Cryptochrome function in non-visual photoreception

描述（由申请人提供）：最近的实验已经证明，具有完全外部视网膜变性的小鼠仍然保留使其昼夜节律与外源性亮-暗周期同步的能力，响应于光而收缩其瞳孔，并且用光抑制重要的激素信号（例如褪黑激素）。视网膜神经节细胞的一个子集最近已被证明是直接光响应。目前尚不清楚这些反应背后的原因。隐花色素是一个与光裂合酶相关的黄素基蛋白家族，是内层视网膜中的潜在色素。缺乏隐花色素功能的视网膜退化小鼠表现出对光的行为节律性和瞳孔反应性的敏感性显著降低。 使用遗传学和生理学方法的组合，研究人员提出测试的假设，隐花色素作为色素在视网膜退化小鼠的视网膜内层。提出了四个具体目标：（1）。测定该色素对有和无隐花色素功能的视网膜变性（rd/rd）小鼠瞳孔反应的作用谱、动力学和漂白特性; 2.）比较隐花色素功能正常小鼠和隐花色素功能不正常小鼠的视网膜内生理学和直接神经节细胞光反应性;建立基因拯救模式， 哺乳动物隐花色素在遗传无效背景中的眼睛特异性表达，并进行系统诱变以描绘小鼠眼睛中隐花色素功能的必要结构域;和4.）利用酵母双杂交系统研究哺乳动物隐花色素与潜在下游信号分子的光依赖性相互作用。本工作的长期目标是了解非视觉眼部光转导的机制，从色素到神经信号转导。这种辐射检测途径所提供的全部生理功能尚不清楚，但可能包括主昼夜节律起搏器与外部光暗周期的同步、季节性激素波动和睡眠-觉醒周期的光调制。已知眼科疾病患者的亚群具有昼夜节律紊乱引起的睡眠障碍的高风险;了解眼睛与负责这些行为的皮质下脑中心通信的精确机制将大大增强对这些疾病的病理生理学的理解。

DESCRIPTION (provided by applicant): Recent experiments have demonstrated that mice with complete outer retinal degeneration still retain the ability to synchronize their circadian rhythms to exogenous light-dark cycles, constrict their pupils in response to light, and suppress important hormonal signals (such as melatonin) with light. A subset of retinal ganglion cells have recently been shown to be directly photoresponsive. The photopigment(s) underlying these responses are presently unknown. The cryptochromes are a family of flavin-based proteins related to photolyase that are potential photopigments in the inner retina. Retinal degenerate mice lacking cryptochrome function show markedly decreased sensitivity to light for behavioral rhythmicity and pupillary responsiveness. Using a combination of genetic and physiologic approaches, the investigators propose testing the hypothesis that cryptochromes function as photopigments in the inner retina of retinal degenerate mice. Four specific aims are proposed: 1.) Determine the action spectrum, kinetics, and bleaching properties of the photopigment(s) for pupillary responsive-ness in retinal degenerate (rd/rd) mice with and without cryptochrome function; 2.) Compare inner retinal physiology and direct ganglion cell photoresponsive-ness between mice with and without cryptochrome function; 3.) Establish genetic rescue paradigms for the eye-specific expression of mammalian cryptochromes in genetically null backgrounds and perform systematic mutagenesis to delineate essential domains of cryptochrome function in the mouse eye; and 4.) Utilize the yeast two-hybrid system to characterize the light-dependent interaction of mammalian cryptochrome with potential downstream signaling molecules. The long-term objective of this work is to understand the mechanisms of non-visual ocular phototransduction, from photopigment to neural signal transduction. The full range of physiology subserved by this irradiance detection pathway is unknown but likely includes synchronization of the master circadian pacemaker to the external light-dark cycle, seasonal hormone fluctuations, and light-modulation of the sleep-wakefulness cycle. Subsets of patients with ophthalmologic disease are known to be at high risk for sleep disorders arising from circadian desynchronization; understanding the precise mechanisms by which the eye communicates with the subcortical brain centers responsible for these behaviors will greatly enhance understanding of the pathophysiology of these disorders.