Ma Lijuan, Lin Chunxia, Teng Siyong, Chai Yongping, Bähring Robert, Vardanyan Vitya, Li Liang, Pongs Olaf, Hui Rutai
Sino-German Laboratory for Molecular Medicine, Fuwai Hospital, Peking Union Medical College and Chinese Academy of Medical Sciences, 167 Beilishilu, Beijing 100037, China.
Cardiovasc Res. 2003 Sep 1;59(3):612-9. doi: 10.1016/s0008-6363(03)00510-8.
To identify the underlying genetic basis of a Chinese pedigree with Long QT syndrome, the causally related genes were screened in a family and the functional consequence of the identified gene mutation was evaluated in vitro.
Mutations in the five defined Long QT syndrome related genes were screened with polymerase chain reaction and single-strand conformation polymorphism methods and direct sequencing. The electrophysiological properties of the identified mutation were characterized in the Xenopus oocyte heterologous expression system.
A novel missense mutation, G to A at position 154 in the KCNE1 gene was identified in a Chinese Long QT syndrome family, which leads to an amino acid substitution of arginine (R) for glycine (G) at position 52 (G52R-KCNE1). Of 26 family members (one DNA was not available), seven were mutation carriers and two of them with normal electrocardiogram. Compared with wild-type KCNE1/KCNQ1 channels, coexpression of G52R-KCNE1 with KCNQ1 in Xenopus oocytes did not amplify the KCNQ1 current amplitudes and slightly changed the activation kinetics of the KCNQ1 channels. Coexpression of KCNQ1 together with wild type KCNE1 and G52R-KCNE1 reduced the wild-type I(ks) current amplitude by 50%, whereas other biophysical properties of the I(ks) were not altered.
Our findings indicate that glycine52 in the transmembrane domain is critical for KCNE1 function. The mutant G52R-KCNE1 has a dominant negative effect on I(ks) current, which reduces the I(ks) current amplitude and leads to a prolongation of the cardiac action potential. This could underlie the molecular mechanism of ventricular arrhythmias and sudden death in those patients.
为确定一个患有长QT综合征的中国家系的潜在遗传基础，对一个家族中的致病相关基因进行筛选，并在体外评估所鉴定基因突变的功能后果。
采用聚合酶链反应、单链构象多态性方法和直接测序法，对五个已确定的与长QT综合征相关的基因进行突变筛选。在非洲爪蟾卵母细胞异源表达系统中对所鉴定突变的电生理特性进行表征。
在中国一个长QT综合征家族中鉴定出KCNE1基因第154位的一个新的错义突变，由G突变为A，导致第52位氨基酸由甘氨酸（G）替换为精氨酸（R）（G52R-KCNE1）。在26名家族成员中（有一份DNA样本不可用），7人为突变携带者，其中2人心电图正常。与野生型KCNE1/KCNQ1通道相比，在非洲爪蟾卵母细胞中G52R-KCNE1与KCNQ1共表达并未增大KCNQ1电流幅度，而是略微改变了KCNQ1通道的激活动力学。KCNQ1与野生型KCNE1和G52R-KCNE1共同表达使野生型I(ks)电流幅度降低了50%，而I(ks)的其他生物物理特性未改变。
我们的研究结果表明，跨膜结构域中的甘氨酸52对KCNE1功能至关重要。突变体G52R-KCNE1对I(ks)电流具有显性负性作用，可降低I(ks)电流幅度并导致心脏动作电位延长。这可能是这些患者室性心律失常和猝死的分子机制基础。
