献;（3）探讨雌激素对mGnRHR基因表达的调控机制;（4）利用“敲入”小鼠模型，在体内研究SURG-1和SURG-2（AP-1）元件对mGnRHR基因表达和激素调控的作用。由于GnRHR代表最终接收和介导促性腺激素对GnRH反应的位点，因此了解GnRHR表达的调节机制对我们了解哺乳动物健康和疾病的生殖生理学非常重要，并可能确定治疗干预的新靶点。

DESCRIPTION (provided by applicant): The hypothalamic decapeptide, gonadotropin-releasing hormone (GnRH), is the key neuroendocrine regulator of mammalian reproductive development and function. GnRH binds to its target, the GnRH receptor (GnRHR), on pituitary gonadotropes to affect the synthesis and intermittent release of the gonadotropins, luteiriizing hormone (LH) and follicle-stimulating hormone (FSH). Thus GnRH, via the GnRHR, plays a pivotal role in the coordination of reproductive events. Levels of GnRHR in the gonadotrope are tightly regulated and the responses of gonadotropes to GnRH correlate directly with the concentration of GnRHR on the cell surface. Several hormones, most notably GnRH itself and estrogen are critical regulators of transcriptional activation of the GnRHR gene. The overall goal of this application is to understand in detail both the molecular mechanisms and physiological consequences of this hormonal regulation of the GnRHR gene in vitro and in vivo. We have recently identified and characterized several c/s-elements, and their cognate DMA-binding trans-factors, involved in gonadotrope-specific and regulated GnRHR gene expression in vitro. The objectives of this application are: (1) to understand the molecular mechanisms by which these factors integrate signals to dictate GnRHR expression levels; and (2) to characterize the roles of these factors in the regulation of GnRHR gene transcription in vivo. The Specific Aims are: (1) To further define the roles of Pitx-1 and AP-1 (Jun/Fos) proteins in gonadotrope-specific and GnRH-stimulated expression of the mouse GnRHR (mGnRHR) gene; (2) To fully identify the trans-factors that bind to SURG-1, a novel cis-element which we have identified to be necessary for the optimal response of the GnRHR gene to GnRH, and to define their contributions to GnRH responsiveness; (3) To determine the mechanisms of regulation of mGnRHR gene expression by estrogen; and (4) To determine the contributions of the SURG-1 and SURG-2 (AP-1) elements to mGnRHR gene expression and hormonal regulation in vivo using a "knock-in" mouse model. Inasmuch as the GnRHR represents the site that ultimately receives and mediates gonadotrope responses to GnRH, an understanding of the mechanisms of regulation of GnRHR expression is important to our knowledge of mammalian reproductive physiology in both health and disease, and may identify new targets for therapeutic intervention.