Thomas Dierk, Wimmer Anna-Britt, Karle Christoph A, Licka Manuela, Alter Markus, Khalil Markus, Ulmer Herbert E, Kathöfer Sven, Kiehn Johann, Katus Hugo A, Schoels Wolfgang, Koenen Michael, Zehelein Joerg
Universitätsklinik Heidelberg, Innere Medizin III, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.
Cardiovasc Res. 2005 Aug 15;67(3):487-97. doi: 10.1016/j.cardiores.2005.05.003.
Hereditary long QT syndrome (LQTS) is a genetically heterogeneous disease characterized by prolonged QT intervals and an increased risk for ventricular arrhythmias and sudden cardiac death. Mutations in the voltage-gated potassium channel subunit KCNQ1 induce the most common form of LQTS. KCNQ1 is associated with two different entities of LQTS, the autosomal-dominant Romano-Ward syndrome (RWS), and the autosomal-recessive Jervell and Lange-Nielsen syndrome (JLNS) characterized by bilateral deafness in addition to cardiac arrhythmias. In this study, we investigate and discuss dominant-negative I(Ks) current reduction by a KCNQ1 deletion mutation identified in a RWS family.
Single-strand conformation polymorphism analysis and direct sequencing were used to screen LQTS genes for mutations. Mutant KCNQ1 channels were heterologously expressed in Xenopus oocytes, and potassium currents were recorded using the two-microelectrode voltage clamp technique.
A heterozygous deletion of three nucleotides (CTT) identified in the KCNQ1 gene caused the loss of a single phenylalanine residue at position 339 (KCNQ1-deltaF339). Electrophysiological measurements in the presence and absence of the regulatory beta-subunit KCNE1 revealed that mutant and wild type forms of an N-terminal truncated KCNQ1 subunit (isoform 2) caused much stronger dominant-negative current reduction than the mutant form of the full-length KCNQ1 subunit (isoform 1).
This study highlights the functional relevance of the truncated KCNQ1 splice variant (isoform 2) in establishment and mode of inheritance in long QT syndrome. In the RWS family presented here, the autosomal-dominant trait is caused by multiple dominant-negative effects provoked by heteromultimeric channels formed by wild type and mutant KCNQ1-isoforms in combination with KCNE1.
遗传性长QT综合征（LQTS）是一种基因异质性疾病，其特征为QT间期延长以及室性心律失常和心源性猝死风险增加。电压门控钾通道亚基KCNQ1的突变诱发了最常见形式的LQTS。KCNQ1与LQTS的两种不同类型相关，常染色体显性遗传的 Romano-Ward综合征（RWS），以及常染色体隐性遗传的Jervell和Lange-Nielsen综合征（JLNS），后者除心律失常外还伴有双侧耳聋。在本研究中，我们调查并讨论了在一个RWS家族中鉴定出的KCNQ1缺失突变导致的显性负性I(Ks)电流减少。
采用单链构象多态性分析和直接测序法筛选LQTS基因的突变。将突变型KCNQ1通道在非洲爪蟾卵母细胞中进行异源表达，并使用双微电极电压钳技术记录钾电流。
在KCNQ1基因中鉴定出的三个核苷酸（CTT）杂合缺失导致339位的单个苯丙氨酸残基缺失（KCNQ1-ΔF339）。在存在和不存在调节性β亚基KCNE1的情况下进行的电生理测量显示，N端截短的KCNQ1亚基（异构体2）的突变型和野生型形式比全长KCNQ1亚基（异构体1）的突变型导致更强的显性负性电流减少。
本研究突出了截短的KCNQ1剪接变体（异构体2）在长QT综合征的遗传确立和遗传模式中的功能相关性。在此呈现的RWS家族中，常染色体显性性状是由野生型和突变型KCNQ1异构体与KCNE1组合形成的异源多聚体通道引发的多种显性负性效应所致。
