Circadian Gene Expression Regulates Pulsatile Gonadotropin-Releasing Hormone (GnRH) Secretory Patterns in the Hypothalamic GnRH-Secreting GT1-7 Cell Line
Circadian Gene Expression Regulates Pulsatile Gonadotropin-Releasing Hormone (GnRH) Secretory Patterns in the Hypothalamic GnRH-Secreting GT1-7 Cell Line
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DOI：
10.1523/jneurosci.23-35-11202.2003
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发表时间：
2003-12
期刊：
影响因子：
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通讯作者：
P. Chappell;R. White;P. Mellon
中科院分区：
文献类型：
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作者：
P. Chappell;R. White;P. Mellon
虽然长期以来已经确定，正常促性腺激素释放需要下丘脑的促性腺激素释放激素（GnRH）的间歇性分泌，但GnRH同步释放的分子和细胞机制基本上是未知的。我们使用GT 1 -7小鼠下丘脑细胞系作为GnRH分泌的模型，因为这些细胞以与体内观察到的类似的脉动模式释放GnRH。为了探索可能的分子机制分泌时间，我们调查的分子生物钟在调节GnRH分泌的作用。GT 1 -7细胞表达许多已知的核心生物钟基因，我们证明，这些组件的振荡可以诱导刺激，如血清和腺苷酸环化酶激活剂毛喉素，类似于在成纤维细胞中观察到的效果。引人注目的是，显性负性Clock-Δ19基因的瞬时表达扰乱了GT 1 -7细胞的昼夜节律钟功能，破坏了GnRH分泌的正常超日模式，显著降低了平均脉冲频率。此外，GT 1 -7细胞中负性肢体时钟基因mCry 1的过表达显著增加了GnRH脉冲幅度，而脉冲频率没有相应的变化，表明内源性生物钟与这些细胞中的神经分泌机制偶联，并且可以调节多种分泌参数。最后，在Clock基因中携带体细胞突变的小鼠是生育力低下的，并且表现出发情周期持续时间的显著增加，如阴道细胞学检查所揭示的。这种效应在正常的光/暗（LD）周期中持续存在，表明GnRH神经元中的视交叉上核独立的内源性时钟是引发GnRH分泌正常脉冲模式所必需的。
Although it has long been established that episodic secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamus is required for normal gonadotropin release, the molecular and cellular mechanisms underlying the synchronous release of GnRH are primarily unknown. We used the GT1-7 mouse hypothalamic cell line as a model for GnRH secretion, because these cells release GnRH in a pulsatile pattern similar to that observed in vivo. To explore possible molecular mechanisms governing secretory timing, we investigated the role of the molecular circadian clock in regulation of GnRH secretion. GT1-7 cells express many known core circadian clock genes, and we demonstrate that oscillations of these components can be induced by stimuli such as serum and the adenylyl cyclase activator forskolin, similar to effects observed in fibroblasts. Strikingly, perturbation of circadian clock function in GT1-7 cells by transient expression of the dominant-negative Clock-Δ19 gene disrupts normal ultradian patterns of GnRH secretion, significantly decreasing mean pulse frequency. Additionally, overexpression of the negative limb clock gene mCry1 in GT1-7 cells substantially increases GnRH pulse amplitude without a commensurate change in pulse frequency, demonstrating that an endogenous biological clock is coupled to the mechanism of neurosecretion in these cells and can regulate multiple secretory parameters. Finally, mice harboring a somatic mutation in the Clock gene are subfertile and exhibit a substantial increase in estrous cycle duration as revealed by examination of vaginal cytology. This effect persists in normal light/dark (LD) cycles, suggesting that a suprachiasmatic nucleus-independent endogenous clock in GnRH neurons is required for eliciting normal pulsatile patterns of GnRH secretion.