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Schwartz PJ, Moreno C, Kotta MC, Pedrazzini M, Crotti L, Dagradi F, Castelletti S, Haugaa KH, Denjoy I, Shkolnikova MA, Brink PA, Heradien MJ, Seyen SRM, Spätjens RLHMG, Spazzolini C, Volders PGA. Mutation location and IKs regulation in the arrhythmic risk of long QT syndrome type 1: the importance of the KCNQ1 S6 region. Eur Heart J 2021; 42:4743-4755. [PMID: 34505893 DOI: 10.1093/eurheartj/ehab582] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 07/02/2021] [Accepted: 09/02/2021] [Indexed: 11/13/2022] Open
Abstract
AIMS Mutation type, location, dominant-negative IKs reduction, and possibly loss of cyclic adenosine monophosphate (cAMP)-dependent IKs stimulation via protein kinase A (PKA) influence the clinical severity of long QT syndrome type 1 (LQT1). Given the malignancy of KCNQ1-p.A341V, we assessed whether mutations neighbouring p.A341V in the S6 channel segment could also increase arrhythmic risk. METHODS AND RESULTS Clinical and genetic data were obtained from 1316 LQT1 patients [450 families, 166 unique KCNQ1 mutations, including 277 p.A341V-positive subjects, 139 patients with p.A341-neighbouring mutations (91 missense, 48 non-missense), and 900 other LQT1 subjects]. A first cardiac event represented the primary endpoint. S6 segment missense variant characteristics, particularly cAMP stimulation responses, were analysed by cellular electrophysiology. p.A341-neighbouring mutation carriers had a QTc shorter than p.A341V carriers (477 ± 33 vs. 490 ± 44 ms) but longer than the remaining LQT1 patient population (467 ± 41 ms) (P < 0.05 for both). Similarly, the frequency of symptomatic subjects in the p.A341-neighbouring subgroup was intermediate between the other two groups (43% vs. 73% vs. 20%; P < 0.001). These differences in clinical severity can be explained, for p.A341V vs. p.A341-neighbouring mutations, by the p.A341V-specific impairment of IKs regulation. The differences between the p.A341-neighbouring subgroup and the rest of LQT1 mutations may be explained by the functional importance of the S6 segment for channel activation. CONCLUSION KCNQ1 S6 segment mutations surrounding p.A341 increase arrhythmic risk. p.A341V-specific loss of PKA-dependent IKs enhancement correlates with its phenotypic severity. Cellular studies providing further insights into IKs-channel regulation and knowledge of structure-function relationships could improve risk stratification. These findings impact on clinical management.
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Affiliation(s)
- Peter J Schwartz
- Istituto Auxologico Italiano, IRCCS, Center for Cardiac Arrhythmias of Genetic Origin, Via Pier Lombardo, 22, 20135 Milan, Italy.,Istituto Auxologico Italiano, IRCCS, Laboratory of Cardiovascular Genetics, via Zucchi 18, 20095 Cusano Milanino, MI, Italy
| | - Cristina Moreno
- Department of Cardiology, CARIM, Maastricht University Medical Center, PO Box 5800, 6202 Maastricht, The Netherlands.,Molecular Neurophysiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 35 Convent Dr., Bethesda, MD 20892-3701, USA
| | - Maria-Christina Kotta
- Istituto Auxologico Italiano, IRCCS, Laboratory of Cardiovascular Genetics, via Zucchi 18, 20095 Cusano Milanino, MI, Italy
| | - Matteo Pedrazzini
- Istituto Auxologico Italiano, IRCCS, Laboratory of Cardiovascular Genetics, via Zucchi 18, 20095 Cusano Milanino, MI, Italy
| | - Lia Crotti
- Istituto Auxologico Italiano, IRCCS, Center for Cardiac Arrhythmias of Genetic Origin, Via Pier Lombardo, 22, 20135 Milan, Italy.,Istituto Auxologico Italiano, IRCCS, Laboratory of Cardiovascular Genetics, via Zucchi 18, 20095 Cusano Milanino, MI, Italy.,Department of Cardiovascular, Neural and Metabolic Sciences, Istituto Auxologico Italiano, IRCCS, San Luca Hospital, Piazzale Brescia 20, 20149 Milan, Italy.,Department of Medicine and Surgery, University of Milano-Bicocca, Piazza dell'Ateneo Nuovo, 1, 20126 Milano, Italy
| | - Federica Dagradi
- Istituto Auxologico Italiano, IRCCS, Center for Cardiac Arrhythmias of Genetic Origin, Via Pier Lombardo, 22, 20135 Milan, Italy
| | - Silvia Castelletti
- Istituto Auxologico Italiano, IRCCS, Center for Cardiac Arrhythmias of Genetic Origin, Via Pier Lombardo, 22, 20135 Milan, Italy
| | - Kristina H Haugaa
- ProCardio center for innovation, Department of Cardiology, Oslo University Hospital, Postboks 4950 Nydalen, 0424 Oslo, Norway.,University of Oslo, Postboks 1171, Blindern 0318 Oslo, Norway
| | - Isabelle Denjoy
- Centre de Référence Maladies Cardiaques Héréditaires, Filière Cardiogen, Département de Rythmologie, Groupe Hospitalier Bichat-Claude Bernard, 46 Rue Henri -Huchard, 75877 PARIS Cedex 18, France
| | - Maria A Shkolnikova
- Pirogov Russian National Research Medical University, Research and Clinical Institute for Pediatrics named after Academician Yuri Veltischev, Centre for Cardiac Arrhythmia, Taldomskaya 2, 125412 Moscow, Russian Federation
| | - Paul A Brink
- Department of Internal Medicine, Stellenbosch University, Tygerberg 7505, South Africa
| | - Marshall J Heradien
- Department of Internal Medicine, Stellenbosch University, Tygerberg 7505, South Africa
| | - Sandrine R M Seyen
- Department of Cardiology, CARIM, Maastricht University Medical Center, PO Box 5800, 6202 Maastricht, The Netherlands
| | - Roel L H M G Spätjens
- Department of Cardiology, CARIM, Maastricht University Medical Center, PO Box 5800, 6202 Maastricht, The Netherlands
| | - Carla Spazzolini
- Istituto Auxologico Italiano, IRCCS, Center for Cardiac Arrhythmias of Genetic Origin, Via Pier Lombardo, 22, 20135 Milan, Italy
| | - Paul G A Volders
- Department of Cardiology, CARIM, Maastricht University Medical Center, PO Box 5800, 6202 Maastricht, The Netherlands
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Dotzler SM, Kim CSJ, Gendron WAC, Zhou W, Ye D, Bos JM, Tester DJ, Barry MA, Ackerman MJ. Suppression-Replacement KCNQ1 Gene Therapy for Type 1 Long QT Syndrome. Circulation 2021; 143:1411-1425. [PMID: 33504163 DOI: 10.1161/circulationaha.120.051836] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Type 1 long QT syndrome (LQT1) is caused by loss-of-function variants in the KCNQ1-encoded Kv7.1 potassium channel α-subunit that is essential for cardiac repolarization, providing the slow delayed rectifier current. No current therapies target the molecular cause of LQT1. METHODS A dual-component suppression-and-replacement (SupRep) KCNQ1 gene therapy was created by cloning a KCNQ1 short hairpin RNA and a short hairpin RNA-immune KCNQ1 cDNA modified with synonymous variants in the short hairpin RNA target site, into a single construct. The ability of KCNQ1-SupRep gene therapy to suppress and replace LQT1-causative variants in KCNQ1 was evaluated by means of heterologous expression in TSA201 cells. For a human in vitro cardiac model, induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) were generated from 4 patients with LQT1 (KCNQ1-Y171X, -V254M, -I567S, and -A344A/spl) and an unrelated healthy control. CRISPR-Cas9 corrected isogenic control iPSC-CMs were made for 2 LQT1 lines (correction of KCNQ1-V254M and KCNQ1-A344A/spl). FluoVolt voltage dye was used to measure the cardiac action potential duration (APD) in iPSC-CMs treated with KCNQ1-SupRep. RESULTS In TSA201 cells, KCNQ1-SupRep achieved mutation-independent suppression of wild-type KCNQ1 and 3 LQT1-causative variants (KCNQ1-Y171X, -V254M, and -I567S) with simultaneous replacement of short hairpin RNA-immune KCNQ1 as measured by allele-specific quantitative reverse transcription polymerase chain reaction and Western blot. Using FluoVolt voltage dye to measure the cardiac APD in the 4 LQT1 patient-derived iPSC-CMs, treatment with KCNQ1-SupRep resulted in shortening of the pathologically prolonged APD at both 90% and 50% repolarization, resulting in APD values similar to those of the 2 isogenic controls. CONCLUSIONS This study provides the first proof-of-principle gene therapy for complete correction of long QT syndrome. As a dual-component gene therapy vector, KCNQ1-SupRep successfully suppressed and replaced KCNQ1 to normal wild-type levels. In TSA201 cells, cotransfection of LQT1-causative variants and KCNQ1-SupRep caused mutation-independent suppression and replacement of KCNQ1. In LQT1 iPSC-CMs, KCNQ1-SupRep gene therapy shortened the APD, thereby eliminating the pathognomonic feature of LQT1.
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Affiliation(s)
- Steven M Dotzler
- Department of Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory (S.M.D., C.S.J.K., W.Z., D.Y., J.M.B., D.J.T., M.J.A.), Mayo Clinic, Rochester, MN
| | - C S John Kim
- Department of Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory (S.M.D., C.S.J.K., W.Z., D.Y., J.M.B., D.J.T., M.J.A.), Mayo Clinic, Rochester, MN
| | - William A C Gendron
- Department of Virology & Gene Therapy, Vector and Vaccine Engineering Laboratory (W.A.C.G., M.A.B.), Mayo Clinic, Rochester, MN
| | - Wei Zhou
- Department of Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory (S.M.D., C.S.J.K., W.Z., D.Y., J.M.B., D.J.T., M.J.A.), Mayo Clinic, Rochester, MN
| | - Dan Ye
- Department of Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory (S.M.D., C.S.J.K., W.Z., D.Y., J.M.B., D.J.T., M.J.A.), Mayo Clinic, Rochester, MN
| | - J Martijn Bos
- Department of Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory (S.M.D., C.S.J.K., W.Z., D.Y., J.M.B., D.J.T., M.J.A.), Mayo Clinic, Rochester, MN.,Department of Cardiovascular Medicine/Division of Heart Rhythm Services, Windland Smith Rice Genetic Heart Rhythm Clinic (J.M.B., D.J.T., M.J.A.), Mayo Clinic, Rochester, MN
| | - David J Tester
- Department of Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory (S.M.D., C.S.J.K., W.Z., D.Y., J.M.B., D.J.T., M.J.A.), Mayo Clinic, Rochester, MN.,Department of Cardiovascular Medicine/Division of Heart Rhythm Services, Windland Smith Rice Genetic Heart Rhythm Clinic (J.M.B., D.J.T., M.J.A.), Mayo Clinic, Rochester, MN
| | - Michael A Barry
- Department of Virology & Gene Therapy, Vector and Vaccine Engineering Laboratory (W.A.C.G., M.A.B.), Mayo Clinic, Rochester, MN
| | - Michael J Ackerman
- Department of Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory (S.M.D., C.S.J.K., W.Z., D.Y., J.M.B., D.J.T., M.J.A.), Mayo Clinic, Rochester, MN.,Department of Cardiovascular Medicine/Division of Heart Rhythm Services, Windland Smith Rice Genetic Heart Rhythm Clinic (J.M.B., D.J.T., M.J.A.), Mayo Clinic, Rochester, MN.,Department of Pediatric and Adolescent Medicine/Division of Pediatric Cardiology (M.J.A.), Mayo Clinic, Rochester, MN
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Kato K, Ohno S, Sonoda K, Fukuyama M, Makiyama T, Ozawa T, Horie M. LMNA Missense Mutation Causes Nonsense-Mediated mRNA Decay and Severe Dilated Cardiomyopathy. CIRCULATION-GENOMIC AND PRECISION MEDICINE 2020; 13:435-443. [PMID: 32818388 DOI: 10.1161/circgen.119.002853] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND LMNA is a known causative gene of dilated cardiomyopathy and familial conduction disturbance. Nonsense-mediated mRNA decay, normally caused by nonsense mutations, is a safeguard process to protect cells from deleterious effects of inappropriate proteins from mutated genes. Nonsense-mediated mRNA decay induced by nonstop codon mutations is rare. We investigated the effect of an LMNA missense mutation identified in 2 families affected by cardiac laminopathy. METHODS Genomic DNA and total RNA were isolated from patients' peripheral blood lymphocytes or cardiac tissue. LMNA-coding exons were screened by direct sequencing. Complementary DNAs were generated by a reverse transcription-polymerase chain reaction from total RNA. Quantitative polymerase chain reaction was performed to quantify the LMNA complementary DNA amount by using specific primers for lamins A and C. A minigene splicing reporter experiment was performed to assess the effect of detected variants on RNA splicing. The protein expressions of both isoforms were analyzed by Western blotting. RESULTS We detected a missense variant c.936 G>C (p. Q312H) at the end of exon 5 of LMNA by genomic DNA sequencing in 2 unrelated families affected by dilated cardiomyopathy and cardiac conduction disturbance. This variant was previously reported in a French family suffering from muscular dystrophy and cardiac conduction disturbance. Sequencing of complementary DNA demonstrated that the mutated allele was absent. By quantitative polymerase chain reaction assay, we confirmed a 90% reduction in LMNA complementary DNA. The minigene splicing reporter assay demonstrated a splicing error by the variant. Western blot analysis revealed that lamin A and C expressions were reduced far >50%. CONCLUSIONS We report an LMNA missense mutation found in 2 families, which disrupted a normal splicing site, led to nonsense-mediated mRNA decay, and resulted in severe cardiac laminopathy.
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Affiliation(s)
- Koichi Kato
- Department of Cardiovascular Medicine (K.K., S.O., M.F., T.O., M.H.), Shiga University of Medical Science, Otsu
| | - Seiko Ohno
- Department of Cardiovascular Medicine (K.K., S.O., M.F., T.O., M.H.), Shiga University of Medical Science, Otsu
- Center for Epidemiologic Research in Asia (S.O., M.H.), Shiga University of Medical Science, Otsu
- Department of Bioscience and Genetics, National Cerebral and Cardiovascular Center, Suita (S.O., K.S.)
| | - Keiko Sonoda
- Department of Bioscience and Genetics, National Cerebral and Cardiovascular Center, Suita (S.O., K.S.)
| | - Megumi Fukuyama
- Department of Cardiovascular Medicine (K.K., S.O., M.F., T.O., M.H.), Shiga University of Medical Science, Otsu
| | - Takeru Makiyama
- Department of Cardiovascular Medicine, Kyoto University Graduate School of Medicine, Japan (T.M.)
| | - Tomoya Ozawa
- Department of Cardiovascular Medicine (K.K., S.O., M.F., T.O., M.H.), Shiga University of Medical Science, Otsu
| | - Minoru Horie
- Department of Cardiovascular Medicine (K.K., S.O., M.F., T.O., M.H.), Shiga University of Medical Science, Otsu
- Center for Epidemiologic Research in Asia (S.O., M.H.), Shiga University of Medical Science, Otsu
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4
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Kato K, Ozawa T, Ohno S, Nakagawa Y, Horie M. Postoperative supraventricular tachycardia and polymorphic ventricular tachycardia due to a novel SCN5A variant: a case report of a rare comorbidity that is difficult to diagnose. BMC Cardiovasc Disord 2020; 20:315. [PMID: 32615940 PMCID: PMC7333335 DOI: 10.1186/s12872-020-01601-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Accepted: 06/26/2020] [Indexed: 11/16/2022] Open
Abstract
Background Loss-of-function mutations of human cardiac sodium channel gene SCN5A induce a wide range of arrhythmic disorders. Mutation carriers with co-existing conditions such as congenital heart diseases and histories of cardiac surgeries, could develop complex arrhythmic events that are difficult to diagnose. Case presentation A 41-year-old Japanese male with a history of a surgical closure of an ASD presented impairment of consciousness by wide QRS tachycardia. Because the patient’s baseline ECG in sinus rhythm showed similar QRS axis with right bundle brunch block morphology, we suspected supraventricular tachycardia (SVT). During hospitalization, the patient developed polymorphic ventricular tachycardia that was induced by bradycardia. In an electrophysiological study, the SVT was identified as right atrial incisional tachycardia circulating around the scar in the right atrium. The genetic analysis revealed a heterozygous SCN5A c.4037–4038 del TC, p. L1346HfsX38 variant. We diagnosed this patient as having progressive cardiac conduction disorder (PCCD) and polymorphic VT caused by the mutation. Incisional tachycardia with wide QRS morphology was a by-standing comorbidity related to the history of cardiac surgery which could miss lead the diagnosis. The patient’s SVT was eliminated by radiofrequency catheter ablation. An implantable cardioverter defibrillator (ICD) was implanted for the secondary prevention of polymorphic VT. Cardiac pace-making therapy by the ICD to avoid bradycardia effectively suppressed the patient’s arrhythmic events. Conclusions We treated a patient with a sodium channel gene variant. Co-existing SVT originated by a scar in the right atrium made the diagnosis extremely difficult. A multilateral diagnostic approach using an ECG analysis, an electrophysiological study, and genetic screening enabled effective combination therapy comprised of catheter ablation and an ICD.
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Affiliation(s)
- Koichi Kato
- Department of Cardiovascular Medicine, Shiga University of Medical Science, Otsu, Japan
| | - Tomoya Ozawa
- Department of Cardiovascular Medicine, Shiga University of Medical Science, Otsu, Japan
| | - Seiko Ohno
- Department of Bioscience and Genetics, National Cerebral and Cardiovascular Center, Suita, Japan
| | - Yoshihisa Nakagawa
- Department of Cardiovascular Medicine, Shiga University of Medical Science, Otsu, Japan
| | - Minoru Horie
- Center for Epidemiologic Research in Asia, Shiga University of Medical Science, Otsu, 520-2192, Japan.
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5
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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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6
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Complex aberrant splicing in the induced pluripotent stem cell–derived cardiomyocytes from a patient with long QT syndrome carrying KCNQ1-A344Aspl mutation. Heart Rhythm 2018; 15:1566-1574. [DOI: 10.1016/j.hrthm.2018.05.028] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Indexed: 02/06/2023]
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7
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Wei H, Wu J, Liu Z. Studying KCNQ1 Mutation and Drug Response in Type 1 Long QT Syndrome Using Patient-Specific Induced Pluripotent Stem Cell-Derived Cardiomyocytes. Methods Mol Biol 2018; 1684:7-28. [PMID: 29058180 DOI: 10.1007/978-1-4939-7362-0_2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Patient-specific human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (hiPSC-CMs) are becoming a valuable model for studying inherited cardiac arrhythmias. Type 1 long-QT syndrome is associated with the genetic variants of KCNQ1 gene that encodes Kv7.1, the α-subunit of the voltage-gated potassium channel QKT subfamily member 1 that channels the slow component of the outwardly rectifying K+ channel current in cardiac myocytes. Patient- or disease-specific hiPSC-CM model could facilitate the characterization of the genotype-phenotype relationships and testing of individualized drug responses.Here, we describe the methods in the generation of hiPSC-CMs, molecular and electrophysiological characterizations of their cellular phenotypes associated with KCNQ1/Kv7.1 defects, and evaluation of the effects of K+ channel-specific drugs.
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Affiliation(s)
- Heming Wei
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Republic of Singapore.
| | - Jianjun Wu
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Republic of Singapore
| | - Zhenfeng Liu
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Republic of Singapore
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8
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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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9
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Bohnen MS, Peng G, Robey SH, Terrenoire C, Iyer V, Sampson KJ, Kass RS. Molecular Pathophysiology of Congenital Long QT Syndrome. Physiol Rev 2017; 97:89-134. [PMID: 27807201 PMCID: PMC5539372 DOI: 10.1152/physrev.00008.2016] [Citation(s) in RCA: 114] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Ion channels represent the molecular entities that give rise to the cardiac action potential, the fundamental cellular electrical event in the heart. The concerted function of these channels leads to normal cyclical excitation and resultant contraction of cardiac muscle. Research into cardiac ion channel regulation and mutations that underlie disease pathogenesis has greatly enhanced our knowledge of the causes and clinical management of cardiac arrhythmia. Here we review the molecular determinants, pathogenesis, and pharmacology of congenital Long QT Syndrome. We examine mechanisms of dysfunction associated with three critical cardiac currents that comprise the majority of congenital Long QT Syndrome cases: 1) IKs, the slow delayed rectifier current; 2) IKr, the rapid delayed rectifier current; and 3) INa, the voltage-dependent sodium current. Less common subtypes of congenital Long QT Syndrome affect other cardiac ionic currents that contribute to the dynamic nature of cardiac electrophysiology. Through the study of mutations that cause congenital Long QT Syndrome, the scientific community has advanced understanding of ion channel structure-function relationships, physiology, and pharmacological response to clinically employed and experimental pharmacological agents. Our understanding of congenital Long QT Syndrome continues to evolve rapidly and with great benefits: genotype-driven clinical management of the disease has improved patient care as precision medicine becomes even more a reality.
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Affiliation(s)
- M S Bohnen
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - G Peng
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - S H Robey
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - C Terrenoire
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - V Iyer
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - K J Sampson
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - R S Kass
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
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10
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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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11
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Nekouzadeh A, Rudy Y. Conformational changes of an ion-channel during gating and emerging electrophysiologic properties: Application of a computational approach to cardiac Kv7.1. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2015; 120:18-27. [PMID: 26743208 DOI: 10.1016/j.pbiomolbio.2015.12.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Revised: 12/23/2015] [Accepted: 12/28/2015] [Indexed: 10/22/2022]
Abstract
Ion channels are the "building blocks" of the excitation process in excitable tissues. Despite advances in determining their molecular structure, understanding the relationship between channel protein structure and electrical excitation remains a challenge. The Kv7.1 potassium channel is an important determinant of the cardiac action potential and its adaptation to rate changes. It is subject to beta adrenergic regulation, and many mutations in the channel protein are associated with the arrhythmic long QT syndrome. In this theoretical study, we use a novel computational approach to simulate the conformational changes that Kv7.1 undergoes during activation gating and compute the resulting electrophysiologic function in terms of single-channel and macroscopic currents. We generated all possible conformations of the S4-S5 linker that couples the S3-S4 complex (voltage sensor domain, VSD) to the pore, and all associated conformations of VSD and the pore (S6). Analysis of these conformations revealed that VSD-to-pore mechanical coupling during activation gating involves outward translation of the voltage sensor, accompanied by a translation away from the pore and clockwise twist. These motions cause pore opening by moving the S4-S5 linker upward and away from the pore, providing space for the S6 tails to move away from each other. Single channel records, computed from the simulated motion trajectories during gating, have stochastic properties similar to experimentally recorded traces. Macroscopic current through an ensemble of channels displays two key properties of Kv7.1: an initial delay of activation and fast inactivation. The simulations suggest a molecular mechanism for fast inactivation; a large twist of the VSD following its outward translation results in movement of the base of the S4-S5 linker toward the pore, eliminating open pore conformations to cause inactivation.
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Affiliation(s)
- Ali Nekouzadeh
- Cardiac Bioelectricity and Arrhythmia Center and Departments of Biomedical Engineering and Cell Biology & Physiology, Washington University in St. Louis, 290 Whitaker Hall, 1 Brooking Dr., St. Louis, MO 63130, USA.
| | - Yoram Rudy
- Cardiac Bioelectricity and Arrhythmia Center and Departments of Biomedical Engineering and Cell Biology & Physiology, Washington University in St. Louis, 290 Whitaker Hall, 1 Brooking Dr., St. Louis, MO 63130, USA.
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12
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Yang KC, Nerbonne JM. Mechanisms contributing to myocardial potassium channel diversity, regulation and remodeling. Trends Cardiovasc Med 2015; 26:209-18. [PMID: 26391345 DOI: 10.1016/j.tcm.2015.07.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 07/11/2015] [Accepted: 07/12/2015] [Indexed: 01/19/2023]
Abstract
In the mammalian heart, multiple types of K(+) channels contribute to the control of cardiac electrical and mechanical functioning through the regulation of resting membrane potentials, action potential waveforms and refractoriness. There are similarly vast arrays of K(+) channel pore-forming and accessory subunits that contribute to the generation of functional myocardial K(+) channel diversity. Maladaptive remodeling of K(+) channels associated with cardiac and systemic diseases results in impaired repolarization and increased propensity for arrhythmias. Here, we review the diverse transcriptional, post-transcriptional, post-translational, and epigenetic mechanisms contributing to regulating the expression, distribution, and remodeling of cardiac K(+) channels under physiological and pathological conditions.
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Affiliation(s)
- Kai-Chien Yang
- Department of Pharmacology, National Taiwan University, Taipei, Taiwan; Division of Cardiology, Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan
| | - Jeanne M Nerbonne
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO; Internal Medicine, Washington University School of Medicine, St. Louis, MO; Cardiovascular Division, Washington University School of Medicine, St. Louis, MO.
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13
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Narula N, Tester DJ, Paulmichl A, Maleszewski JJ, Ackerman MJ. Post-mortem Whole exome sequencing with gene-specific analysis for autopsy-negative sudden unexplained death in the young: a case series. Pediatr Cardiol 2015; 36:768-78. [PMID: 25500949 PMCID: PMC4907366 DOI: 10.1007/s00246-014-1082-4] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 12/05/2014] [Indexed: 02/02/2023]
Abstract
Annually, thousands of sudden deaths in individuals under 35 years remain unexplained following comprehensive medico-legal autopsy. Previously, post-mortem genetic analysis by Sanger sequencing of four major cardiac channelopathy genes revealed that approximately one-fourth of these autopsy-negative sudden unexplained death in the young (SUDY) cases harbored an underlying mutation. However, there are now over 100 sudden death-predisposing cardiac channelopathy-, cardiomyopathy-, and metabolic disorder-susceptibility genes. Here, we set out to determine whether post-mortem whole exome sequencing (WES) is an efficient strategy to detect ultra-rare, potentially pathogenic variants. We performed post-mortem WES and gene-specific analysis of 117 sudden death-susceptibility genes for 14 consecutively referred Caucasian SUDY victims (average age at death 17.4 ± 8.6 years) to identify putative SUDY-associated mutations. On average, each SUDY case had 12,758 ± 2,016 non-synonymous variants, of which 79 ± 15 localized to these 117 genes. Overall, eight ultra-rare variants (seven missense, one in-frame insertion) absent in three publically available exome databases were identified in six genes (three in TTN, and one each in CACNA1C, JPH2, MYH7, VCL, RYR2) in seven of 14 cases (50 %). Of the seven missense alterations, two (T171M-CACNA1C, I22160T-TTN) were predicted damaging by three independent in silico tools. Although WES and gene-specific surveillance is an efficient means to detect rare genetic variants that might underlie the pathogenic cause of death, accurate interpretation of each variant is challenging. Great restraint and caution must be exercised otherwise families may be informed prematurely and incorrectly that the root cause has been found.
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Affiliation(s)
- Nupoor Narula
- Department of Internal Medicine/Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN
| | - David J. Tester
- Department of Internal Medicine/Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN,Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, MN
| | - Anna Paulmichl
- Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, MN
| | - Joseph J. Maleszewski
- Department of Internal Medicine/Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN,Department of Laboratory Medicine and Pathology, Divisions of Anatomic Pathology and Molecular Genetics
| | - Michael J. Ackerman
- Department of Internal Medicine/Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN,Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, MN.,Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN,Department of Pediatric and Adolescent Medicine/Division of Pediatric Cardiology, Mayo Clinic, Rochester, MN
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14
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Ma D, Wei H, Lu J, Huang D, Liu Z, Loh LJ, Islam O, Liew R, Shim W, Cook SA. 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. Stem Cell Res Ther 2015; 6:39. [PMID: 25889101 PMCID: PMC4396080 DOI: 10.1186/s13287-015-0027-z] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Revised: 02/27/2015] [Accepted: 02/27/2015] [Indexed: 12/14/2022] Open
Abstract
Introduction Type 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. Methods A 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. Results Compared 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. Conclusions From 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 material The online version of this article (doi:10.1186/s13287-015-0027-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Dongrui Ma
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore.
| | - Heming Wei
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore. .,Cardiovascular & Metabolic Disorders Program, Duke-NUS Graduate Medical School Singapore, 8 College Road, Singapore, 169857, Singapore.
| | - Jun Lu
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore.
| | - Dou Huang
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore.
| | - Zhenfeng Liu
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore.
| | - Li Jun Loh
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore.
| | - Omedul Islam
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore.
| | - Reginald Liew
- Cardiovascular & Metabolic Disorders Program, Duke-NUS Graduate Medical School Singapore, 8 College Road, Singapore, 169857, Singapore.
| | - Winston Shim
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore. .,Cardiovascular & Metabolic Disorders Program, Duke-NUS Graduate Medical School Singapore, 8 College Road, Singapore, 169857, Singapore.
| | - Stuart A Cook
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore. .,Cardiovascular & Metabolic Disorders Program, Duke-NUS Graduate Medical School Singapore, 8 College Road, Singapore, 169857, Singapore. .,National Heart and Lung Institute, Imperial College, South Kensington Campus, London, SW7 2AZ, UK.
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15
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Itoh H, Dochi K, Shimizu W, Denjoy I, Ohno S, Aiba T, Kimura H, Kato K, Fukuyama M, Hasagawa K, Schulze-Bahr E, Guicheney P, Horie M. A Common Mutation of Long QT Syndrome Type 1 in Japan. Circ J 2015; 79:2026-30. [DOI: 10.1253/circj.cj-15-0342] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Hideki Itoh
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science
- Sorbonne Universités, Institut de Recherche sur les Maladies Cardiovasculaires, du Métabolisme et de la Nutrition
- Institute of Cardiometabolism and Nutrition (ICAN)
| | - Kenichi Dochi
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science
| | - Wataru Shimizu
- Division of Cardiology, Department of Internal Medicine, Nippon Medical School
- Division of Arrhythmia and Electrophysiology, Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Center
| | - Isabelle Denjoy
- AP-HP, Hôpital Bichat, Service de Cardiologie, Centre de Référence des Maladies Cardiaques Héréditaires, Université Denis Diderot
| | - Seiko Ohno
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science
| | - Takeshi Aiba
- Division of Arrhythmia and Electrophysiology, Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Center
| | - Hiromi Kimura
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science
| | - Koichi Kato
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science
| | - Megumi Fukuyama
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science
| | - Kanae Hasagawa
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science
| | - Eric Schulze-Bahr
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster
- Interdisciplinary Centre for Clinical Research (IZKF) of the University of Münster
| | - Pascale Guicheney
- Sorbonne Universités, Institut de Recherche sur les Maladies Cardiovasculaires, du Métabolisme et de la Nutrition
- Institute of Cardiometabolism and Nutrition (ICAN)
| | - Minoru Horie
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science
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16
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Imai M, Nakajima T, Kaneko Y, Niwamae N, Irie T, Ota M, Iijima T, Tange S, Kurabayashi M. A novel KCNQ1 splicing mutation in patients with forme fruste LQT1 aggravated by hypokalemia. J Cardiol 2014; 64:121-6. [DOI: 10.1016/j.jjcc.2013.11.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 11/10/2013] [Accepted: 11/20/2013] [Indexed: 10/25/2022]
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17
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Fukuyama M, Ohno S, Wang Q, Shirayama T, Itoh H, Horie M. Nonsense-mediated mRNA decay due to a CACNA1C splicing mutation in a patient with Brugada syndrome. Heart Rhythm 2013; 11:629-34. [PMID: 24321233 DOI: 10.1016/j.hrthm.2013.12.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Indexed: 11/30/2022]
Abstract
BACKGROUND Brugada syndrome (BrS) is an inherited cardiac arrhythmia associated with sudden death due to ventricular fibrillation. Mutations in genes related to the cardiac L-type calcium channel have been reported to be causative of BrS. Generally, the messenger RNA (mRNA) that contains a nonsense mutation is rapidly degraded via its decay pathway, which is known as nonsense-mediated mRNA decay (NMD). Previously, we reported a male patient with BrS who carried c.1896G>A (the first nucleotide of CACNA1C exon 14), which caused a synonymous mutation, p.R632R. OBJECTIVE To examine how the synonymous CACNA1C mutation p.R632R produces the phenotype of BrS, with a special emphasis on the splicing error and NMD processes. METHODS We extracted mRNA from leukocytes of the proband and his 2 children and performed reverse transcription polymerase chain reaction. Complementary DNAs were checked by using direct sequencing and quantitative analysis. RESULTS The subsequent sequence electropherogram of the complementary DNAs did not show the substitution of the nucleotide identified in the genomic DNA of the proband. In the mRNA quantification analysis, we confirmed that reduction in the CACNA1C expression level was suspected to be caused by NMD. CONCLUSIONS Mutant mRNA with a c.1896G>A substitution may be diminished by NMD, and the resultant decrease in CACNA1C message leads to a novel mechanism for inducing BrS that is distinct from that reported previously.
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Affiliation(s)
- Megumi Fukuyama
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Shiga, Japan
| | - Seiko Ohno
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Shiga, Japan
| | - Qi Wang
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Shiga, Japan
| | - Takeshi Shirayama
- Division of Cardiovascular Medicine, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Hideki Itoh
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Shiga, Japan
| | - Minoru Horie
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Shiga, Japan.
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18
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Coto E, Reguero JR, Palacín M, Gómez J, Alonso B, Iglesias S, Martín M, Tavira B, Díaz-Molina B, Morales C, Morís C, Rodríguez-Lambert JL, Corao AI, Díaz M, Alvarez V. Resequencing the whole MYH7 gene (including the intronic, promoter, and 3' UTR sequences) in hypertrophic cardiomyopathy. J Mol Diagn 2012; 14:518-24. [PMID: 22765922 DOI: 10.1016/j.jmoldx.2012.04.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Revised: 04/03/2012] [Accepted: 04/11/2012] [Indexed: 01/14/2023] Open
Abstract
MYH7 mutations are found in ~20% of hypertrophic cardiomyopathy (HCM) patients. Currently, mutational analysis is based on the sequencing of the coding exons and a few exon-flanking intronic nucleotides, resulting in omission of single-exon deletions and mutations in internal intronic, promoter, and 3' UTR regions. We amplified and sequenced large MYH7 fragments in 60 HCM patients without previously identified sarcomere mutations. Lack of aberrant PCR fragments excluded single-exon deletions in the patients. Instead, we identified several new rare intronic variants. An intron 26 single nucleotide insertion (-5 insC) was predicted to affect pre-mRNA splicing, but allele frequencies did not differ between patients and controls (n = 150). We found several rare promoter variants in the patients compared to controls, some of which were in binding sites for transcription factors and could thus affect gene expression. Only one rare 3' UTR variant (c.*29T>C) found in the patients was absent among the controls. This nucleotide change would not affect the binding of known microRNAs. Therefore, MYH7 mutations outside the coding exon sequences would be rarely found among HCM patients. However, changes in the promoter region could be linked to the risk of developing HCM. Further research to define the functional effect of these variants on gene expression is necessary to confirm the role of the MYH7 promoter in cardiac hypertrophy.
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Affiliation(s)
- Eliecer Coto
- Molecular Genetics-Laboratory of Medicine-Renal Foundation (IRSIN-FRIAT), University Central Hospital Asturias (HUCA), Oviedo, Spain.
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19
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Klassen T, Davis C, Goldman A, Burgess D, Chen T, Wheeler D, McPherson J, Bourquin T, Lewis L, Villasana D, Morgan M, Muzny D, Gibbs R, Noebels J. Exome sequencing of ion channel genes reveals complex profiles confounding personal risk assessment in epilepsy. Cell 2011; 145:1036-48. [PMID: 21703448 DOI: 10.1016/j.cell.2011.05.025] [Citation(s) in RCA: 234] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Revised: 04/21/2011] [Accepted: 05/20/2011] [Indexed: 11/25/2022]
Abstract
Ion channel mutations are an important cause of rare Mendelian disorders affecting brain, heart, and other tissues. We performed parallel exome sequencing of 237 channel genes in a well-characterized human sample, comparing variant profiles of unaffected individuals to those with the most common neuronal excitability disorder, sporadic idiopathic epilepsy. Rare missense variation in known Mendelian disease genes is prevalent in both groups at similar complexity, revealing that even deleterious ion channel mutations confer uncertain risk to an individual depending on the other variants with which they are combined. Our findings indicate that variant discovery via large scale sequencing efforts is only a first step in illuminating the complex allelic architecture underlying personal disease risk. We propose that in silico modeling of channel variation in realistic cell and network models will be crucial to future strategies assessing mutation profile pathogenicity and drug response in individuals with a broad spectrum of excitability disorders.
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Affiliation(s)
- Tara Klassen
- Department of Neurology, Baylor College of Medicine, Houston, TX 77030, USA
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20
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Tsuji-Wakisaka K, Akao M, Ishii TM, Ashihara T, Makiyama T, Ohno S, Toyoda F, Dochi K, Matsuura H, Horie M. Identification and functional characterization of KCNQ1 mutations around the exon 7-intron 7 junction affecting the splicing process. Biochim Biophys Acta Mol Basis Dis 2011; 1812:1452-9. [PMID: 21810471 DOI: 10.1016/j.bbadis.2011.07.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Revised: 06/28/2011] [Accepted: 07/18/2011] [Indexed: 10/18/2022]
Abstract
BACKGROUND KCNQ1 gene encodes the delayed rectifier K(+) channel in cardiac muscle, and its mutations cause long QT syndrome type 1 (LQT1). Especially exercise-related cardiac events predominate in LQT1. We previously reported that a KCNQ1 splicing mutation displays LQT1 phenotypes. METHODS AND RESULTS We identified novel mutation at the third base of intron 7 (IVS7 +3A>G) in exercise-induced LQT1 patients. Minigene assay in COS7 cells and RT-PCR analysis of patients' lymphocytes demonstrated the presence of exon 7-deficient mRNA in IVS7 +3A>G, as well as c.1032G>A, but not in c.1022C>T. Real-time RT-PCR demonstrated that both IVS7 +3A>G and c.1032G>A carrier expressed significant amounts of exon-skipping mRNAs (18.8% and 44.8% of total KCNQ1 mRNA). Current recordings from Xenopus oocytes injected cRNA by simulating its ratios of exon skipping displayed a significant reduction in currents to 64.8 ± 4.5% for IVS7 +3A>G and to 41.4 ± 9.5% for c.1032G>A carrier, respectively, compared to the condition without splicing error. Computer simulation incorporating these quantitative results revealed the pronounced QT prolongation under beta-adrenergic stimulation in IVS7 +3A>G carrier model. CONCLUSION Here we report a novel splicing mutation IVS7 +3A>G, identified in a family with mild form LQT1 phenotypes, and examined functional outcome in comparison with three other variants around the exon 7-intron 7 junction. In addition to c.1032G>A mutation, IVS7 +3A>G generates exon-skipping mRNAs, and thereby causing LQT1 phenotype. The severity of clinical phenotypes appeared to differ between the two splicing-related mutations and to result from the amount of resultant mRNAs and their functional consequences.
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Affiliation(s)
- Keiko Tsuji-Wakisaka
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan
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21
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Shimizu W, Horie M. Phenotypic Manifestations of Mutations in Genes Encoding Subunits of Cardiac Potassium Channels. Circ Res 2011; 109:97-109. [DOI: 10.1161/circresaha.110.224600] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Since 1995, when a potassium channel gene,
hERG
(human ether-à-go-go-related gene), now referred to as
KCNH2
, encoding the rapid component of cardiac delayed rectifier potassium channels was identified as being responsible for type 2 congenital long-QT syndrome, a number of potassium channel genes have been shown to cause different types of inherited cardiac arrhythmia syndromes. These include congenital long-QT syndrome, short-QT syndrome, Brugada syndrome, early repolarization syndrome, and familial atrial fibrillation. Genotype-phenotype correlations have been investigated in some inherited arrhythmia syndromes, and as a result, gene-specific risk stratification and gene-specific therapy and management have become available, particularly for patients with congenital long-QT syndrome. In this review article, the molecular structure and function of potassium channels, the clinical phenotype due to potassium channel gene mutations, including genotype-phenotype correlations, and the diverse mechanisms underlying the potassium channel gene–related diseases will be discussed.
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Affiliation(s)
- Wataru Shimizu
- From the Division of Arrhythmia and Electrophysiology, Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Center (W.S.), Suita, Japan, and the Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science (M.H.), Otsu, Japan
| | - Minoru Horie
- From the Division of Arrhythmia and Electrophysiology, Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Center (W.S.), Suita, Japan, and the Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science (M.H.), Otsu, Japan
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22
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Doi T, Makiyama T, Morimoto T, Haruna Y, Tsuji K, Ohno S, Akao M, Takahashi Y, Kimura T, Horie M. A Novel
KCNJ2
Nonsense Mutation, S369X, Impedes Trafficking and Causes a Limited Form of Andersen-Tawil Syndrome. ACTA ACUST UNITED AC 2011; 4:253-60. [DOI: 10.1161/circgenetics.110.958157] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Background—
Mutations in
KCNJ2
, a gene encoding the inward rectifier K
+
channel Kir2.1, are associated with Andersen-Tawil syndrome (ATS), which is characterized by (1) ventricular tachyarrhythmias associated with QT (QU)-interval prolongation, (2) periodic paralysis, and (3) dysmorphic features.
Methods and Results—
We identified a novel
KCNJ2
mutation, S369X, in a 13-year-old boy with prominent QU-interval prolongation and mild periodic paralysis. The mutation results in the truncation at the middle of the cytoplasmic C-terminal domain that eliminates the endoplasmic reticulum (ER)-to-Golgi export signal. Current recordings from Chinese hamster ovary cells transfected with
KCNJ2
-S369X exhibited significantly smaller K
+
currents compared with
KCNJ2
wild type (WT) (1 μg each) (−84±14 versus −542±46 picoamperes per picofarad [pA/pF]; −140 mV;
P
<0.0001). Coexpression of the WT and S369X subunits did not show a dominant-negative suppression effect but yielded larger currents than those of WT+S369X (−724±98 pA/pF>−[84+542] pA/pF; 1 μg each; −140 mV). Confocal microscopy analysis showed that the fluorescent protein-tagged S369X subunits were predominantly retained in the ER when expressed alone; however, the expression of S369X subunits to the plasma membrane was partially restored when coexpressed with WT. Fluorescence resonance energy transfer analysis demonstrated direct protein-protein interactions between WT and S369X subunits in the intracellular compartment.
Conclusions—
The S369X mutation causes a loss of the ER export motif. However, the trafficking deficiency can be partially rescued by directly assembling with the WT protein, resulting in a limited restoration of plasma membrane localization and channel function. This alleviation may explain why our patient presented with a relatively mild ATS phenotype.
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Affiliation(s)
- Takahiro Doi
- From the Department of Cardiovascular Medicine (T.D., T. Makiyama, Y.H., K.T., S.O., T.K.) and Center for Medical Education (T. Morimoto), Kyoto University, Graduate School of Medicine, Kyoto, Japan; Department of Cardiovascular Medicine, National Hospital Organization Kyoto Medical Center, Kyoto, Japan (M.A.); Takahashi Clinic for Pediatric Cardiology, Otsu, Japan (Y.T.); and Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan (M.H.)
| | - Takeru Makiyama
- From the Department of Cardiovascular Medicine (T.D., T. Makiyama, Y.H., K.T., S.O., T.K.) and Center for Medical Education (T. Morimoto), Kyoto University, Graduate School of Medicine, Kyoto, Japan; Department of Cardiovascular Medicine, National Hospital Organization Kyoto Medical Center, Kyoto, Japan (M.A.); Takahashi Clinic for Pediatric Cardiology, Otsu, Japan (Y.T.); and Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan (M.H.)
| | - Takeshi Morimoto
- From the Department of Cardiovascular Medicine (T.D., T. Makiyama, Y.H., K.T., S.O., T.K.) and Center for Medical Education (T. Morimoto), Kyoto University, Graduate School of Medicine, Kyoto, Japan; Department of Cardiovascular Medicine, National Hospital Organization Kyoto Medical Center, Kyoto, Japan (M.A.); Takahashi Clinic for Pediatric Cardiology, Otsu, Japan (Y.T.); and Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan (M.H.)
| | - Yoshisumi Haruna
- From the Department of Cardiovascular Medicine (T.D., T. Makiyama, Y.H., K.T., S.O., T.K.) and Center for Medical Education (T. Morimoto), Kyoto University, Graduate School of Medicine, Kyoto, Japan; Department of Cardiovascular Medicine, National Hospital Organization Kyoto Medical Center, Kyoto, Japan (M.A.); Takahashi Clinic for Pediatric Cardiology, Otsu, Japan (Y.T.); and Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan (M.H.)
| | - Keiko Tsuji
- From the Department of Cardiovascular Medicine (T.D., T. Makiyama, Y.H., K.T., S.O., T.K.) and Center for Medical Education (T. Morimoto), Kyoto University, Graduate School of Medicine, Kyoto, Japan; Department of Cardiovascular Medicine, National Hospital Organization Kyoto Medical Center, Kyoto, Japan (M.A.); Takahashi Clinic for Pediatric Cardiology, Otsu, Japan (Y.T.); and Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan (M.H.)
| | - Seiko Ohno
- From the Department of Cardiovascular Medicine (T.D., T. Makiyama, Y.H., K.T., S.O., T.K.) and Center for Medical Education (T. Morimoto), Kyoto University, Graduate School of Medicine, Kyoto, Japan; Department of Cardiovascular Medicine, National Hospital Organization Kyoto Medical Center, Kyoto, Japan (M.A.); Takahashi Clinic for Pediatric Cardiology, Otsu, Japan (Y.T.); and Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan (M.H.)
| | - Masaharu Akao
- From the Department of Cardiovascular Medicine (T.D., T. Makiyama, Y.H., K.T., S.O., T.K.) and Center for Medical Education (T. Morimoto), Kyoto University, Graduate School of Medicine, Kyoto, Japan; Department of Cardiovascular Medicine, National Hospital Organization Kyoto Medical Center, Kyoto, Japan (M.A.); Takahashi Clinic for Pediatric Cardiology, Otsu, Japan (Y.T.); and Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan (M.H.)
| | - Yoshiaki Takahashi
- From the Department of Cardiovascular Medicine (T.D., T. Makiyama, Y.H., K.T., S.O., T.K.) and Center for Medical Education (T. Morimoto), Kyoto University, Graduate School of Medicine, Kyoto, Japan; Department of Cardiovascular Medicine, National Hospital Organization Kyoto Medical Center, Kyoto, Japan (M.A.); Takahashi Clinic for Pediatric Cardiology, Otsu, Japan (Y.T.); and Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan (M.H.)
| | - Takeshi Kimura
- From the Department of Cardiovascular Medicine (T.D., T. Makiyama, Y.H., K.T., S.O., T.K.) and Center for Medical Education (T. Morimoto), Kyoto University, Graduate School of Medicine, Kyoto, Japan; Department of Cardiovascular Medicine, National Hospital Organization Kyoto Medical Center, Kyoto, Japan (M.A.); Takahashi Clinic for Pediatric Cardiology, Otsu, Japan (Y.T.); and Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan (M.H.)
| | - Minoru Horie
- From the Department of Cardiovascular Medicine (T.D., T. Makiyama, Y.H., K.T., S.O., T.K.) and Center for Medical Education (T. Morimoto), Kyoto University, Graduate School of Medicine, Kyoto, Japan; Department of Cardiovascular Medicine, National Hospital Organization Kyoto Medical Center, Kyoto, Japan (M.A.); Takahashi Clinic for Pediatric Cardiology, Otsu, Japan (Y.T.); and Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan (M.H.)
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23
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Barc J, Briec F, Schmitt S, Kyndt F, Le Cunff M, Baron E, Vieyres C, Sacher F, Redon R, Le Caignec C, Le Marec H, Probst V, Schott JJ. Screening for Copy Number Variation in Genes Associated With the Long QT Syndrome. J Am Coll Cardiol 2011; 57:40-7. [DOI: 10.1016/j.jacc.2010.08.621] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2010] [Revised: 07/16/2010] [Accepted: 08/10/2010] [Indexed: 11/28/2022]
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24
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Hedley PL, Jørgensen P, Schlamowitz S, Wangari R, Moolman-Smook J, Brink PA, Kanters JK, Corfield VA, Christiansen M. The genetic basis of long QT and short QT syndromes: A mutation update. Hum Mutat 2009; 30:1486-511. [DOI: 10.1002/humu.21106] [Citation(s) in RCA: 318] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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25
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Sakaguchi T, Itoh H, Ding WG, Tsuji K, Nagaoka I, Oka Y, Ashihara T, Ito M, Yumoto Y, Zenda N, Higashi Y, Takeyama Y, Matsuura H, Horie M. Hydroxyzine, a first generation H(1)-receptor antagonist, inhibits human ether-a-go-go-related gene (HERG) current and causes syncope in a patient with the HERG mutation. J Pharmacol Sci 2008; 108:462-71. [PMID: 19057127 DOI: 10.1254/jphs.08178fp] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
QT prolongation, a risk factor for arrhythmias, can result from genetic variants in one (or more) of the genes governing cardiac repolarization as well as intake of drugs known to affect a cardiac K(+) channel encoded by human ether-a-go-go-related gene (HERG). In this paper, we will report a case of drug-induced long QT syndrome associated with an H(1)-receptor antagonist, hydroxyzine, in which a mutation was identified in the HERG gene. After taking 75 mg of hydroxyzine for several days, a 34-year-old female began to experience repetitive syncope. The deleterious effect of hydroxyzine was suspected because QTc interval shortened from 630 to 464 ms after cessation of the drug. Later on, the patient was found to harbor an A614V-HERG mutation. By using the patch-clamp technique in the heterologous expression system, we examined the functional outcome of the A614V mutation and confirmed a dominant-negative effect on HERG expression. Hydroxyzine concentration-dependently inhibited both wild-type (WT) and WT/A614V-HERG K(+) currents. Half-maximum block concentrations of WT and WT/A614V-HERG K(+) currents were 0.62 and 0.52 microM, respectively. Thus, accidental combination of genetic mutation and intake of hydroxyzine appeared to have led to a severe phenotype, probably, syncope due to torsade de pointes.
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Affiliation(s)
- Tomoko Sakaguchi
- Department of Cardiovascular Medicine, Shiga University of Medical Science, Japan
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26
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Crotti L, Lewandowska MA, Schwartz PJ, Insolia R, Pedrazzini M, Bussani E, Dagradi F, George AL, Pagani F. A KCNH2 branch point mutation causing aberrant splicing contributes to an explanation of genotype-negative long QT syndrome. Heart Rhythm 2008; 6:212-8. [PMID: 19187913 DOI: 10.1016/j.hrthm.2008.10.044] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2008] [Accepted: 10/30/2008] [Indexed: 10/21/2022]
Abstract
BACKGROUND Genetic screening of long QT syndrome (LQTS) fails to identify disease-causing mutations in about 30% of patients. So far, molecular screening has focused mainly on coding sequence mutations or on substitutions at canonical splice sites. OBJECTIVE The purpose of this study was to explore the possibility that intronic variants not at canonical splice sites might affect splicing regulatory elements, lead to aberrant transcripts, and cause LQTS. METHOD Molecular screening was performed through DHPLC and sequence analysis. The role of the intronic mutation identified was assessed with a hybrid minigene splicing assay. RESULTS A three-generation LQTS family was investigated. Molecular screening failed to identify an obvious disease-causing mutation in the coding sequences of the major LQTS genes but revealed an intronic A-to-G substitution in KCNH2 (IVS9-28A/G) cosegregating with the clinical phenotype in family members. In vitro analysis proved that the mutation disrupts the acceptor splice site definition by affecting the branch point (BP) sequence and promoting intron retention. We further demonstrated a tight functional relationship between the BP and the polypyrimidine tract, whose weakness is responsible for the pathological effect of the IVS9-28A/G mutation. CONCLUSIONS We identified a novel BP mutation in KCNH2 that disrupts the intron 9 acceptor splice site definition and causes LQT2. The present finding demonstrates that intronic mutations affecting pre-mRNA processing may contribute to the failure of traditional molecular screening in identifying disease-causing mutations in LQTS subjects and offers a rationale strategy for the reduction of genotype-negative cases.
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Affiliation(s)
- Lia Crotti
- Department of Cardiology, University of Pavia, and IRCCS Fondazione Policlinico S. Matteo, Pavia, Italy.
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27
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Bhuiyan ZA, Momenah TS, Amin AS, Al-Khadra AS, Alders M, Wilde AA, Mannens MM. An intronic mutation leading to incomplete skipping of exon-2 in KCNQ1 rescues hearing in Jervell and Lange-Nielsen syndrome. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 98:319-27. [DOI: 10.1016/j.pbiomolbio.2008.10.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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28
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Gong Q, Zhang L, Moss AJ, Vincent GM, Ackerman MJ, Robinson JC, Jones MA, Tester DJ, Zhou Z. A splice site mutation in hERG leads to cryptic splicing in human long QT syndrome. J Mol Cell Cardiol 2008; 44:502-9. [PMID: 18272172 DOI: 10.1016/j.yjmcc.2008.01.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2007] [Revised: 01/09/2008] [Accepted: 01/10/2008] [Indexed: 10/22/2022]
Abstract
Mutations in the human ether-a-go-go-related gene (hERG) cause type 2 long QT syndrome. In this study, we investigated the pathogenic mechanism of the hERG splice site mutation 2398+1G>C and the genotype-phenotype relationship of mutation carriers in three unrelated kindreds with long QT syndrome. The effect of 2398+1G>C on mRNA splicing was studied by analysis of RNA isolated from lymphocytes of index patients and using minigenes expressed in HEK293 cells and neonatal rat ventricular myocytes. RT-PCR analysis revealed that the 2398+1G>C mutation disrupted the normal splicing and activated a cryptic splice donor site in intron 9, leading to the inclusion of 54 nt of the intron 9 sequence in hERG mRNA. The cryptic splicing resulted in an in-frame insertion of 18 amino acids in the middle of the cyclic nucleotide binding domain. In patch clamp experiments the splice mutant did not generate hERG current. Western blot and immunostaining studies showed that the mutant expressed an immature form of hERG protein that failed to reach the plasma membrane. Coexpression of the mutant and wild-type channels led to a dominant negative suppression of wild-type channel function by intracellular retention of heteromeric channels. Our results demonstrate that 2398+1G>C activates a cryptic site and generates a full-length hERG protein with an insertion of 18 amino acids, which leads to a trafficking defect of the mutant channel.
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Affiliation(s)
- Qiuming Gong
- Division of Cardiovascular Medicine, Oregon Health and Science University, Portland, OR , USA
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29
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Moss AJ, Shimizu W, Wilde AAM, Towbin JA, Zareba W, Robinson JL, Qi M, Vincent GM, Ackerman MJ, Kaufman ES, Hofman N, Seth R, Kamakura S, Miyamoto Y, Goldenberg I, Andrews ML, McNitt S. Clinical aspects of type-1 long-QT syndrome by location, coding type, and biophysical function of mutations involving the KCNQ1 gene. Circulation 2007; 115:2481-9. [PMID: 17470695 PMCID: PMC3332528 DOI: 10.1161/circulationaha.106.665406] [Citation(s) in RCA: 306] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BACKGROUND Type-1 long-QT syndrome (LQTS) is caused by loss-of-function mutations in the KCNQ1-encoded I(Ks) cardiac potassium channel. We evaluated the effect of location, coding type, and biophysical function of KCNQ1 mutations on the clinical phenotype of this disorder. METHODS AND RESULTS We investigated the clinical course in 600 patients with 77 different KCNQ1 mutations in 101 proband-identified families derived from the US portion of the International LQTS Registry (n=425), the Netherlands' LQTS Registry (n=93), and the Japanese LQTS Registry (n=82). The Cox proportional hazards survivorship model was used to evaluate the independent contribution of clinical and genetic factors to the first occurrence of time-dependent cardiac events from birth through age 40 years. The clinical characteristics, distribution of mutations, and overall outcome event rates were similar in patients enrolled from the 3 geographic regions. Biophysical function of the mutations was categorized according to dominant-negative (> 50%) or haploinsufficiency (< or = 50%) reduction in cardiac repolarizing I(Ks) potassium channel current. Patients with transmembrane versus C-terminus mutations (hazard ratio, 2.06; P<0.001) and those with mutations having dominant-negative versus haploinsufficiency ion channel effects (hazard ratio, 2.26; P<0.001) were at increased risk for cardiac events, and these genetic risks were independent of traditional clinical risk factors. CONCLUSIONS This genotype-phenotype study indicates that in type-1 LQTS, mutations located in the transmembrane portion of the ion channel protein and the degree of ion channel dysfunction caused by the mutations are important independent risk factors influencing the clinical course of this disorder.
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MESH Headings
- Adolescent
- Adrenergic beta-Antagonists/therapeutic use
- Adult
- Child
- Child, Preschool
- Codon, Nonsense
- Death, Sudden, Cardiac/epidemiology
- Death, Sudden, Cardiac/prevention & control
- Female
- Frameshift Mutation
- Genetic Predisposition to Disease
- Genotype
- Heart Arrest/epidemiology
- Humans
- Infant
- Infant, Newborn
- Ion Transport/genetics
- Japan/epidemiology
- KCNQ1 Potassium Channel/chemistry
- KCNQ1 Potassium Channel/genetics
- KCNQ1 Potassium Channel/physiology
- Kaplan-Meier Estimate
- Male
- Membrane Potentials
- Models, Molecular
- Mutagenesis, Insertional
- Mutation
- Mutation, Missense
- Netherlands/epidemiology
- Phenotype
- Potassium/metabolism
- Proportional Hazards Models
- Protein Structure, Tertiary
- Protein Transport
- RNA Splice Sites/genetics
- Registries
- Risk Factors
- Romano-Ward Syndrome/complications
- Romano-Ward Syndrome/drug therapy
- Romano-Ward Syndrome/genetics
- Romano-Ward Syndrome/mortality
- Sequence Deletion
- Syncope/epidemiology
- United States/epidemiology
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Affiliation(s)
- Arthur J Moss
- Cardiology Division, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.
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