Circadian Regulation of Gonadotropin-Releasing Hormone

描述(申请人提供)：虽然众所周知，正常的哺乳动物生殖依赖于下丘脑的促性腺激素释放激素(GnRH)的脉动性分泌，但目前尚不清楚这种异常定时的脉冲释放的核心是什么细胞和分子机制。此外，虽然以前的研究表明24小时生物钟参与控制生殖激素的分泌，但仍不清楚生物钟如何调节同步分泌GnRH的幅度或频率来调节生殖。该实验室的初步工作表明，GnRH分泌的GT1-7细胞不仅表达了所有的分子时钟成分，而且转录产物在这些培养的细胞中以昼夜节律的方式振荡。值得注意的是，在灌流的GT1-7细胞中，通过瞬时转染显性-负性时钟，扰乱了正常的分泌脉冲模式，表明GriRH神经元内的细胞内生物钟可以调节分泌。为了进一步研究这一点，以下建议将1)使用体外和体内模型来确定GnRH特定的分子时钟对正常生殖状态所需释放模式的必要性，2)研究潜在的细胞内机制，包括转录调节和细胞兴奋性的特性，潜在的GnRH的昼夜节律时钟调节，以及3)探索交叉上核(SCN)，大脑的主时钟，在影响GnRH分泌中的作用，以及细胞特异性分子振荡器在这一调节中的参与。这一提议的结果有可能回答许多基本问题，如促性腺激素释放激素“脉冲发生器”的性质，以及细胞与细胞之间的交流如何改变分泌模式以产生排卵前激增。此外，这些研究还可以深入了解内分泌神经分泌的更广泛机制，并通过展示转录振荡如何在多细胞和组织水平上控制同步事件，从而调节从细胞代谢到胞吐的众多生物过程，甚至协调一系列复杂的行为，从而推动昼夜生物学领域的发展。潜在的应用可能为治疗由下丘脑生殖神经分泌功能障碍引起的一系列生理性疾病带来新的方向，包括多囊卵巢综合征和原发理想性性腺功能减退。

DESCRIPTION (provided by applicant): Whereas it has long been known that normal mammalian reproduction depends upon the pulsatile secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamus, it is yet unclear what cellular and molecular mechanisms lie at the heart of this exceptionally timed pulse release. Additionally, while previous studies have implicated the 24-hour biological clock in the control of reproductive hormone secretion, it remains unknown how the circadian clock might modulate the amplitude or frequency of synchronous GnRH secretory release to regulate reproduction. Preliminary work in this laboratory demonstrates that not only are all molecular clock components expressed in the GnRH-secreting GT1-7 cell line, but that transcripts oscillate in these cultured cells with a circadian period. Strikingly, perturbation of the clock in perifused GT1-7 cells, via transient transfection of a dominant-negative Clock, disrupts normal secretory pulse patterns, showing that an intracellular circadian clock within GriRH neurons can modulate secretion. To investigate this further, the following proposal will 1) use in vitro and in vivo models to determine the necessity of a GnRH-specific molecular clock on patterns of release required for proper reproductive status, 2) examine potential intracellular mechanisms, including transcriptional regulation and properties of cell excitability, underlying circadian clock modulation of GnRH, and 3) explore the role of the suprachiasmatic nucleus (SCN), the brain's master clock, in influencing GnRH secretion, and the involvement of cell-specific molecular oscillators in this regulation. Results from this proposal have the potential to answer many fundamental questions regarding the nature of the GnRH "pulse generator", and how patterns of secretion may be altered by cell-cell communication to produce preovulatory surges. Additionally, these studies could provide insight into broader mechanisms of endocrine neurosecretion, and advance the field of circadian biology by demonstrating how transcriptional oscillations can control synchronous events at the multi-cellular and tissue level, in order to regulate numerous biological processes, from cellular metabolism to exocytosis, and even to orchestrate complex series of behaviors. Potential applications could lead to new directions in treating a range of physiological disorders that result from malfunction of hypothalamic reproductive neurosecretion, including polycystic ovarian syndrome and primary ideopathic hypogonadism.