KRT6A基因I462S新生突变导致Ⅰ型先天性厚甲症

A de nono I462S mutation in the KRT6A gene is associated with pachyonychia congenita type Ⅰ

目的研究I型先天性厚甲症患者KRT6A基因突变情况,为建立该病的基因诊断与遗传咨询提供依据。方法提取1例I型先天性厚甲症患者及家系成员和50名正常对照外周血白细胞基因组DNA.设计针对KRT6A基因的特异引物,采用聚合酶链反应(PCR)扩增基因的全部编码序列,DNA直接测序明确具体的突变位置和方式,限制性内切酶反应验证基因突变。结果 PCR结合DNA测序发现患者KRT6A基因第7外显子存在异常;第1385位核苷酸由胸腺嘧啶(T)突变为鸟嘌呤(G),导致KRT6A角蛋白2B螺旋区末端第462位密码子由异亮氨酸(I)变成丝氨酸(S),即发生1462S错义突变。患者父母及与家系无血缘关系的50名正常对照均未发现此突变,提示I462S为一种新生突变(de novo mutation)。结论 KRT6A基因1462S新生错义突变是导致该例患者I型先天性厚甲症的特异突变。

Objective To analyze the KRT6A gene mutation and mutating patterns in a sporadic Chinese patient with Pachyonychia congenita ( PC) -1 so as to provide a basis for gene diagnosis and genetic counseling of this disorder. Methods Genomic DNA was extracted from whole blood by standard methods from a female patient with PC-1 and her parents, and from 50 normal, unrelated individuals. Primers for specific amplification of the structural KRT6A gene without co amplification of homologous genes were designed and synthesized. All exons of the gene and their flanking intronic sequences were amplified using polymerase chain reaction (PCR) and subjected to automatic DNA sequencing. The mutation was confirmed by Mbo I restriction digestion of the KRT6A-specific PCR products. Results Direct sequencing of the PCR products revealed a novel heterozygous missense mutation, I462S in the KRT6A gene, which resulted from T to G transversion at nucleotide 1385 (1385T > G) in exon 7 was detected in the patient. This mutation would result in the substitution of Isoleucine by Serine at codon 462 (I462S) located in the end 2B domain of keratin 6A. No such mutation was found in the patient's parents by sequencing of PCR products and this mutation was confirmed in the patient and excluded from both parents and 50 normal, unrelated controls by restriction analysis of PCR fragments using Mbo I enzyme. Conclusions A de novo missense mutation in the KRT6A gene, I462S, has been found in a sporadic PC-1 patient. The identification of this novel mutation in the KRT6A gene provides further evidence that mutation in the KRT6A gene causes PC-1 phenotype.