Molecular analysis of the mammalian circulation rhythm

从小鼠脑中分离到一种新的哺乳动物时期互补DNA mPer2。mPer2编码PAS-结构域（PAS，存在于PER、ARNT、SIM中的二聚化结构域）的氨基酸序列与mPer1和果蝇期（dPer）相似，表明mPer2与dPer的同源物mPer1是一个家族。mPer2 mRNA主要在哺乳动物的生物钟中枢视交叉上核（SCN）中表达。在持续黑暗条件下，SCN中强烈的昼夜节律性表达支持mPer2作为节律性起搏器。恒定黑暗条件下mPer2 mRNA的表达高峰出现在傍晚，光暗条件下mPer2 mRNA的表达高峰出现在熄灯时间，说明mPer2 mRNA的表达模式与白昼型时钟mPer1不同。分离到了哺乳动物周期基因家族的新成员mPer3，并对其在小鼠脑中的表达模式进行了分析。与mPer1、mPer2和Drosophila Period一样，mPer3具有二聚化结构域（PAS）和细胞质定位结构域（O…More LD）。mPer3转录本在视交叉上核（SCN）中显示出明显的昼夜节律。与mPer1和mPer2不同，mPer3的表达不受光照的影响。在SCN外的血管终末膜器官（OVLT）中也发现了mPer3的循环表达，OVLT是调节有节奏的促性腺激素产生和热原诱导的发热现象的潜在关键区域。因此，mPer3可能对SCN内外的起搏器功能都有贡献。为了了解光如何影响哺乳动物的生物钟，我们研究了光对mPer1的影响，mPer1是果蝇的一种同源序列，在SCN中表现出强烈的节律性表达。mPer1通过短时间暴露在足以重置时钟的光下迅速诱导，剂量响应曲线显示mPer1诱导既具有互易性，又与显性节律的相移有很强的相关性。因此mPer1在暗表达和对光的反应中都与神经孢子菌时钟基因frq相似。在SCN内，mPer1的诱导现象似乎是局部的，这表明在这个昼夜节律中心有两种类型的时钟（光响应和光不响应）。少

A new mammalian period complementary DNA, mPer2, has been isolated from mouse brain. The amino acid sequence of mPer2, encoding PAS-domain (PAS, a dimerization domain present in PER, ARNT, SIM), is similar to mPer1 and Drosophila Period (dPer), indicating that mPer2 is a family with mPer1, a homologue of dPer. The mPer2 mRNA is predominantly expressed in the suprachiasmatic nucleus (SCN), the center of biological clocks in mammals. A robust circadian rhythmic expression in the SCN in constant darkness supports mPer2 to be a rhythmic pacemaker. The peak of its expression is at evening in constant dark condition and light-off time in light-dark condition, indicating that expression pattern of mPer2 mRNA is different from day-type clock mPer1.A new member of the mammalian period gene family, mPer3, was isolated and its expression pattern characterized in the mouse brain. Like mPer1, mPer2 and Drosophila Period, mPer3 has a dimerization domain (PAS) and a cytoplasmic localization domain (O … More LD). mPer3 transcripts showed a clear circadian rhythm in the suprachiasmatic nucleus (SCN). Expression of mPer3 was not induced by exposure to light at any phase of the clock, distinguishing this gene from mPer1 and mPer2. Cycling expression of mPer3 was also found outside the SCN in the organum vasculosum lamina terminalis (OVLT), a potentially key region regulating rhythmic gonadotropin production and a pyrogen-induced febrile phenomena. Thus, mPer3 may contribute to pacemaker functions both inside and outside the SCN.To underst how light might entrain a mammalian circadian clock, we examined the effects of light on mPer1, a sequence homolog of Drosophila per, that exhibits robust rhythmic expression in the SCN. mPer1 is rapidly induced by short duration exposure to light at levels sufficient to reset the clock, and dose response curves reveal that mPer1 induction shows both reciprocity and a strong correlation with phase shifting of the overt rhythm. Thus in both the phasing of dark expression and the response to light mPer1 is similar to Neurospora clock gene frq. Within the SCN there appears to be localization of the induction phenomenon of mPer1, suggesting two types of clocks (light-responsive and light-unresponsive) being localized in this circadian center. Less