Steenhard B M, Besharse J C
Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
J Neurosci. 2000 Dec 1;20(23):8572-7. doi: 10.1523/JNEUROSCI.20-23-08572.2000.
A circadian clock is located in the retinal photoreceptors of the African clawed frog Xenopus laevis. These photoreceptor clocks are thought to govern a wide variety of output rhythms, including melatonin release and gene expression. Both light and dopamine phase shift the retinal clock in a phase-dependent manner. Two homologs of the Drosophila period gene have been cloned in Xenopus, and one of these (xPer2) is acutely regulated by light. Light and dopamine induce xPer2 mRNA in a similar manner. In addition, the increase of xPer2 mRNA in response to light and dopamine is the same at all times of day tested. In contrast, xPer1 mRNA exhibits circadian oscillations but is relatively insensitive to phase-shifting treatments of light or dopamine. Our data suggest that xPer2 functions as the molecular link between the light/dark cycle and the circadian clock.
生物钟位于非洲爪蟾(非洲爪蟾)的视网膜光感受器中。这些光感受器生物钟被认为控制着各种各样的输出节律,包括褪黑素释放和基因表达。光和多巴胺都以相位依赖的方式使视网膜生物钟发生相位移动。在爪蟾中已克隆出果蝇周期基因的两个同源物,其中一个(xPer2)受光的急性调节。光和多巴胺以相似的方式诱导xPer2 mRNA。此外,在一天中所有测试时间,xPer2 mRNA对光和多巴胺的反应增加是相同的。相比之下,xPer1 mRNA表现出昼夜节律振荡,但对光或多巴胺的相位移动处理相对不敏感。我们的数据表明,xPer2作为光/暗周期与生物钟之间的分子联系发挥作用。