中国一先天性无虹膜家系PAX6基因新致病突变位点的筛查及验证

背景 先天性无虹膜是临床上罕见的先天性遗传性眼病.研究显示,配对盒转录因子6基因(PAX6)与先天性无虹膜症密切相关,但不同患者中PAX6基因的突变位点不同. 目的 对中国一常染色体显性遗传先天性无虹膜家系进行PAX6基因突变位点分析. 方法 于2014年8月在郑州大学第一附属医院收集一汉族先天性无虹膜家系,采集该家系9名成员及同期100名健康体检者的外周静脉血10 ml,采用标准酚-氯仿提取法提取基因组DNA,对PCR扩增产物进行测序、对比及突变分析.采用实时荧光定量PCR法验证和比较该家系中患病者与该家系表型正常者和健康对照者淋巴细胞中PAX6 mRNA的相对含量. 结果 该家系共3代9名成员,遗传方式符合常染色体显性遗传.家系中共5例患病者,成年患病者均表现为虹膜缺失和白内障,儿童患病者表现为无虹膜;其他4名家系成员表型正常.测序结果显示,家系患病者均存在11号染色体PAX6基因10号外显子的移码突变,第796位核糖核苷酸G缺失(c.796 del G),产生提前终止密码子,而家系正常成员及100名对照者均无此突变.实时荧光定量PCR结果显示,家系中患病者淋巴细胞中PAX6 mRNA表达水平比家系中正常成员约低50％,差异有统计学意义(Z=-2.449,P=0.016). 结论 PAX6基因c.796 del G为此先天性无虹膜家系的致病突变位点,扩增了PAX6基因突变谱.

A novel PAX6 mutation in a Chinese family with congenital aniridia

Background Aniridia is a rare congenital hereditary eye disease.Studies determined that PAX6 gene mutation is closely associated with congenital aniridia,but the mutation locus are varied.Objective This study was to identify virulence mutation locus of PAX6 gene of a Chinese family pedigree with autosomal dominant aniridia.Methods A Chinese family affected with autosomal dominant aniridia was collected and examined in Affiliated First Hospital of Zhengzhou University in August 2014.Periphery blood of 10 ml was collected from all the families and 100 unrelated health controls.The genomic DNA was extracted by standardized phenol-chloroform method,and all exons and splicing junctions of PAX6 were amplified by PCR.Real-time fluorescence quantitative PCR was performed to examine the relative expression of PAX6 mRNA in patients and normal phenotype families and heahh controls.This study protocol was approved by Ethic Committee of Affiliated First Hospital of Zhengzhou University and complied with Helsinki Declaration.Written informed consent was obtained from subjects or custodian before any medical examination.Results This Chinese family inclued 3 generations and 9 members,with a classic autosomal dominant inheritance mode.Five patients were found,showing the absence of iris and cataract in 3 adult patients and only absence of the iris in 2 children,and other 4 members showed the normal phenotype.A novel heterozygous PAX6 deletion mutation c.796 del G (p.A266 fs) (GenBank ID:KP255960) in exon 10 was exclusively found in all affected individuals but not in any of the unaffected families or unrelated health controls.PAX6 mRNA level in lymphocytes was about 50％ lower in aniridia patients than in unaffected family members,indicating that this mutation caused nonsense-mediated mRNA decay.Conclusions A novel deletion mutation in PAX6 gene results in an abnormal PAX6 COOH-terminal extension in the Chinese aniridia family.This finding expands the mutation spectrum of PAX6 gene.