先天性无虹膜患者的基因型-表型分析

Genetic screening of the congenital aniridia and genotype-phenotype analysis

目的分析先天性无虹膜患者基因型与表型之间的关系。方法应用全外显子组测序对3例先天性无虹膜家系进行致病基因筛查,重点分析PAX6相关基因变异,并应用Sanger测序与定量聚合酶链式反应(PCR)验证相关变异。结果基因分析显示,2例先证者的PAX 6基因分别存在c.949 C>T无义变异和c.141+1 G>T剪切变异,另1例检测到染色体11p13的重复变异(chr11:31531331-31827959),该区域包含了PAX 6、ELP 4基因。PAX 6结构基因变异患者的表型符合典型无虹膜的特征,主要表现为虹膜完全缺失,黄斑发育不全/眼球震颤及小角膜;11p13的重复变异患者主要表现为小眼球合并小角膜、黄斑发育不全/眼球震颤及虹膜发育不良。结论完全PAX 6拷贝重复可能导致PAX 6表达过量,引起以小眼球合并小角膜,黄斑发育不良为特征的严重眼部异常,其虹膜异常累及较轻微,区别于PAX 6单倍剂量不足所致的典型无虹膜。

Objective To explore the genotype-phenotype correlation among 3 pedigrees affected with congenital aniridia.Methods Clinical data and genomic DNA were collected and genetic variations were screened by whole-exome sequencing,with an emphasis on PAX6-related genes.Suspected variations were verified by Sanger sequencing and quantitative polymerase chain reaction(PCR).Written informed consent was obtained from the parents of each propositus prior to entering study cohort.This study protocol was approved by Ethic Committee of Henan Eye Hospital(No.HNEECKY-2017(6)).Results Genetic analysis identified that a nonsense c.949 C>T variation and an c.141+1 G>T splicing variation of the PAX 6 gene in two of the probands,while the remainder has carried a duplication in 11 p13(chr11:31531331-31827959)encompassing the PAX 6 and ELP 4 genes.Phenotype analysis showed that the probands carrying the nonsense and splicing variations had classical features including complete aniridia,macular hypoplasia,microcornea and nystagmus;the proband carrying the 11p13 duplication had microphthalmos,microcornea,macular dysplasia,iris dysgenesis,and nystagmus.Conclusions The 11p13 duplication involving the PAX 6 gene may have caused over-expression of PAX 6 gene,resulting in severe eye abnormalities including microphthalmos and microcornea,macular dysplasia and nystagmus.The relatively mild iris dysgenesis has distinguishing it from classical aniridia due to PAX 6 haploinsufficiency.