Allen G C, Farnell Y, Bell-Pedersen D, Cassone V M, Earnest D J
Department of Human Anatomy and Medical Neurobiology, Texas A&M University Health Science Center, College of Medicine, College Station, TX 77843-1114, USA.
Neuroscience. 2004;127(4):989-99. doi: 10.1016/j.neuroscience.2004.06.003.
While peripheral tissues and serum-shocked fibroblasts express rhythmic oscillations in clock gene expression, only the suprachiasmatic nucleus (SCN) is capable of endogenous, self-sustained rhythmicity and of functioning as a pacemaker by imposing rhythmic properties upon other cells. To differentially examine the molecular elements necessary for the distinctive rhythm-generating and pacemaking properties of the SCN, the effects of antisense inhibition of Clock expression on the rhythms in 2-deoxyglucose uptake and Per gene expression were compared in immortalized SCN cells and a fibroblast cell line. Similar to changes in molecular and physiological rhythmicity observed in the SCN of Clock mutant mice, the rhythmic pattern of Per2 expression was disrupted and the period of metabolic rhythmicity was increased in SCN2.2 cells subjected to antisense inhibition of Clock. NIH/3T3 fibroblasts cocultured with antisense-treated SCN2.2 cells showed metabolic rhythms with comparable increases in period and decreases in rhythm amplitude. Per2 expression in these cocultured fibroblasts exhibited a similar reduction in peak levels, but was marked by non-24 h or irregular peak-to-peak intervals. In serum-shocked NIH/3T3 fibroblasts, oscillations in Per2, Bmal1, and Cry1 expression persisted with some change in rhythm amplitude during antisense inhibition of CLOCK, demonstrating that feedback interactions between Clock and other core components of the clock mechanism may be regulated differently in SCN2.2 cells and fibroblasts. The present results suggest that CLOCK is differentially involved in the generation of endogenous molecular and metabolic rhythmicity within SCN2.2 cells and in the regulation of their specific outputs that control rhythmic processes in NIH/3T3 cells.
虽然外周组织和血清休克的成纤维细胞在时钟基因表达中表现出节律性振荡，但只有视交叉上核（SCN）能够产生内源性、自我维持的节律性，并通过将节律特性强加于其他细胞而发挥起搏器的作用。为了差异地研究SCN独特的节律产生和起搏特性所必需的分子元件，在永生化的SCN细胞和成纤维细胞系中比较了Clock表达的反义抑制对2-脱氧葡萄糖摄取节律和Per基因表达的影响。与在Clock突变小鼠的SCN中观察到的分子和生理节律性变化相似，在接受Clock反义抑制的SCN2.2细胞中，Per2表达的节律模式被破坏，代谢节律的周期增加。与反义处理的SCN2.2细胞共培养的NIH/3T3成纤维细胞表现出代谢节律，其周期有类似的增加，节律幅度有下降。这些共培养的成纤维细胞中Per2的表达在峰值水平上有类似的降低，但以非24小时或不规则峰峰间隔为特征。在血清休克的NIH/3T3成纤维细胞中，在CLOCK反义抑制期间，Per2、Bmal1和Cry1表达的振荡持续存在，节律幅度有一些变化，这表明Clock与时钟机制的其他核心成分之间的反馈相互作用在SCN2.2细胞和成纤维细胞中可能受到不同的调节。目前的结果表明，CLOCK在SCN2.2细胞内源性分子和代谢节律的产生以及对NIH/3T3细胞中控制节律过程的特定输出的调节中发挥着不同的作用。
