Yamamoto S, Shigeyoshi Y, Ishida Y, Fukuyama T, Yamaguchi S, Yagita K, Moriya T, Shibata S, Takashima N, Okamura H
Department of Anatomy and Brain Science, Kobe University School of Medicine, Chuo-ku, Kobe 650-0017, Japan.
J Comp Neurol. 2001 Feb 19;430(4):518-32.
Recent progress in study on the molecular component of mammalian clocks has claimed that mammals and Drosophila share the similar fundamental clock oscillating system. In the present study, we investigated expression of Per1, the first gene of the mammalian homolog of the Drosophila clock gene period, in the hamster brain, and we also examined its circadian expression pattern in the mammalian clock center, the suprachiasmatic nucleus (SCN). In situ hybridization using isotope-labeled cRNA probes revealed a wide and region-specific distribution of Per1 in the hamster brain and spinal cord. High levels of Per1 were found in the internal granular layer of the granular cells of the olfactory bulb, anterior olfactory nuclei, tenia tecta, olfactory tubercle, piriform cortex, suprachiasmatic nucleus, and gyrus dentatus of hippocampus. Moderate levels of expression were detected in many brain regions including the granular layer of the cerebellum, anterior paraventricular thalamic nucleus, caudate-putamen, inferior colliculus, pontine nuclei, inferior olive, and nucleus of the solitary tract. We examined the circadian profile of hamster Per1 mRNA in the SCN in constant darkness and found that Per1 expression showed a peak at subjective day (circadian time [CT] 4) and formed a trough at subjective night (CT16-CT20). A brief exposure of light at CT16 could acutely induce large quantities of Per1 mRNA in the hamster SCN, except for its dorsomedial subdivision. These findings suggest that the characteristics of Per1 gene expression in the mammalian circadian center (showing a peak in the daytime and a trough in the nighttime and a rapid inducibility by light) are common among mammalian species. Lastly, in hamster brain, Per1 gene is also inducible in extra-SCN brain nuclei, since light at night also elicited Per1 mRNA in neurons of the hypothalamic paraventricular nucleus.
哺乳动物生物钟分子成分的研究进展表明，哺乳动物和果蝇具有相似的基本生物钟振荡系统。在本研究中，我们调查了仓鼠脑中果蝇生物钟基因period的哺乳动物同源基因Per1的首个基因的表达情况，并检测了其在哺乳动物生物钟中心视交叉上核（SCN）中的昼夜表达模式。使用同位素标记的cRNA探针进行原位杂交显示，Per1在仓鼠脑和脊髓中分布广泛且具有区域特异性。在嗅球颗粒细胞的内颗粒层、前嗅核、带状层、嗅结节、梨状皮质、视交叉上核和海马齿状回中发现了高水平的Per1。在许多脑区检测到中等水平的表达，包括小脑颗粒层、丘脑前室旁核、尾状核-壳核、下丘、脑桥核、下橄榄核和孤束核。我们在持续黑暗条件下检测了仓鼠SCN中Per1 mRNA的昼夜变化情况，发现Per1表达在主观日（昼夜时间[CT]4）达到峰值，在主观夜（CT16 - CT20）形成低谷。在CT16短暂光照可急性诱导仓鼠SCN中大量Per1 mRNA的产生，但背内侧亚区除外。这些发现表明，Per1基因在哺乳动物昼夜中心的表达特征（白天达到峰值，夜间形成低谷，且对光具有快速诱导性）在哺乳动物物种中较为常见。最后，在仓鼠脑中，Per1基因在SCN以外的脑核中也可被诱导，因为夜间光照也能在下丘脑室旁核神经元中引发Per1 mRNA的表达。
