Discovery of molecular mechanisms of identified cycling genes using a gene chip in the suprachiasmatic nucleus

我们利用基因芯片鉴定了视交叉上核（SCN）中的101个循环基因。接下来，利用原位杂交技术，我们检测了这些基因在SCN中是否有节律性表达，并检测了一些基因的节律性表达。在LD和DD的SCN中，ID2均呈现振荡表达，夜间高，白天低。我们认为ID2作为转录的负调节因子，可能是Per转录的良好候选调节因子。此外，Dexras1和HSPa5 mRNA的表达具有昼夜节律性，在夜间达到峰值，这些基因的表达主要存在于SCN的背内侧部分（DMSCN）。我们采用原位杂交方法研究了Per基因在稳定光暗条件下大鼠SCN中的表达谱，并特别参考了在SCN腹外侧部分（VLSCN）的诱导。在LD条件下，SCN中Pen和Per2基因的表达开始于光照后30分钟，而在DD条件下，VLSCN直到光照后2小时才开始表达Per基因。因此，Per基因在白天早期的表达很可能是由于主观夜间的光照所致。这些发现表明，Per基因参与昼夜节律时钟与环境时间的日常同步。此外，我们证明了LD周期的突变会破坏大鼠SCN中昼夜节律成分的同步振荡。光感受区VLSCN移动迅速，而DMSCN移动相对较慢。在LD周期移位后，SCN内内源性振荡的这种分离和缓慢的再同步提示了构成时差反应的生理症状的机制。然后，这些发现表明，在SCN中存在潜在的两个振荡器。

We identified cycling 101 genes in the suprachiasmatic nucleus(SCN) using a gene chip. Next, using in situ hybridization, we examined whether these genes expresses rhythmically or not in the SCN and detected rhythmic expression of some genes. The SCN showed oscillatory expression of ID2 in both LD and DD, high during the night, low during the day. We suggested that ID2 works as a negative regulator of the transcription and may be good candidate for the modulator of Per transcription.In addition, Dexras1 and HSPa5 mRNA expression showed circadian rhythm, peaked during night and these genes expression were found predominantly in the dorsomedial portion of the SCN(DMSCN).We investigated expression profiles of Per genes in the rat SCN in steady light-dark condition by in situ hybridization method, with special reference to the induction in the ventrolateral portion of the SCN(VLSCN). In the LD condition, the onset of the Pen and Per2 genes expression in the SCN began 30 minutes after lights on, while the VLSCN did not expression Per genes until 2hours after lights on in DD. Therefore, it is likely that the expression of Per genes during the early daytime is caused by the exposure to light during subjective night. These findings suggest that the involvement of Per genes in the daily synchronization of the circadian clock to environment time. Also, we demonstrate that an abrupt shift in the LD cycle disrupts the synchronous oscillation of circadian components in the rat SCN. The VLSCN, photoreceptive region, shifted rapidly, but the DMSCN were relatively slow to shift. This dissociation and slow resynchronization of endogenous oscillators within the SCN after an LD cycle shift suggests a mechanism for the physiological symptoms that constitute jet lag. Then these finding suggested that there are potential two oscillators in the SCN.