Properties and Mechanisms of Melanopsin Photoreception

描述（由申请人提供）：我们建议研究通过视网膜中的非经典感光细胞群体有效调节哺乳动物生物钟的机制。这些内在光敏神经节细胞（ipRGC）表达称为黑视素的G蛋白偶联受体。黑视蛋白的光子捕获激活ipRGC，ipRGC将动作电位直接传递到视交叉上核（surachiasmatic nucleus）中的主昼夜节律钟以及其他大脑区域。IpRGC是生物钟对光的反应所必需的，黑视蛋白光转导在这一过程中起着重要作用。我们的首要假设是，黑视素光转导是针对昼夜光感受。更具体地说，生物钟在时间和空间的宽间隔上对光子进行求和，减少光强度的局部波动的影响，以获得整体光水平的准确表示。时钟使用此信息将自身与本地时间同步。然而，在昼夜光感受的时空总和的基础还不清楚。我们的目标是在此背景下剖析ipRGC光响应。我们将研究允许ipRGC在照明期间连续发出信号的机制，这对于时间求和是必要的。此外，我们将探讨黑视素光转导的亚细胞组织如何允许ipRGC响应于广泛的视觉空间进行空间求和。我们的方法是使用BAC转基因小鼠来识别ipRGC，所述转基因小鼠驱动黑视素启动子下的荧光蛋白的表达，并且采用体外电生理学和光刺激的组合，其允许在生物物理水平上进行分析。这项工作的重要性在于ipRGC是生物钟的主要调节因子，生物钟控制着细胞中高达五分之一的所有表达基因。 给予组织。生物钟失调与癌症、肥胖、精神疾病和其他疾病有关。通过在昼夜节律生物学框架内对ipRGC光感受的系统研究，我们的研究有可能揭示维持健康和在疾病中受损的机制。

DESCRIPTION (provided by applicant): We propose to investigate the mechanisms that allow effective regulation of the mammalian circadian clock by a population of non-classical photoreceptor cells in the retina. These intrinsically photosensitive ganglion cells (ipRGCs) express a G-protein coupled receptor called melanopsin. Photon capture by melanopsin activates ipRGCs, which transmit action potentials directly to the master circadian clock in the suprachiasmatic nucleus, among other brain regions. IpRGCs are absolutely required for the clock to respond to light and melanopsin phototransduction plays an important role in this process. Our overarching hypothesis is that melanopsin phototransduction is tailored to circadian photoreception. More specifically, the circadian clock sums photons over broad intervals of time and space, diminishing the impact of local fluctuations in light intensity to obtin an accurate representation of the overall light level. The clock uses this information to synchronize itself to local time. However, the basis of spatiotemporal summation in circadian photoreception is not yet understood. Our goal is to dissect the ipRGC light response in this context. We will investigate the mechanisms that allow ipRGCs to signal continuously during illumination, which is necessary for temporal summation. In addition, we will explore how the subcellular organization of melanopsin phototransduction allows ipRGCs to respond to broad expanses of visual space for spatial summation. Our approach is to identify ipRGCs using a BAC-transgenic mouse that drives expression of a fluorescent protein under the melanopsin promoter, and employ a combination of in vitro electrophysiology and optical stimulation that allows analysis at the biophysical level. The significance of this work is that ipRGCs are the principal regulators of the clock, and the clock controls up to a fifth of all expressed genes in a given tissue. Dysregulation of the clock is implicated in cancer, obesity, mental illness, and othe ailments. Through a systematic investigation of ipRGC photoreception within the framework of circadian biology, our research has the potential to reveal mechanisms that maintain health and are compromised in disease.