1
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Jaouadi H, Théron A, Hourdain J, Martel H, Nguyen K, Habachi R, Deharo JC, Collart F, Avierinos JF, Zaffran S. SCN5A Variants as Genetic Arrhythmias Triggers for Familial Bileaflet Mitral Valve Prolapse. Int J Mol Sci 2022; 23:ijms232214447. [PMID: 36430924 PMCID: PMC9692711 DOI: 10.3390/ijms232214447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 11/16/2022] [Accepted: 11/18/2022] [Indexed: 11/22/2022] Open
Abstract
Mitral valve prolapse (MVP) is a common valvular heart defect with variable outcomes. Several studies reported MVP as an underestimated cause of life-threatening arrhythmias and sudden cardiac death (SCD), mostly in young adult women. Herein, we report a clinical and genetic investigation of a family with bileaflet MVP and a history of syncopes and resuscitated sudden cardiac death. Using family based whole exome sequencing, we identified two missense variants in the SCN5A gene. A rare variant SCN5A:p.Ala572Asp and the well-known functional SCN5A:p.His558Arg polymorphism. Both variants are shared between the mother and her daughter with a history of resuscitated SCD and syncopes, respectively. The second daughter with prodromal MVP as well as her healthy father and sister carried only the SCN5A:p.His558Arg polymorphism. Our study is highly suggestive of the contribution of SCN5A mutations as the potential genetic cause of the electric instability leading to ventricular arrhythmias in familial MVP cases with syncope and/or SCD history.
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Affiliation(s)
- Hager Jaouadi
- Marseille Medical Genetics, INSERM, Aix Marseille Université, U1251 Marseille, France
- Correspondence: (H.J.); (S.Z.); Tel.: +33-4-9132-4936 (H.J. & S.Z.); Fax: +33-4-9179-7227 (H.J. & S.Z.)
| | - Alexis Théron
- Marseille Medical Genetics, INSERM, Aix Marseille Université, U1251 Marseille, France
- Department of Cardiac Surgery, La Timone Hospital, 13005 Marseille, France
| | - Jérôme Hourdain
- Department of Cardiology, La Timone Hospital, 13005 Marseille, France
| | - Hélène Martel
- Department of Cardiology, La Timone Hospital, 13005 Marseille, France
| | - Karine Nguyen
- Marseille Medical Genetics, INSERM, Aix Marseille Université, U1251 Marseille, France
- Department of Medical Genetics, Timone Enfant Hospital, 13005 Marseille, France
| | - Raja Habachi
- Department of Cardiology, La Timone Hospital, 13005 Marseille, France
| | | | - Frédéric Collart
- Department of Cardiac Surgery, La Timone Hospital, 13005 Marseille, France
| | - Jean-François Avierinos
- Marseille Medical Genetics, INSERM, Aix Marseille Université, U1251 Marseille, France
- Department of Cardiology, La Timone Hospital, 13005 Marseille, France
| | - Stéphane Zaffran
- Marseille Medical Genetics, INSERM, Aix Marseille Université, U1251 Marseille, France
- Correspondence: (H.J.); (S.Z.); Tel.: +33-4-9132-4936 (H.J. & S.Z.); Fax: +33-4-9179-7227 (H.J. & S.Z.)
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Lopes-Marques M, Silva R, Serrano C, Gomes V, Cardoso A, Prata MJ, Amorim A, Azevedo L. Complex interactions between p.His558Arg and linked variants in the sodium voltage-gated channel alpha subunit 5 (Na V 1.5). PeerJ 2022; 10:e13913. [PMID: 35996667 PMCID: PMC9392453 DOI: 10.7717/peerj.13913] [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: 02/24/2022] [Accepted: 07/27/2022] [Indexed: 01/19/2023] Open
Abstract
Common genetic polymorphisms may modify the phenotypic outcome when co-occurring with a disease-causing variant, and therefore understanding their modulating role in health and disease is of great importance. The polymorphic p.His558Arg variant of the sodium voltage-gated channel alpha subunit 5 (Na V 1.5) encoded by the SCN5A gene is a case in point, as several studies have shown it can modify the clinical phenotype in a number of cardiac diseases. To evaluate the genetic backgrounds associated with this modulating effect, we reanalysed previous electrophysiological findings regarding the p.His558Arg variant and further assessed its patterns of genetic diversity in human populations. The Na V 1.5 p.His558Arg variant was found to be in linkage disequilibrium with six other polymorphic variants that previously were also associated with cardiac traits in GWAS analyses. On account of this, incongruent reports that Arg558 allele can compensate, aggravate or have no effect on Na V 1.5, likely might have arose due to a role of p.His558Arg depending on the additional linked variants. Altogether, these results indicate a major influence of the epistatic interactions between SCN5A variants, revealing also that phenotypic severity may depend on the polymorphic background associated to each individual genome.
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Affiliation(s)
- Monica Lopes-Marques
- IPATIMUP-Institute of Molecular Pathology and Immunology, University of Porto, Porto, Portugal,Faculty of Sciences, University of Porto, Porto, Portugal,Population Genetics and Evolution, Institute of Innovation and Investigation in Health (i3S), Porto, Portugal
| | - Raquel Silva
- Center for Interdisciplinary Research in Health (CIIS), Universidade Católica Portuguesa, Faculdade de Medicina Dentária, Viseu, Portugal
| | - Catarina Serrano
- IPATIMUP-Institute of Molecular Pathology and Immunology, University of Porto, Porto, Portugal,Faculty of Sciences, University of Porto, Porto, Portugal,Population Genetics and Evolution, Institute of Innovation and Investigation in Health (i3S), Porto, Portugal
| | - Verónica Gomes
- IPATIMUP-Institute of Molecular Pathology and Immunology, University of Porto, Porto, Portugal,Population Genetics and Evolution, Institute of Innovation and Investigation in Health (i3S), Porto, Portugal
| | - Ana Cardoso
- IPATIMUP-Institute of Molecular Pathology and Immunology, University of Porto, Porto, Portugal,Faculty of Sciences, University of Porto, Porto, Portugal,Population Genetics and Evolution, Institute of Innovation and Investigation in Health (i3S), Porto, Portugal
| | - Maria João Prata
- IPATIMUP-Institute of Molecular Pathology and Immunology, University of Porto, Porto, Portugal,Faculty of Sciences, University of Porto, Porto, Portugal,Population Genetics and Evolution, Institute of Innovation and Investigation in Health (i3S), Porto, Portugal
| | - Antonio Amorim
- IPATIMUP-Institute of Molecular Pathology and Immunology, University of Porto, Porto, Portugal,Faculty of Sciences, University of Porto, Porto, Portugal,Population Genetics and Evolution, Institute of Innovation and Investigation in Health (i3S), Porto, Portugal
| | - Luisa Azevedo
- IPATIMUP-Institute of Molecular Pathology and Immunology, University of Porto, Porto, Portugal,Faculty of Sciences, University of Porto, Porto, Portugal,Population Genetics and Evolution, Institute of Innovation and Investigation in Health (i3S), Porto, Portugal
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Daimi H, Lozano-Velasco E, Aranega A, Franco D. Genomic and Non-Genomic Regulatory Mechanisms of the Cardiac Sodium Channel in Cardiac Arrhythmias. Int J Mol Sci 2022; 23:1381. [PMID: 35163304 PMCID: PMC8835759 DOI: 10.3390/ijms23031381] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 12/30/2021] [Accepted: 01/06/2022] [Indexed: 12/19/2022] Open
Abstract
Nav1.5 is the predominant cardiac sodium channel subtype, encoded by the SCN5A gene, which is involved in the initiation and conduction of action potentials throughout the heart. Along its biosynthesis process, Nav1.5 undergoes strict genomic and non-genomic regulatory and quality control steps that allow only newly synthesized channels to reach their final membrane destination and carry out their electrophysiological role. These regulatory pathways are ensured by distinct interacting proteins that accompany the nascent Nav1.5 protein along with different subcellular organelles. Defects on a large number of these pathways have a tremendous impact on Nav1.5 functionality and are thus intimately linked to cardiac arrhythmias. In the present review, we provide current state-of-the-art information on the molecular events that regulate SCN5A/Nav1.5 and the cardiac channelopathies associated with defects in these pathways.
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Affiliation(s)
- Houria Daimi
- Biochemistry and Molecular Biology Laboratory, Faculty of Pharmacy, University of Monastir, Monastir 5000, Tunisia
| | - Estefanía Lozano-Velasco
- Department of Experimental Biology, University of Jaen, 23071 Jaen, Spain; (E.L.-V.); (A.A.); (D.F.)
- Medina Foundation, Technology Park of Health Sciences, Av. del Conocimiento, 34, 18016 Granada, Spain
| | - Amelia Aranega
- Department of Experimental Biology, University of Jaen, 23071 Jaen, Spain; (E.L.-V.); (A.A.); (D.F.)
- Medina Foundation, Technology Park of Health Sciences, Av. del Conocimiento, 34, 18016 Granada, Spain
| | - Diego Franco
- Department of Experimental Biology, University of Jaen, 23071 Jaen, Spain; (E.L.-V.); (A.A.); (D.F.)
- Medina Foundation, Technology Park of Health Sciences, Av. del Conocimiento, 34, 18016 Granada, Spain
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Hu RM, Song EJ, Tester DJ, Deschenes I, Ackerman MJ, Makielski JC, Tan BH. Expression defect of the rare variant/Brugada mutation R1512W depends upon the SCN5A splice variant background and can be rescued by mexiletine and the common polymorphism H558R. Channels (Austin) 2021; 15:253-261. [PMID: 33535892 PMCID: PMC7872018 DOI: 10.1080/19336950.2021.1875645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 01/08/2021] [Accepted: 01/08/2021] [Indexed: 12/01/2022] Open
Abstract
Background : Mutations in SCN5A that decrease Na current underlie arrhythmia syndromes such as the Brugada syndrome (BrS). SCN5A in humans has two splice variants, one lacking a glutamine at position 1077 (Q1077del) and one containing Q1077. We investigated the effect of splice variant background on loss-of-function and rescue for R1512W, a mutation reported to cause BrS. Methods and results : We made the mutation in both variants and expressed them in HEK-293 cells for voltage-clamp study. After 24 hours of transfection, the current expression level of R1512W was reduced by ~50% in both Q1077del and Q1077 compared to the wild-type (WT) channel, respectively. The activation and inactivation midpoint were not different between WT and mutant channels in both splice variant backgrounds. However, slower time constants of recovery and enhanced intermediate inactivation were observed for R1512W/Q1077 compared with WT-Q1077, while the recovery and intermediate inactivation parameters of R1512W/Q1077del were similar to WT-Q1077del. Furthermore, both mexiletine and the common polymorphism H558R restored peak sodium current (INa) amplitude of the mutant channel by increasing the cell surface expression of SCN5A. Conclusion : These findings provide further evidence that the splice variant affects the molecular phenotype with implications for the clinical phenotype, and they provide insight into the expression defect mechanisms and potential treatment in BrS.
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Affiliation(s)
- Rou-Mu Hu
- Department of Cardiology, Heart Center & Beijing Key Laboratory of Hypertension, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison, WI, USA
| | - Evelyn J. Song
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - David J. Tester
- Departments of Medicine, Pediatrics, and Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN, USA
| | - Isabelle Deschenes
- Department of Physiology and Cell Biology, The Dorothy M. Davis Heart and Lung Research Institute, Frick Center for Heart Failure and Arrhythmia, the Ohio State University, Columbus, OH, USA
| | - Michael J. Ackerman
- Departments of Medicine, Pediatrics, and Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN, USA
| | - Jonathan C. Makielski
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison, WI, USA
| | - Bi-Hua Tan
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison, WI, USA
- Department of Physiology and Cell Biology, The Dorothy M. Davis Heart and Lung Research Institute, Frick Center for Heart Failure and Arrhythmia, the Ohio State University, Columbus, OH, USA
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5
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Daniel LL, Yang T, Kroncke B, Hall L, Stroud D, Roden DM. SCN5A variant R222Q generated abnormal changes in cardiac sodium current and action potentials in murine myocytes and Purkinje cells. Heart Rhythm 2019; 16:1676-1685. [PMID: 31125670 PMCID: PMC6825529 DOI: 10.1016/j.hrthm.2019.05.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Indexed: 12/19/2022]
Abstract
BACKGROUND The cardiac sodium channel (SCN5A) mutation R222Q neutralizes a positive charge in the domain I voltage sensor. Mutation carriers display very frequent ectopy and dilated cardiomyopathy. OBJECTIVES To describe the effect of SCN5A R222Q on murine myocyte and Purkinje fiber electrophysiology, and identify underlying mechanisms. METHODS We generated mice carrying humanized wild-type (H) and mutant (RQ) SCN5A channels. We characterized whole-heart and isolated ventricular and Purkinje myocyte properties. RESULTS RQ/RQ mice were not viable. INa from RQ/H ventricular myocytes displayed increased "window current" and hyperpolarizing shifts in both inactivation and activation compared to H/H, as previously reported in heterologous expression systems. Surprisingly, action potentials were markedly abbreviated in RQ/H myocytes (action potential durations at 90% repolarization: 12.6 ± 1.3 ms vs 29.1 ± 1.0 ms in H/H, P < .01, n = 10 each). We identified a large [K+]o-dependent outward gating pore current in RQ/H but not H/H myocytes, and decreasing [K+]o elicited early afterdepolarizations (EADs) and triggered activity in isolated myocytes and ectopic beats in whole hearts. Further, RQ/H Purkinje cells displayed striking, consistent low-voltage EADs. In vivo, however, RQ/H mice displayed little ectopy and contractile function was normal. CONCLUSION While SCN5A R222Q increases plateau inward sodium current, action potentials were unexpectedly shortened, likely reflecting an outward gating-pore current. Low extracellular potassium increased this pore current, and was arrhythmogenic in vitro and ex vivo.
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Affiliation(s)
- Laura L Daniel
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee; Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Tao Yang
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee; Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Brett Kroncke
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee; Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Lynn Hall
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Dina Stroud
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Dan M Roden
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee; Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee; Department of Biomedical Informatics, Vanderbilt University Medical Center, Nashville, Tennessee.
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6
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Neubauer J, Wang Z, Rougier JS, Abriel H, Rieubland C, Bartholdi D, Haas C, Medeiros-Domingo A. Functional characterization of a novel SCN5A variant associated with long QT syndrome and sudden cardiac death. Int J Legal Med 2019; 133:1733-1742. [DOI: 10.1007/s00414-019-02141-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Accepted: 08/06/2019] [Indexed: 12/14/2022]
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7
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Giudicessi JR, Roden DM, Wilde AAM, Ackerman MJ. Classification and Reporting of Potentially Proarrhythmic Common Genetic Variation in Long QT Syndrome Genetic Testing. Circulation 2019; 137:619-630. [PMID: 29431662 DOI: 10.1161/circulationaha.117.030142] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The acquired and congenital forms of long QT syndrome represent 2 distinct but clinically and genetically intertwined disorders of cardiac repolarization characterized by the shared final common pathway of QT interval prolongation and risk of potentially life-threatening arrhythmias. Over the past 2 decades, our understanding of the spectrum of genetic variation that (1) perturbs the function of cardiac ion channel macromolecular complexes and intracellular calcium-handling proteins, (2) underlies acquired/congenital long QT syndrome susceptibility, and (3) serves as a determinant of QT interval duration in the general population has grown exponentially. In turn, these molecular insights led to the development and increased utilization of clinically impactful genetic testing for congenital long QT syndrome. However, the widespread adoption and potential misinterpretation of the 2015 American College of Medical Genetics and Genomics variant classification and reporting guidelines may have contributed unintentionally to the reduced reporting of common genetic variants, with compelling epidemiological and functional evidence to support a potentially proarrhythmic role in patients with congenital and acquired long QT syndrome. As a result, some genetic testing reports may fail to convey the full extent of a patient's genetic susceptibility for a potentially life-threatening arrhythmia to the ordering healthcare professional. In this white paper, we examine the current classification and reporting (or lack thereof) of potentially proarrhythmic common genetic variants and investigate potential mechanisms to facilitate the reporting of these genetic variants without increasing the risk of diagnostic miscues.
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Affiliation(s)
- John R Giudicessi
- Departments of Cardiovascular Medicine and Internal Medicine, Clinician-Investigator Training Program, Mayo Clinic, Rochester, MN (J.R.G)
| | - Dan M Roden
- Departments of Biomedical Informatics, Medicine, and Pharmacology, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN (D.M.R.)
| | - Arthur A M Wilde
- Department of Clinical and Experimental Cardiology, Academic Medical Center, University of Amsterdam, The Netherlands (A.A.M.W.)
| | - Michael J Ackerman
- Departments of Cardiovascular Diseases, Pediatrics, and Molecular Pharmacology and Experimental Therapeutics, Divisions of Heart Rhythm Services and Pediatric Cardiology, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, MN (M.J.A.)
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8
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Mazzaccara C, Limongelli G, Petretta M, Vastarella R, Pacileo G, Bonaduce D, Salvatore F, Frisso G. A common polymorphism in the SCN5A gene is associated with dilated cardiomyopathy. J Cardiovasc Med (Hagerstown) 2019; 19:344-350. [PMID: 29782370 PMCID: PMC6012048 DOI: 10.2459/jcm.0000000000000670] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Aims SCN5A is a disease-causing gene associated with familial dilated cardiomyopathy (FDC). We examined the possible association between a common polymorphism in the SCN5A gene (c.1673A>G-p.H558R; rs1805124) and the risk of dilated cardiomyopathy (DCM) occurrence. Methods We genotyped 185 DCM cases (familial DCM, idiopathic DCM and postischemic DCM) and 251 controls for the p.H558R polymorphism in the SCN5A gene, to test the association of the molecular epidemiology of the individuals with the presence/absence of various types of DCM. Results Our results showed that the rs1805124 polymorphism was significantly associated with DCM, and the association was more significant in patients with FDC; furthermore, in these individuals, the less frequent GG genotype was associated with a 7.39-fold increased risk of disease [95% confidence interval (95% CI) = 2.88–18.96; P < 0.0001] compared with the AA genotype. Moreover, logistic regression analysis showed that GG carriers had a higher risk of DCM than AA + AG carriers (odds ratio = 5.45, 95% CI = 2.23–13.35; P < 0.001). No association was observed between the rs1805124 and DCM risk in postischemic DCM patients. Conclusion Our study demonstrates an association between familial DCM and the rs1805124 polymorphism in the SCN5A gene, which may unravel additional genetic predisposition to the development of a multifactorial disease as DCM.
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Affiliation(s)
- Cristina Mazzaccara
- CEINGE-Biotecnologie Avanzate s.c.a r.l.,Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università di Napoli 'Federico II'
| | - Giuseppe Limongelli
- Dipartimento di Scienze Cardiotoraciche e Respiratorie, Università degli Studi della Campania 'Luigi Vanvitelli', A.O. Monaldi, Azienda dei Colli
| | - Mario Petretta
- Dipartimento di Scienze Mediche Traslazionali, Università di Napoli 'Federico II'
| | - Rossella Vastarella
- Dipartimento di Scienze Cardiotoraciche e Respiratorie, Università degli Studi della Campania 'Luigi Vanvitelli', A.O. Monaldi, Azienda dei Colli
| | - Giuseppe Pacileo
- Dipartimento di Scienze Cardiotoraciche e Respiratorie, Università degli Studi della Campania 'Luigi Vanvitelli', A.O. Monaldi, Azienda dei Colli
| | - Domenico Bonaduce
- Dipartimento di Scienze Mediche Traslazionali, Università di Napoli 'Federico II'
| | - Francesco Salvatore
- CEINGE-Biotecnologie Avanzate s.c.a r.l.,IRCCS-Fondazione SDN, Napoli, Italy
| | - Giulia Frisso
- CEINGE-Biotecnologie Avanzate s.c.a r.l.,Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università di Napoli 'Federico II'
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Wilders R. Cellular Mechanisms of Sinus Node Dysfunction in Carriers of the SCN5A-E161K Mutation and Role of the H558R Polymorphism. Front Physiol 2018; 9:1795. [PMID: 30618807 PMCID: PMC6305593 DOI: 10.3389/fphys.2018.01795] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 11/29/2018] [Indexed: 12/16/2022] Open
Abstract
Background: Carriers of the E161K mutation in the SCN5A gene, encoding the NaV1.5 pore-forming α-subunit of the ion channel carrying the fast sodium current (INa), show sinus bradycardia and occasional exit block. Voltage clamp experiments in mammalian expression systems revealed a mutation-induced 2.5- to 4-fold reduction in INa peak current density as well as a +19 mV shift and reduced steepness of the steady-state activation curve. The highly common H558R polymorphism in NaV1.5 limits this shift to +13 mV, but also introduces a -10 mV shift in steady-state inactivation. Aim: We assessed the cellular mechanism by which the E161K mutation causes sinus node dysfunction in heterozygous mutation carriers as well as the potential role of the H558R polymorphism. Methods: We incorporated the mutation-induced changes in INa into the Fabbri-Severi model of a single human sinoatrial node cell and the Maleckar et al. human atrial cell model, and carried out simulations under control conditions and over a wide range of acetylcholine levels. Results: In absence of the H558R polymorphism, the E161K mutation increased the basic cycle length of the sinoatrial node cell from 813 to 866 ms. In the simulated presence of 10 and 25 nM acetylcholine, basic cycle length increased from 1027 to 1131 and from 1448 to 1795 ms, respectively. The increase in cycle length was the result of a significant slowing of diastolic depolarization. The mutation-induced reduction in INa window current had reduced the contribution of the mutant component of INa to the net membrane current during diastolic depolarization to effectively zero. Highly similar results were obtained in presence of the H558R polymorphism. Atrial excitability was reduced, both in absence and presence of the H558R polymorphism, as reflected by an increase in threshold stimulus current and a concomitant decrease in capacitive current of the atrial cell. Conclusion: We conclude that the experimentally identified mutation-induced changes in INa can explain the clinically observed sinus bradycardia and potentially the occasional exit block. Furthermore, we conclude that the common H558R polymorphism does not significantly alter the effects of the E161K mutation and can thus not explain the reduced penetrance of the E161K mutation.
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Affiliation(s)
- Ronald Wilders
- Department of Medical Biology, Amsterdam University Medical Centers, Amsterdam, Netherlands
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10
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Moreau A, Chahine M. A New Cardiac Channelopathy: From Clinical Phenotypes to Molecular Mechanisms Associated With Na v1.5 Gating Pores. Front Cardiovasc Med 2018; 5:139. [PMID: 30356750 PMCID: PMC6189448 DOI: 10.3389/fcvm.2018.00139] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 09/19/2018] [Indexed: 12/19/2022] Open
Abstract
Voltage gated sodium channels (NaV) are broadly expressed in the human body. They are responsible for the initiation of action potentials in excitable cells. They also underlie several physiological processes such as cognitive, sensitive, motor, and cardiac functions. The NaV1.5 channel is the main NaV expressed in the heart. A dysfunction of this channel is usually associated with the development of pure electrical disorders such as long QT syndrome, Brugada syndrome, sinus node dysfunction, atrial fibrillation, and cardiac conduction disorders. However, mutations of Nav1.5 have recently been linked to the development of an atypical clinical entity combining complex arrhythmias and dilated cardiomyopathy. Although several Nav1.5 mutations have been linked to dilated cardiomyopathy phenotypes, their pathogenic mechanisms remain to be elucidated. The gating pore may constitute a common biophysical defect for all NaV1.5 mutations located in the channel's VSDs. The creation of such a gating pore may disrupt the ionic homeostasis of cardiomyocytes, affecting electrical signals, cell morphology, and cardiac myocyte function. The main objective of this article is to review the concept of gating pores and their role in structural heart diseases and to discuss potential pharmacological treatments.
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Affiliation(s)
- Adrien Moreau
- PhyMedExp, Université de Montpellier, INSERM, CNRS, Montpellier, France
| | - Mohamed Chahine
- CERVO Research Centre, Institut Universitaire en Santé Mentale de Québec, Quebec City, QC, Canada.,Department of Medicine, Université Laval, Quebec City, QC, Canada
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11
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Verkerk AO, Amin AS, Remme CA. Disease Modifiers of Inherited SCN5A Channelopathy. Front Cardiovasc Med 2018; 5:137. [PMID: 30327767 PMCID: PMC6174200 DOI: 10.3389/fcvm.2018.00137] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Accepted: 09/10/2018] [Indexed: 12/19/2022] Open
Abstract
To date, a large number of mutations in SCN5A, the gene encoding the pore-forming α-subunit of the primary cardiac Na+ channel (NaV1.5), have been found in patients presenting with a wide range of ECG abnormalities and cardiac syndromes. Although these mutations all affect the same NaV1.5 channel, the associated cardiac syndromes each display distinct phenotypical and biophysical characteristics. Variable disease expressivity has also been reported, where one particular mutation in SCN5A may lead to either one particular symptom, a range of various clinical signs, or no symptoms at all, even within one single family. Additionally, disease severity may vary considerably between patients carrying the same mutation. The exact reasons are unknown, but evidence is increasing that various cardiac and non-cardiac conditions can influence the expressivity and severity of inherited SCN5A channelopathies. In this review, we provide a summary of identified disease entities caused by SCN5A mutations, and give an overview of co-morbidities and other (non)-genetic factors which may modify SCN5A channelopathies. A comprehensive knowledge of these modulatory factors is not only essential for a complete understanding of the diverse clinical phenotypes associated with SCN5A mutations, but also for successful development of effective risk stratification and (alternative) treatment paradigms.
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Affiliation(s)
- Arie O Verkerk
- Department of Clinical and Experimental Cardiology, Heart Centre, Academic Medical Center, Amsterdam, Netherlands.,Department of Medical Biology, Academic Medical Center, Amsterdam, Netherlands
| | - Ahmad S Amin
- Department of Clinical and Experimental Cardiology, Heart Centre, Academic Medical Center, Amsterdam, Netherlands
| | - Carol Ann Remme
- Department of Clinical and Experimental Cardiology, Heart Centre, Academic Medical Center, Amsterdam, Netherlands
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Ter Bekke RMA, Isaacs A, Barysenka A, Hoos MB, Jongbloed JDH, Hoorntje JCA, Patelski ASM, Helderman-van den Enden ATJM, van den Wijngaard A, Stoll M, Volders PGA. Heritability in a SCN5A-mutation founder population with increased female susceptibility to non-nocturnal ventricular tachyarrhythmia and sudden cardiac death. Heart Rhythm 2017; 14:1873-1881. [PMID: 28782696 DOI: 10.1016/j.hrthm.2017.07.036] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Indexed: 12/19/2022]
Abstract
BACKGROUND Heritable cardiac-sodium channel dysfunction is associated with various arrhythmia syndromes, some predisposing to ventricular fibrillation. Phenotypic diversity among carriers of identical-by-descent mutations is often remarkable, suggesting influences of genetic modifiers. OBJECTIVE The purpose of this study was to identify a unique SCN5A-mutation founder population with mixed clinical phenotypes and sudden cardiac death, and to investigate the heritability of electromechanical traits besides the SCN5A-mutation effect. METHODS The 16-generation founder population segregating SCN5A c.4850_4852delTCT, p.(Phe1617del), was comprehensively phenotyped. Variance component analysis was used to evaluate the mutation's effects and assess heritability. RESULTS In 45 p.(Phe1617del) positives, the mutation associated strongly with QTc prolongation (472 ± 60 ms vs 423 ± 35 ms in 26 mutation negatives; P <.001; odds ratio for long-QT syndrome 22.4; 95% confidence interval 4.5-224.2; P <.001) and electromechanical window (EMW) negativity (-29 ± 47 ms vs 34 ± 26 ms; P <.001). Overlapping phenotypes including conduction delay and Brugada syndrome were noted in 19. Polymorphic ventricular tachyarrhythmias occurred mostly in the daytime, after arousal-evoked heart-rate acceleration and repolarization prolongation. Cox proportional hazards regression analysis revealed female gender as an independent risk factor for cardiac events (hazard ratio 5.1; 95% confidence interval 1.6-16.3; P = .006). p.(Phe1617del) was an important determinant of QTcbaseline, QTcmax, and EMW, explaining 18%, 28%, and 37%, respectively, of the trait's variance. Significant heritability was observed for PQ interval (P = .003) after accounting for the p.(Phe1617del) effect. CONCLUSION This SCN5A-p.(Phe1617del) founder population with phenotypic divergence and overlap reveals long-QT syndrome-related and arousal-evoked ventricular tachyarrhythmias with a female preponderance. Variance component analysis indicates additional genetic variance for PQ interval hidden in the genome, besides a dominant p.(Phe1617del) effect on QTc and EMW.
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Affiliation(s)
- Rachel M A Ter Bekke
- Department of Cardiology, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Aaron Isaacs
- Maastricht Centre for Systems Biology (MaCSBio) and Department of Biochemistry, CARIM, Maastricht University, Maastricht, The Netherlands
| | - Andrei Barysenka
- Department of Genetic Epidemiology, Institute of Human Genetics, University of Münster, Münster, Germany
| | - Marije B Hoos
- Department of Cardiology, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University Medical Centre, Maastricht, The Netherlands; Department of Clinical Genetics, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Jan D H Jongbloed
- Department of Genetics, University of Groningen, University Medical Centre Groningen, Groningen, The Netherlands
| | - Jan C A Hoorntje
- Department of Cardiology, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University Medical Centre, Maastricht, The Netherlands; Department of Cardiology, Zuyderland Medical Centre, Heerlen, The Netherlands
| | | | | | - Arthur van den Wijngaard
- Department of Clinical Genetics, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Monika Stoll
- Maastricht Centre for Systems Biology (MaCSBio) and Department of Biochemistry, CARIM, Maastricht University, Maastricht, The Netherlands; Department of Genetic Epidemiology, Institute of Human Genetics, University of Münster, Münster, Germany
| | - Paul G A Volders
- Department of Cardiology, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University Medical Centre, Maastricht, The Netherlands.
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Veltmann C, Barajas-Martinez H, Wolpert C, Borggrefe M, Schimpf R, Pfeiffer R, Cáceres G, Burashnikov E, Antzelevitch C, Hu D. Further Insights in the Most Common SCN5A Mutation Causing Overlapping Phenotype of Long QT Syndrome, Brugada Syndrome, and Conduction Defect. J Am Heart Assoc 2016; 5:JAHA.116.003379. [PMID: 27381756 PMCID: PMC5015375 DOI: 10.1161/jaha.116.003379] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Background Phenotypic overlap of type 3 long QT syndrome (LQT3), Brugada syndrome (BrS), cardiac conduction disease (CCD), and sinus node dysfunction (SND) is observed with SCN5A mutations. SCN5A‐E1784K is the most common mutation associated with BrS and LQTS3. The present study examines the genotype–phenotype relationship in a large family carrying SCN5A‐E1784K and SCN5A‐H558R polymorphism. Methods and Results Clinical work‐up, follow‐up, and genetic analysis were performed in 35 family members. Seventeen were SCN5A‐E1784K positive. They also displayed QTc prolongation, and either BrS, CCD, or both. One carrier exhibited SND. The presence of SCN5A‐H558R did not significantly alter the phenotype of SCN5A‐E1784K carriers. Fourteen SCN5A‐E1784K patients underwent implantable cardioverter‐defibrillator (ICD) implantation; 4 developed VF and received appropriate ICD shocks after 8±3 months of follow‐up. One patient without ICD also developed VF after 6.7 years. These 5 cases carried both SCN5A‐E1784K and SCN5A‐H558R. Functional characterization was achieved by expressing SCN5A variants in TSA201 cells. Peak (INa,P) or late (INa,L) sodium currents were recorded using whole‐cell patch‐clamp techniques. Co‐expression of SCN5A‐E1784K and SCN5A‐WT reduced INa,P to 70.03% of WT, shifted steady‐state inactivation by −11.03 mV, and increased INa,L from 0.14% to 1.86% of INa,P. Similar changes were observed when SCN5A‐E1784K was co‐expressed with SCN5A‐H558R. Conclusions We demonstrate a strong genotype‐phenotype correlation with complete penetrance for BrS, LQTS, or CCD in the largest family harboring SCN5A‐E1784K mutation described so far. Phenotype of LQTS is present during all decades of life, whereas CCD develops with increasing age. Phenotypic overlap may explain the high event rate in carriers.
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Affiliation(s)
- Christian Veltmann
- Rhythmology and Electrophysiology, Department of Cardiology and Angiology Hannover Medical School, Hannover, Germany
| | | | - Christian Wolpert
- Klinik für Innere Medizin, Cardiology Klinikum Ludwigsburg, Ludwigsburg, Germany
| | - Martin Borggrefe
- 1st Department of Medicine-Cardiology, University Medical Centre Mannheim, Mannheim, Germany DZHK partner site Heidelberg/Mannheim, Mannheim, Germany
| | - Rainer Schimpf
- 1st Department of Medicine-Cardiology, University Medical Centre Mannheim, Mannheim, Germany DZHK partner site Heidelberg/Mannheim, Mannheim, Germany
| | - Ryan Pfeiffer
- Molecular Genetic Department, Masonic Medical Research Laboratory, Utica, NY, USA
| | - Gabriel Cáceres
- Molecular Genetic Department, Masonic Medical Research Laboratory, Utica, NY, USA
| | - Elena Burashnikov
- Molecular Genetic Department, Masonic Medical Research Laboratory, Utica, NY, USA
| | | | - Dan Hu
- Molecular Genetic Department, Masonic Medical Research Laboratory, Utica, NY, USA
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Post-mortem whole-exome sequencing (WES) with a focus on cardiac disease-associated genes in five young sudden unexplained death (SUD) cases. Int J Legal Med 2016; 130:1011-1021. [PMID: 26846766 DOI: 10.1007/s00414-016-1317-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 01/13/2016] [Indexed: 01/01/2023]
Abstract
Sudden death of healthy young adults in the absence of any medical reason is generally categorised as autopsy-negative sudden unexplained death (SUD). Approximately 30 % of all SUD cases can be explained by lethal sequence variants in cardiac genes causing disturbed ion channel functions (channelopathies) or minimal structural heart abnormalities (cardiomyopathies). The aim of this study was to perform whole-exome sequencing (WES) in five young SUD cases in order to identify potentially disease-causing mutations with a focus on 184 genes associated with cardiac diseases or sudden death. WES analysis enabled the identification of damaging-predicted cardiac sequence alterations in three out of five SUD cases. Two SUD victims carried disease-causing variants in long QT syndrome (LQTS)-associated genes (KCNH2, SCN5A). In a third case, WES identified variants in two genes involved in mitral valve prolapse and thoracic aortic aneurism (DCHS1, TGFβ2). The genome of a fourth case carried several minor variants involved in arrhythmia pointing to a multigene influence that might have contributed to sudden death. Our results confirm that post-mortem genetic testing in SUD cases in addition to the conventional autopsy can help to identify familial cardiac diseases and can contribute to the identification of genetic risk factors for sudden death.
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Lee YS, Olaopa MA, Jung BC, Lee SH, Shin DG, Park HS, Cho Y, Han SM, Lee MH, Kim YN. Genetic Variation of SCN5A in Korean Patients with Sick Sinus Syndrome. Korean Circ J 2016; 46:63-71. [PMID: 26798387 PMCID: PMC4720851 DOI: 10.4070/kcj.2016.46.1.63] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Revised: 05/18/2015] [Accepted: 07/07/2015] [Indexed: 11/12/2022] Open
Abstract
Background and Objectives Due to recent studies that have shown an association between the genetic variation of SCN5A and sick sinus syndrome (SSS), we sought to determine if a similar correlation existed in Korean patients with SSS. Subjects and Methods We enrolled 30 patients with SSS who showed a sinus pause (longer than 3.0 s) in Holter monitoring, in addition to 80 controls. All exons including the putative splicing sites of the SCN5A gene were amplified by polymerase chain reaction and sequenced either directly or following subcloning. Wild-type and single nucleotide polymorphisms were expressed in human embryonic kidney cells, and the peak sodium current (INa) was analyzed using the whole-cell patch-clamp technique. Results A total of 9 genetic variations were identified: 7 variations (G87A-A29A, IVS9-3C>A, A1673G-H558R, G3823A-D1275N, T5457C-D1819D, T5963G-L1988R, and C5129T-S1710L) had been previously reported, and 2 variants (A3075T-E1025D and T4847A-F1616Y) were novel; the potential structural effects of F1616Y were analyzed in a three-dimensional model of the SCN5A domain. Patch-clamp studies at room temperature demonstrated that the peak INa was significantly increased by 140% in HEK cells transfected with F1616Y compared with wild-type (-335.13 pA/pF±24.04, n=8 vs. -139.95 pA/pF±23.76, n=7, respectively). Furthermore, the voltage dependency of the activation and steady-state inactivation of F1616Y were leftward-shifted compared with wild-type (Vh activation=-55.36 mv±0.22, n=8 vs. Vh activation=-44.21 mV±0.17, n=7; respectively; Vh inactivation=-104.47 mV±0.21, n=7 vs. Vh inactivation=-84.89 mV±0.09, n=12, respectively). Conclusion F1616Y may be associated with SSS.
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Affiliation(s)
- Young Soo Lee
- Division of Cardiology, Catholic University of Daegu, Daegu, Korea
| | - Michael A Olaopa
- Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis, IN, USA
| | | | | | | | - Hyoung Seob Park
- Department of Internal Medicine, Keimyung University, Daegu, Korea
| | | | | | - Myung Hoon Lee
- D&P Biotech, Daegu, Korea.; Department of Biochemistry and Cell Biology, Kyungpook National University, Daegu, Korea
| | - Yoon Nyun Kim
- Department of Internal Medicine, Keimyung University, Daegu, Korea
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Veerman CC, Wilde AAM, Lodder EM. The cardiac sodium channel gene SCN5A and its gene product NaV1.5: Role in physiology and pathophysiology. Gene 2015; 573:177-87. [PMID: 26361848 DOI: 10.1016/j.gene.2015.08.062] [Citation(s) in RCA: 111] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2015] [Revised: 07/31/2015] [Accepted: 08/27/2015] [Indexed: 12/18/2022]
Abstract
The gene SCN5A encodes the main cardiac sodium channel NaV1.5. This channel predominates the cardiac sodium current, INa, which underlies the fast upstroke of the cardiac action potential. As such, it plays a crucial role in cardiac electrophysiology. Over the last 60years a tremendous amount of knowledge regarding its function at the electrophysiological and molecular level has been acquired. Furthermore, genetic studies have shown that mutations in SCN5A are associated with multiple cardiac diseases (e.g. Brugada syndrome, Long QT syndrome, conduction disease and cardiomyopathy), while genetic variation in the general population has been associated with differences in cardiac conduction and risk of arrhythmia through genome wide association studies. In this review we aim to give an overview of the current knowledge (and the gaps therein) on SCN5A and NaV1.5.
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Affiliation(s)
- Christiaan C Veerman
- Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, The Netherlands
| | - Arthur A M Wilde
- Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, The Netherlands.
| | - Elisabeth M Lodder
- Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, The Netherlands.
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Robyns T, Nuyens D, Van Casteren L, Corveleyn A, De Ravel T, Heidbuchel H, Willems R. Reduced Penetrance and Variable Expression of SCN5A Mutations and the Importance of Co-inherited Genetic Variants: Case Report and Review of the Literature. Indian Pacing Electrophysiol J 2014; 14:133-49. [PMID: 24948852 PMCID: PMC4032780 DOI: 10.1016/s0972-6292(16)30754-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Mutations in the SCN5A gene are responsible for multiple phenotypical presentations including Brugada syndrome, long QT syndrome, progressive familial heart block, sick sinus syndrome, dilated cardiomyopathy, lone atrial fibrillation and multiple overlap syndromes. These different phenotypic expressions of a mutation in a single gene can be explained by variable expression and reduced penetrance. One of the possible explanations of these phenomena is the co-inheritance of genetic variants. We describe a family where the individuals exhibit a compound heterozygosity in the SCN5A gene including a mutation (R1632H) and a new variant (M858L). Individuals with both the mutation and new variant present with a more severe phenotype including spontaneous atrial tachyarrhythmia at young age. We give an overview of the different phenotypes of "SCN5A disease" and discuss the importance of co-inherited genetic variants in the expression of SCN5A disease.
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Affiliation(s)
- T Robyns
- Department of Cardiovascular Medicine, University Hospitals Leuven, Leuven, Belgium
| | - D Nuyens
- Department of Cardiovascular Medicine, University Hospitals Leuven, Leuven, Belgium
| | - L Van Casteren
- Department of Cardiovascular Medicine, University Hospitals Leuven, Leuven, Belgium
| | - A Corveleyn
- Center for Human Genetics, University Hospitals Leuven, Leuven, Belgium
| | - T De Ravel
- Center for Human Genetics, University Hospitals Leuven, Leuven, Belgium
| | - H Heidbuchel
- Department of Cardiovascular Medicine, University Hospitals Leuven, Leuven, Belgium
| | - R Willems
- Department of Cardiovascular Medicine, University Hospitals Leuven, Leuven, Belgium
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Moreau A, Gosselin-Badaroudine P, Chahine M. Biophysics, pathophysiology, and pharmacology of ion channel gating pores. Front Pharmacol 2014; 5:53. [PMID: 24772081 PMCID: PMC3982104 DOI: 10.3389/fphar.2014.00053] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2014] [Accepted: 03/12/2014] [Indexed: 12/19/2022] Open
Abstract
Voltage sensor domains (VSDs) are a feature of voltage gated ion channels (VGICs) and voltage sensitive proteins. They are composed of four transmembrane (TM) segments (S1–S4). Currents leaking through VSDs are called omega or gating pore currents. Gating pores are caused by mutations of the highly conserved positively charged amino acids in the S4 segment that disrupt interactions between the S4 segment and the gating charge transfer center (GCTC). The GCTC separates the intracellular and extracellular water crevices. The disruption of S4–GCTC interactions allows these crevices to communicate and create a fast activating and non-inactivating alternative cation-selective permeation pathway of low conductance, or a gating pore. Gating pore currents have recently been shown to cause periodic paralysis phenotypes. There is also increasing evidence that gating pores are linked to several other familial diseases. For example, gating pores in Nav1.5 and Kv7.2 channels may underlie mixed arrhythmias associated with dilated cardiomyopathy (DCM) phenotypes and peripheral nerve hyperexcitability (PNH), respectively. There is little evidence for the existence of gating pore blockers. Moreover, it is known that a number of toxins bind to the VSD of a specific domain of Na+ channels. These toxins may thus modulate gating pore currents. This focus on the VSD motif opens up a new area of research centered on developing molecules to treat a number of cell excitability disorders such as epilepsy, cardiac arrhythmias, and pain. The purpose of the present review is to summarize existing knowledge of the pathophysiology, biophysics, and pharmacology of gating pore currents and to serve as a guide for future studies aimed at improving our understanding of gating pores and their pathophysiological roles.
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Affiliation(s)
- Adrien Moreau
- Centre de Recherche de L'Institut Universitaire en Santé Mentale de Québec Quebec City, QC, Canada
| | | | - Mohamed Chahine
- Centre de Recherche de L'Institut Universitaire en Santé Mentale de Québec Quebec City, QC, Canada ; Department of Medicine, Université Laval Quebec City, QC, Canada
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Gosselin-Badaroudine P, Moreau A, Chahine M. Nav 1.5 mutations linked to dilated cardiomyopathy phenotypes: Is the gating pore current the missing link? Channels (Austin) 2013; 8:90-4. [PMID: 24300601 DOI: 10.4161/chan.27179] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Nav 1.5 dysfunctions are commonly linked to rhythms disturbances that include type 3 long QT syndrome (LQT3), Brugada syndrome (BrS), sick sinus syndrome (SSS) and conduction defects. Recently, this channel protein has been also linked to structural heart diseases such as dilated cardiomyopathy (DCM).
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Affiliation(s)
| | - Adrien Moreau
- Centre de recherche; Institut universitaire en santé mentale de Québec; Quebec City, QC Canada
| | - Mohamed Chahine
- Centre de recherche; Institut universitaire en santé mentale de Québec; Quebec City, QC Canada; Department of Medicine; Université Laval; Quebec City, QC Canada
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Cooper DN, Krawczak M, Polychronakos C, Tyler-Smith C, Kehrer-Sawatzki H. Where genotype is not predictive of phenotype: towards an understanding of the molecular basis of reduced penetrance in human inherited disease. Hum Genet 2013; 132:1077-130. [PMID: 23820649 PMCID: PMC3778950 DOI: 10.1007/s00439-013-1331-2] [Citation(s) in RCA: 417] [Impact Index Per Article: 37.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Accepted: 06/15/2013] [Indexed: 02/06/2023]
Abstract
Some individuals with a particular disease-causing mutation or genotype fail to express most if not all features of the disease in question, a phenomenon that is known as 'reduced (or incomplete) penetrance'. Reduced penetrance is not uncommon; indeed, there are many known examples of 'disease-causing mutations' that fail to cause disease in at least a proportion of the individuals who carry them. Reduced penetrance may therefore explain not only why genetic diseases are occasionally transmitted through unaffected parents, but also why healthy individuals can harbour quite large numbers of potentially disadvantageous variants in their genomes without suffering any obvious ill effects. Reduced penetrance can be a function of the specific mutation(s) involved or of allele dosage. It may also result from differential allelic expression, copy number variation or the modulating influence of additional genetic variants in cis or in trans. The penetrance of some pathogenic genotypes is known to be age- and/or sex-dependent. Variable penetrance may also reflect the action of unlinked modifier genes, epigenetic changes or environmental factors. At least in some cases, complete penetrance appears to require the presence of one or more genetic variants at other loci. In this review, we summarize the evidence for reduced penetrance being a widespread phenomenon in human genetics and explore some of the molecular mechanisms that may help to explain this enigmatic characteristic of human inherited disease.
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Affiliation(s)
- David N. Cooper
- Institute of Medical Genetics, School of Medicine, Cardiff University, Heath Park, Cardiff, CF14 4XN UK
| | - Michael Krawczak
- Institute of Medical Informatics and Statistics, Christian-Albrechts University, 24105 Kiel, Germany
| | | | - Chris Tyler-Smith
- The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SA UK
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LI NING, WANG RONGRONG, HOU CUIHONG, ZHANG YINHUI, TENG SIYONG, PU JIELIN. A heterozygous missense SCN5A mutation associated with early repolarization syndrome. Int J Mol Med 2013; 32:661-7. [PMID: 23799537 DOI: 10.3892/ijmm.2013.1422] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Accepted: 09/10/2012] [Indexed: 11/06/2022] Open
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Abstract
Syncope and risk of sudden death due to ventricular tachyarrhythmia are the common manifestations of several inherited disorders. Abnormalities of the genetic makeup may directly affect proteins controlling cardiac excitability in a structurally normal heart. Other diseases manifest primarily with ventricular arrhythmias even though the genetic mutations cause structural abnormalities of the myocardium. This is the case of arrhythmogenic right ventricular cardiomyopathy and hypertrophic cardiomyopathy. Groundbreaking discoveries, starting from the 1990s until the beginning of the current decade, have provided fundamental knowledge on the major genes that confer an increased risk of arrhythmias and sudden death. Stems of such knowledge are the availability of genetic diagnosis, genotype-phenotype correlation, and genotype-based risk stratification schemes currently used in the clinical practice. This review provides a concise description of the known genes and key mechanisms involved in the pathogenesis of inherited arrhythmias. In addition, we outline possibilities, limitations, advantages, and potential threats of genetically screening for these genes.
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One case, 3 rare simultaneous findings: intramyocardial bronchogenic cyst, P.H558R variant of SCN5A gene, and granular cell tumor of the esophagus. Am J Forensic Med Pathol 2012; 33:335-8. [PMID: 22835975 DOI: 10.1097/paf.0b013e318264e9ef] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We describe the sudden death of a 42-year-old white man. The decedent was a healthy young man with a short clinical history of chest pain, fatigue, dizziness, and pyrosis. Two weeks before his death, he underwent medical evaluation for the aforementioned symptoms. Electrocardiogram, chest x-ray, and serum troponin were all within normal limits. Gastroesophageal reflux disease was suspected, and the decedent was treated with omeprazole. Medicolegal autopsy disclosed an incidental intramyocardial bronchogenic cyst and p.H558R variant of the SCN5A gene. The cyst was located between the epicardium and myocardium of the posterior face of the left superior ventricular wall, adjacent to the base of the heart. An incidental granular cell tumor of the esophagus was also identified, which was likely unrelated to death.
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Olesen MS, Yuan L, Liang B, Holst AG, Nielsen N, Nielsen JB, Hedley PL, Christiansen M, Olesen SP, Haunsø S, Schmitt N, Jespersen T, Svendsen JH. High prevalence of long QT syndrome-associated SCN5A variants in patients with early-onset lone atrial fibrillation. ACTA ACUST UNITED AC 2012; 5:450-9. [PMID: 22685113 DOI: 10.1161/circgenetics.111.962597] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND Atrial fibrillation (AF) is the most common cardiac arrhythmia. The cardiac sodium channel, Na(V)1.5, plays a pivotal role in setting the conduction velocity and the initial depolarization of the cardiac myocytes. We hypothesized that early-onset lone AF was associated with genetic variation in SCN5A. METHODS AND RESULTS The coding sequence of SCN5A was sequenced in 192 patients with early-onset lone AF. Eight nonsynonymous mutations (T220I, R340Q, T1304M, F1596I, R1626H, D1819N, R1897W, and V1951M) and 2 rare variants (S216L in 2 patients and F2004L) were identified. Of 11 genopositive probands, 6 (3.2% of the total population) had a variant previously associated with long QT syndrome type 3 (LQTS3). The prevalence of LQTS3-associated variants in the patients with lone AF was much higher than expected, compared with the prevalence in recent exome data (minor allele frequency, 1.6% versus 0.3%; P=0.003), mainly representing the general population. The functional effects of the mutations were analyzed by whole cell patch clamp in HEK293 cells; for 5 of the mutations previously associated with LQTS3, patch-clamp experiments showed an increased sustained sodium current, suggesting a mechanistic overlap between LQTS3 and early-onset lone AF. In 9 of 10 identified mutations and rare variants, we observed compromised biophysical properties affecting the transient peak current. CONCLUSIONS In a cohort of patients with early-onset lone AF, we identified a high prevalence of SCN5A mutations previously associated with LQTS3. Functional investigations of the mutations revealed both compromised transient peak current and increased sustained current.
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Affiliation(s)
- Morten S Olesen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, Copenhagen, Denmark.
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Myburgh R, Hochfeld WE, Dodgen TM, Ker J, Pepper MS. Cardiovascular pharmacogenetics. Pharmacol Ther 2011; 133:280-90. [PMID: 22123178 DOI: 10.1016/j.pharmthera.2011.11.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Accepted: 11/04/2011] [Indexed: 12/25/2022]
Abstract
Human genetic variation in the form of single nucleotide polymorphisms as well as more complex structural variations such as insertions, deletions and copy number variants, is partially responsible for the clinical variation seen in response to pharmacotherapeutic drugs. This affects the likelihood of experiencing adverse drug reactions and also of achieving therapeutic success. In this paper, we review key studies in cardiovascular pharmacogenetics that reveal genetic variations underlying the outcomes of drug treatment in cardiovascular disease. Examples of genetic associations with drug efficacy and toxicity are described, including the roles of genetic variability in pharmacokinetics (e.g. drug metabolizing enzymes) and pharmacodynamics (e.g. drug targets). These findings have functional implications that could lead to the development of genetic tests aimed at minimizing drug toxicity and optimizing drug efficacy in cardiovascular medicine.
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Affiliation(s)
- Renier Myburgh
- Department of Immunology, Faculty of Health Sciences, University of Pretoria, South Africa
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Walzik S, Schroeter A, Benndorf K, Zimmer T. Alternative splicing of the cardiac sodium channel creates multiple variants of mutant T1620K channels. PLoS One 2011; 6:e19188. [PMID: 21552533 PMCID: PMC3084281 DOI: 10.1371/journal.pone.0019188] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Accepted: 03/22/2011] [Indexed: 12/19/2022] Open
Abstract
Alternative splicing creates several Nav1.5 transcripts in the mammalian myocardium and in various other tissues including brain, dorsal root ganglia, breast cancer cells as well as neuronal stem cell lines. In total nine Nav1.5 splice variants have been discovered. Four of them, namely Nav1.5a, Nav1.5c, Nav1.5d, and Nav1.5e, generate functional channels in heterologous expression systems. The significance of alternatively spliced transcripts for cardiac excitation, in particular their role in SCN5A channelopathies, is less well understood. In the present study, we systematically investigated electrophysiological properties of mutant T1620K channels in the background of all known functional Nav1.5 splice variants in HEK293 cells. This mutation has been previously associated with two distinct cardiac excitation disorders: with long QT syndrome type 3 (LQT3) and isolated cardiac conduction disease (CCD). When investigating the effect of the T1620K mutation, we noticed similar channel defects in the background of hNav1.5, hNav1.5a, and hNav1.5c. In contrast, the hNav1.5d background produced differential effects: In the mutant channel, some gain-of-function features did not emerge, whereas loss-of-function became more pronounced. In case of hNav1.5e, the neonatal variant of hNav1.5, both the splice variant itself as well as the corresponding mutant channel showed electrophysiological properties that were distinct from the wild-type and mutant reference channels, hNav1.5 and T1620K, respectively. In conclusion, our data show that alternative splicing is a mechanism capable of generating a variety of functionally distinct wild-type and mutant hNav1.5 channels. Thus, the cellular splicing machinery is a potential player affecting genotype-phenotype correlations in SCN5A channelopathies.
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Affiliation(s)
- Stefan Walzik
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| | - Annett Schroeter
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| | - Klaus Benndorf
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| | - Thomas Zimmer
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
- * E-mail:
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Napolitano C, Cummings S. Genetics for the Electrophysiologist: Take Home Messages for the Clinician. Card Electrophysiol Clin 2010; 2:623-634. [PMID: 28770724 DOI: 10.1016/j.ccep.2010.09.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Syncope and risk of sudden death caused by ventricular tachyarrhythmia are the common manifestations of several inherited disorders. The abnormalities of the genetic makeup may directly affect proteins controlling cardiac excitability in a structurally normal heart. Other diseases manifest primarily with ventricular arrhythmias even if the genetic mutations cause structural abnormalities of the myocardium, such as arrhythmogenic right ventricular cardiomyopathy and hypertrophic cardiomyopathy. The groundbreaking discoveries that began in the 1990s and continued until the beginning of the current decade gathered fundamental knowledge about the major genes controlling cardiac excitability and conferring an increased risk of severe arrhythmias. Stemming from such knowledge is the availability of genetic diagnosis, genotype-phenotype correlation, and genotype-based risk stratification schemes. This article provides a concise description of the known genes and key mechanisms involved in the pathogenesis of inherited arrhythmias and outlines the possibilities, limitations, advantages, and potential threats of genetic testing for inherited arrhythmogenic syndromes.
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Affiliation(s)
- Carlo Napolitano
- Molecular Cardiology Laboratories, IRCCS Fondazione Salvatore Maugeri, Via Maugeri 10, 27100, Pavia, Italy; Cadiovascular Genetics, Leon Charney Division of Cardiology, New York University Medical Center, 403 East 34th Street, RIV 4th Floor, New York, NY 10016, USA
| | - Samori Cummings
- Cadiovascular Genetics, Leon Charney Division of Cardiology, New York University Medical Center, 403 East 34th Street, RIV 4th Floor, New York, NY 10016, USA
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Postema PG, Mosterd A, Hofman N, Alders M, Wilde AAM. Sodium channelopathies: do we really understand what's going on? J Cardiovasc Electrophysiol 2010; 22:590-3. [PMID: 20812931 DOI: 10.1111/j.1540-8167.2010.01892.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Long-QT syndrome, Brugada syndrome, and conduction disease may be caused by mutations in the cardiac sodium channel gene SCN5A, and from the ECG one can already presume either a gain- or a loss-of-function defect. We describe a family harboring 2 SCN5A mutations: the ΔKPQ mutation, the "classical" gain-of-function mutation associated with Long-QT syndrome, and the I1660V mutation, a loss-of-function mutation associated with Brugada syndrome. However, we were surprised by the result of genetic testing in this family. One son who carried the ΔKPQ mutation but not the I1660V mutation did not show the expected Long-QT phenotype but, unexpectedly, showed a conduction disease/Brugada phenotype.
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Affiliation(s)
- Pieter G Postema
- Department of Cardiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
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Multiple loss-of-function mechanisms contribute to SCN5A-related familial sick sinus syndrome. PLoS One 2010; 5:e10985. [PMID: 20539757 PMCID: PMC2881866 DOI: 10.1371/journal.pone.0010985] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2009] [Accepted: 04/26/2010] [Indexed: 12/11/2022] Open
Abstract
Background To identify molecular mechanisms underlying SCN5A-related sick sinus syndrome (SSS), a rare type of SSS, in parallel experiments we elucidated the electrophysiological properties and the cell surface localization of thirteen human Nav1.5 (hNav1.5) mutant channels previously linked to this disease. Methodology/Principal Findings Mutant hNav1.5 channels expressed by HEK293 cells and Xenopus oocytes were investigated by whole-cell patch clamp and two-microelectrode voltage clamp, respectively. HEK293 cell surface biotinylation experiments quantified the fraction of correctly targeted channel proteins. Our data suggested three distinct mutant channel subtypes: Group 1 mutants (L212P, P1298L, DelF1617, R1632H) gave peak current densities and cell surface targeting indistinguishable from wild-type hNav1.5. Loss-of-function of these mutants resulted from altered channel kinetics, including a negative shift of steady-state inactivation and a reduced voltage dependency of open-state inactivation. Group 2 mutants (E161K, T220I, D1275N) gave significantly reduced whole-cell currents due to impaired cell surface localization (D1275N), altered channel properties at unchanged cell surface localization (T220I), or a combination of both (E161K). Group 3 mutant channels were non-functional, due to an almost complete lack of protein at the plasma membrane (T187I, W1421X, K1578fs/52, R1623X) or a probable gating/permeation defect with normal surface localisation (R878C, G1408R). Conclusions/Significance This study indicates that multiple molecular mechanisms, including gating abnormalities, trafficking defects, or a combination of both, are responsible for SCN5A-related familial SSS.
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