CREB and ICER, the Yin and Yang of FSH-beta regulation by pulsatile GnRH

描述(申请人提供)：在我的博士后研究期间，我一直对生殖的神经内分泌控制和促性腺激素解码脉动性GnRH信号的机制感兴趣，GnRH信号从下丘脑的GnRH神经元释放出来。这一奖项将为我实现成为一名独立调查员的长期目标提供机会，补充布里格姆和妇女医院提供的领导力、研究和道德培训项目。在搏动性促性腺激素释放激素的控制下，垂体卵泡刺激素和黄体生成素的产生是生育所必需的。与黄体生成素不同，垂体促性腺激素释放激素的转录和分泌优先于脉动性促性腺激素释放激素的慢频率而不是快频率。造成这种差异的机制尚不清楚。本项目的目的是阐明促性腺激素释放激素脉冲频率依赖的差异控制卵泡刺激素转录和随后的卵泡刺激素合成的潜在机制。使用我们的灌流系统和小鼠促性腺激素衍生的LüT2细胞系模型，我们先前已经证明，CREB的GnRH激活在较低的GnRH脉冲频率下介导FSHç的优先诱导，而ICER在较高的GnRH脉冲频率下被诱导，并拮抗CREB的刺激效应。脉动性促性腺激素释放激素调节CREB和ICER表达、激活和调节的分子机制尚不清楚。我建议将我们之前在细胞系中的体外观察扩展到体内的小鼠模型，并预测促性腺激素特异性CREB和ICER缺陷的小鼠模型将进一步证明这些转录因子在解码来自下丘脑的振荡GnRH信号方面的关键功能，表现出周期性中断和生殖功能受损。具体目的是确定两种转录因子--cAMP反应元件结合蛋白(CREB)和可诱导cAMP早期抑制因子(ICER)--如何介导促性腺激素对促性腺激素搏动性GnRH的差异反应，从而促进生殖功能。为了实现这些目标，我们提出了以下目标：1)研究脉冲性GnRH对PKA活性和CREB磷酸化状态的调控机制，从而优先以慢频率和快频率刺激FSH？转录；2)研究以GnRH脉冲频率依赖的方式调节ICER的合成、作用和降解的途径；3)研究促性腺激素中CREB和ICER基因的干扰对体内FSH？转录和生殖功能的影响。阐明促性腺激素释放激素调节卵泡刺激素转录的机制可能为多囊卵巢综合征(PCOS)和下丘脑闭经(HA)等生殖疾病提供新的治疗靶点。

DESCRIPTION (provided by applicant): During my post-doctoral fellowship, I have continued my interest in the neuroendocrine control of reproduction and the mechanism by which the gonadotrope decodes the pulsatile GnRH signal, released from GnRH neurons in the hypothalamus. This award will provide the opportunity to meet my long-term goal of becoming an independent investigator, supplementing the leadership, research, and ethical training programs offered by Brigham and Women's Hospital. Production of pituitary FSH and LH, under the control of pulsatile GnRH, is essential for fertility. Pituitary FSHß-subunit (FSHß) transcription and hence FSH secretion are preferentially stimulated at slow rather than fast frequencies of pulsatile GnRH, in contrast to LHß. The mechanisms for this disparity are not known. The goal of this project is to elucidate the underlying mechanisms that contribute to the GnRH pulse frequency-dependent differential control of FSHß transcription and subsequent FSH synthesis. Using our perifusion system and the murine gonadotrope-derived LßT2 cell line model, we have shown previously that GnRH activation of CREB mediates preferential induction of FSHß at slower GnRH pulse frequencies, whereas ICER is induced at high GnRH pulse frequencies and antagonizes the stimulatory effects of CREB. The molecular mechanisms by which pulsatile GnRH regulates CREB and ICER expression, activation, and regulation remain poorly understood. I propose to extend our prior in vitro observations in cell lines to in vivo mouse models, and predict that gonadotrope-specific CREB and ICER deficient mouse models will further demonstrate the critical function of these transcription factors in decoding oscillatoy GnRH signals from the hypothalamus, by demonstrating disrupted cyclicity and impaired reproductive function. The specific objectives are to determine the manner in which two transcription factors, cAMP response element binding protein (CREB) and inducible cAMP early repressor (ICER), mediate the differential response of FSHß to pulsatile GnRH in the gonadotrope to contribute to reproductive function. To achieve these objectives, the following aims are proposed: 1) Investigate the mechanisms by which PKA activity and CREB phosphorylation status are regulated by pulsatile GnRH to preferentially stimulate FSHß transcription at slow versus fast frequencies; 2) Investigate the pathways that regulate ICER synthesis, action and degradation in a GnRH pulse frequency-dependent manner; 3) Study the effect of CREB and ICER gene disruption in gonadotropes on FSHß transcription and reproductive function in vivo. The elucidation of the mechanisms by which FSHß transcription is regulated by pulsatile GnRH could provide novel therapeutic targets for reproductive disorders such as polycystic ovarian syndrome (PCOS) and hypothalamic amenorrhea (HA).