Circadian Rhythm Generation and Tissue Specific Functions of the Clock genes

尽管生物钟基因在多种组织中表达，但在哺乳动物中，只有视交叉上核（SCN）作为支配所有身体功能的主时钟发挥作用。使用时钟基因突变小鼠、转基因小鼠以及野生型动物检测时钟基因的组织特异性功能。对新的生物钟基因的功能也进行了研究. Clock基因的功能及其在SCN组织组装中的意义Clock突变小鼠在持续黑暗条件下出现行为学异常，这被认为是由于突变的Clock蛋白缺乏转录激活作用所致。我们培养的SCN时钟小鼠无论是在器官型切片或分散的细胞在多电极盘和自发放电连续监测从个别SCN神经元。在同种异体Clock小鼠中，77%的SCN神经元在切片培养中表现出昼夜节律，而在分散细胞培养中仅14%表现出昼夜节律。在野生型小鼠中，分别有95%和46%的SCN神经元表现出放电节律。结果表明，Clock突变延长了单个SCN神经元的周期，但不影响节律的产生，并进一步表明完整SCN组织中具有强烈细胞间通讯的完整细胞集合对于节律的表达至关重要. Dec是分子时钟DEC 1和DEC 2的新型调节因子，它们是碱性螺旋-环-螺旋（bHLH）转录因子，通过与BMAL 1的直接蛋白质-蛋白质相互作用和/或竞争E-box元件而抑制CLOCK/BMAL 1诱导的Per 1启动子的反式激活。DEC 1和DEC 2在SCN中以昼夜节律的方式表达，在主观日中具有峰值。一个简短的光脉冲诱导DEC 1，但不是DEC 2的表达在SCN中的相位依赖性的方式。这些结果表明DEC 1和DEC 2是哺乳动物分子时钟的新型调节因子。

Although clock genes are expressed in various tissues, only the suprachiasmatic nucleus (SCN) functions as the master clock governing all the bodily functions in mammals. The tissue specific functions of the clock genes were examined using clock gene mutant mice, transgenic mice as well as wild type animals. Functions of novel clock genes were also examined.1. Function of clock gene Clock and significance of the SCN tissue assemblageClock mutant mice become behaviorally arrhythmic under the continuous darkness, which has been considered due to a lack of transcription activation by mutant Clock protein. We cultured the SCN of Clock mice either in an organotypic slice or in dispersed cells on a multi-electrode dish and spontaneous firing was continuously monitored from individual SCN neurons. In homozygout Clock mice, 77% of the SCN neurons showed circadian firing rhythms in slice culture, while only 14% showed in dispersed cell culture. In wild type mice, 95 and 46% of SCN neurons showed firing rhythms, respectively. The results indicated that Clock mutation lengthened the period of individual SCN neurons but did not affects the rhythm generation, and further suggested that the intact cell assemblage with intense cell-cell communication in the intact SCN tissue is critical for the rhythm expression.2. Dec is the novel regulator of the molecular clockDEC1 and DEC2, basic helix-loop-helix (bHLH) transcription factors, repressed CLOCK/BMAL1 induced transactivation of the Per1 promoter through direct protein-protein interactions with BMAL1 and/or competition for E-box elements. DEC1 and DEC2 are expressed in the SCN in a circadian fashion with a peak in the subjective day. A brief light pulse induced DEC1 but not DEC2 expression in the SCN in a phase-dependent manner. These results indicate that DEC1 and DEC2 are novel regulators of the mammalian molecular clock.