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Characterization of a Novel Missense Mutation in the Pore of HERG in a Patient with Long QT Syndrome
Author(s) -
YOSHIDA HIDETADA,
HORIE MINORU,
OTANI HIDEO,
TAKANO MAKOTO,
TSUJI KEIKO,
KUBOTA TOMOYUKI,
FUKUNAMI MASATAKE,
SASAYAMA SHIGETAKE
Publication year - 1999
Publication title -
journal of cardiovascular electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.193
H-Index - 138
eISSN - 1540-8167
pISSN - 1045-3873
DOI - 10.1111/j.1540-8167.1999.tb00304.x
Subject(s) - herg , missense mutation , long qt syndrome , patch clamp , mutation , mutant , microbiology and biotechnology , wild type , medicine , chemistry , biophysics , genetics , potassium channel , biology , electrophysiology , qt interval , gene
HERG Mutation and Long QT Syndrome. introduction : A new strategy to elucidate the molecular mechanisms underlying the long QT syndrome (LQTS) is now available with genetic mutational analyses and characterization of ion channel mutations. Methods and Results : In a 26‐year‐old woman with LQTS, we identified a novel missense mutation in the pore of HERG by using polymerase chain reaction/single‐strand conformation polymorphism (PCR/SSCF) and sequencing of her genomic DNA. The mutation resulted in an amino acid substitution of a positively charged lysine for a highly conserved uncharged asparagine at codon 629 (N629K). Whole cell, patch clamp studies were conducted in COS7 cells by transfecting with wild‐type (WT) and/or the mutant N629K HERG . The WT HERG produced an I Kr ‐like, E‐4031‐sensitive conductance with an inward rectification. In contrast, the cells transfected with the N629K HERG did not display any time‐dependent current. Cotransfection of WT and N629K HERG (at a ratio of 1:1) produced a significantly smaller conductance when compared with WT HERG (WT 59.9 ± 7.3 pA/pF [n = 22] vs WT+N629K 5.5 ± 2.3 pA/pF [n = 11]; P < 0.01), but did not alter K + ion selectivity and tail current‐voltage dependence. Because aprindine hydrochloride was effective in preventing ventricular tachycardias, we also tested the effect of the drug on WT HERG (I Kr ) and KvLQT1/KCNE1 (I Ks ) currents expressed in COS7. Conclusion : Functional analyses of a novel missense mutation in the pore of HERG suggest that the mutation causes marked reduction of I Kr via a dominant negative effect.