ENVIRONMENTAL FACTORS IN USHERS SYNDROME

Usher综合征的特征是先天性听力损失和 进行性视网膜变性。这种疾病占了大多数 涉及遗传性听力和视力障碍的病例。引座者的是 在大约十几种遗传综合征中是独一无二的，涉及耳朵和 眼睛，因为它的作用相对有限。这些几乎是 完全局限于听觉、视觉，有时还包括前庭 系统。最初的损失是受体细胞的损失--毛细胞 耳蜗和前庭，以及眼睛的光感受器。虽然 Usher‘s被细分为三个表型类型，即遗传型 这种疾病的形式要多得多。事实上，多个类型 亚瑟的这种受限制的影响表明，所有形式的 疾病作用于一个或几个常见的结构或过程 耳和眼的感觉上皮细胞。自从一连串的事件发生在 感觉传导在耳朵和眼睛中是非常不同的，这是一种常见的 焦点可能涉及细胞代谢的某个方面(S)。一直以来都是 知道长时间暴露在强光下会导致永久性氧化 视网膜受损(例如，Noell，1963)。同样，听力损失 暴露在噪音中所产生的物质被认为与氧化有关 损害(Siedman等人，1993年)。Usher的表达可能涉及到 未充分清除或修复与活性氧有关的损伤 在正常感觉过程中产生的物种(RO) 转导。与ROS相关的损害已被牵连到导致或 加重几种神经退行性疾病(Gotz等人，1994年)。 受损细胞抵御ROS相关损害的能力较差 脂质、蛋白质和DNA，并且不太能区分 产生ROS的反应。目前，人们对此几乎一无所知。 ROS在感觉上皮细胞遗传性变性中的作用。在这 修改后的应用，我们建议探讨ROS在耳蜗和 两种亚瑟综合征候选小鼠模型的视网膜变性， TUBBY和SHAKER-1这些都得到了Usher的模型的支持 他们与亚瑟的表型相似的基础和他们的遗传学(吉布森 等人，1995；Well等人，1995；Heckenliavy等人，1994；Ohlemiller等人 Al.，1995)。我们将在体内定位和量化ROS的形成 用氧化敏感剂对这两种模型的视网膜和Corti器官 荧光指示剂、2，7-二氯二乙酸酯荧光素和激光 共聚焦显微镜。感觉上皮细胞将在两个年龄段进行检查： 在实质性神经变性开始之前的幼年动物中，以及 在年长的动物中，细胞正在丢失。中等噪音和光线 暴露将被用来解决ROS水平是否是活动 依附的。此外，组织内还含有重要的内源性物质 抗氧化剂谷胱甘肽将在类似的条件下进行测定。 氧化损伤会降低谷胱甘肽的含量，因此评估其 浓度可能为ROS持续升高提供证据 荧光指示剂的检测灵敏度。

Usher's syndrome is characterized by combined congenital hearing loss and progressive retinal degeneration. The disease accounts for the majority of cases involving inherited deficits of both hearing and vision. Usher's is unique among the roughly dozen hereditary syndromes involving the ear and eye in that its effects are relatively restricted. These are almost entirely limited to the auditory, visual, and sometimes vestibular systems. The initial loss is a loss of receptor cells--the hair cells of the cochlea and vestibule, and the photoreceptors of the eye. Although Usher's has been subdivided into three phenotypic classes, the genetic forms of this disease number many more. The fact that the multiple types of Usher's have such circumscribed effects suggests that all forms of this disease act upon one or a few structures or processes common to the sensory epithelia of the ear and eye. Since the cascade of events in sensory transduction is quite different in the ear and eye, one common focus may involve some aspect(s) of cellular metabolism. It has long been known that prolonged exposure to intense light causes permanent oxidative damage to the retina (e.g., Noell, 1963). Likewise, hearing losses resulting from noise exposure have been suggested to involve oxidative damage (Siedman et al., 1993). The expression of Usher's may involve inadequate removal or repair of damage associated with reactive oxygen species (ROS) which are generated in the course of normal sensory transduction. ROS-related damage has been implicated as causing or exaCerbating several neurodegenerative diseases (Gotz et al., 1994). Compromised cells are less capable of fending off ROS-related damage to lipids, proteins and DNA, and are less able to compartmentalize the reactions that generate ROS. Presently, almost nothing is known about the role of ROS in inherited degeneration of sensory epithelia. In this revised application, we propose to explore the role of ROS in cochlear and retinal degeneration in two candidate mouse models of Usher's syndrome, tubby and shaker-1. These have received support as Usher's models on the basis of their phenotypic similarity to Usher's and their genetics (Gibson et al., 1995; Well et al, 1995; Heckenlively et al., 1994; Ohlemiller et al., 1995). We will localize and quantify ROS formation in vivo in the organ of Corti and retina of these two models using an oxidation-sensitive fluorescent indicator, 2,7-dichlorofluorescin diacetate, and laser confocal microscopy. The sensory epithelia will be examined at two ages: in young animals prior to the onset of substantial neurodegeneration, and in older animals in which cell loss is ongoing. Moderate noise and light exposure will be used to address whether ROS levels are activity dependent. In addition, tissue content of an important endogenous antioxidant, glutathione, will be determined under similar conditions. Glutathione content is decreased by oxidative injury, so assessment of its concentration may provide evidence for ongoing ROS elevation that is below the detection sensitivity of fluorescent indicators.