Photic Sensitivity of the Circadian Entrainment Pathway

描述（由申请人提供）：昼夜节律起搏器驱动几乎所有生物（包括人类）的无数生理和行为24小时节律。这些起搏器可以用来同步内部生理过程，并预测或预测周期性的环境事件。然而，为了对生物体有用，内源性昼夜节律起搏器必须与环境时间同步或携带。许多起搏器的主要诱导因子是环境光循环，光诱导过程已经在哺乳动物中得到了很好的研究。人类昼夜节律干扰的异常与特定的睡眠障碍有关，包括睡眠阶段提前综合征、非24小时睡眠-觉醒综合征、“时差”以及与倒班工作相关的疾病。最近，哺乳动物昼夜节律起搏器的重要组成部分已经被发现，使用小鼠作为模型系统。已经确定了几个昼夜节律基因，这些“时钟”基因及其产物的相互作用似乎在下丘脑视交叉上核（哺乳动物昼夜节律起搏器的位置）神经元的分子反馈回路中起作用。在这些基因中，mPer1和mPer2似乎在昼夜节律机制中起着至关重要的双重作用——既是完整的时钟基因，也是光携带通路的重要组成部分——光携带通路是一种携带光信息以重置和同步分子昼夜节律机制的神经通路。我的长期目标包括表征在mPer2突变小鼠中介导昼夜节律夹带的光通路的功能操作。功能行为分析为完整动物体内生物钟的分子分析和起搏器的运作提供了宝贵的联系。本应用的实验主要集中在四个方面：1)我们将表征mPer2和野生型小鼠在昼夜周期的几个阶段的光诱导通路的响应性。2)我们将直接比较两种常用的昼夜光反应测定法（在恒定黑暗的昼夜节律周期1和7上测量）。重要的是，这个比较将包括野生型和mPer2突变小鼠。3)我们将量化携带mPer2（brdm1）突变小鼠的光携带途径对光脉冲辐照度和持续时间的敏感性，比较野生型小鼠的光敏感性特征。4)我们将表征mPer2突变小鼠完成LD周期的携带，以确定mPer2（brdm1）突变小鼠的光敏性变化如何影响昼夜节律起搏器的携带。总之，这些实验将为mPer2和野生型小鼠的昼夜节律光反应提供全面的功能分析，并为未来在细胞和分子水平上解剖哺乳动物昼夜节律机制和光携带途径提供关键的实验工具。

DESCRIPTION (provided by applicant): Circadian pacemakers drive innumerable physiological and behavioral 24 h rhythms in almost all organisms - including humans. These pacemakers can be used to synchronize internal physiological processes and to anticipate or predict periodic environmental events. To be useful for organisms, however, endogenous circadian pacemakers must be synchronized or entrained to environmental time. The principal entraining agent for many pacemakers is the environmental light cycle and the process of photic entrainment has been well studied in mammals. Abnormalities in human circadian entrainment have been implicated in specific sleep disorders including advanced sleep phase syndrome, non-24h sleep-wake syndrome, as well as "jet lag" and disorders related to shift-work. Recently, significant components of the mammalian circadian pacemaker have been uncovered using the mouse as a model system. Several circadian genes have been identified and the interactions of these "clock" genes and their products appear to operate as a molecular feedback loop within neurons of the hypothalamic suprachiasmatic nucleus - the site of a mammalian circadian pacemaker. Among these genes mPer1 and mPer2 appear to play a crucial dual-role within the circadian mechanism -- acting as both integral clock genes as well as important components of the photic entrainment path-way -- the neural pathway that carries light information to reset and synchronize the molecular circadian mechanism. My long-term objectives include characterizing the functional operation of the photic pathway that mediates circadian entrainment in mPer2 mutant mice. Functional behavioral analyses provide an invaluable link between molecular analyses of the circadian clock and the operation of the pacemaker within intact animals. Experiments in this application focus upon 4 specific aims: 1) We will characterize the responsiveness of the photic entrainment pathway for the mPer2 and wild type mice at several phases of the circadian cycle. 2) We will directly compare two commonly used assays of circadian photic responsiveness (measured on circadian cycles 1 and 7 of constant darkness). Importantly this comparison will include both wild type as well as mPer2 mutant mice. 3) We will quantify the sensitivity of the photic entrainment pathway to the irradiance and duration of light pulses in mice carrying the mPer2(brdm1) mutation, comparing the characteristics of photic sensitivity measured for wild-type mice. 4) We will characterize entrainment of mPer2-mutant mice to complete LD cycles to determine how changes in photic sensitivity in mPer2(brdm1) mutant mice may influence the entrainment of the circadian pacemaker. Together these experiments will provide a comprehensive functional analysis of circadian photic responses in the mPer2 and wild type mice -- and furnish critical experimental tools for future dissections [of] the mammalian circadian mechanism and photic entrainment pathway at the cellular and molecular levels.