REPRODUCTIVE PHYSIOLOGY OF GONADOTROPIN SYNTHESIS

描述(申请人提供)：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与其靶标GnRH受体(GnRHR)结合，影响促性腺激素、黄体生成素(LH)和卵泡刺激素(FSH)的合成和间歇性释放。因此，GnRH通过GnRHR在生殖活动的协调中起着关键作用。促性腺激素释放激素受体水平受到严格调控，促性腺激素释放激素对促性腺激素释放激素的反应与细胞表面的促性腺激素释放激素受体浓度直接相关。几种激素，尤其是GnRH本身和雌激素是GnRHR基因转录激活的关键调节因素。这项应用的总体目标是详细了解GnRHR基因在体外和体内这种激素调节的分子机制和生理后果。我们最近已经发现并鉴定了几个c/S元件及其同源的DMA结合反式因子，它们参与了体外促性腺激素特异性和调节GnRHR基因的表达。本应用的目的是：(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。其具体目的是：(1)进一步明确Pitx-1和AP-1(Jun/Fos)蛋白在促性腺激素特异性和GnRH刺激的小鼠GnRHR(MGnRHR)基因表达中的作用；(2)充分鉴定与SURG-1结合的反式因子，SURG-1是我们发现的GnRHR基因对GnRH的最佳反应所必需的新的顺式元件，并确定它们在GnRH应答中的作用；(3)确定雌激素调节mGnRHR基因表达的机制；以及(4)利用“敲入”小鼠模型，确定SURG-1和SURG-2(AP-1)元件在体内对mGnRHR基因表达和激素调节的贡献。由于GnRHR代表着最终接收和介导促性腺激素对GnRH反应的部位，了解GnRHR表达的调节机制对于我们了解哺乳动物的生殖生理在健康和疾病方面都是重要的，并可能为治疗干预寻找新的靶点。

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.