目的 对一个表型独特的常染色体显性遗传白内障家系进行超微结构及其疾病相关基因的定位和克隆研究。 方法 对该家系成员进行详细眼部检查；白内障术中取混浊晶状体皮质进行常规病理切片和电镜检查；抽取家系成员外周血5ml并提取DNA，采取微卫星遗传标记与该家系疾病相关基因位点进行连锁分析并对疾病相关侯选基因PCR扩增后直接测序，检测其突变位点。 结果 该家系所有患者均表现为珊瑚状伴针刺状混浊，并间杂有金属样反光。晶状体纤维细胞出现局灶性退行性变，细胞内异常高密度物质沉积和细胞间距增宽。γ-晶状体蛋白基因为其疾病相关基因，并发现γD-晶状体蛋白基因外显子2第70位核苷酸胞嘧啶突变为腺嘌呤。 结论 此研究证实了γ-晶状体蛋白基因为遗传性先天性白内障的疾病相关侯选基因并发现了新的基因突变方式。

Special Fasciculiform Cataract Caused by a New Mutation of γ-Crystallin Gene.
Xingchao Shentu*, Ke Yao*,
Eye Center, Affiliated Second Hospital, College of Medicine, Zhejiang University
＆ Ophthalmology Institute of Zhejiang University

Abstracts
Purpose: To identify the ultrastructure change and the genetic defect for a special fasciculiform autosomal dominant congenital cataract (ADCC), which affected a Chinese family.
Methods: Members of the Chinese family with this special fasciculiform ADCC were studied. Clinical examination, light and transmission electron microscopy observation for the removed lens tissue, linkage analyses with the polymorphisms of microsatellite markers and mutational analyses of candidate genes with direct sequencing were performed.
Results: Thirteen individuals of the family were affected with the special fasciculiform ADCC, which showed no variability among affected family members. The lens fiber cells showed focal degeneration alterations, globular highly dense deposit intracellular and the enlarged intercellular space. This ADCC was associated with locus on chromosome 2q33-35. Mutational analyses of the CRYG candidate gene identified a C→A heterozygous transversion at nucleotide position 70 in CRYGD exon2, which cosegregated with the ADCC and was not observed in 100 control of various ethnic backgrounds.
Conclusion: This study revealed a new missense mutation in the CRYGD gene that led to a special fasciculiform ADCC and supported the role of CRYGD in human cataract formation.