Circadian Regulation of Gonadotropin-Releasing Hormone

描述（由申请人提供）：尽管人们早就知道正常哺乳动物的生殖取决于下丘脑促性腺激素释放激素（GnRH）的脉冲式分泌，但尚不清楚这种异常定时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小时生物钟控制生殖激素分泌，但仍然不清楚昼夜节律钟如何调节同步GnRH分泌释放的幅度或频率以调节生殖。在这个实验室的初步工作表明，不仅是所有的分子时钟组件中表达的GnRH分泌的GT 1 - 7细胞系，但这些培养的细胞与昼夜节律周期的转录振荡。引人注目的是，在灌注的GT 1 - 7细胞中，通过显性负时钟的瞬时转染，扰乱了正常的分泌脉冲模式，表明GriRH神经元内的细胞内昼夜节律钟可以调节分泌。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特异性分子钟对适当生殖状态所需的释放模式的必要性，2）检查潜在的细胞内机制，包括转录调节和细胞兴奋性的特性，GnRH的生物钟调节，以及3）探索视交叉上核（SCN）的作用，大脑的主时钟，在影响GnRH分泌，并参与细胞特异性分子振荡器在这种调节。从这个建议的结果有可能回答许多基本问题的GnRH“脉冲发生器”的性质，以及如何分泌的模式可能会改变细胞间的通信产生排卵前激增。此外，这些研究可以提供更广泛的内分泌神经分泌机制的见解，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来推进昼夜节律生物学领域，以调节从细胞代谢到胞吐作用的许多生物过程，甚至协调一系列复杂的行为。潜在的应用可能会导致新的方向，在治疗一系列的生理疾病，导致下丘脑生殖神经分泌功能障碍，包括多囊卵巢综合征和原发性特发性性腺功能减退症。

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.