Gap-Junction-Medicated Cell Death in Rod-Cone Dystrophie

描述（由申请人提供）：色素性视网膜炎（RP）是一组遗传介导的退行性视网膜疾病，表现出广泛的表型。在各种形式的RP的病理基础上存在明显的异质性，但在已知的病例中，相当大的百分比是由于视紫红质或其他杆状特异性蛋白质突变引起的。然而，尽管遗传缺陷仅在视杆光感受器中表达，否则健康的视锥光感受器总是死亡，导致严重的视力障碍。这一提议的主要目的是验证一种假设，即疾病从垂死的视杆细胞传播到基因正常的视锥细胞是一种“旁观者”效应，由存在于这些光感受器亚型之间的间隙连接介导。根据这一观点，触发凋亡过程的物质通过细胞间隙连接通道将促凋亡信号从患病的杆状细胞传递到邻近的锥体细胞。如果间隙连接是光感受器变性非细胞自主传播的重要因素，阻断通过这些通道的传播可能提供一种新的治疗干预形式，使锥细胞免于其邻居的命运。

DESCRIPTION (provided by applicant): Retinitis pigmentosa (RP) constitutes a group of genetically-mediated, degenerative retinal diseases that display a broad range of phenotypes. There is appreciable heterogeneity in the pathologies that underlie the various forms of RP, but of the known cases, a substantial percentage arise as a consequence of mutations in rhodopsin or other rod-specific proteins. However, despite the fact that the genetic defect is expressed solely in the rod photoreceptors, otherwise healthy cone photoreceptors invariably die, resulting in severe visual impairment. The principal goal of this proposal is to test the hypothesis that the spread of the disease from dying rods to genetically normal cones is a form of "bystander" effect, mediated by the gap junctions that exist between these photoreceptor subtypes. On this view, agents that trigger the apoptotic process permeate the intercellular gap-junctional channels to carry proapoptotic signals from diseased rods to neighboring cones. If gap junctions are a significant factor in the non-cell-autonomous spread of photoreceptor degeneration, blocking transmission through these channels may provide a novel form of therapeutic intervention that would enable cones to be spared the fate of their neighbors. The experiments we plan to conduct will help to determine whether the cone photoreceptors of transgenic mice that express rod-specific gene defects exhibit a significantly higher survival when the gap-junctional protein (connexin36) that couples their rods and cones is disrupted. Cx36 "knockout" mice are available, and we propose to cross them with mice expressing various rod-specific mutations that result in rod-cone dystrophy. Cone structure and function will be assessed by a panel of histological, immunocytochemical, and electrophysiological methods. In addition, we plan to conduct a series of molecular biological and biochemical studies to examine further connexin expression in mammalian photoreceptors, and to identify proapoptotic agents that are able to permeate the intercellular channels.