ALPHA-CRYSTALLIN FUNCTION IN LENS BIOLOGY

描述(申请人提供)：白内障是导致视力丧失的最常见原因，占全球失明的45%。白内障手术每年花费美国医疗保险系统约50亿美元。流行病学研究表明，人类白内障的发病机制涉及遗传、环境和其他与疾病相关的危险因素。晶状体蛋白占晶状体总蛋白的90%，对晶状体透明度起着关键作用。遗传性白内障在儿童失明中占相当大的比例，这些白内障中有50%是有遗传基础的。最近在识别编码？、？的基因点突变方面取得了很大进展。晶状体蛋白和会导致遗传性人类在出生或早期患上白内障。对这些单基因形式的白内障的功能研究可以为年龄相关性白内障的病因提供重要的信息。晶状体蛋白是晶状体上皮细胞和纤维细胞中表达的两种多肽的聚合体。为了了解遗传性白内障的病因，我们利用基于胚胎干细胞的技术，建立了表达与人类常染色体显性遗传性白内障连锁的晶状体蛋白突变1A-R49C和1B-R120G的敲入小鼠模型。这些小鼠在早期阶段就会患上白内障，并将成为了解疾病过程的重要工具。特殊目的1将验证这样的假设，即在突变蛋白在发育中的晶状体中表达后不久，α-晶体蛋白突变会导致上皮和纤维细胞的破坏。第二个特定目的是验证突变的β-晶体蛋白、细胞骨架蛋白和黏附分子之间的相互作用破坏晶状体细胞的正常发育的假说。第三个特定目标将检验这样的假设，即突变的A-或B-晶体蛋白破坏了正常晶状体蛋白质的动态平衡，导致蛋白质异常降解。将进行生化、细胞生物学和遗传学研究。这些研究结果将为晶状体发育和白内障形成的分子基础提供新的见解，并可能促进延缓或预防白内障的策略的发展。 与公共卫生相关：白内障的形成--一种使正常透明的晶状体变得模糊的现象--是全世界最常见的致盲原因。白内障手术是美国医疗保险年度医疗保健费用中最大的费用之一。白内障以影响老年人而闻名，但非综合征性先天性白内障发生在早期，会导致严重的视力障碍。遗传和环境因素已被发现在老年性白内障中起着重要作用。晶体蛋白是眼晶状体中含量非常丰富的蛋白质，晶体蛋白基因的突变已被证明是许多遗传性白内障的原因。遗传性白内障表现为临床和遗传上的异质性晶状体病理，白内障的病因、形态和潜在的生化和细胞生物学机制之间的关系尚不清楚。这个项目将解决尚未回答的问题，以了解由两种不同的阿尔法晶体蛋白基因突变引起的白内障的分子机制，这两种突变导致人类白内障。对导致儿童早期白内障的基因突变的机制研究是一个重要的研究领域，特别是因为它意味着理解更常见的年龄相关性白内障的疾病病因。

DESCRIPTION (provided by applicant): Cataract formation is the most common cause of vision loss, accounting for 45% of blindness worldwide. Cataract operations cost the US Medicare system ~$5 billion annually. Epidemiological studies show that the pathogenesis of human cataracts involves genetic, environmental, and other disease-associated risk factors. Lens crystallins account for 90% of the total lens proteins and play a key role in lens transparency. Hereditary cataracts account for a significant proportion of childhood blindness, and 50% of these cataracts have a genetic basis. Much recent progress has been made in identifying point mutations in genes that encode ?, ? and ?-crystallins and lead to hereditary human cataracts at birth or an early age. Functional studies on these monogenic forms of cataract could provide important information about the etiology of age-related cataracts. ?-crystallin is an aggregate of two polypeptides 1A and 1B which are expressed in lens epithelial and fiber cells. To understand disease etiology in hereditary cataracts, we have generated knock-in mouse models expressing the ?- crystallin mutations 1A-R49C and 1B-R120G linked with human autosomal dominant hereditary cataracts, using embryonic stem cell-based technologies. These mice develop cataracts at an early stage and will be an important tool to understand disease process. Specific Aim 1 will test the hypothesis that the ?A-crystallin mutant causes epithelial and fiber cell disruption soon after the mutant protein is expressed in the developing lens. The second Specific Aim tests the hypothesis that the interaction between mutant ?-crystallin, cytoskeletal proteins and adhesion molecules disrupts the normal development of the lens cells. The third Specific Aim will test the hypothesis that mutant ?A- or ?B-crystallin disrupt normal lens protein homeostasis leading to abnormal protein degradation. Biochemical, cell biological and genetic studies will be performed. The results of these studies will provide new insights into molecular basis of lens development and cataract formation, and may promote the development of strategies to delay or prevent cataracts. PUBLIC HEALTH RELEVANCE: Cataract formation - a clouding of the normally clear lens - is the most common cause of blindness worldwide. Cataract surgery is one of the largest expenses in the annual Medicare healthcare costs in the U.S. Cataracts are better known for affecting older people, but non-syndromic congenital cataracts occur at an early age and cause a significant visual impairment. Genetic and environmental factors have been found to play an important part in age-related cataracts. Crystallins are highly abundant proteins of the eye lens, and mutations in crystallins genes have been shown to be the cause of many inherited cataracts. Hereditary cataracts show clinically and genetically heterogeneous lens pathology, and the relationships between cataract etiology, morphology and underlying biochemical and cell biological mechanisms remain unclear. This project will address unanswered questions to understand the molecular mechanism for cataracts caused by two different mutations in alpha crystallin genes that cause human cataracts. Mechanistic studies of genetic mutations that cause early childhood cataracts are an important area of research particularly because of its implications to understand disease etiology for the more common age-related cataracts.