HORMONAL CONTROL OF GENE EXPRESSION IN THE GONADOTROPE

正常的生殖功能需要在下丘脑、垂体和性腺水平精确协调荷尔蒙调节。在垂体前叶，促性腺激素是整合激素信号的控制中心，产生黄体生成素和卵泡刺激素来调节生殖。该细胞通过GnRH受体对来自下丘脑的促性腺激素释放激素(GnRH)脉冲作出反应，通过激活素受体对内分泌和自分泌激活素和卵泡抑素作出反应，并对来自性腺的类固醇激素反馈作出反应。在研究项目I中，。我们的重点将集中在GnRH和激活素调节促性腺激素中的Lh和GnRH受体基因表达的细胞和分子机制上。我们的模型系统是小鼠，因为S可以方便地操纵转基因技术获得的基因组，并有能力开发我们的永生小鼠垂体促性腺激素细胞系，它同时表达LH亚单位、激活素B、卵泡生成素、激活素、促性腺激素释放激素和类固醇受体。在前两个目标中，这些细胞系将被用来研究促性腺激素调节的分子基础。我们已经证明，恒定的GnRH或其第二信使将下调LbetaT细胞中的LHBeta亚单位基因，短期或脉动性GnRH将诱导LHBeta亚单位基因的表达。在特定的目标1中，我们将确定LHBeta基因的长期抑制、短期和脉动性诱导的信号通路及其转录靶点，以及GnRH诱导α亚基基因的机制。激活素通过诱导GnRH受体mRNA使促性腺激素对GnRH敏感，而卵泡刺激素则抵消这一反应。我们已经在小鼠GnRH受体基因中定位了对激活素/卵泡刺激素调节反应的序列，并证明了激活素治疗诱导和卵泡刺激素抑制核DNA结合蛋白的活性。在特定的目标2中，我们将研究激活素对GnRH受体基因的诱导和对α亚基基因的抑制。小鼠α亚单位基因由GnRH通过ETS结合位点在αT3细胞中进行调节。在特定的目标3中，我们将讨论MAPKinase信号通过ETS蛋白在转基因小鼠的GnRH作用中的作用。此外，我们还将研究激活素信号在转基因小鼠促性腺激素中的生理作用。

Normal reproductive function requires the precise orchestration of hormonal regulation at the hypothalamic, pituitary, and gonadal levels. Within the anterior pituitary, the gonadotrope serves as the control center for integration of hormonal signals, producing luteinizing hormone (LH) and follicle-stimulating hormone to regulate reproduction. This cell responds to pulses of gonadotropin-releasing hormone (GnRH) from the hypothalamus through the GnRH receptor, to endocrine and autocrine activin and follistatin through activin receptors, and to steroid hormone feedback from the gonads. In Research Project I,. Our focus will be the cellular and molecular mechanisms of GnRH and activin regulation of LH and GnRH receptor gene expression in the gonadotrope. Our model system is the mouse, due to the facile manipulation s of the genome attainable by transgenic technology and the ability to exploit our immortal mouse pituitary gonadotrope cell lines that express both LH subunits, activin B, follistatin, and activin, GnRH, and steroid receptors. In the first two aims, these cell lines will be used to investigate the molecular basis of hormonal regulation in the gonadotrope. We have demonstrated that constant GnRH or its second messengers will down regulate, and short-term or pulsatile GnRH will induce, the LHBeta subunit gene in the LbetaT cells. In Specific Aim 1, we will determine the signaling pathways and their transcriptional targets for long-term repression, and short-term and pulsatile induction of the LHBeta gene, and the mechanism for induction of the Alpha-subunit gene by GnRH. Activin sensitizes the gonadotrope to GnRH by inducing the GnRH receptor mRNA, while follistatin counteracts this response. We have mapped the sequences responsive to activin/follistatin regulation in the mouse GnRH receptor gene and demonstrated that activin treatment induces, and follistatin represses, the activity of a nuclear DNA-binding protein. In Specific Aim 2 we will investigate the induction of the GnRH receptor gene and the repression of the alpha-subunit gene by activin. The mouse alpha-subunit gene is regulated by GnRH in alpha T3 cells through an Ets binding site. In Specific Aim 3, we will address the role of MAPKinase signaling through Ets proteins in GnRH action in transgenic mice. In addition, we will investigate the physiological role of activin signaling exclusively in the gonadotrope in transgenic mice.