MECHANISMS OF ADAPTATION IN MAMMALIAN CONES

描述（由申请人提供）：视锥细胞仅占人类光感受器的5%，但对我们的日间视力至关重要。AMD是最突出的视锥视觉障碍，对老年人有重大影响，并且视锥丧失导致法律的失明。这对于 哺乳动物视锥细胞作为白天光感受器的功能，它们在光破坏后迅速再生其视觉色素。这是通过两种途径实现的。典型的视网膜色素上皮（RPE）视觉周期为视杆细胞和视锥细胞提供11-顺式视网膜发色团。相比之下，新的视网膜视觉周期依赖于穆勒细胞提供11-顺式视黄醇，其只能在通过未知的脱氢酶将其氧化为11-顺式视黄醇后被视锥细胞利用。正如我们在过去五年中所证明的那样，视网膜视觉周期在白天视觉中起着至关重要的作用，它将视锥细胞的功能范围扩展到明亮的光线，并驱动它们快速适应黑暗。哺乳动物视网膜中视锥细胞的缺乏使得视锥细胞特异性的分子和生物化学研究极具挑战性。因此，使视锥细胞而不是视杆细胞能够使用视网膜视觉周期的分子机制尚不清楚。突变的rd 7小鼠，其中缺乏杆转录因子Nr 2 e3，并有杆，除了其杆基因表达锥基因的子集，为我们提供了一个独特的机会，以确定控制访问视网膜视觉周期的分子机制。这个提议的中心假设是光感受器的分子特性控制它们使用视网膜视觉周期的能力。具体来说，我们将证明，在rd 7杆的视锥细胞基因的一个子集的表达是足够的，使他们能够使用11-顺式视黄醇的色素再生和访问视网膜的视觉周期。rd 7杆的表达分析使我们能够确定视黄醇脱氢酶10（RDH 10）作为视锥细胞特异性基因和可能的关键酶，氧化11-顺式视黄醇作为视网膜视觉周期的一部分。我们将使用功能缺失和获得突变小鼠来证明RDH 10在视网膜视觉周期中的作用。总的来说，这里概述的实验将确定使视锥细胞能够进入视网膜视觉周期并快速再生其视觉色素的分子机制，这是白天在明亮和快速变化的光线条件下视锥细胞介导的视觉的关键特性。 它们还将为治疗由错误的RPE视觉周期引起的视觉障碍提供新的治疗工具。

DESCRIPTION (provided by applicant): Cones represent only 5% of photoreceptors in humans, but are critical for our daytime vision. AMD, the most prominent cone vision disorder, has a major impact on the elderly, and cone loss results in legal blindness. It is critical for the function of mammalian cones as daytime photoreceptors that they regenerate their visual pigment rapidly following its destruction by light. This is made possible by two pathways. The canonical retinal pigment epithelium (RPE) visual cycle provides 11-cis retinal chromophore to both rods and cones. In contrast, the novel retina visual cycle relies on Muller cells to provide 11- cis retinol, which can be utilized only by cones after they oxidize it to 11-cis retinal by an unknown dehydrogenase. As we demonstrated over the past five years, the retina visual cycle plays a crucial role in daytime vision by extending the functional range of cones to bright light and by driving their rapid dark adaptation. The scarcity of cones in the mammalian retina makes molecular and biochemical cone-specific studies extremely challenging. As a result, the molecular mechanism that enables cones, but not rods, to use the retina visual cycle is not understood. The mutant rd7 mouse, which lacks the rod transcription factor Nr2e3 and has rods that in addition to its rod genes express a subset of cone genes, provides us with a unique opportunity to identify the molecular mechanism controlling access to the retina visual cycle. The central hypothesis of this proposal is that the molecular properties of photoreceptors control their ability to use the retina visual cycle. Specifically, we will demonstrate that the expressionof a subset of cone genes in the rd7 rods is sufficient to enable them to use 11-cis retinol for pigment regeneration and to access the retina visual cycle. Expression analysis of rd7 rods has allowed us to identify retinol dehydrogenase 10 (RDH10) as a cone-specific gene and the likely key enzyme that oxidizes 11-cis retinol as part of the retina visual cycle. We will use loss and gain of function mutant mice to demonstrate the role of RDH10 in the retina visual cycle. Collectively, the experiments outlined here will identify the molecular mechanism that enables cones to access the retina visual cycle and regenerate rapidly their visual pigment, a property that is critical for daytime, cone-mediated vision in bright and rapidly changing light conditions. They will also provide new therapeutic tools for the treatment of visual disorders caused by faulty RPE visual cycle.