QT间期延长综合征病人ankyrin-B基因突变的解析

摘要

目的确定ankyrin-B基因突变在日本人群QT间期延长综合征中的发病率以及ankyrin-B基因突变与QT间期延长综合征之间的关系.方法我们对相互之间无血缘关系的日本人群已确诊的QT间期延长综合征患者78例(男28例,女50例)进行了研究.在征得患者的同意之后,从其白细胞中提取纯化基因组DNA并行多聚酶链式反应(PCR)扩增.随即对扩增的DNA行单链构像多态性(SSCP)分析.而后将突变或异常的SSCP产物分离后,采用自动荧光测序仪检测DNA序列.最后再用150例正常健康人的DNA作为对照,对上述经测序确认的误义点突变进行PCR-限制性片段长度多态性分析,以进一步证实误义点突变的真实性和可靠性.结果我们在一例确诊的QT间期延长综合征患者的ankyrin-B基因的4603碱基位点上发现了从T到A的突变(T4603A).出现于基因的第40号外显子上的该误义点突变,导致了氨基酸序列第1535位点上的色氨酸残基被精氨酸残基所取代(W1535R).而该氨基酸序列正位于ankyrin-B基因高度保守的调节区域.结论新发现的位于ankyrin-B基因调节区域的误义点突变可能是导致4型QT间期延长综合征的原因之一,而该突变似乎并不是导致日本人群4型QT间期延长综合征的主要病因.%Objectives To identify the ankyrin-B gene mutations that cause long QT syndrome (LQTS) and determine the prevalence of such mutations in Japanese patients with LQTS. Methods We conducted a search for ankyrin-B gene mutation in 78 unrelated patients with LQTS (28 males and 50 females, aged 2 to 89 years). With informed consent from all the subjects and/or their parents, genomic DNA was purified from the white blood cells of the patients and amplified using polymerase chain reaction (PCR). Single-strand conformational polymorphism (SSCP) analysis of the amplified DNA was performed to screen for mutations and aberrant SSCP products were isolated and sequenced by dye terminator cycle sequencing method using an automated fluorescent sequencer. PCR and restriction fragment length polymorphism (PCR-RFLP) analysis was carried out to further confirm the missense mutations by comparison with samples from 150 normal healthy individuals.Results We identified a T to A transition mutation at position 4 603 in exon 40, resulting in the substitution of arginine for a tryptophan at amino acid residue 1 535 (W1535R) in the regulatory domain of 220-kD ankyrin-B, which is a highly conserved domain shared by different species. Conclusions This novel missense mutation in the ankyrin-B gene may bea cause of type 4LQTS. Ankyrin-B gene mutation might not play the major role in LQTS in Japanese.