晶状体结构蛋白基因（CRYBA4）突变导致不同遗传模式先天性白内障的机制研究

Congenital cataract, characterized as lens opacities, is the cause of approximately one third of blindness in infants. βA4-crystallin is one of the major soluble proteins in human lens. To date, mutations in CRYBA4 gene have been associated with human congenital cataract. Unlike the other members in β-crystallin family (βA1-crystallin, βA3-crystallin, βB1-crystallin and βB2-crystallin) which have been confirmed causing the disease by changing the protein structure, stability, solubility and crystallin subunit interactions, the pathogenic mechanisms of mutant βA4-crystallins is still unclear. All of the reported CRYBA4 gene mutations caused autosomal dominant congenital cataracts. While our previous study identified a novel CRYBA4 mutation which caused the congenital cataract inherited in autosomal recessive pattern. In this study, we will compare the protein structure, stability, solubility and crystallin subunit interactions of the above mutants which induced congenital cataract with different inheritance patterns. In vitro incubation and biophysical studies will be performed in order to compare the different properties among wild-type homo-oligomer, mutant homo-oligomers and hetero-oligomers and reveal the pathogenic mechanism of different inheritance modes caused by different mutants. This project will pave the way for elucidating the physiology of βA4-crystallin and the relationship between abnormal proteins and cataractgenesis. Also, it will provide scientific basis for development of prevention, control and treatment strategy against congenital cataract.

先天性白内障，即晶状体浑浊，是约三分之一儿童盲的致盲原因。βA4晶状体蛋白是晶状体内的重要可溶性蛋白，编码该蛋白的CRYBA4基因突变可致先天性白内障。β晶状体蛋白家族中的突变型βA1、βA3、βB1、βB2已被证实通过改变蛋白结构、稳定性、溶解度及与其他晶状体蛋白相互作用等方式致病，但目前突变型βA4的致病机制尚不明确。目前报道的CRYBA4突变均以常染色显性遗传，申请人前期研究发现一导致常染色隐性遗传先天性白内障的CRYBA4基因新突变。本课题拟针对上述导致不同遗传模式先天性白内障的多个CRYBA4基因突变展开研究，采用体外蛋白孵育及生物波谱手段比较野生型、突变型同源寡聚体蛋白和异源寡聚体蛋白的理化特性，揭示突变型βA4致不同遗传模式先天性白内障的机理。本课题实施将为βA4的生理功能及该蛋白异常与先天性白内障发生的关系提供新思路，从而为先天性白内障的基因治疗及药物研制提供新的科学依据。

先天性白内障，即晶状体浑浊，是约三分之一儿童盲的致盲原因。βA4晶状体蛋白是晶状体内的重要可溶性蛋白，编码该蛋白的CRYBA4基因突变可致先天性白内障。β晶状体蛋白家族中的突变型βA1、βA3、βB1、βB2已被证实通过改变蛋白结构、稳定性、溶解度及与其他晶状体蛋白相互作用等方式致病，但目前突变型βA4的致病机制尚不明确。综上所述，本研究项目建立了βA4晶状体蛋白的原核表达系统并探索了CRYBA4蛋白质纯化体系，通过生物波谱手段比较野生型、突变型蛋白的理化特性，应用酵母双杂交的方法检测野生型及突变型βA4晶状体蛋白与其他晶状体蛋白间相互作用，从而揭示突变型βA4引起先天性白内障的致病机制，提示突变型βA4晶状体蛋白引起蛋白的错误折叠，降低蛋白稳定性，阻碍其与βB1晶状体蛋白相互作用，导致先天性白内障的发生。本课题实施为βA4的生理功能及该蛋白异常与先天性白内障发生的关系提供新思路，从而为先天性白内障的基因治疗及药物研制提供新的科学依据。