Regulation of Immediate Early Genes by GnRH in the Gonadotrope

描述（由申请人提供）：本申请的总体目标是确定GnRH诱导垂体促性腺激素中立即早期基因的机制，并确定它们在GnRH脉动性调节促性腺激素β亚基表达中的作用。促性腺激素β亚基基因在垂体前叶促性腺中特异性表达，以响应来自下丘脑的GnRH脉冲。它们是合成异二聚体糖蛋白、促黄体生成素（LH）和促卵泡激素（FSH）的限制因素。它们在整个月经周期中的差异表达对生殖功能至关重要。在此，我们利用新的方法来描述其差异表达的机制。我们建议分析被GnRH激活诱导促性腺激素β基因表达的直接早期基因c-Fos和Egr-1的表达和调控。在本文的三个目的中，我们将比较和对比这些直接早期基因的表达，以阐明它们的诱导分子机制及其在LH和FSH β亚基基因差异表达中的作用。在第一个目标中，我们将确定Egr-1和LH β与c-Fos和FSH β最大表达的最佳GnRH脉冲频率或幅度。在第二个和第三个目标中，我们将分析GnRH激活的信号转导途径，这些信号转导途径与立即早期基因的表达有关，特别强调生理性脉动GnRH。这项R03提案的结果将为我们理解促性腺激素基因表达的分子机制，以及哺乳动物生殖系统的生理和病理生理提供实质性的贡献。该申请的长期目标是提供关键结果，在PI之前在促性腺激素释放激素（GnRH）调节促性腺激素基因表达方面的成就基础上建立一个独立的研究项目，并开发R01应用。未来的R01将提出利用基因组学、GnRH诱导促性腺激素中立即早期基因的机制以及这些基因在体内的功能，利用转基因小鼠，扩大我们对GnRH调控垂体基因表达的理解。哺乳动物的生育能力是通过调节促性腺激素基因的表达和分泌，在垂体促性腺细胞群水平上整合不同的调节信号来调节的。促性腺激素基因表达水平的功能障碍可导致病理生理障碍，如不孕症、性早熟、多囊卵巢综合征和促性腺功能低下。因此，了解控制促性腺激素基因表达的分子机制将有助于深入了解生殖系统的生理和病理生理学。

DESCRIPTION (provided by applicant): The overall goal of this application is to ascertain the mechanism of GnRH induction of immediate-early genes in the pituitary gonadotrope and determine their role in pulsatile GnRH regulation of the gonadotropin beta-subunit expression. Gonadotropin beta-subunit genes are specifically expressed in the anterior pituitary gonadotrope in response to GnRH pulses from the hypothalamus. They are the limiting factors in synthesis of the heterodimeric glycoproteins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Their differential expression throughout the menstrual cycle is critical for reproductive function. Herein, we utilize novel approaches to delineate the mechanisms underlying their differential expression. We propose to analyze the expression and regulation of the immediate-early genes, c-Fos and Egr-1, that are activated by GnRH to induce expression of gonadotropin beta genes. In the three aims of this proposal, we will compare and contrast the expression of these immediate-early genes to elucidate the molecular mechanisms of their induction and their roles in differential expression of the LH versus FSH beta-subunit genes. In the first aim, we will determine optimal GnRH pulse frequency or amplitude for maximal expression of Egr-1 and LH beta versus the expression of c-Fos and FSH beta. In the second and third aims, we will analyze the signal transduction pathways activated by GnRH that are implicated in the expression of the immediate-early genes, with a special emphasis on physiologic pulsatile GnRH. Results obtained from this R03 proposal will make substantial contributions to our understanding of the molecular mechanisms that affect gene expression in the gonadotrope and provide insight into the physiology and pathophysiology of the mammalian reproductive system. A long-term goal of this application is to provide key results to establish an independent research program building on the PI's previous accomplishments in gonadotropin-releasing hormone (GnRH) regulation of gonadotropin gene expression and develop an R01 application. This future R01 will propose to expand our understanding of GnRH regulation of gene expression in the pituitary using genomics, the mechanisms of GnRH induction of immediate-early genes in the gonadotrope, and the function of these genes in vivo, utilizing genetically modified mice. Fertility in mammals is regulated by the integration of different regulatory signals that occurs at the level of the gonadotrope cell population in the pituitary gland, through modulation of gonadotropin gene expression and secretion. Dysfunction at the level of gonadotrope gene expression can lead to pathophysiologic disorders such as infertility, precocious puberty, polycystic ovarian syndrome, and hypogonadotropic hypogonadism. Thus, understanding the molecular mechanisms governing gonadotrope gene expression will lead to insight into the physiology and pathophysiology of the reproductive system.