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Nakajima T, Tamura S, Kawabata-Iwakawa R, Itoh H, Hasegawa H, Kobari T, Harasawa S, Sekine A, Nishiyama M, Kurabayashi M, Imoto K, Kaneko Y, Nakatani Y, Horie M, Ishii H. Novel KCNQ1 Q234K variant, identified in patients with long QT syndrome and epileptiform activity, induces both gain- and loss-of-function of slowly activating delayed rectifier potassium currents. Front Physiol 2024; 15:1401822. [PMID: 39100276 PMCID: PMC11294085 DOI: 10.3389/fphys.2024.1401822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2024] [Accepted: 06/10/2024] [Indexed: 08/06/2024] Open
Abstract
Introduction KCNQ1 and KCNE1 form slowly activating delayed rectifier potassium currents (IKs). Loss-of-function of IKs by KCNQ1 variants causes type-1 long QT syndrome (LQTS). Also, some KCNQ1 variants are reported to cause epilepsy. Segment 4 (S4) of voltage-gated potassium channels has several positively-charged amino acids that are periodically aligned, and acts as a voltage-sensor. Intriguingly, KCNQ1 has a neutral-charge glutamine at the third position (Q3) in the S4 (Q234 position in KCNQ1), which suggests that the Q3 (Q234) may play an important role in the gating properties of IKs. We identified a novel KCNQ1 Q234K (substituted for a positively-charged lysine) variant in patients (a girl and her mother) with LQTS and epileptiform activity on electroencephalogram. The mother had been diagnosed with epilepsy. Therefore, we sought to elucidate the effects of the KCNQ1 Q234K on gating properties of IKs. Methods Wild-type (WT)-KCNQ1 and/or Q234K-KCNQ1 were transiently expressed in tsA201-cells with KCNE1 (E1) (WT + E1-channels, Q234K + E1-channels, and WT + Q234K + E1-channels), and membrane currents were recorded using whole-cell patch-clamp techniques. Results At 8-s depolarization, current density (CD) of the Q234K + E1-channels or WT + Q234K + E1-channels was significantly larger than the WT + E1-channels (WT + E1: 701 ± 59 pA/pF; Q234K + E1: 912 ± 50 pA/pF, p < 0.01; WT + Q234K + E1: 867 ± 48 pA/pF, p < 0.05). Voltage dependence of activation (VDA) of the Q234K + E1-channels or WT + Q234K + E1-channels was slightly but significantly shifted to depolarizing potentials in comparison to the WT + E1-channels ([V1/2] WT + E1: 25.6 ± 2.6 mV; Q234K + E1: 31.8 ± 1.7 mV, p < 0.05; WT + Q234K + E1: 32.3 ± 1.9 mV, p < 0.05). Activation rate of the Q234K + E1-channels or WT + Q234K + E1-channels was significantly delayed in comparison to the WT + E1-channels ([half activation time] WT + E1: 664 ± 37 ms; Q234K + E1: 1,417 ± 60 ms, p < 0.01; WT + Q234K + E1: 1,177 ± 71 ms, p < 0.01). At 400-ms depolarization, CD of the Q234K + E1-channels or WT + Q234K + E1-channels was significantly decreased in comparison to the WT + E1-channels (WT + E1: 392 ± 42 pA/pF; Q234K + E1: 143 ± 12 pA/pF, p < 0.01; WT + Q234K + E1: 209 ± 24 pA/pF, p < 0.01) due to delayed activation rate and depolarizing shift of VDA. Conclusion The KCNQ1 Q234K induced IKs gain-of-function during long (8-s)-depolarization, while loss of-function during short (400-ms)-depolarization, which indicates that the variant causes LQTS, and raises a possibility that the variant may also cause epilepsy. Our data provide novel insights into the functional consequences of charge addition on the Q3 in the S4 of KCNQ1.
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Affiliation(s)
- Tadashi Nakajima
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Shuntaro Tamura
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Reika Kawabata-Iwakawa
- Division of Integrated Oncology Research, Gunma University Initiative for Advanced Research, Maebashi, Japan
| | - Hideki Itoh
- Division of Patient Safety, Hiroshima University Hospital, Hiroshima, Japan
| | - Hiroshi Hasegawa
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Takashi Kobari
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Shun Harasawa
- Division of Neurology, Japanese Red Cross Maebashi Hospital, Maebashi, Japan
| | - Akiko Sekine
- Division of Neurology, Japanese Red Cross Maebashi Hospital, Maebashi, Japan
| | | | - Masahiko Kurabayashi
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Keiji Imoto
- National Institutes of Natural Sciences, Tokyo, Japan
| | - Yoshiaki Kaneko
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Yosuke Nakatani
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Minoru Horie
- Department of Cardiovascular Medicine, Shiga University of Medical Science, Ohtsu, Japan
| | - Hideki Ishii
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
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Sveinbjornsson G, Benediktsdottir BD, Sigfusson G, Norland K, Davidsson OB, Thorolfsdottir RB, Tragante V, Arnadottir GA, Jensson BO, Katrinardottir H, Fridriksdottir R, Gudmundsdottir H, Aegisdottir HM, Fridriksson B, Thorgeirsson G, Magnusson V, Oddsson A, Sulem P, Gudbjartsson DF, Holm H, Arnar DO, Stefansson K. Screening for Rare Coding Variants That Associate With the QTc Interval in Iceland. J Am Heart Assoc 2023:e029845. [PMID: 37449562 PMCID: PMC10382112 DOI: 10.1161/jaha.123.029845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Accepted: 05/17/2023] [Indexed: 07/18/2023]
Abstract
Background Long-QT syndrome (LQTS) is a cardiac repolarization abnormality that can lead to sudden cardiac death. The most common causes are rare coding variants in the genes KCNQ1, KCNH2, and SCN5A. The data on LQTS epidemiology are limited, and information on expressivity and penetrance of pathogenic variants is sparse. Methods and Results We screened for rare coding variants associated with the corrected QT (QTc) interval in Iceland. We explored the frequency of the identified variants, their penetrance, and their association with severe events. Twelve variants were associated with the QTc interval. Five in KCNQ1, 3 in KCNH2, 2 in cardiomyopathy genes MYBPC3 and PKP2, and 2 in genes where coding variants have not been associated with the QTc interval, ISOC1 and MYOM2. The combined carrier frequency of the 8 variants in the previously known LQTS genes was 530 per 100 000 individuals (1:190). p.Tyr315Cys and p.Leu273Phe in KCNQ1 were associated with having a mean QTc interval longer than 500 ms (P=4.2×10-7; odds ratio [OR], 38.6; P=8.4×10-10, OR, 26.5; respectively), and p.Leu273Phe was associated with sudden cardiac death (P=0.0034; OR, 2.99). p.Val215Met in KCNQ1 was carried by 1 in 280 Icelanders, had a smaller effect on the QTc interval (P=1.8×10-44; effect, 22.8 ms), and did not associate with severe clinical events. Conclusions The carrier frequency of associating variants in LQTS genes was higher than previous estimates of the prevalence of LQTS. The variants have variable effects on the QTc interval, and carriers of p.Tyr315Cys and p.Leu273Phe have a more severe disease than carriers of p.Val215Met. These data could lead to improved identification, risk stratification, and a more precise clinical approach to those with QTc prolongation.
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Affiliation(s)
| | - Bara D Benediktsdottir
- Internal Medicine, Landspitali-The National University Hospital of Iceland Reykjavik Iceland
| | - Gunnlaugur Sigfusson
- Children's Medical Center Landspítali-The National University Hospital of Iceland Reykjavík Iceland
| | | | | | | | | | | | | | | | | | | | | | | | | | - Vidar Magnusson
- The Capital District Fire and Rescue Service Reykjavik Iceland
- Department of Anesthesia, Landspitali The National University Hospital of Iceland Reykjavik Iceland
| | | | | | - Daniel F Gudbjartsson
- deCODE Genetics/Amgen, Inc. Reykjavik Iceland
- Faculty of Electrical and Computer Engineering University of Iceland Reykjavik Iceland
| | - Hilma Holm
- deCODE Genetics/Amgen, Inc. Reykjavik Iceland
| | - David O Arnar
- deCODE Genetics/Amgen, Inc. Reykjavik Iceland
- Faculty of Medicine University of Iceland Reykjavik Iceland
- Cardiovascular Center, Landspitali The National University Hospital of Iceland Reykjavik Iceland
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3
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Wang Z, Wang L, Liu W, Hu D, Gao Y, Ge Q, Liu X, Li L, Wang Y, Wang S, Li C. Pathogenic mechanism and gene correction for LQTS-causing double mutations in KCNQ1 using a pluripotent stem cell model. Stem Cell Res 2019; 38:101483. [PMID: 31226583 DOI: 10.1016/j.scr.2019.101483] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Revised: 06/04/2019] [Accepted: 06/10/2019] [Indexed: 02/06/2023] Open
Abstract
AIMS To establish a KCNQ1 mutant-specific induced pluripotent stem cell (iPSC) model of a Chinese inherited long QT syndrome (LQTS) patient and to explore the pathogenesis of KCNQ1 mutations. METHODS AND RESULTS (1) Two patient-specific iPSC lines from the proband were obtained. (2) The experiments produced spontaneously beating cardiomyocytes (CMs) from patient iPSCs. Splicing mutation c. 605-2A > G in iPSC-derived cardiomyocytes (iPSC-CMs) resulted in the skipping of exon 4, exons 3-4, or exons 3-6 in KCNQ1 transcription what was observed in the patient's peripheral leukocytes. (3) Action potential duration (APD) at 50% and 90% repolarization (APD50 and APD90) of the patient's iPSC-derived ventricular-like-CMs was significantly longer than that of the control. Moreover, early after depolarization (EAD) and coupled beats were observed only in L1-iPSC-CMs. (4) A c.815G > A corrected iPSC line was obtained by using the clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR associated protein 9 (Cas9) system. CONCLUSION (1) Cardiomyocytes with spontaneous pulsation were successfully differentiated from LQTS patient-specific iPSC lines. (2) For KCNQ1 splicing mutations, there is a chance that splicing patterns in peripheral leukocytes are similar to that in patient iPSC-CMs. (3) The truncated KCNQ1 proteins induced by such splicing mutation might cause Iks decrease, which in turn produced APD prolongation and triggered activities. (4) Our data showed that CRISPR-Cas9 system could be used to rescue the LQTS-related mutations.
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Affiliation(s)
- Zhen Wang
- Heart Center, Peking University People's Hospital, Beijing, China
| | - Lipeng Wang
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing, China
| | - Wenling Liu
- Heart Center, Peking University People's Hospital, Beijing, China
| | - Dayi Hu
- Heart Center, Peking University People's Hospital, Beijing, China
| | - Yuanfeng Gao
- Heart Center, Peking University People's Hospital, Beijing, China
| | - Qing Ge
- Heart Center, Peking University People's Hospital, Beijing, China
| | - Xin Liu
- Heart Center, Peking University People's Hospital, Beijing, China
| | - Lei Li
- Heart Center, Peking University People's Hospital, Beijing, China
| | - Yangming Wang
- Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, Peking University, Beijing, China.
| | - Shiqiang Wang
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing, China.
| | - Cuilan Li
- Heart Center, Peking University People's Hospital, Beijing, China.
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4
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Dharmawan T, Nakajima T, Ohno S, Iizuka T, Tamura S, Kaneko Y, Horie M, Kurabayashi M. Identification of a novel exon3 deletion of RYR2 in a family with catecholaminergic polymorphic ventricular tachycardia. Ann Noninvasive Electrocardiol 2019; 24:e12623. [PMID: 30615235 PMCID: PMC6850420 DOI: 10.1111/anec.12623] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Revised: 11/01/2018] [Accepted: 11/13/2018] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND RYR2, encoding cardiac ryanodine receptor, is the major responsible gene for catecholaminergic polymorphic ventricular tachycardia (CPVT). Meanwhile, KCNJ2, encoding inward-rectifier potassium channel (IK1 ), can be the responsible gene for atypical CPVT. We recently encountered a family with CPVT and sought to identify a responsible gene variant. METHODS A targeted panel sequencing (TPS) was employed in the proband. Copy number variation (CNV) in RYR2 was identified by focusing on read numbers in the TPS and long-range PCR. Cascade screening was conducted by a Sanger method and long-range PCR. KCNJ2 wild-type (WT) or an identified variant was expressed in COS-1 cells, and whole-cell currents (IK1 ) were recorded using patch-clamp techniques. RESULTS A 40-year-old female experienced cardiopulmonary arrest while cycling. Her ECG showed sinus bradycardia with prominent U-waves (≥0.2 mV). She had left ventricular hypertrabeculation at apex. Exercise induced frequent polymorphic ventricular arrhythmias. Her sister died suddenly at age 35 while bouldering. Her father and paternal aunt, with prominent U-waves, received permanent pacemaker due to sinus node dysfunction. The initial TPS and cascade screening identified a KCNJ2 E118D variant in all three symptomatic patients. However, after focusing on read numbers, we identified a novel exon3 deletion of RYR2 (RYR2-exon3 deletion) in all of them. Functional analysis revealed that KCNJ2 E118D generated IK1 indistinguishable from KCNJ2 WT, even in the presence of catecholaminergic stimulation. CONCLUSIONS Focusing on the read numbers in the TPS enabled us to identify a novel CNV, RYR2-exon3 deletion, which was associated with phenotypic features of this family.
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Affiliation(s)
- Tommy Dharmawan
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Tadashi Nakajima
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Seiko Ohno
- Department of Bioscience and Genetics, National Cerebral and Cardiovascular Center, Suita, Japan.,Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan
| | - Takashi Iizuka
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Shuntaro Tamura
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Yoshiaki Kaneko
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Minoru Horie
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan.,Center for Epidemiologic Research in Asia, Shiga University of Medical Science, Otsu, Japan
| | - Masahiko Kurabayashi
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
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5
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Kapplinger JD, Erickson A, Asuri S, Tester DJ, McIntosh S, Kerr CR, Morrison J, Tang A, Sanatani S, Arbour L, Ackerman MJ. KCNQ1 p.L353L affects splicing and modifies the phenotype in a founder population with long QT syndrome type 1. J Med Genet 2017; 54:390-398. [PMID: 28264985 PMCID: PMC5502312 DOI: 10.1136/jmedgenet-2016-104153] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 11/30/2016] [Accepted: 12/19/2016] [Indexed: 12/23/2022]
Abstract
Background Variable expressivity and incomplete penetrance between individuals with identical long QT syndrome (LQTS) causative mutations largely remain unexplained. Founder populations provide a unique opportunity to explore modifying genetic effects. We examined the role of a novel synonymous KCNQ1 p.L353L variant on the splicing of exon 8 and on heart rate corrected QT interval (QTc) in a population known to have a pathogenic LQTS type 1 (LQTS1) causative mutation, p.V205M, in KCNQ1-encoded Kv7.1. Methods 419 adults were genotyped for p.V205M, p.L353L and a previously described QTc modifier (KCNH2-p.K897T). Adjusted linear regression determined the effect of each variant on QTc, alone and in combination. In addition, peripheral blood RNA was extracted from three controls and three p.L353L-positive individuals. The mutant transcript levels were assessed via qPCR and normalised to overall KCNQ1 transcript levels to assess the effect on splicing. Results For women and men, respectively, p.L353L alone conferred a 10.0 (p=0.064) ms and 14.0 (p=0.014) ms increase in QTc and in men only a significant interaction effect in combination with the p.V205M (34.6 ms, p=0.003) resulting in a QTc of ∼500 ms. The mechanism of p.L353L's effect was attributed to approximately threefold increase in exon 8 exclusion resulting in ∼25% mutant transcripts of the total KCNQ1 transcript levels. Conclusions Our results provide the first evidence that synonymous variants outside the canonical splice sites in KCNQ1 can alter splicing and clinically impact phenotype. Through this mechanism, we identified that p.L353L can precipitate QT prolongation by itself and produce a clinically relevant interactive effect in conjunction with other LQTS variants.
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Affiliation(s)
- Jamie D Kapplinger
- Mayo Medical School, Mayo Clinic, Rochester, Minnesota, USA.,Department of Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minnesota, USA
| | - Anders Erickson
- Division of Medical Sciences, University of Victoria, Victoria, British Columbia, Canada
| | - Sirisha Asuri
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
| | - David J Tester
- Division of Heart Rhythm Services, Department of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota, USA
| | - Sarah McIntosh
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Charles R Kerr
- Division of Cardiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Julie Morrison
- Gitxsan Health Society, Hazelton, British Columbia, Canada
| | - Anthony Tang
- Department of Medicine, University of Western Ontario, London, Ontario, Canada
| | - Shubhayan Sanatani
- Division of Cardiology, Department of Pediatrics, University of British Columbia, BC Children's Hospital, Vancouver, British Columbia, Canada
| | - Laura Arbour
- Division of Medical Sciences, University of Victoria, Victoria, British Columbia, Canada.,Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Michael J Ackerman
- Mayo Medical School, Mayo Clinic, Rochester, Minnesota, USA.,Department of Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minnesota, USA.,Division of Heart Rhythm Services, Department of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota, USA.,Division of Pediatric Cardiology, Department of Pediatrics, Mayo Clinic, Rochester, Minnesota, USA
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6
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Ohya S, Kito H, Hatano N, Muraki K. Recent advances in therapeutic strategies that focus on the regulation of ion channel expression. Pharmacol Ther 2016; 160:11-43. [PMID: 26896566 DOI: 10.1016/j.pharmthera.2016.02.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
A number of different ion channel types are involved in cell signaling networks, and homeostatic regulatory mechanisms contribute to the control of ion channel expression. Profiling of global gene expression using microarray technology has recently provided novel insights into the molecular mechanisms underlying the homeostatic and pathological control of ion channel expression. It has demonstrated that the dysregulation of ion channel expression is associated with the pathogenesis of neural, cardiovascular, and immune diseases as well as cancers. In addition to the transcriptional, translational, and post-translational regulation of ion channels, potentially important evidence on the mechanisms controlling ion channel expression has recently been accumulated. The regulation of alternative pre-mRNA splicing is therefore a novel therapeutic strategy for the treatment of dominant-negative splicing disorders. Epigenetic modification plays a key role in various pathological conditions through the regulation of pluripotency genes. Inhibitors of pre-mRNA splicing and histone deacetyalase/methyltransferase have potential as potent therapeutic drugs for cancers and autoimmune and inflammatory diseases. Moreover, membrane-anchoring proteins, lysosomal and proteasomal degradation-related molecules, auxiliary subunits, and pharmacological agents alter the protein folding, membrane trafficking, and post-translational modifications of ion channels, and are linked to expression-defect channelopathies. In this review, we focused on recent insights into the transcriptional, spliceosomal, epigenetic, and proteasomal regulation of ion channel expression: Ca(2+) channels (TRPC/TRPV/TRPM/TRPA/Orai), K(+) channels (voltage-gated, KV/Ca(2+)-activated, KCa/two-pore domain, K2P/inward-rectifier, Kir), and Ca(2+)-activated Cl(-) channels (TMEM16A/TMEM16B). Furthermore, this review highlights expression of these ion channels in expression-defect channelopathies.
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Affiliation(s)
- Susumu Ohya
- Department of Pharmacology, Division of Pathological Sciences, Kyoto Pharmaceutical University, Kyoto 607-8414, Japan.
| | - Hiroaki Kito
- Department of Pharmacology, Division of Pathological Sciences, Kyoto Pharmaceutical University, Kyoto 607-8414, Japan
| | - Noriyuki Hatano
- Laboratory of Cellular Pharmacology, School of Pharmacy, Aichi-Gakuin University, Nagoya 464-8650, Japan
| | - Katsuhiko Muraki
- Laboratory of Cellular Pharmacology, School of Pharmacy, Aichi-Gakuin University, Nagoya 464-8650, Japan.
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7
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Sogo T, Morikawa K, Kurata Y, Li P, Ichinose T, Yuasa S, Nozaki D, Miake J, Ninomiya H, Shimizu W, Fukuda K, Yamamoto K, Shirayoshi Y, Hisatome I. 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; 4:9-17. [PMID: 31245483 PMCID: PMC6581809 DOI: 10.1016/j.reth.2015.12.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 12/17/2015] [Accepted: 12/24/2015] [Indexed: 02/03/2023] Open
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 IKs; 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 IKs-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 IKs reduction, which may render the patient vulnerable to generation of EADs and arrhythmias. M437V mutation of KCNQ1 reduces channel conductance without trafficking defect. Reduced IKs of the mutant channel accounts for the prolongation of APD and QTc. Lack of medical history in this case is due to relatively small reduction in IKs. The patient is more vulnerable to generation of EAD and TdP than healthy subjects.
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Key Words
- 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
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Affiliation(s)
- Tatsufumi Sogo
- 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
| | - Kumi Morikawa
- Center for Promoting Next-Generation Highly Advanced Medicine, Tottori University Hospital, 36-1 Nishi-cho, Yonago 683-8504, Japan
| | - Yasutaka Kurata
- Department of Physiology, Kanazawa Medical University, 1-1 Daigaku, Uchinada-machi, Ishikawa 920-0293, Japan
| | - Peili Li
- 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
| | - Takafumi Ichinose
- 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
| | - Shinsuke Yuasa
- Department of Cardiology, Keio University School of Medicine, 35 Shinano-machi Shinjuku-ku, Tokyo 160-8582, Japan
| | - Daizou Nozaki
- 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
| | - Junichiro Miake
- 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
| | - Haruaki Ninomiya
- Department of Biological Regulation, School of Health Science, Tottori University Faculty of Medicine, 36-1 Nishi-cho, Yonago 683-8503, Japan
| | - Wataru Shimizu
- Department of Cardiology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603, Japan
| | - Keiichi Fukuda
- Department of Cardiology, Keio University School of Medicine, 35 Shinano-machi Shinjuku-ku, Tokyo 160-8582, Japan
| | - Kazuhiro Yamamoto
- 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
| | - Yasuaki Shirayoshi
- 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
| | - Ichiro Hisatome
- 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.,Center for Promoting Next-Generation Highly Advanced Medicine, Tottori University Hospital, 36-1 Nishi-cho, Yonago 683-8504, Japan
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Nakajima T, Kaneko Y, Saito A, Ota M, Iijima T, Kurabayashi M. Enhanced fast-inactivated state stability of cardiac sodium channels by a novel voltage sensor SCN5A mutation, R1632C, as a cause of atypical Brugada syndrome. Heart Rhythm 2015; 12:2296-304. [PMID: 26031372 DOI: 10.1016/j.hrthm.2015.05.032] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Indexed: 12/19/2022]
Abstract
BACKGROUND Mutations in SCN5A, which encodes the cardiac voltage-gated sodium channels, can be associated with multiple electrophysiological phenotypes. A novel SCN5A R1632C mutation, located in the domain IV-segment 4 voltage sensor, was identified in a young male patient who had a syncopal episode during exercise and presented with atrial tachycardia, sinus node dysfunction, and Brugada syndrome. OBJECTIVE We sought to elucidate the functional consequences of the R1632C mutation. METHODS The wild-type (WT) or R1632C SCN5A mutation was coexpressed with β1 subunit in tsA201 cells, and whole-cell sodium currents (INa) were recorded using patch-clamp methods. RESULTS INa density, measured at -20 mV from a holding potential of -120 mV, for R1632C was significantly lower than that for WT (R1632C: -433 ± 52 pA/pF, n = 14; WT: -672 ± 90 pA/pF, n = 15; P < .05); however, no significant changes were observed in the steady-state activation and fast inactivation rate. The steady-state inactivation curve for R1632C was remarkably shifted to hyperpolarizing potentials compared with that for WT (R1632C: V1/2 = -110.7 ± 0.8 mV, n = 16; WT: V1/2 = -85.9 ± 2.5 mV, n = 17; P < .01). The steady-state fast inactivation curve for R1632C was also shifted to the same degree. Recovery from fast inactivation after a 20-ms depolarizing pulse for R1632C was remarkably delayed compared with that for WT (R1632C: τ = 246.7 ± 14.3 ms, n = 8; WT: τ = 3.7 ± 0.3 ms, n = 8; P < .01). Repetitive depolarizing pulses at various cycle lengths greatly attenuated INa for R1632C than that for WT. CONCLUSION R1632C showed a loss of function of INa by an enhanced fast-inactivated state stability because of a pronounced impairment of recovery from fast inactivation, which may explain the phenotypic manifestation observed in our patient.
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Affiliation(s)
- Tadashi Nakajima
- Department of Medicine and Biological Science, Gunma University Graduate School of Medicine, Maebashi, Japan.
| | - Yoshiaki Kaneko
- Department of Medicine and Biological Science, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Akihiro Saito
- Department of Medicine and Biological Science, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Masaki Ota
- Department of Medicine and Biological Science, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Takafumi Iijima
- Department of Medicine and Biological Science, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Masahiko Kurabayashi
- Department of Medicine and Biological Science, Gunma University Graduate School of Medicine, Maebashi, Japan
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Curran J, Mohler PJ. Alternative Paradigms for Ion Channelopathies: Disorders of Ion Channel Membrane Trafficking and Posttranslational Modification. Annu Rev Physiol 2015; 77:505-24. [DOI: 10.1146/annurev-physiol-021014-071838] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Jerry Curran
- The Dorothy M. Davis Heart & Lung Research Institute,
- Department of Physiology and Cell Biology, and
| | - Peter J. Mohler
- The Dorothy M. Davis Heart & Lung Research Institute,
- Department of Physiology and Cell Biology, and
- Department of Internal Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210;
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