© 2000 by European Society of Cardiology
Copyright © 2000, European Society of Cardiology
Novel mutations in KvLQT1 that affect Iks activation through interactions with Isk
aInstitut de Pharmacologie Moléculaire et Cellulaire, CNRS, 660 Route des lucioles, 06560 Sophia Antipolis, France
bINSERM U523, Institut de Myologie, Institut Fédératif de Recherche Cœur, Muscle et Vaisseaux No. 14, Groupe Hospitalier Pitié-Salpêtrière, Paris, France
cService de Biochimie B, Hôpital Pitié-Salpêtrière, Paris, France
dService de Cardiologie, Hôpital Lariboisière, Paris, France
* Corresponding author. Tel.: +33-4-9395-7734; fax: +33-4-9395-7704 barhanin{at}ipmc.cnrs.fr
Objectives: We report the functional expression of four KCNQ1 mutations affecting arginine residues and resulting in Romano–Ward (RW) and the Jervell and Lange–Nielsen (JLN) congenital long QT syndromes. Results: The R539W and R190Q mutations were found in typical RW families with an autosomal dominant transmission. The R243H mutation was found in a compound heterozygous JLN patient who presents with deafness and cardiac symptoms. The fourth mutation, R533W, was a new case of recessive form of the RW syndrome since homozygous carriers experienced syncopes but showed no deafness, whereas the heterozygous carriers were asymptomatic. The R190Q mutation failed to produce functional homomeric channels. The R243H, R533W and R539W mutations induced a positive voltage shift of the channel activation but only when co-expressed with IsK, pointing out the critical role of these positively charged residues in the modulation of the gating properties of KvLQT1 by IsK. The positive shift induced by R533W was merely 15%. This small effect was compatible with the recessive character of the RW phenotype transmission. The average QTc was significantly longer (P<0.01) in patients carrying mutations inducing a total loss of channel function and those patients were also prone to cardiac adverse symptoms (whether syncopes or sudden death) to a greater extent (62 vs. 21%, P<0.001). Conclusions: Novel mutations are described that induce a voltage shift of the channel activation only in the presence of IsK. They appear associated with a milder cardiac phenotype.
KEYWORDS Congenital defects; Ion channels; K-channel; Long QT syndrome; Ventricular arrhythmias
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