Characterization of a novel KCNQ1 mutation for type 1 long QT syndrome and assessment of the therapeutic potential of a novel IKs activator using patient-specific induced pluripotent stem cell-derived cardiomyocytes

Abstract

IntroductionType 1 long QT syndrome (LQT1) is a common type of cardiac channelopathy associated with loss-of-function mutations of KCNQ1. Currently there is a lack of drugs that target the defected slowly activating delayed rectifier potassium channel (IKs). With LQT1 patient-specific human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (hiPSC-CMs), we tested the effects of a selective IKs activator ML277 on reversing the disease phenotypes.MethodsA LQT1 family with a novel heterozygous exon 7 deletion in the KCNQ1 gene was identified. Dermal fibroblasts from the proband and her healthy father were reprogrammed to hiPSCs and subsequently differentiated into hiPSC-CMs.ResultsCompared with the control, LQT1 patient hiPSC-CMs showed reduced levels of wild type KCNQ1 mRNA accompanied by multiple exon skipping mRNAs and a ~50% reduction of the full length Kv7.1 protein. Patient hiPSC-CMs showed reduced IKs current (tail current density at 30 mV: 0.33 ± 0.02 vs. 0.92 ± 0.21, P < 0.05) and prolonged action potential duration (APD) (APD 50 and APD90: 603.9 ± 39.2 vs. 319.3 ± 13.8 ms, P < 0.005; and 671.0 ± 41.1 vs. 372.9 ± 14.2 ms, P < 0.005). ML277, a small molecule recently identified to selectively activate KV7.1, reversed the decreased IKs and partially restored APDs in patient hiPSC-CMs.ConclusionsFrom a LQT1 patient carrying a novel heterozygous exon7 deletion mutation of KCNQ1, we generated hiPSC-CMs that faithfully recapitulated the LQT1 phenotypes that are likely associated with haploinsufficiency and trafficking defect of KCNQ1/Kv7.1. The small molecule ML277 restored IKs function in hiPSC-CMs and could have therapeutic value for LQT1 patients.Electronic supplementary materialThe online version of this article (doi:10.1186/s13287-015-0027-z) contains supplementary material, which is available to authorized users.

The Effects of Pharmacological Compounds on Beat Rate Variations in Human Long QT-Syndrome Cardiomyocytes

“…The ion channel activator ML277 has been shown to augment specifically I Ks current and shorten the action potential duration in both healthy and LQT-CMs [46, 47]. Similarly, in this study, the ML277 shortened the cFPD although the effect was relatively mild in these hiPSC-CM clusters at 1-2 μM concentration.…”

“…For bisoprolol, 260 nM (upper limit of the therapeutic serum concentration) and 520 nM (twice the upper limit of the therapeutic concentration) concentrations were used. ML277 (I Ks channel activator) concentrations of 1 μM and 2 μM were chosen based on previous reports [46, 47]. The concentrations of I Ks blocker JNJ303 (300 nM and 1000 nM) were chosen based on our previous study [41].…”

Integrating cardiomyocytes from human pluripotent stem cells in safety pharmacology: has the time come?

“…The green area defines the normal QT interval range for humans. Data are shown as mean ± SD: 1, (Malan et al , 2016); 2, (Rocchetti/Sala et al , unpublished); 3, (Zhang et al , 2014); 4, (Zhang et al , 2014); 5, (Davis et al , 2012); 6, (Rocchetti/Sala et al , unpublished); 7, (Bellin et al , 2013); 8, (Sala et al , 2016); 9, (Bizy et al , 2013); 10, (Ma et al , 2013); 11, (Ma et al , 2015); 12, (Ma et al , 2015); 13, (Gibson et al , 2014a); 14, (Itzhaki et al , 2011); 15, (Gibson et al , 2014c); 16, (Lu et al , 2014); 17, (Gibson et al , 2014b); 18, (Mehta et al , 2014). (B) and (C) Composition of extracellular buffers (B) and pipette solutions (C) for current clamp experiments.…”

Induced pluripotent stem cells: at the heart of cardiovascular precision medicine

“…Ma et al subsequently showed that hiPSC-CMs carrying a different KCNQ1 mutation (exon 7 del) not only faithfully recapitulated patients’ clinical phenotypes but also responded to ML277, a novel drug under development for arrhythmia suppression. 59 Egashira et al performed EP testing on hiPSC-CMs derived from a young survivor of sudden cardiac death (SCD) with clinical suspicion of LQT1. 58 They found a novel KCNQ1 mutation (1893delC) associated with a trafficking defect in Kv7.1 that was thought to be the culprit of the patient’s progressive clinical course.…”