Electrophysiological properties of iPS cell-derived cardiomyocytes from a patient with long QT syndrome type 1 harboring the novel mutation M437V of KCNQ1

Tatsufumi Sogo; Kumi Morikawa; Yasutaka Kurata; Peili Li; Takafumi Ichinose; Shinsuke Yuasa; Daizou Nozaki; Junichiro Miake; Haruaki Ninomiya; Wataru Shimizu; Keiichi Fukuda; Kazuhiro Yamamoto; Yasuaki Shirayoshi; Ichiro Hisatome

doi:10.1016/j.reth.2015.12.001

Electrophysiological properties of iPS cell-derived cardiomyocytes from a patient with long QT syndrome type 1 harboring the novel mutation M437V of KCNQ1

Regen Ther. 2016 Feb 15:4:9-17. doi: 10.1016/j.reth.2015.12.001. eCollection 2016 Jun.

Authors

Affiliations

¹ Division of Regenerative Medicine and Therapeutics, Department of Genetic Medicine and Regenerative Therapeutics, Tottori University Graduate School of Medical Science, 86 Nishi-cho, Yonago 683-8503, Japan.
² Center for Promoting Next-Generation Highly Advanced Medicine, Tottori University Hospital, 36-1 Nishi-cho, Yonago 683-8504, Japan.
³ Department of Physiology, Kanazawa Medical University, 1-1 Daigaku, Uchinada-machi, Ishikawa 920-0293, Japan.
⁴ Department of Cardiology, Keio University School of Medicine, 35 Shinano-machi Shinjuku-ku, Tokyo 160-8582, Japan.
⁵ Division of Cardiovascular Medicine, Endocrinology and Metabolism, Department of Molecular Medicine and Therapeutics, Tottori University Faculty of Medicine, 86-1 Nishi-cho, Yonago 683-8504, Japan.
⁶ Department of Biological Regulation, School of Health Science, Tottori University Faculty of Medicine, 36-1 Nishi-cho, Yonago 683-8503, Japan.
⁷ Department of Cardiology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603, Japan.

Abstract

Introduction: Long QT syndrome type 1 (LQT1) is caused by mutations in KCNQ1 coding slowly-activating delayed-rectifier K⁺ channels. We identified the novel missense mutation M437V of KCNQ1 in a LQT1 patient. Here, we employed iPS cell (iPSC)-derived cardiomyocytes to investigate electrophysiological properties of the mutant channel and LQT1 cardiomyocytes.

Methods: To generate iPSCs from the patient and a healthy subject, peripheral blood T cells were reprogrammed by Sendai virus vector encoding human OCT3/4, SOX2, KLF4, and c-MYC. Cardiomyocytes were prepared from iPSCs and human embryonic stem cells using a cytokine-based two-step differentiation method and were subjected to patch clamp experiments.

Results: LQT1 iPSC-derived cardiomyocytes exhibited prolongation of action potential duration (APD), which was due to a reduction of the KCNQ1-mediated current I_Ks; Na⁺, Ca²⁺ and other K⁺ channel currents were comparable. When expressed in HEK293 and COS7 cells, the mutant KCNQ1 was normally expressed in the plasma membrane but generated smaller currents than the wild type. Isoproterenol significantly prolonged APDs of LQT1 cardiomyocytes, while shortening those of healthy ones. A mathematical model for I_Ks-reduced human ventricular myocytes reproduced APD prolongation and generation of early afterdepolarizations (EADs) under β-adrenergic stimulation.

Conclusions: QT prolongation of the LQT1 patient with the mutation M437V of KCNQ1 was caused by I_Ks reduction, which may render the patient vulnerable to generation of EADs and arrhythmias.

Keywords: AP(D), action potential (duration); C-terminus mutation; EAD, early afterdepolarization; EB, embryoid body; ESC, embryonic stem cell; Early afterdepolarization; HP, holding potential; ICaL, L-type Ca2+ channel current; IK1, inward-rectifier K+ channel current; IKr, rapidly-activating delayed-rectifier K+ channel current; IKs, slowly-activating delayed-rectifier K+ channel current; INa, sodium channel current; KCNQ1; LQT1; LQTS, long QT syndrome; TdP, Torsade de points; iPS cell; iPSC, induced pluripotent stem cell.