Circadian Organization of the Retina

描述(申请人提供)：视网膜既是一个感觉器官，也是一个自我维持的神经生物钟。作为视觉的主要感觉器官，视网膜执行将物理光刺激转换和编码为神经信号的初始步骤，然后通过视神经将视觉和光信息传输到大脑的其余部分。固有的视网膜生物钟通过调节视网膜神经元，并通过有节奏的基因表达和有节奏的神经递质(如多巴胺和褪黑素)的释放来重新配置视网膜回路，将整个视网膜的感觉功能塑造为高敏锐度的“白天”和高灵敏度的“夜间”状态。虽然视网膜生物钟对视网膜的生理和代谢产生了广泛的影响，但其潜在的细胞和分子机制还不是很清楚。这项研究的长期目标是阐明哺乳动物视网膜生物钟的基本机制及其对视网膜感觉功能的控制。在即将到来的获奖期，我们建议研究特定的生物钟基因和细胞群在视网膜生物钟中的功能作用，以及视网膜钟调节视网膜敏感性的机制。具体地说，我们建议研究以下问题：特定目标I：视网膜昼夜节律时钟的分子组织。利用核心生物钟基因PER1、PER2、Cry1、Cry2、Clock和NPAS2被敲除的小鼠品系，我们将测试这些基因中的每一个在小鼠视网膜生物钟中的功能作用。特定目标II.视网膜昼夜节律时钟的细胞组织利用单细胞发光成像和通过携带核心时钟基因BMal1的花环等位基因和Cre重组酶细胞特异性表达的小鼠系对分子生物钟功能的特定操纵，我们将试图确定视网膜中的哪些细胞群体是昼夜节律起搏器。特定目标III.视网膜功能的生物钟控制。使用分子遗传学方法，我们将测试哪些细胞和递质通路对：(1)使用ERG控制视网膜的昼夜节律敏感性，以及(2)视网膜时钟的光携带。这些目标的完成将使我们深入了解视觉功能和敏感度在许多生物体中根据一天中的时间进行调节的潜在机制，包括人类。这些发现将是理解正常视网膜功能的基础，视网膜作为一个模型生物时钟系统，有助于我们理解与感光细胞变性和近视相关的临床相关的昼夜节律和多巴胺能视网膜机制。 与公共健康相关：我们的视力在一天中的不同时间是不同的，因为我们的视网膜在一天中的不同时间工作不同。这些功能性的日常节律并不是对日常明暗循环的简单反应，但正如它们在持续黑暗中的持续表现所表明的那样，它们是视网膜中一种内源性的、自我维持的生物钟的公开表达，该生物钟驱动着视网膜生理和新陈代谢的许多节律。视网膜生物钟调节视网膜功能，使之适合白天或夜间的视力。此外，视网膜时钟在一天中的不同时间对视网膜光损伤具有不同的易感性，在致盲的视网膜色素性疾病中发生改变，并影响黄斑水肿和近视的发展。增加对视网膜昼夜节律时钟的了解对于理解人类的视觉及其保存和阐明这种模型神经昼夜节律起搏器的机制是重要的。

DESCRIPTION (provided by applicant): The retina is both a sensory organ and a self-sustained neural circadian clock. As the primary sensory organ for vision, the retina performs the initial steps of transduction and encoding of physical light stimuli into neural signals, and then transmits visual and photic information to the rest of the brain via the optic nerve. The intrinsic retinal circadian clock shapes overall retinal sensory function into high acuity "day" and high sensitivity "night" states by modulating retinal neurons and reconfiguring retinal circuits through rhythmic gene expression and rhythmic of release of modulatory neurotransmitters such as dopamine and melatonin. Although the retinal circadian clock exerts extensive influence over retinal physiology and metabolism, the underlying cellular and molecular mechanisms of the retinal circadian clock are not well understood. The long-term goal of the research proposed here is to elucidate the fundamental mechanisms of the mammalian retinal circadian clock and its control of retinal sensory function. For the upcoming award period we propose to examine the functional role of specific circadian clock genes and cell populations in the retinal circadian clock, as well as the mechanisms by which the retinal clock modulates retinal sensitivity. Specifically, we propose to examine the following issues: Specific Aim I: Molecular Organization of the Retinal Circadian Clock. Using mouse lines in which the core circadian clock genes Per1, Per2, Cry1, Cry2, Clock and NPAS2 are knocked out we will test the functional role of each of these genes in the mouse retinal circadian clock. Specific Aim II. Cellular Organization of the Retinal Circadian Clock. Using single-cell luminescence imaging and cell- specific manipulation of molecular circadian clock function via mouse lines carrying floxed alleles of the core clock gene Bmal1 and cell-specific expression of Cre recombinase, we will seek to determine which cell populations in the retina are circadian pacemakers. Specific Aim III. Circadian Clock Control of Retinal Function. Using molecular genetic approaches, we will test which cells and transmitter pathways are critical for: (1) circadian control of retinal sensitivity using the ERG, and (2) light entrainment of the retinal clock. Completion of these aims will provide insight into the underlying mechanisms by which visual function and sensitivity is modulated according to time of day in many organisms, including humans. These findings will be fundamental for understanding normal retinal function, the retina as a model biological clock system, and contribute to our understanding of clinically relevant circadian and dopaminergic retinal mechanisms associated with photoreceptor degeneration and myopia. PUBLIC HEALTH RELEVANCE: Our vision is different at different times of day because our retina works differently at different times of day. These functional daily rhythms are not simple responses to the daily light-dark cycle, but, as demonstrated by their persistence in constant darkness, they are the overt expression of an endogenous, self-sustained circadian clock in the retina that drives many rhythms in retinal physiology and metabolism. The retinal circadian clock adjusts retinal function, biasing it appropriately for day or night vision. In addition, the retinal clock imparts differential vulnerability to retinal light damage at different times of day, is altered in the blinding disease retinitis pigmentosa, and influences macular edema and the development of myopia. Increased understanding of the retinal circadian clock is important to understanding human vision and its preservation and to elucidating the mechanisms of this model neural circadian pacemaker.