三个先天性无虹膜症家系中PAX6基因的突变分析

摘要

背景 人类配对盒基因(PAX6)编码一个转录调节子,对眼和大脑形态的形成起关键作用.PAX6突变可导致许多先天性眼部发育异常,如先天性无虹膜症,通常为常染色体显性遗传方式. 目的 对三个先天性无虹膜症家系成员进行PAX6基因分析,探索这些家系发病的遗传基础. 方法 收集三个先天性无虹膜症家系的5例患病者和正常成员13名的外周血标本提取DNA,根据PAX6基因的序列设计4～ 13外显子序列,通过聚合酶链反应(PCR)扩增引物并测序,将目标序列与已发表的PAX6基因序列进行对比分析.结果 三个家系中共有5例患病者,在家系A中2例患者发现一个杂合突变(c.718 C＞T),导致第240位氨基酸由精氨酸突变为终止密码子(p.A rg240X),而其他正常表型者未发现此突变.家系B中的患病者和正常成员均未检测到PAX6基因的突变.家系C中1例患病者发现c.331 delG(p.Val111SerfsX13)的缺失突变,此单个碱基的缺失造成了移码突变,使PAX6蛋白羧基端的299个氨基酸缺失,而此家系的其他正常表型成员未发现此突变. 结论 家系A和家系C先天性无虹膜症的致病与PAX6基因的突变有关.%Background Human paired box gene 6 (PAX6) encodes a transcriptional regulator.It is essential for eye and brain morphogenesis.Mutation of PAX6 gene is responsible for many congenital ocular malformations,such as aniridia.Aniridia is a autosomal dominant inheritance mode. Objective In this study,PAX6 gene mutation was analyzed in three Chinese families with aniridia through polymerase chain reaction (PCR) and sequencing. Methods The blood specimens were collected from 5 suffers and normal individuals of 3 aniridia families to extract DNA.The sequences of extron 4-13 were designed based on PAX6 gene.The primer was amplified by PCR and sequenced and compared with the known PAX6 gene sequence.This study complied with Declaration of Helsinki and approved by ethic committee of Sichuan University.Written informed consent was obtained from each individual before any medial examination. Results There were 5 suffers in the 3 families.A heterozygous mutation (c.718 C＞T) in PAX6 gene was identified in 2 patients of family A.This mutation caused an amino acid substitution of arginine to termination codon at position 240 ( p.Arg240X) of PAX6 protein.No similar change in the normal families.No any the alteration of PAX6 gene was detected in family B whatever suffers and normal individuals.In family C,a deletion mutation of c.331 delG ( p.Val111 SerfsX13 ) in PAX6 gene was found.The deletion of one base caused frame shift mutation of PAX6 protein,and no such mutation was seen in other families. Conclusions Mutation of PAX6 gene appeares to be causative mutations of the disease in family A and C.