HORMONAL CONTROL OF GENE EXPRESSION IN THE GONADOTROPE

正常的生殖功能需要下丘脑、垂体和性腺水平的激素调节的精确协调。 在垂体前叶内，促性腺激素作为激素信号整合的控制中心，产生促黄体生成素（LH）和促卵泡激素以调节生殖。 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，.我们的重点将是促性腺激素释放激素和激活素调节LH和促性腺激素释放激素受体基因表达的细胞和分子机制。 我们的模型系统是小鼠，这是由于通过转基因技术可以容易地操纵基因组，并且能够利用我们的永生小鼠垂体促性腺细胞系，该细胞系表达LH亚单位、激活素B、卵泡抑素和激活素、GnRH和类固醇受体。 在前两个目标中，这些细胞系将用于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，短期或脉冲式GnRH将诱导，LHBeta亚单位基因在LbetaT细胞。 在具体目标1中，我们将确定LHBeta基因的长期抑制、短期和脉冲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使促性腺激素细胞对GnRH敏感，而卵泡抑素抵消这种反应。我们已经绘制了小鼠GnRH受体基因中激活素/卵泡抑素调节的序列，并证明激活素治疗诱导和卵泡抑素抑制核DNA结合蛋白的活性。 在具体目标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-亚基基因通过Ets结合位点由α T3细胞中的GnRH调节。 在具体目标3中，我们将讨论通过Ets蛋白在转基因小鼠中GnRH作用中的MAP激酶信号传导的作用。此外，我们将调查的生理作用，激活素信号专门在转基因小鼠的促性腺细胞。

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.