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Zaytseva AK, Kulichik OE, Kostareva AA, Zhorov BS. Biophysical mechanisms of myocardium sodium channelopathies. Pflugers Arch 2024; 476:735-753. [PMID: 38424322 DOI: 10.1007/s00424-024-02930-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Revised: 02/15/2024] [Accepted: 02/16/2024] [Indexed: 03/02/2024]
Abstract
Genetic variants of gene SCN5A encoding the alpha-subunit of cardiac voltage-gated sodium channel Nav1.5 are associated with various diseases, including long QT syndrome (LQT3), Brugada syndrome (BrS1), and progressive cardiac conduction disease (PCCD). In the last decades, the great progress in understanding molecular and biophysical mechanisms of these diseases has been achieved. The LQT3 syndrome is associated with gain-of-function of sodium channels Nav1.5 due to impaired inactivation, enhanced activation, accelerated recovery from inactivation or the late current appearance. In contrast, BrS1 and PCCD are associated with the Nav1.5 loss-of-function, which in electrophysiological experiments can be manifested as reduced current density, enhanced fast or slow inactivation, impaired activation, or decelerated recovery from inactivation. Genetic variants associated with congenital arrhythmias can also disturb interactions of the Nav1.5 channel with different proteins or drugs and cause unexpected reactions to drug administration. Furthermore, mutations can affect post-translational modifications of the channels and their sensitivity to pH and temperature. Here we briefly review the current knowledge on biophysical mechanisms of LQT3, BrS1 and PCCD. We focus on limitations of studies that use heterologous expression systems and induced pluripotent stem cells (iPSC) derived cardiac myocytes and summarize our understanding of genotype-phenotype relations of SCN5A mutations.
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Affiliation(s)
- Anastasia K Zaytseva
- Almazov National Medical Research Centre, St. Petersburg, Russia.
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia.
| | - Olga E Kulichik
- Almazov National Medical Research Centre, St. Petersburg, Russia
| | | | - Boris S Zhorov
- Almazov National Medical Research Centre, St. Petersburg, Russia
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
- McMaster University, Hamilton, Canada
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2
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Abramochkin D, Li B, Zhang H, Kravchuk E, Nesterova T, Glukhov G, Shestak A, Zaklyazminskaya E, Sokolova OS. Novel Gain-of-Function Mutation in the Kv11.1 Channel Found in the Patient with Brugada Syndrome and Mild QTc Shortening. Biochemistry (Mosc) 2024; 89:543-552. [PMID: 38648771 DOI: 10.1134/s000629792403012x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 02/20/2024] [Accepted: 02/27/2024] [Indexed: 04/25/2024]
Abstract
Brugada syndrome (BrS) is an inherited disease characterized by right precordial ST-segment elevation in the right precordial leads on electrocardiograms (ECG), and high risk of life-threatening ventricular arrhythmia and sudden cardiac death (SCD). Mutations in the responsible genes have not been fully characterized in the BrS patients, except for the SCN5A gene. We identified a new genetic variant, c.1189C>T (p.R397C), in the KCNH2 gene in the asymptomatic male proband diagnosed with BrS and mild QTc shortening. We hypothesize that this variant could alter IKr-current and may be causative for the rare non-SCN5A-related form of BrS. To assess its pathogenicity, we performed patch-clamp analysis on IKr reconstituted with this KCNH2 mutation in the Chinese hamster ovary cells and compared the phenotype with the wild type. It appeared that the R397C mutation does not affect the IKr density, but facilitates activation, hampers inactivation of the hERG channels, and increases magnitude of the window current suggesting that the p.R397C is a gain-of-function mutation. In silico modeling demonstrated that this missense mutation potentially leads to the shortening of action potential in the heart.
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Affiliation(s)
- Denis Abramochkin
- Shenzhen MSU-BIT University, Shenzhen, China.
- Lomonosov Moscow State University, 119234, Moscow, Russia
| | - Bowen Li
- Shenzhen MSU-BIT University, Shenzhen, China.
| | - Han Zhang
- Shenzhen MSU-BIT University, Shenzhen, China.
| | | | - Tatiana Nesterova
- Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, Ekaterinburg, 620049, Russia.
- Institute of Natural Sciences and Mathematics, Ural Federal University, Ekaterinburg, 620075, Russia
| | - Grigory Glukhov
- Shenzhen MSU-BIT University, Shenzhen, China.
- Lomonosov Moscow State University, 119234, Moscow, Russia
| | - Anna Shestak
- Petrovsky National Research Center of Surgery, Moscow, 119991, Russia.
| | | | - Olga S Sokolova
- Shenzhen MSU-BIT University, Shenzhen, China.
- Lomonosov Moscow State University, 119234, Moscow, Russia
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Semino F, Darche FF, Bruehl C, Koenen M, Skladny H, Katus HA, Frey N, Draguhn A, Schweizer PA. GPD1L-A306del modifies sodium current in a family carrying the dysfunctional SCN5A-G1661R mutation associated with Brugada syndrome. Pflugers Arch 2024; 476:229-242. [PMID: 38036776 DOI: 10.1007/s00424-023-02882-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 11/06/2023] [Accepted: 11/08/2023] [Indexed: 12/02/2023]
Abstract
Loss-of-function variants of SCN5A, encoding the sodium channel alpha subunit Nav1.5 are associated with high phenotypic variability and multiple cardiac presentations, while underlying mechanisms are incompletely understood. Here we investigated a family with individuals affected by Brugada Syndrome (BrS) of different severity and aimed to unravel the underlying genetic and electrophysiological basis.Next-generation sequencing was used to identify the genetic variants carried by family members. The index patient, who was severely affected by arrhythmogenic BrS, carried previously uncharacterized variants of Nav1.5 (SCN5A-G1661R) and glycerol-3-phosphate dehydrogenase-1-like protein (GPD1L-A306del) in a double heterozygous conformation. Family members exclusively carrying SCN5A-G1661R showed asymptomatic Brugada ECG patterns, while another patient solely carrying GPD1L-A306del lacked any clinical phenotype.To assess functional mechanisms, Nav1.5 channels were transiently expressed in HEK-293 cells in the presence and absence of GPD1L. Whole-cell patch-clamp recordings revealed loss of sodium currents after homozygous expression of SCN5A-G1661R, and reduction of current amplitude to ~ 50% in cells transfected with equal amounts of wildtype and mutant Nav1.5. Co-expression of wildtype Nav1.5 and GPD1L showed a trend towards increased sodium current amplitudes and a hyperpolarizing shift in steady-state activation and -inactivation compared to sole SCN5A expression. Application of the GPD1L-A306del variant shifted steady-state activation to more hyperpolarized and inactivation to more depolarized potentials.In conclusion, SCN5A-G1661R produces dysfunctional channels and associates with BrS. SCN5A mediated currents are modulated by co-expression of GDP1L and this interaction is altered by mutations in both proteins. Thus, additive genetic burden may aggravate disease severity, explaining higher arrhythmogenicity in double mutation carriers.
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Affiliation(s)
- Francesca Semino
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany
- Institute of Physiology and Pathophysiology, Heidelberg University, Heidelberg, Germany
| | - Fabrice F Darche
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany
| | - Claus Bruehl
- Institute of Physiology and Pathophysiology, Heidelberg University, Heidelberg, Germany
| | - Michael Koenen
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany
- Department of Molecular Neurobiology, Max Planck Institute for Medical Research, Heidelberg, Germany
| | - Heyko Skladny
- SYNLAB MVZ Humangenetik Mannheim GmbH, Mannheim, Germany
| | - Hugo A Katus
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany
- German Center for Cardiovascular Research (DZHK), Partner Site Heidelberg/Mannheim, Heidelberg, Germany
| | - Norbert Frey
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany
- German Center for Cardiovascular Research (DZHK), Partner Site Heidelberg/Mannheim, Heidelberg, Germany
| | - Andreas Draguhn
- Institute of Physiology and Pathophysiology, Heidelberg University, Heidelberg, Germany
| | - Patrick A Schweizer
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.
- German Center for Cardiovascular Research (DZHK), Partner Site Heidelberg/Mannheim, Heidelberg, Germany.
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Chiang DY, Verkerk AO, Victorio R, Shneyer BI, van der Vaart B, Jouni M, Narendran N, Kc A, Sampognaro JR, Vetrano-Olsen F, Oh JS, Buys E, de Jonge B, Shah DA, Kiviniemi T, Burridge PW, Bezzina CR, Akhmanova A, MacRae CA. The Role of MAPRE2 and Microtubules in Maintaining Normal Ventricular Conduction. Circ Res 2024; 134:46-59. [PMID: 38095085 DOI: 10.1161/circresaha.123.323231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Accepted: 11/28/2023] [Indexed: 01/06/2024]
Abstract
BACKGROUND Brugada syndrome is associated with loss-of-function SCN5A variants, yet these account for only ≈20% of cases. A recent genome-wide association study identified a novel locus within MAPRE2, which encodes EB2 (microtubule end-binding protein 2), implicating microtubule involvement in Brugada syndrome. METHODS A mapre2 knockout zebrafish model was generated using CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/clustered regularly interspaced short palindromic repeat-associated protein 9) and validated by Western blot. Larval hearts at 5 days post-fertilization were isolated for voltage mapping and immunocytochemistry. Adult fish hearts were used for ECG, patch clamping, and immunocytochemistry. Morpholinos were injected into embryos at 1-cell stage for knockdown experiments. A transgenic zebrafish line with cdh2 tandem fluorescent timer was used to study adherens junctions. Microtubule plus-end tracking and patch clamping were performed in human induced pluripotent stem cell derived cardiomyocytes (iPSC-CMs) with MAPRE2 knockdown and knockout, respectively. RESULTS Voltage mapping of mapre2 knockout hearts showed a decrease in ventricular maximum upstroke velocity of the action potential and conduction velocity, suggesting loss of cardiac voltage-gated sodium channel function. ECG showed QRS prolongation in adult knockout fish, and patch clamping showed decreased sodium current density in knockout ventricular myocytes and arrhythmias in knockout iPSC-CMs. Confocal imaging showed disorganized adherens junctions and mislocalization of mature Ncad (N-cadherin) with mapre2 loss of function, associated with a decrease of detyrosinated tubulin. MAPRE2 knockdown in iPSC-CMs led to an increase in microtubule growth velocity and distance, indicating changes in microtubule dynamics. Finally, knockdown of ttl encoding tubulin tyrosine ligase in mapre2 knockout larvae rescued tubulin detyrosination and ventricular maximum upstroke velocity of the action potential. CONCLUSIONS Genetic ablation of mapre2 led to a decrease in voltage-gated sodium channel function, a hallmark of Brugada syndrome, associated with disruption of adherens junctions, decrease of detyrosinated tubulin as a marker of microtubule stability, and changes in microtubule dynamics. Restoration of the detyrosinated tubulin fraction with ttl knockdown led to rescue of voltage-gated sodium channel-related functional parameters in mapre2 knockout hearts. Taken together, our study implicates microtubule dynamics in the modulation of ventricular conduction.
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Affiliation(s)
- David Y Chiang
- Cardiovascular Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (D.Y.C., R.V., N.N., A.K., J.R.S., F.V.-O., J.S.O., E.B., C.A.M.)
| | - Arie O Verkerk
- Department of Experimental Cardiology, Heart Center (A.O.V., C.R.B.), Academic Medical Center, Amsterdam UMC, the Netherlands
| | - Rachelle Victorio
- Cardiovascular Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (D.Y.C., R.V., N.N., A.K., J.R.S., F.V.-O., J.S.O., E.B., C.A.M.)
| | - Boris I Shneyer
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, the Netherlands (B.I.S., B.v.d.V., A.A.)
| | - Babet van der Vaart
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, the Netherlands (B.I.S., B.v.d.V., A.A.)
| | - Mariam Jouni
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL (M.J., D.A.S., P.W.B.)
| | - Nakul Narendran
- Cardiovascular Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (D.Y.C., R.V., N.N., A.K., J.R.S., F.V.-O., J.S.O., E.B., C.A.M.)
| | - Ashmita Kc
- Cardiovascular Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (D.Y.C., R.V., N.N., A.K., J.R.S., F.V.-O., J.S.O., E.B., C.A.M.)
| | - James R Sampognaro
- Cardiovascular Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (D.Y.C., R.V., N.N., A.K., J.R.S., F.V.-O., J.S.O., E.B., C.A.M.)
| | - Franki Vetrano-Olsen
- Cardiovascular Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (D.Y.C., R.V., N.N., A.K., J.R.S., F.V.-O., J.S.O., E.B., C.A.M.)
| | - John S Oh
- Cardiovascular Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (D.Y.C., R.V., N.N., A.K., J.R.S., F.V.-O., J.S.O., E.B., C.A.M.)
| | - Eva Buys
- Cardiovascular Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (D.Y.C., R.V., N.N., A.K., J.R.S., F.V.-O., J.S.O., E.B., C.A.M.)
| | - Berend de Jonge
- Department of Medical Biology (B.d.J.), Academic Medical Center, Amsterdam UMC, the Netherlands
| | - Disheet A Shah
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL (M.J., D.A.S., P.W.B.)
| | - Tuomas Kiviniemi
- Heart Center, Turku University Hospital and University of Turku, Finland (T.K.)
| | - Paul W Burridge
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL (M.J., D.A.S., P.W.B.)
| | - Connie R Bezzina
- Department of Experimental Cardiology, Heart Center (A.O.V., C.R.B.), Academic Medical Center, Amsterdam UMC, the Netherlands
| | - Anna Akhmanova
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, the Netherlands (B.I.S., B.v.d.V., A.A.)
| | - Calum A MacRae
- Cardiovascular Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (D.Y.C., R.V., N.N., A.K., J.R.S., F.V.-O., J.S.O., E.B., C.A.M.)
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5
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Abstract
BACKGROUND Three types of characteristic ST-segment elevation are associated with Brugada syndrome but only type 1 is diagnostic. Why only type 1 ECG is diagnostic remains unanswered. METHODS Computer simulations were performed in single cells, 1-dimensional cables, and 2-dimensional tissues to investigate the effects of the peak and late components of the transient outward potassium current (Ito), sodium current, and L-type calcium current (ICa,L) as well as other potassium currents on the genesis of ECG morphologies and phase 2 reentry (P2R). RESULTS Although a sufficiently large peak Ito was required to result in the type 1 ECG pattern and P2R, increasing the late component of Ito converted type 1 ECG to type 2 ECG and suppressed P2R. Increasing the peak Ito promoted spiral wave breakup, potentiating the transition from tachycardia to fibrillation, but increasing the late Ito prevented spiral wave breakup by flattening the action potential duration restitution and preventing P2R. A sufficiently large ICa,L conductance was needed for P2R to occur, but once above the critical conductance, blocking ICa,L promoted P2R. However, selectively blocking the window and late components of ICa,L suppressed P2R, countering the effect of the late Ito. Blocking either the peak or late components of sodium current promoted P2R, with the late sodium current blockade having the larger effect. As expected, increasing other potassium currents potentiated P2R, with ATP-sensitive potassium current exhibiting a larger effect than rapid and slow component of the delayed rectifier potassium current. CONCLUSIONS The peak Ito promotes type 1 ECG and P2R, whereas the late Ito converts type 1 ECG to type 2 ECG and suppresses P2R. Blocking the peak ICa,L and either the peak or the late sodium current promotes P2R, whereas blocking the window and late ICa,L suppresses P2R. These results provide important insights into the mechanisms of arrhythmogenesis and potential therapeutic targets for treatment of Brugada syndrome. Graphic Abstract: A graphic abstract is available for this article.
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Affiliation(s)
- Zhaoyang Zhang
- Department of physics, School of Physical Science and Technology, Ningbo University, Ningbo, Zhejiang 315211, China
| | - Peng-Sheng Chen
- Department of Cardiology, Cedars Sinai Medical Center, Los Aneles, CA 90048, USA
| | - James N. Weiss
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
| | - Zhilin Qu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
- Department of Computational Medicine, David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
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Takla M, Edling CE, Zhang K, Saadeh K, Tse G, Salvage SC, Huang CL, Jeevaratnam K. Transcriptional profiles of genes related to electrophysiological function in Scn5a +/- murine hearts. Physiol Rep 2021; 9:e15043. [PMID: 34617689 PMCID: PMC8495800 DOI: 10.14814/phy2.15043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 08/13/2021] [Accepted: 08/13/2021] [Indexed: 11/24/2022] Open
Abstract
The Scn5a gene encodes the major pore-forming Nav 1.5 (α) subunit, of the voltage-gated Na+ channel in cardiomyocytes. The key role of Nav 1.5 in action potential initiation and propagation in both atria and ventricles predisposes organisms lacking Scn5a or carrying Scn5a mutations to cardiac arrhythmogenesis. Loss-of-function Nav 1.5 genetic abnormalities account for many cases of the human arrhythmic disorder Brugada syndrome (BrS) and related conduction disorders. A murine model with a heterozygous Scn5a deletion recapitulates many electrophysiological phenotypes of BrS. This study examines the relationships between its Scn5a+/- genotype, resulting transcriptional changes, and the consequent phenotypic presentations of BrS. Of 62 selected protein-coding genes related to cardiomyocyte electrophysiological or homeostatic function, concentrations of mRNA transcribed from 15 differed significantly from wild type (WT). Despite halving apparent ventricular Scn5a transcription heterozygous deletion did not significantly downregulate its atrial expression, raising possibilities of atria-specific feedback mechanisms. Most of the remaining 14 genes whose expression differed significantly between WT and Scn5a+/- animals involved Ca2+ homeostasis specifically in atrial tissue, with no overlap with any ventricular changes. All statistically significant changes in expression were upregulations in the atria and downregulations in the ventricles. This investigation demonstrates the value of future experiments exploring for and clarifying links between transcriptional control of Scn5a and of genes whose protein products coordinate Ca2+ regulation and examining their possible roles in BrS.
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Affiliation(s)
- Michael Takla
- Faculty of Health and Medical ScienceUniversity of SurreyGuildfordUK
- Christ’s CollegeUniversity of CambridgeCambridgeUK
| | | | - Kevin Zhang
- Faculty of Health and Medical ScienceUniversity of SurreyGuildfordUK
- School of MedicineImperial College LondonLondonUK
| | - Khalil Saadeh
- Faculty of Health and Medical ScienceUniversity of SurreyGuildfordUK
- Clinical SchoolUniversity of CambridgeCambridgeUK
| | - Gary Tse
- Faculty of Health and Medical ScienceUniversity of SurreyGuildfordUK
- Second Hospital of Tianjin Medical UniversityTianjinChina
| | | | - Christopher L.‐H. Huang
- Faculty of Health and Medical ScienceUniversity of SurreyGuildfordUK
- Department of BiochemistryUniversity of CambridgeCambridgeUK
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Wang Z, Vermij SH, Sottas V, Shestak A, Ross-Kaschitza D, Zaklyazminskaya EV, Hudmon A, Pitt GS, Rougier JS, Abriel H. Calmodulin binds to the N-terminal domain of the cardiac sodium channel Na v1.5. Channels (Austin) 2020; 14:268-286. [PMID: 32815768 PMCID: PMC7515574 DOI: 10.1080/19336950.2020.1805999] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The cardiac voltage-gated sodium channel Nav1.5 conducts the rapid inward sodium current crucial for cardiomyocyte excitability. Loss-of-function mutations in its gene SCN5A are linked to cardiac arrhythmias such as Brugada Syndrome (BrS). Several BrS-associated mutations in the Nav1.5 N-terminal domain (NTD) exert a dominant-negative effect (DNE) on wild-type channel function, for which mechanisms remain poorly understood. We aim to contribute to the understanding of BrS pathophysiology by characterizing three mutations in the Nav1.5 NTD: Y87C-here newly identified-, R104W, and R121W. In addition, we hypothesize that the calcium sensor protein calmodulin is a new NTD binding partner. Recordings of whole-cell sodium currents in TsA-201 cells expressing WT and variant Nav1.5 showed that Y87C and R104W but not R121W exert a DNE on WT channels. Biotinylation assays revealed reduction in fully glycosylated Nav1.5 at the cell surface and in whole-cell lysates. Localization of Nav1.5 WT channel with the ER did not change in the presence of variants, as shown by transfected and stained rat neonatal cardiomyocytes. We demonstrated that calmodulin binds the Nav1.5 NTD using in silico modeling, SPOTS, pull-down, and proximity ligation assays. Calmodulin binding to the R121W variant and to a Nav1.5 construct missing residues 80-105, a predicted calmodulin-binding site, is impaired. In conclusion, we describe the new natural BrS Nav1.5 variant Y87C and present first evidence that calmodulin binds to the Nav1.5 NTD, which seems to be a determinant for the DNE.
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Affiliation(s)
- Zizun Wang
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - Sarah H. Vermij
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - Valentin Sottas
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
- Department of Molecular and Cellular Genetics, Lonza BioPharma Ltd, Visp, Switzerland
| | - Anna Shestak
- Ibex, Petrovskiy Russian Scientific Center of Surgery, Moscow, Russia
| | | | | | - Andy Hudmon
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, Indiana, USA
| | - Geoffrey S. Pitt
- Cardiovascular Research Institute, Weill Cornell Medical College, New York, USA
| | | | - Hugues Abriel
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
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8
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Hong L, Zhang M, Sridhar A, Darbar D. Pathogenic mutations perturb calmodulin regulation of Na v1.8 channel. Biochem Biophys Res Commun 2020; 533:168-174. [PMID: 32948286 PMCID: PMC11038804 DOI: 10.1016/j.bbrc.2020.08.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 08/05/2020] [Indexed: 12/19/2022]
Abstract
The voltage-gated sodium channels play a key role in the generation and propagation of the cardiac action potential. Emerging data indicate that the Nav1.8 channel, encoded by the SCN10A gene, is a modulator of cardiac conduction and variation in the gene has been associated with arrhythmias such as atrial fibrillation (AF) and Brugada syndrome (BrS). The voltage gated sodium channels contain a calmodulin (CaM)-binding IQ domain involved in channel slow inactivation, we here investigated the role of CaM regulation of Nav1.8 channel function, and showed that CaM enhanced slow inactivation of the Nav1.8 channel and hyperpolarized steady-state inactivation curve of sodium currents. The effects of CaM on the channel gating were disrupted in the Nav1.8 channel truncated IQ domain. We studied Nav1.8 IQ domain mutations associated with AF and BrS, and found that a BrS-linked mutation (R1863Q) reduced the CaM-induced hyperpolarization shift, AF-linked mutations (R1869C and R1869G) disrupted CaM-induced enhanced inactivation, and effects of CaM on both development and recovery from slow inactivation were attenuated in all pathogenic mutations. Our findings indicate a role of CaM in the regulation of Nav1.8 channel function in cardiac arrhythmias.
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Affiliation(s)
- Liang Hong
- Department of Medicine, University of Illinois at Chicago, Chicago, IL, USA.
| | - Meihong Zhang
- Department of Medicine, University of Illinois at Chicago, Chicago, IL, USA
| | - Arvind Sridhar
- Department of Medicine, University of Illinois at Chicago, Chicago, IL, USA
| | - Dawood Darbar
- Department of Medicine, University of Illinois at Chicago, Chicago, IL, USA; Department of Pharmacology, University of Illinois at Chicago, Chicago, IL, USA; Jesse Brown Veterans Administration, Chicago, IL, USA.
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9
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Tsumoto K, Ashihara T, Naito N, Shimamoto T, Amano A, Kurata Y, Kurachi Y. Specific decreasing of Na + channel expression on the lateral membrane of cardiomyocytes causes fatal arrhythmias in Brugada syndrome. Sci Rep 2020; 10:19964. [PMID: 33203944 PMCID: PMC7673036 DOI: 10.1038/s41598-020-76681-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 11/02/2020] [Indexed: 12/31/2022] Open
Abstract
Reduced cardiac sodium (Na+) channel current (INa) resulting from the loss-of-function of Na+ channel is a major cause of lethal arrhythmias in Brugada syndrome (BrS). Inspired by previous experimental studies which showed that in heart diseases INa was reduced along with expression changes in Na+ channel within myocytes, we hypothesized that the local decrease in INa caused by the alteration in Na+ channel expression in myocytes leads to the occurrence of phase-2 reentry, the major triggering mechanism of lethal arrhythmias in BrS. We constructed in silico human ventricular myocardial strand and ring models, and examined whether the Na+ channel expression changes in each myocyte cause the phase-2 reentry in BrS. Reducing Na+ channel expression in the lateral membrane of each myocyte caused not only the notch-and-dome but also loss-of-dome type action potentials and slowed conduction, both of which are typically observed in BrS patients. Furthermore, the selective reduction in Na+ channels on the lateral membrane of each myocyte together with spatial tissue heterogeneity of Na+ channel expression caused the phase-2 reentry and phase-2 reentry-mediated reentrant arrhythmias. Our data suggest that the BrS phenotype is strongly influenced by expression abnormalities as well as genetic abnormalities of Na+ channels.
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Affiliation(s)
- Kunichika Tsumoto
- Department of Physiology II, Kanazawa Medical University, 1-1 Daigaku, Uchinada, 920-0293, Japan.
- Department of Pharmacology, Graduate School of Medicine, Osaka University, 2-2 Yamada-oka, Suita, 565-0871, Japan.
| | - Takashi Ashihara
- Department of Medical Informatics and Biomedical Engineering, Shiga University of Medical Science, Seta Tsukinowa-cho, Otsu, 520-2192, Japan
| | - Narumi Naito
- Department of Bioinformatics, College of Life Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, 525-8577, Japan
| | - Takao Shimamoto
- Department of Bioinformatics, College of Life Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, 525-8577, Japan
| | - Akira Amano
- Department of Bioinformatics, College of Life Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, 525-8577, Japan
| | - Yasutaka Kurata
- Department of Physiology II, Kanazawa Medical University, 1-1 Daigaku, Uchinada, 920-0293, Japan
| | - Yoshihisa Kurachi
- Department of Pharmacology, Graduate School of Medicine, Osaka University, 2-2 Yamada-oka, Suita, 565-0871, Japan
- Glocal Center for Medical Engineering and Informatics, Osaka University, 2-2 Yamada-oka, Suita, 565-0871, Japan
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10
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Pérez-Agustín A, Pinsach-Abuin M, Pagans S. Role of Non-Coding Variants in Brugada Syndrome. Int J Mol Sci 2020; 21:ijms21228556. [PMID: 33202810 PMCID: PMC7698069 DOI: 10.3390/ijms21228556] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 11/09/2020] [Accepted: 11/10/2020] [Indexed: 12/15/2022] Open
Abstract
Brugada syndrome (BrS) is an inherited electrical heart disease associated with a high risk of sudden cardiac death (SCD). The genetic characterization of BrS has always been challenging. Although several cardiac ion channel genes have been associated with BrS, SCN5A is the only gene that presents definitive evidence for causality to be used for clinical diagnosis of BrS. However, more than 65% of diagnosed cases cannot be explained by variants in SCN5A or other genes. Therefore, in an important number of BrS cases, the underlying mechanisms are still elusive. Common variants, mostly located in non-coding regions, have emerged as potential modulators of the disease by affecting different regulatory mechanisms, including transcription factors (TFs), three-dimensional organization of the genome, or non-coding RNAs (ncRNAs). These common variants have been hypothesized to modulate the interindividual susceptibility of the disease, which could explain incomplete penetrance of BrS observed within families. Altogether, the study of both common and rare variants in parallel is becoming increasingly important to better understand the genetic basis underlying BrS. In this review, we aim to describe the challenges of studying non-coding variants associated with disease, re-examine the studies that have linked non-coding variants with BrS, and provide further evidence for the relevance of regulatory elements in understanding this cardiac disorder.
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Affiliation(s)
- Adrian Pérez-Agustín
- Department of Medical Sciences, School of Medicine, University of Girona, 17003 Girona, Spain;
- Biomedical Research Institute of Girona, 17190 Salt, Spain;
| | | | - Sara Pagans
- Department of Medical Sciences, School of Medicine, University of Girona, 17003 Girona, Spain;
- Biomedical Research Institute of Girona, 17190 Salt, Spain;
- Correspondence:
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11
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Aizawa Y, Fujisawa T, Katsumata Y, Kohsaka S, Kunitomi A, Ohno S, Sonoda K, Hayashi H, Hojo R, Fukamizu S, Nagase S, Ito S, Nakajima K, Nishiyama T, Kimura T, Kurita Y, Furukawa Y, Takatsuki S, Ogawa S, Nakazato Y, Sumiyoshi M, Kosaki K, Horie M, Fukuda K. Sex-Dependent Phenotypic Variability of an SCN5A Mutation: Brugada Syndrome and Sick Sinus Syndrome. J Am Heart Assoc 2018; 7:e009387. [PMID: 30371189 PMCID: PMC6222934 DOI: 10.1161/jaha.118.009387] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Accepted: 07/12/2018] [Indexed: 11/25/2022]
Abstract
Background Brugada syndrome ( BS ) is known to be 9 times more prevalent in males than females. However, little is known about the development of sick sinus syndrome in female members with familial BS . Methods and Results Familial BS patients and family members, both from our institutions and collaborating sites that specialize in clinical care of BS , participated in this study. We collected information on their clinical and genetic background, along with the inheritance patterns of BS . Detailed information on each case with familial BS is described. A total of 7 families, including 25 BS patients (12 females and 13 males), were included. Seven were probands and 18 were family members. Ten out of the 12 female patients and none of the 13 male patients developed sick sinus syndrome. Sudden death or spontaneous ventricular fibrillation occurred in 7 out of 13 male patients and 2 out of 12 female patients. Conclusions Familial BS existed in which female patients developed sick sinus syndrome but male patients did not. Some of those female patients with sick sinus syndrome had unrecognized BS . Information should be collected not only regarding a family history of sudden death or BS , but also whether a pacemaker was implanted in female members.
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Affiliation(s)
| | | | | | | | | | - Seiko Ohno
- Shiga University of Medical ScienceOtsuJapan
- National Cerebral and Cardiovascular CenterSuitaJapan
| | - Keiko Sonoda
- Shiga University of Medical ScienceOtsuJapan
- National Cerebral and Cardiovascular CenterSuitaJapan
| | | | | | | | | | | | | | | | | | - Yasuo Kurita
- International University of Health & WelfareTokyoJapan
| | | | | | - Satoshi Ogawa
- International University of Health & WelfareTokyoJapan
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12
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Liu J, Bayer JD, Aschar-Sobbi R, Wauchop M, Spears D, Gollob M, Vigmond EJ, Tsushima R, Backx PH, Chauhan VS. Complex interactions in a novel SCN5A compound mutation associated with long QT and Brugada syndrome: Implications for Na+ channel blocking pharmacotherapy for de novo conduction disease. PLoS One 2018; 13:e0197273. [PMID: 29791480 PMCID: PMC5965851 DOI: 10.1371/journal.pone.0197273] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 04/30/2018] [Indexed: 11/29/2022] Open
Abstract
Background The SCN5A mutation, P1332L, is linked to a malignant form of congenital long QT syndrome, type 3 (LQT3), and affected patients are highly responsive to the Na+ channel blocking drug, mexiletine. In contrast, A647D is an atypical SCN5A mutation causing Brugada syndrome. An asymptomatic male with both P1332L and A647D presented with varying P wave/QRS aberrancy and mild QTc prolongation which did not shorten measurably with mexiletine. Objective We characterized the biophysical properties of P1332L, A647D and wild-type (WT) Na+ channels as well as their combinations in order to understand our proband’s phenotype and to guide mexilitine therapy. Methods Na+ channel biophysics and mexilitine-binding kinetics were assessed using heterologous expression studies in CHO-K1 cells and human ventricular myocyte modeling. Results Compared to WT, P1332L channels displayed a hyperpolarizing shift in inactivation, slower inactivation and prominent late Na+ currents (INa). While A647D had no effect on the biophysical properties of INa, it reduced peak and late INa density when co-expressed with either WT or P1332L. Additionally, while P1332L channels had greater sensitivity to block by mexiletine compared to WT, this was reduced in the presence of A647D. Modelling studies revealed that mixing P1332L with A647D channels, action potential durations were shortened compared to P1332L, while peak INa was reduced compared to either A647D coexpressing with WT or WT alone. Conclusions While A647D mitigates the lethal LQT3 phenotype seen with P1332L, it also reduces mexilitine sensitivity and decreases INa density. These results explain our proband’s mild repolarization abnormality and prominent conduction defect in the atria and ventricles, but also suggest that expression of P1332L with A647D yields a novel disease phenotype for which mexiletine pharmacotherapy is no longer suitable.
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Affiliation(s)
- Jie Liu
- Department of Biology, York University, Toronto, Ontario, Canada
| | - Jason D. Bayer
- Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University Foundation, Pessac, France
- University of Bordeaux, IMB, UMR 5251, Talance, France
| | | | - Marianne Wauchop
- Department of Biology, York University, Toronto, Ontario, Canada
| | - Danna Spears
- Peter Munk Cardiac Center, Division of Cardiology, University Health Network, Toronto, Ontario, Canada
| | - Michael Gollob
- Peter Munk Cardiac Center, Division of Cardiology, University Health Network, Toronto, Ontario, Canada
| | - Edward J. Vigmond
- Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University Foundation, Pessac, France
- University of Bordeaux, IMB, UMR 5251, Talance, France
| | - Robert Tsushima
- Department of Biology, York University, Toronto, Ontario, Canada
| | - Peter H. Backx
- Department of Biology, York University, Toronto, Ontario, Canada
- Peter Munk Cardiac Center, Division of Cardiology, University Health Network, Toronto, Ontario, Canada
- * E-mail: (PB); (VC)
| | - Vijay S. Chauhan
- Peter Munk Cardiac Center, Division of Cardiology, University Health Network, Toronto, Ontario, Canada
- * E-mail: (PB); (VC)
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13
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Abstract
E1784K is the most common mixed syndrome SCN5a mutation underpinning both Brugada syndrome type 1 (BrS1) and Long-QT syndrome type 3 (LQT3). The charge reversal mutant enhances the late sodium current (INa) passed by the cardiac voltage-gated sodium channel (NaV1.5), delaying cardiac repolarization. Exercise-induced triggers, like elevated temperature and cytosolic calcium, exacerbate E1784K late INa. In this study, we tested the effects of Ranolazine, the late INa blocker, on voltage-dependent and kinetic properties of E1784K at elevated temperature and cytosolic calcium. We used whole-cell patch clamp to measure INa from wild type and E1784K channels expressed in HEK293 cells. At elevated temperature, Ranolazine attenuated gain-of-function in E1784K by decreasing late INa, hyperpolarizing steady-state fast inactivation, and increasing use-dependent inactivation. Both elevated temperature and cytosolic calcium hampered the capacity of Ranolazine to suppress E1784K late INa. In-silico action potential (AP) simulations were done using a modified O'Hara Rudy (ORd) cardiac model. Simulations showed that Ranolazine failed to shorten AP duration, an effect augmented at febrile temperatures. The drug-channel interaction is clearly affected by external triggers, as reported previously with ischemia. Determining drug efficacy under various physiological states in SCN5a cohorts is crucial for accurate management of arrhythmias.
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Affiliation(s)
- Mena Abdelsayed
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| | - Manpreet Ruprai
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| | - Peter C Ruben
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada.
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14
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Huang L, Wu KH, Zhang L, Wang Q, Tang S, Wu Q, Jiang PH, Lin JJC, Guo J, Wang L, Loh SH, Cheng J. Critical Roles of Xirp Proteins in Cardiac Conduction and Their Rare Variants Identified in Sudden Unexplained Nocturnal Death Syndrome and Brugada Syndrome in Chinese Han Population. J Am Heart Assoc 2018; 7:e006320. [PMID: 29306897 PMCID: PMC5778954 DOI: 10.1161/jaha.117.006320] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2017] [Accepted: 11/16/2017] [Indexed: 12/24/2022]
Abstract
BACKGROUND Sudden unexplained nocturnal death syndrome (SUNDS) remains an autopsy negative entity with unclear etiology. Arrhythmia has been implicated in SUNDS. Mutations/deficiencies in intercalated disc components have been shown to cause arrhythmias. Human cardiomyopathy-associated 1 (XIRP1) and 3 (XIRP2) are intercalated disc-associated, Xin repeats-containing proteins. Mouse Xirp1 is necessary for the integrity of intercalated disc and for the surface expression of transient outward and delayed rectifier K+ channels, whereas mouse Xirp2 is required for Xirp1 intercalated disc localization. Thus, XIRP1 and XIRP2 may be potentially causal genes for SUNDS. METHODS AND RESULTS We genetically screened XIRP genes in 134 sporadic SUNDS victims and 22 Brugada syndrome (BrS) cases in a Chinese Han population. We identified 16 rare variants (6 were in silico predicted as deleterious) in SUNDS victims, including a novel variant, XIRP2-E215K. There were also four rare variants (2 were in silico predicted as deleterious) detected in BrS cases, including a novel variant, XIRP2-L2718P. Interestingly, among these 20 variants, we detected 2 likely pathogenic variants: a nonsense variant (XIRP2-Q2875*) and a frameshift variant (XIRP2-T2238QfsX7). Analyzing available Xirp2 knockout mice, we further found that mouse hearts without Xirp2 exhibited prolonged PR and QT intervals, slow conduction velocity, atrioventricular conduction block, and an abnormal infranodal ventricular conduction system. Whole-cell patch-clamp detected altered ionic currents in Xirp2-/- cardiomyocytes, consistent with the observed association between Xirp2 and Nav1.5/Kv1.5 in co-immunoprecipitation. CONCLUSIONS This is the first report identifying likely pathogenic XIRP rare variants in arrhythmogenic disorders such as SUNDS and Brugada syndrome, and showing critical roles of Xirp2 in cardiac conduction.
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Affiliation(s)
- Lei Huang
- Department of Forensic Pathology, Zhongshan School of Medicine Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Kuo-Ho Wu
- Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei, Taiwan
- Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan
- Institute of Physiology, National Defense Medical Center, Taipei, Taiwan
- Institute of Pharmacology, National Defense Medical Center, Taipei, Taiwan
| | - Liyong Zhang
- Department of Forensic Pathology, Zhongshan School of Medicine Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Qinchuan Wang
- Department of Biology, University of Iowa, Iowa City, IA
| | - Shuangbo Tang
- Department of Forensic Pathology, Zhongshan School of Medicine Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Qiuping Wu
- Department of Forensic Pathology, Zhongshan School of Medicine Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Pei-Hsiu Jiang
- Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan
- Institute of Physiology, National Defense Medical Center, Taipei, Taiwan
| | | | - Jian Guo
- BGI-Shenzhen, Shenzhen, Guangdong, China
- China National GeneBank BGI-Shenzhen, Shenzhen, Guangdong, China
| | - Lin Wang
- BGI-Shenzhen, Shenzhen, Guangdong, China
- China National GeneBank BGI-Shenzhen, Shenzhen, Guangdong, China
| | - Shih-Hurng Loh
- Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei, Taiwan
- Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan
- Institute of Pharmacology, National Defense Medical Center, Taipei, Taiwan
| | - Jianding Cheng
- Department of Forensic Pathology, Zhongshan School of Medicine Sun Yat-sen University, Guangzhou, Guangdong, China
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15
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Selga E, Sendfeld F, Martinez-Moreno R, Medine CN, Tura-Ceide O, Wilmut SI, Pérez GJ, Scornik FS, Brugada R, Mills NL. Sodium channel current loss of function in induced pluripotent stem cell-derived cardiomyocytes from a Brugada syndrome patient. J Mol Cell Cardiol 2018; 114:10-19. [PMID: 29024690 PMCID: PMC5807028 DOI: 10.1016/j.yjmcc.2017.10.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Revised: 09/15/2017] [Accepted: 10/04/2017] [Indexed: 12/24/2022]
Abstract
Brugada syndrome predisposes to sudden death due to disruption of normal cardiac ion channel function, yet our understanding of the underlying cellular mechanisms is incomplete. Commonly used heterologous expression models lack many characteristics of native cardiomyocytes and, in particular, the individual genetic background of a patient. Patient-specific induced pluripotent stem (iPS) cell-derived cardiomyocytes (iPS-CM) may uncover cellular phenotypical characteristics not observed in heterologous models. Our objective was to determine the properties of the sodium current in iPS-CM with a mutation in SCN5A associated with Brugada syndrome. Dermal fibroblasts from a Brugada syndrome patient with a mutation in SCN5A (c.1100G>A, leading to Nav1.5_p.R367H) were reprogrammed to iPS cells. Clones were characterized and differentiated to form beating clusters and sheets. Patient and control iPS-CM were structurally indistinguishable. Sodium current properties of patient and control iPS-CM were compared. These results were contrasted with those obtained in tsA201 cells heterologously expressing sodium channels with the same mutation. Patient-derived iPS-CM showed a 33.1-45.5% reduction in INa density, a shift in both activation and inactivation voltage-dependence curves, and faster recovery from inactivation. Co-expression of wild-type and mutant channels in tsA201 cells did not compromise channel trafficking to the membrane, but resulted in a reduction of 49.8% in sodium current density without affecting any other parameters. Cardiomyocytes derived from iPS cells from a Brugada syndrome patient with a mutation in SCN5A recapitulate the loss of function of sodium channel current associated with this syndrome; including pro-arrhythmic changes in channel function not detected using conventional heterologous expression systems.
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Affiliation(s)
- Elisabet Selga
- Cardiovascular Genetics Centre, Department of Medical Sciences, University of Girona, Girona, Spain; Institut d'Investigació Biomèdica de Girona (IDIBGI), Girona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Spain
| | - Franziska Sendfeld
- Scottish Centre for Regenerative Medicine, University of Edinburgh, United Kingdom; BHF/University Centre for Cardiovascular Sciences, University of Edinburgh, United Kingdom
| | - Rebecca Martinez-Moreno
- Cardiovascular Genetics Centre, Department of Medical Sciences, University of Girona, Girona, Spain; Institut d'Investigació Biomèdica de Girona (IDIBGI), Girona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Spain
| | - Claire N Medine
- Scottish Centre for Regenerative Medicine, University of Edinburgh, United Kingdom; BHF/University Centre for Cardiovascular Sciences, University of Edinburgh, United Kingdom
| | - Olga Tura-Ceide
- Department of Pulmonary Medicine, Hospital Clinic-Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Respiratorias, University of Barcelona, Spain
| | - Sir Ian Wilmut
- Scottish Centre for Regenerative Medicine, University of Edinburgh, United Kingdom
| | - Guillermo J Pérez
- Cardiovascular Genetics Centre, Department of Medical Sciences, University of Girona, Girona, Spain; Institut d'Investigació Biomèdica de Girona (IDIBGI), Girona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Spain
| | - Fabiana S Scornik
- Cardiovascular Genetics Centre, Department of Medical Sciences, University of Girona, Girona, Spain; Institut d'Investigació Biomèdica de Girona (IDIBGI), Girona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Spain
| | - Ramon Brugada
- Cardiovascular Genetics Centre, Department of Medical Sciences, University of Girona, Girona, Spain; Institut d'Investigació Biomèdica de Girona (IDIBGI), Girona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Spain; Hospital Josep Trueta, Girona, Spain
| | - Nicholas L Mills
- BHF/University Centre for Cardiovascular Sciences, University of Edinburgh, United Kingdom.
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16
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Miller DC, Harmer SC, Poliandri A, Nobles M, Edwards EC, Ware JS, Sharp TV, McKay TR, Dunkel L, Lambiase PD, Tinker A. Ajmaline blocks I Na and I Kr without eliciting differences between Brugada syndrome patient and control human pluripotent stem cell-derived cardiac clusters. Stem Cell Res 2017; 25:233-244. [PMID: 29172153 PMCID: PMC5727153 DOI: 10.1016/j.scr.2017.11.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 10/09/2017] [Accepted: 11/03/2017] [Indexed: 12/14/2022] Open
Abstract
The class Ia anti-arrhythmic drug ajmaline is used clinically to unmask latent type I ECG in Brugada syndrome (BrS) patients, although its mode of action is poorly characterised. Our aims were to identify ajmaline's mode of action in human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (CMs), and establish a simple BrS hiPSC platform to test whether differences in ajmaline response could be determined between BrS patients and controls. Control hiPSCs were differentiated into spontaneously contracting cardiac clusters. It was found using multi electrode array (MEA) that ajmaline treatment significantly lengthened cluster activation-recovery interval. Patch clamping of single CMs isolated from clusters revealed that ajmaline can block both INa and IKr. Following generation of hiPSC lines from BrS patients (absent of pathogenic SCN5A sodium channel mutations), analysis of hiPSC-CMs from patients and controls revealed that differentiation and action potential parameters were similar. Comparison of cardiac clusters by MEA showed that ajmaline lengthened activation-recovery interval consistently across all lines. We conclude that ajmaline can block both depolarisation and repolarisation of hiPSC-CMs at the cellular level, but that a more refined integrated tissue model may be necessary to elicit differences in its effect between BrS patients and controls. hiPSC lines generated and differentiated from BrS patients lacking SCN5A mutations Ajmaline lengthens the activation-recovery interval of hPSC cardiac clusters Ajmaline effect consistent between BrS patient and control hPSC cardiac clusters Patch clamp analysis of hiPSC-CMs reveals ajmaline blocks both INa and IKr
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Affiliation(s)
- Duncan C Miller
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK; Barts Cancer Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Stephen C Harmer
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Ariel Poliandri
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Muriel Nobles
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Elizabeth C Edwards
- National Heart and Lung Institute, NIHR Royal Brompton Cardiovascular BRU, Imperial College London, London, UK
| | - James S Ware
- National Heart and Lung Institute, NIHR Royal Brompton Cardiovascular BRU, Imperial College London, London, UK
| | - Tyson V Sharp
- Barts Cancer Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Tristan R McKay
- School of Healthcare Science, Manchester Metropolitan University, Manchester, UK
| | - Leo Dunkel
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Pier D Lambiase
- Institute of Cardiovascular Science, UCL and Barts Heart Centre, London, UK
| | - Andrew Tinker
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK.
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17
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Corrado D, Zorzi A, Cerrone M, Rigato I, Mongillo M, Bauce B, Delmar M. Relationship Between Arrhythmogenic Right Ventricular Cardiomyopathy and Brugada Syndrome: New Insights From Molecular Biology and Clinical Implications. Circ Arrhythm Electrophysiol 2016; 9:e003631. [PMID: 26987567 PMCID: PMC4800833 DOI: 10.1161/circep.115.003631] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Domenico Corrado
- From the Departments of Cardiac, Thoracic, and Vascular Sciences (D.C., A.Z., I.R., B.B.) and Biomedical Sciences (M.M.), University of Padua, Padova, Italy; and The Leon H. Charney Division of Cardiology, New York University School of Medicine (M.C., M.D.).
| | - Alessandro Zorzi
- From the Departments of Cardiac, Thoracic, and Vascular Sciences (D.C., A.Z., I.R., B.B.) and Biomedical Sciences (M.M.), University of Padua, Padova, Italy; and The Leon H. Charney Division of Cardiology, New York University School of Medicine (M.C., M.D.)
| | - Marina Cerrone
- From the Departments of Cardiac, Thoracic, and Vascular Sciences (D.C., A.Z., I.R., B.B.) and Biomedical Sciences (M.M.), University of Padua, Padova, Italy; and The Leon H. Charney Division of Cardiology, New York University School of Medicine (M.C., M.D.)
| | - Ilaria Rigato
- From the Departments of Cardiac, Thoracic, and Vascular Sciences (D.C., A.Z., I.R., B.B.) and Biomedical Sciences (M.M.), University of Padua, Padova, Italy; and The Leon H. Charney Division of Cardiology, New York University School of Medicine (M.C., M.D.)
| | - Marco Mongillo
- From the Departments of Cardiac, Thoracic, and Vascular Sciences (D.C., A.Z., I.R., B.B.) and Biomedical Sciences (M.M.), University of Padua, Padova, Italy; and The Leon H. Charney Division of Cardiology, New York University School of Medicine (M.C., M.D.)
| | - Barbara Bauce
- From the Departments of Cardiac, Thoracic, and Vascular Sciences (D.C., A.Z., I.R., B.B.) and Biomedical Sciences (M.M.), University of Padua, Padova, Italy; and The Leon H. Charney Division of Cardiology, New York University School of Medicine (M.C., M.D.)
| | - Mario Delmar
- From the Departments of Cardiac, Thoracic, and Vascular Sciences (D.C., A.Z., I.R., B.B.) and Biomedical Sciences (M.M.), University of Padua, Padova, Italy; and The Leon H. Charney Division of Cardiology, New York University School of Medicine (M.C., M.D.)
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18
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Sottas V, Abriel H. Negative-dominance phenomenon with genetic variants of the cardiac sodium channel Nav1.5. Biochim Biophys Acta 2016; 1863:1791-8. [PMID: 26907222 DOI: 10.1016/j.bbamcr.2016.02.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 02/15/2016] [Accepted: 02/19/2016] [Indexed: 02/07/2023]
Abstract
During the past two decades, many pathological genetic variants in SCN5A, the gene encoding the pore-forming subunit of the cardiac (monomeric) sodium channel Na(v)1.5, have been described. Negative dominance is a classical genetic concept involving a "poison" mutant peptide that negatively interferes with the co-expressed wild-type protein, thus reducing its cellular function. This phenomenon has been described for genetic variants of multimeric K(+) channels, which mechanisms are well understood. Unexpectedly, several pathologic SCN5A variants that are linked to Brugada syndrome also demonstrate such a dominant-negative (DN) effect. The molecular determinants of these observations, however, are not yet elucidated. This review article summarizes recent findings that describe the mechanisms underlying the DN phenomenon of genetic variants of K(+), Ca(2+), Cl(-) and Na(+) channels, and in particular Brugada syndrome variants of Na(v)1.5. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Integration of Developmental and Environmental Cues in the Heart edited by Marcus Schaub and Hughes Abriel.
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Affiliation(s)
- Valentin Sottas
- Department of Clinical Research, Ion Channel Research Group, University of Bern, Switzerland
| | - Hugues Abriel
- Department of Clinical Research, Ion Channel Research Group, University of Bern, Switzerland.
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Kim KH, Rosen A, Hussein SMI, Puviindran V, Korogyi AS, Chiarello C, Nagy A, Hui CC, Backx PH. Irx3 is required for postnatal maturation of the mouse ventricular conduction system. Sci Rep 2016; 6:19197. [PMID: 26786475 PMCID: PMC4726432 DOI: 10.1038/srep19197] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Accepted: 12/07/2015] [Indexed: 12/17/2022] Open
Abstract
The ventricular conduction system (VCS) orchestrates the harmonious contraction in every heartbeat. Defects in the VCS are often associated with life-threatening arrhythmias and also promote adverse remodeling in heart disease. We have previously established that the Irx3 homeobox gene regulates rapid electrical propagation in the VCS by modulating the transcription of gap junction proteins Cx40 and Cx43. However, it is unknown whether other factors contribute to the conduction defects observed in Irx3 knockout (Irx3(-/-)) mice. In this study, we show that during the early postnatal period, Irx3(-/-) mice develop morphological defects in the VCS which are temporally dissociated from changes in gap junction expression. These morphological defects were accompanied with progressive changes in the cardiac electrocardiogram including right bundle branch block. Hypoplastic VCS was not associated with increased apoptosis of VCS cardiomyocytes but with a lack of recruitment and maturation of ventricular cardiomyocytes into the VCS. Computational analysis followed by functional verification revealed that Irx3 promotes VCS-enriched transcripts targeted by Nkx2.5 and/or Tbx5. Altogether, these results indicate that, in addition to ensuring the appropriate expression of gap junctional channels in the VCS, Irx3 is necessary for the postnatal maturation of the VCS, possibly via its interactions with Tbx5 and Nkx2.5.
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Affiliation(s)
- Kyoung-Han Kim
- Program in Developmental & Stem Cell Biology, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - Anna Rosen
- The Heart and Stroke Richard Lewar Centre of Excellence, University of Toronto, Toronto, ON M5S 3E2, Canada
- Departments of Physiology and Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Samer M. I. Hussein
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario M5G 1X5, Canada
- Centre Hospitalier Universitaire de Québec Research Center and Faculty of Medicine, Laval University, Quebec City, QC G1V 4G2, Canada
| | - Vijitha Puviindran
- Program in Developmental & Stem Cell Biology, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - Adam S. Korogyi
- The Heart and Stroke Richard Lewar Centre of Excellence, University of Toronto, Toronto, ON M5S 3E2, Canada
- Departments of Physiology and Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Carmelina Chiarello
- The Heart and Stroke Richard Lewar Centre of Excellence, University of Toronto, Toronto, ON M5S 3E2, Canada
- Departments of Physiology and Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Andras Nagy
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario M5G 1X5, Canada
- Institute of Medical Science and Department of Obstetrics and Gynaecology, University of Toronto, Toronto, Ontario M5T 3H7, Canada
| | - Chi-chung Hui
- Program in Developmental & Stem Cell Biology, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Peter H. Backx
- The Heart and Stroke Richard Lewar Centre of Excellence, University of Toronto, Toronto, ON M5S 3E2, Canada
- Departments of Physiology and Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
- Peter Munk Cardiac Centre and Division of Cardiology, University Health Network, Toronto ON
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Takahashi K, Sasano T, Sugiyama K, Kurokawa J, Tamura N, Soejima Y, Sawabe M, Isobe M, Furukawa T. High-fat diet increases vulnerability to atrial arrhythmia by conduction disturbance via miR-27b. J Mol Cell Cardiol 2016; 90:38-46. [PMID: 26654778 DOI: 10.1016/j.yjmcc.2015.11.034] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Revised: 11/07/2015] [Accepted: 11/30/2015] [Indexed: 02/02/2023]
Abstract
BACKGROUND Lifestyle-related diseases, such as obesity and dyslipidemia are important risk factors for atrial fibrillation (AF). However, the underlying mechanism linking these diseases and AF has not been fully investigated. METHODS Adult male mice were fed a high-fat diet (HFD) or vehicle (NC) for 2 months. Electrocardiography and in vivo electrophysiological study were performed. Mice were then sacrificed for quantification of mRNA, microRNA, and protein in atria, in addition to histological analysis. Conduction velocity (CV) in right atrium was measured by optical mapping in Langendorff perfused hearts. Cultured atrial cardiomyocytes were treated with palmitate with or without a specific microRNA inhibitor. Twelve hours after stimulation, cells were lysed, and subjected to analysis with qPCR and Western blotting. RESULTS HFD mice showed prolonged P wave duration, increased inducibility of sustained atrial tachycardia, and reduced atrial CV than NC mice. HFD mice also showed increased expression in inflammatory cytokines, whereas fibrotic area and signals relating fibrosis were not changed. HFD mice demonstrated reduced expression of Cx40 in mRNA and protein levels, and its lateralized expression in atria. MicroRNA array analysis revealed that miR-27b expression was up-regulated in HFD mice, and luciferase assay confirmed the direct interaction between miR-27b and Cx40 3'UTR. In palmitate-stimulated atrial cardiomyocytes, miR-27b up-regulation and Cx40 down-regulation were observed, while expression of inflammatory cytokines was not altered. Inhibition of miR-27b with antisense oligonucleotides reversed the alteration caused by palmitate stimulation. CONCLUSION HFD may increase the vulnerability to atrial arrhythmia by down-regulation of Cx40 via miR-27b, rather than fibrosis, which is independent of inflammation.
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Affiliation(s)
- Kentaro Takahashi
- Department of Cardiovascular Medicine, Tokyo Medical and Dental University School of Medicine, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Tetsuo Sasano
- Department of Biofunctional Informatics, Tokyo Medical and Dental University School of Health Care Sciences, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan.
| | - Koji Sugiyama
- Department of Cardiovascular Medicine, Tokyo Medical and Dental University School of Medicine, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Junko Kurokawa
- Department of Bio-informational Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Noriko Tamura
- Department of Cardiovascular Medicine, Tokyo Medical and Dental University School of Medicine, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Yurie Soejima
- Department of Molecular Pathology, Tokyo Medical and Dental University School of Health Care Sciences, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Motoji Sawabe
- Department of Molecular Pathology, Tokyo Medical and Dental University School of Health Care Sciences, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Mitsuaki Isobe
- Department of Cardiovascular Medicine, Tokyo Medical and Dental University School of Medicine, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Tetsushi Furukawa
- Department of Bio-informational Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
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Zeng Z, Zhou J, Hou Y, Liang X, Zhang Z, Xu X, Xie Q, Li W, Huang Z. Electrophysiological characteristics of a SCN5A voltage sensors mutation R1629Q associated with Brugada syndrome. PLoS One 2013; 8:e78382. [PMID: 24167619 PMCID: PMC3805610 DOI: 10.1371/journal.pone.0078382] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Accepted: 09/14/2013] [Indexed: 12/18/2022] Open
Abstract
Brugada syndrome (BrS) is an inherited arrhythmogenic syndrome leading to sudden cardiac death, partially associated with autosomal dominant mutations in SCN5A, which encodes the cardiac sodium channel alpha-subunit (Nav1.5). To date some SCN5A mutations related with BrS have been identified in voltage sensor of Nav1.5. Here, we describe a dominant missense mutation (R1629Q) localized in the fourth segment of domain IV region (DIV-S4) in a Chinese Han family. The mutation was identified by direct sequencing of SCN5A from the proband's DNA. Co-expression of Wild-type (WT) or R1629Q Nav1.5 channel and hβ1 subunit were achieved in human embryonic kidney cells by transient transfection. Sodium currents were recorded using whole cell patch-clamp protocols. No significant changes between WT and R1629Q currents were observed in current density or steady-state activation. However, hyperpolarized shift of steady-state inactivation curve was identified in cells expressing R1629Q channel (WT: V1/2 = -81.1 ± 1.3 mV, n = 13; R1629Q: V1/2 = -101.7 ± 1.2 mV, n = 18). Moreover, R1629Q channel showed enhanced intermediate inactivation and prolonged recovery time from inactivation. In summary, this study reveals that R1629Q mutation causes a distinct loss-of-function of the channel due to alter its electrophysiological characteristics, and facilitates our understanding of biophysical mechanisms of BrS.
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Affiliation(s)
- Zhipeng Zeng
- Department of Cardiology, the First Affiliated Hospital of Xiamen University, Xiamen, China
| | - Jieqiong Zhou
- Department of Cardiology, the First Affiliated Hospital of Xiamen University, Xiamen, China
| | - Yuxi Hou
- Department of Cardiology, the First Affiliated Hospital of Xiamen University, Xiamen, China
| | - Xiaojing Liang
- Department of Cardiology, the First Affiliated Hospital of Xiamen University, Xiamen, China
| | - Ziguan Zhang
- Department of Cardiology, the First Affiliated Hospital of Xiamen University, Xiamen, China
| | - Xuejing Xu
- Department of Cardiology, the First Affiliated Hospital of Xiamen University, Xiamen, China
| | - Qiang Xie
- Department of Cardiology, the First Affiliated Hospital of Xiamen University, Xiamen, China
| | - Weihua Li
- Department of Cardiology, the First Affiliated Hospital of Xiamen University, Xiamen, China
- * E-mail: (ZH); (WL)
| | - Zhengrong Huang
- Department of Cardiology, the First Affiliated Hospital of Xiamen University, Xiamen, China
- * E-mail: (ZH); (WL)
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Hennessey JA, Marcou CA, Wang C, Wei EQ, Wang C, Tester DJ, Torchio M, Dagradi F, Crotti L, Schwartz PJ, Ackerman MJ, Pitt GS. FGF12 is a candidate Brugada syndrome locus. Heart Rhythm 2013; 10:1886-94. [PMID: 24096171 DOI: 10.1016/j.hrthm.2013.09.064] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Indexed: 02/06/2023]
Abstract
BACKGROUND Less than 30% of the cases of Brugada syndrome (BrS) have an identified genetic cause. Of the known BrS-susceptibility genes, loss-of-function mutations in SCN5A or CACNA1C and their auxiliary subunits are most common. On the basis of the recent demonstration that fibroblast growth factor (FGF) homologous factors (FHFs; FGF11-FGF14) regulate cardiac Na(+) and Ca(2+) channel currents, we hypothesized that FHFs are candidate BrS loci. OBJECTIVE The goal of this study was to test whether FGF12 is a candidate BrS locus. METHODS We used quantitative polymerase chain reaction to identify the major FHF expressed in the human ventricle and then queried a phenotype-positive, genotype-negative BrS biorepository for FHF mutations associated with BrS. We queried the effects of an identified mutant with biochemical analyses combined with electrophysiological assessment. We designed a novel rat ventricular cardiomyocyte system in which we swapped the endogenous FHF with the identified mutant and defined its effects on multiple ionic currents in their native milieu and on the cardiac action potential. RESULTS We identified FGF12 as the major FHF expressed in the human ventricle. In 102 individuals in the biorepository, we identified a single missense mutation in FGF12-B (Q7R-FGF12). The mutant reduced binding to the NaV1.5 C terminus, but not to junctophilin-2. In adult rat cardiac myocytes, Q7R-FGF12, but not wild-type FGF12, reduced Na(+) channel current density and availability without affecting Ca(2+) channel function. Furthermore, the mutant, but not wild-type FGF12, reduced action potential amplitude, which is consistent with a mutant-induced loss of Na(+) channel function. CONCLUSIONS These multilevel investigations strongly suggest that Q7R-FGF12 is a disease-associated BrS mutation. Moreover, these data suggest for the first time that FHF effects on Na(+) and Ca(2+) channels are separable. Most significantly, this study establishes a new method to analyze effects of human arrhythmogenic mutations on cardiac ionic currents.
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Affiliation(s)
- Jessica A Hennessey
- Departments of Medicine/Cardiology and Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina
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Zumhagen S, Veldkamp MW, Stallmeyer B, Baartscheer A, Eckardt L, Paul M, Remme CA, Bhuiyan ZA, Bezzina CR, Schulze-Bahr E. A heterozygous deletion mutation in the cardiac sodium channel gene SCN5A with loss- and gain-of-function characteristics manifests as isolated conduction disease, without signs of Brugada or long QT syndrome. PLoS One 2013; 8:e67963. [PMID: 23840796 PMCID: PMC3695936 DOI: 10.1371/journal.pone.0067963] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 05/23/2013] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND The SCN5A gene encodes for the α-subunit of the cardiac sodium channel NaV1.5, which is responsible for the rapid upstroke of the cardiac action potential. Mutations in this gene may lead to multiple life-threatening disorders of cardiac rhythm or are linked to structural cardiac defects. Here, we characterized a large family with a mutation in SCN5A presenting with an atrioventricular conduction disease and absence of Brugada syndrome. METHOD AND RESULTS In a large family with a high incidence of sudden cardiac deaths, a heterozygous SCN5A mutation (p.1493delK) with an autosomal dominant inheritance has been identified. Mutation carriers were devoid of any cardiac structural changes. Typical ECG findings were an increased P-wave duration, an AV-block I° and a prolonged QRS duration with an intraventricular conduction delay and no signs for Brugada syndrome. HEK293 cells transfected with 1493delK showed strongly (5-fold) reduced Na(+) currents with altered inactivation kinetics compared to wild-type channels. Immunocytochemical staining demonstrated strongly decreased expression of SCN5A 1493delK in the sarcolemma consistent with an intracellular trafficking defect and thereby a loss-of-function. In addition, SCN5A 1493delK channels that reached cell membrane showed gain-of-function aspects (slowing of the fast inactivation, reduction in the relative fraction of channels that fast inactivate, hastening of the recovery from inactivation). CONCLUSION In a large family, congregation of a heterozygous SCN5A gene mutation (p.1493delK) predisposes for conduction slowing without evidence for Brugada syndrome due to a predominantly trafficking defect that reduces Na(+) current and depolarization force.
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Affiliation(s)
- Sven Zumhagen
- Institute for Genetics of Heart Diseases, Department of Cardiovascular Medicine, University Hospital Münster, Münster, Germany.
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Zakliaz'minskaia EV, Shestak AG, Revishvili AS, Pronicheva IV, Podoliak DG, Nechaenko MA, Poliakov AV, Dzemeshkevich SL. [Clinic and genetic polymorphism of Brugada syndrome in Russian patients, caused by mutation in SCN5A gene]. Khirurgiia (Mosk) 2013:49-53. [PMID: 23503384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Brugada syndrome (BrS) is an inherited cardiac arrhythmic disorder, characterized by ST-segment elevation in right precordial leads V1-V2>2 mm, pseudo right bundle branch block (RBBB), T-wave inversion and an increased risk of cardiac sudden death (SCD) due to molymorphic VT. It is estimated to be responsible for 12% of SCD cases and about 20% of deaths in patients with structurally normal hearts in autopsy. Mutations in the SCN5A gene account 15-30% of all cases. Clinical, instrumental and genetic analyses were performed for 25 Russian probands with BrS (19 males and 6 female). Phenotype-genotype correlation was studied in SCN5A-positive and SCN5A-negative patients. Rare genetic variants in SCN5A gene were found in 7 of 21 Russian probands (28%). Two variants affect protein splicing (c.IVS16DS-5A>G and c.IVS24AS+1G>A), three missense mutations (p,Y87C, p.R893H and p.S1787N), one in-frame deletion p.del848l, and one non-sense-mutation p.E553X. All mutations were unique for each family. There were no clinical or instrumental parameters were found to be effective in prediction of SCN5A mutations. The protocols of genetic counceling for SCN5A-positive and SCN5A-negative families were established.
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Mercier A, Clément R, Harnois T, Bourmeyster N, Faivre JF, Findlay I, Chahine M, Bois P, Chatelier A. The β1-subunit of Na(v)1.5 cardiac sodium channel is required for a dominant negative effect through α-α interaction. PLoS One 2012; 7:e48690. [PMID: 23133651 PMCID: PMC3486797 DOI: 10.1371/journal.pone.0048690] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Accepted: 10/01/2012] [Indexed: 12/03/2022] Open
Abstract
Brugada syndrome (BrS) is an inherited autosomal dominant cardiac channelopathy. Several mutations on the cardiac sodium channel Nav1.5 which are responsible for BrS lead to misfolded proteins that do not traffic properly to the plasma membrane. In order to mimic patient heterozygosity, a trafficking defective mutant, R1432G was co-expressed with Wild Type (WT) Nav1.5 channels in HEK293T cells. This mutant significantly decreased the membrane Na current density when it was co-transfected with the WT channel. This dominant negative effect did not result in altered biophysical properties of Nav1.5 channels. Luminometric experiments revealed that the expression of mutant proteins induced a significant reduction in membrane expression of WT channels. Interestingly, we have found that the auxiliary Na channel β1-subunit was essential for this dominant negative effect. Indeed, the absence of the β1-subunit prevented the decrease in WT sodium current density and surface proteins associated with the dominant negative effect. Co-immunoprecipitation experiments demonstrated a physical interaction between Na channel α-subunits. This interaction occurred only when the β1-subunit was present. Our findings reveal a new role for β1-subunits in cardiac voltage-gated sodium channels by promoting α-α subunit interaction which can lead to a dominant negative effect when one of the α-subunits shows a trafficking defective mutation.
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Affiliation(s)
- Aurélie Mercier
- Institut de Physiologie et Biologie Cellulaires, FRE 3511, CNRS/Université de Poitiers, Pôle Biologie Santé, Poitiers, France
| | - Romain Clément
- Institut de Physiologie et Biologie Cellulaires, FRE 3511, CNRS/Université de Poitiers, Pôle Biologie Santé, Poitiers, France
| | - Thomas Harnois
- Institut de Physiologie et Biologie Cellulaires, FRE 3511, CNRS/Université de Poitiers, Pôle Biologie Santé, Poitiers, France
- CHU de Poitiers, Poitiers, France
| | - Nicolas Bourmeyster
- Institut de Physiologie et Biologie Cellulaires, FRE 3511, CNRS/Université de Poitiers, Pôle Biologie Santé, Poitiers, France
- CHU de Poitiers, Poitiers, France
| | - Jean-François Faivre
- Institut de Physiologie et Biologie Cellulaires, FRE 3511, CNRS/Université de Poitiers, Pôle Biologie Santé, Poitiers, France
| | - Ian Findlay
- Institut de Physiologie et Biologie Cellulaires, FRE 3511, CNRS/Université de Poitiers, Pôle Biologie Santé, Poitiers, France
- Laboratoire de Physiologie des Cellules Cardiaques et Vasculaires, Institut de Physiologie et Biologie Cellulaires, FRE 3511 CNRS, Université François-Rabelais, Faculté des Sciences, Tours, France
| | - Mohamed Chahine
- Institut universitaire en santé mentale de Québec, Université Laval, Québec, Québec, Canada
| | - Patrick Bois
- Institut de Physiologie et Biologie Cellulaires, FRE 3511, CNRS/Université de Poitiers, Pôle Biologie Santé, Poitiers, France
| | - Aurélien Chatelier
- Institut de Physiologie et Biologie Cellulaires, FRE 3511, CNRS/Université de Poitiers, Pôle Biologie Santé, Poitiers, France
- * E-mail:
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Abstract
The Brugada Syndrome (BS) is a "channellopathy," characterized by ion (e.g., sodium, calcium, and potassium) channel dysfunction and typical ECG alterations, originally described by Osher and Wolff in 1953 and further elucidated by Josep and Pedro Brugada in 1991. BS is typically associated with a high risk for sudden cardiac death (SCD) in young and otherwise healthy adults. Although in several patients the heart is structurally normal, subtle structural abnormalities in the right ventricular outflow tract are increasingly been reported. The worldwide prevalence of this disorder is still uncertain, and there are some significant regional differences. The syndrome is characterized by a strong genetic basis, and several mutations have been identified in genes encoding subunits of cardiac sodium, potassium, and calcium channels, as well as in genes involved in the trafficking or regulation of these channels. Accordingly, eight types of BS (from BS1 to BS8) have already been described, involving mutations in SCN5A, GPD1-L, CACNA1c, CACNB2b, SCN1B, KCNE3, SCN3B, and HCN4 genes. The vast majority (i.e., up to two-third) of BS patients is asymptomatic, whereas the leading clinical manifestation is polymorphic ventricular tachycardia that can degenerate into ventricular fibrillation (VF) and SCD. The diagnosis is still challenging, and ECG abnormalities represent one component of the diagnostic criteria which also include clinical and demographic data. Although molecular genetic testing is effective in detecting mutations in 20-38% of BS patients, it represents an appealing option for stratifying the risk of adverse events as well as for prenatal testing.
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MESH Headings
- Adult
- Brugada Syndrome/complications
- Brugada Syndrome/genetics
- Brugada Syndrome/metabolism
- Brugada Syndrome/physiopathology
- Death, Sudden, Cardiac/etiology
- Death, Sudden, Cardiac/prevention & control
- Electrocardiography
- Genetic Testing
- Heart Ventricles/metabolism
- Heart Ventricles/physiopathology
- Humans
- Mutation
- Potassium Channels/genetics
- Risk Factors
- Sodium Channels/genetics
- Tachycardia, Ventricular/complications
- Tachycardia, Ventricular/genetics
- Tachycardia, Ventricular/metabolism
- Tachycardia, Ventricular/physiopathology
- Ventricular Dysfunction, Right/complications
- Ventricular Dysfunction, Right/genetics
- Ventricular Dysfunction, Right/metabolism
- Ventricular Dysfunction, Right/physiopathology
- Ventricular Fibrillation/complications
- Ventricular Fibrillation/genetics
- Ventricular Fibrillation/metabolism
- Ventricular Fibrillation/physiopathology
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Affiliation(s)
- Giuseppe Lippi
- U.O. Diagnostica Ematochimica, Dipartimento di Patologia e Medicina di Laboratorio, Azienda Ospedaliero-Universitaria di Parma, Parma, Italy.
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Giudicessi JR, Ye D, Tester DJ, Crotti L, Mugione A, Nesterenko VV, Albertson RM, Antzelevitch C, Schwartz PJ, Ackerman MJ. Transient outward current (I(to)) gain-of-function mutations in the KCND3-encoded Kv4.3 potassium channel and Brugada syndrome. Heart Rhythm 2011; 8:1024-32. [PMID: 21349352 DOI: 10.1016/j.hrthm.2011.02.021] [Citation(s) in RCA: 188] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Accepted: 02/15/2011] [Indexed: 11/18/2022]
Abstract
BACKGROUND Brugada syndrome (BrS) is a sudden death-predisposing genetic condition characterized electrocardiographically by ST segment elevation in the leads V(1)-V(3). Given the prominent role of the transient outward current (I(to)) in BrS pathogenesis, we hypothesized that rare gain-of-function mutations in KCND3 may serve as a pathogenic substrate for BrS. METHODS Comprehensive mutational analysis of KCND3-encoded Kv4.3 (I(to)) was conducted using polymerase chain reaction, denaturing high performance liquid chromatography, and direct sequencing of DNA derived from 86 unrelated BrS1-8 genotype-negative BrS patients. DNA from 780 healthy individuals was examined to assess allelic frequency for nonsynonymous variants. Putative BrS-associated Kv4.3 mutations were engineered and coexpressed with wild-type KChIP2 in HEK293 cells. Wild-type and mutant I(to) ion currents were recorded using whole-cell patch clamp. RESULTS Two BrS1-8 genotype-negative cases possessed novel Kv4.3 missense mutations. Both Kv4.3-L450F and Kv4.3-G600R were absent in 1,560 reference alleles and involved residues highly conserved across species. Both Kv4.3-L450F and Kv4.3-G600R demonstrated a gain-of-function phenotype, increasing peak I(to) current density by 146.2% (n = 15, P <.05) and 50.4% (n = 15, P <.05), respectively. Simulations using a Luo-Rudy II action potential (AP) model demonstrated the stable loss of the AP dome as a result of the increased I(to) maximal conductance associated with the heterozygous expression of either L450F or G600R. CONCLUSIONS These findings provide the first molecular and functional evidence implicating novel KCND3 gain-of-function mutations in the pathogenesis and phenotypic expression of BrS, with the potential for a lethal arrhythmia being precipitated by a genetically enhanced I(to) current gradient within the right ventricle where KCND3 expression is the highest.
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Affiliation(s)
- John R Giudicessi
- Department of Medicine (Division of Cardiovascular Diseases), Department of Pediatrics (Division of Pediatric Cardiology), and Department of Molecular Pharmacology and Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minnesota, USA.
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Jeevaratnam K, Zhang Y, Guzadhur L, Duehmke RM, Lei M, Grace AA, Huang CLH. Differences in sino-atrial and atrio-ventricular function with age and sex attributable to the Scn5a+/- mutation in a murine cardiac model. Acta Physiol (Oxf) 2010; 200:23-33. [PMID: 20331542 DOI: 10.1111/j.1748-1716.2010.02110.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIM To investigate the interacting effects of age and sex on electrocardiographic (ECG) features of Scn5a(+/-) mice modelling Brugada syndrome. METHODS Recordings were performed on anaesthetized wild-type (WT) and Scn5a(+/-) mice and differences attributable to these risk factors statistically stratified. RESULTS Scn5a(+/-) exerted sex-dependent effects upon sino-atrial function that only became apparent with age. RR intervals were greater in old male than in old female Scn5a(+/-). Atrio-ventricular (AV) conduction was slower in young female mice, whether WT and Scn5a(+/-), than the corresponding young male WT and Scn5a(+/-). However, PR intervals lengthened with age in male but not in female Scn5a(+/-) giving the greatest PR intervals in old male Scn5a(+/-) compared with either old male WT or young male Scn5a(+/-) mice. In contrast, PR intervals were similar in old female Scn5a(+/-) and in old female WT. QTc was prolonged in Scn5a(+/-) compared with WT, and female Scn5a(+/-) compared with female WT. Age-dependent alterations in durations of ventricular repolarization relative to WT affected male but not female Scn5a(+/-). Thus, T-wave durations were greater in old male Scn5a(+/-) compared with old male WT, but indistinguishable between old female Scn5a(+/-) and old female WT. Finally, analysis for combined interactions of genotype, age and sex demonstrated no effects on P wave and QRS durations and QTc intervals. CONCLUSION We demonstrate for the first time that age, sex and genotype exert both independent and interacting ECG effects. The latter suggest alterations in cardiac pacemaker function, atrio-ventricular conduction and ventricular repolarization greatest in ageing male Scn5a(+/-).
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Affiliation(s)
- K Jeevaratnam
- Physiological Laboratory, University of Cambridge, Cambridge, UK
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Schulze-Bahr E. Making sense in a nonsense reading frame: suppression of cardiac sodium channel dysfunction. Cardiovasc Res 2009; 83:423-4. [PMID: 19528082 DOI: 10.1093/cvr/cvp196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Teng S, Gao L, Paajanen V, Pu J, Fan Z. Readthrough of nonsense mutation W822X in the SCN5A gene can effectively restore expression of cardiac Na+ channels. Cardiovasc Res 2009; 83:473-80. [PMID: 19377070 DOI: 10.1093/cvr/cvp116] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
AIMS Nonsense mutations in the SCN5A gene result in truncated, non-functional derivatives of the cardiac Na+ channel and thus cause arrhythmias. Studies of other genes suggest that pathogenic phenotypes of nonsense mutations may be alleviated by enhancing readthrough, which enables ribosomes to ignore premature termination codons and produce full-length proteins. Thus, we studied the functional restoration of nonsense-mutated SCN5A. METHODS AND RESULTS HEK293 cells were transfected with SCN5A cDNA or its mutant carrying W822X, a nonsense mutation associated with Brugada syndrome and sudden cardiac death. The effects of readthrough-enhancing reagents on Na+ channel expression and function were examined in the transfected cells. W822X robustly reduced Na+ current, decreasing maximal Na+ current to <3% of the wild-type level, and inhibited the expression of full-length Na+ channels. When readthrough was enhanced by either reducing translational fidelity with aminoglycosides or decreasing translation termination efficiency with small-interfering RNA against eukaryotic release factor eRF3a, Na+ current of the mutant was restored to approximately 30% of the wild-type level; western blot and immunochemical staining analyses showed the increased expression of full-length channels. When the wild-type and mutant cDNAs were co-transfected, readthrough-enhancing reagents increased Na+ current from 56% to 74% of the wild-type level. Analysis of Na+ channel kinetics showed that the channels expressed from the mutant cDNA under readthrough-enhancing conditions retained the functions of wild-type channels. CONCLUSION Readthrough-enhancing reagents can effectively suppress SCN5A nonsense mutations and may restore the expression of full-length Na+ channels with normal functions, which might prevent sudden cardiac death in mutation carriers.
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Affiliation(s)
- Siyong Teng
- Cardiovascular Institute and Fuwai Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
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Ehrlich JR. Arrhythmogenic Brugada syndrome substrate: a proof of principle. Cardiovasc Res 2009; 81:635-6. [PMID: 19136529 DOI: 10.1093/cvr/cvp008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Kwiatkowski A. Long QT and Brugada syndromes: a new insight into arrhythmogenesis and sudden death. Folia Med Cracov 2009; 50:5-119. [PMID: 19806998] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
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Petitprez S, Jespersen T, Pruvot E, Keller DI, Corbaz C, Schläpfer J, Abriel H, Kucera JP. Analyses of a novel SCN5A mutation (C1850S): conduction vs. repolarization disorder hypotheses in the Brugada syndrome. Cardiovasc Res 2008; 78:494-504. [PMID: 18252757 DOI: 10.1093/cvr/cvn023] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Séverine Petitprez
- Department of Pharmacology and Toxicology, University of Lausanne, 27, Bugnon, 1005 Lausanne, Vaud, Switzerland
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Vecchietti S, Rivolta I, Severi S, Napolitano C, Priori SG, Cavalcanti S. Computer simulation of wild-type and mutant human cardiac Na+ current. Med Biol Eng Comput 2007; 44:35-44. [PMID: 16929919 DOI: 10.1007/s11517-005-0017-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Long QT syndrome (LQTS) and Brugada syndrome (BrS) are inherited diseases predisposing to ventricular arrhythmias and sudden death. Genetic studies linked LQTS and BrS to mutations in genes encoding for cardiac ion channels. Recently, two novel missense mutations at the same codon in the gene encoding the cardiac Na+ channel (SCN5A) have been identified: Y1795C (causing the LQTS phenotype) and Y1795H (causing the BrS phenotype). Functional studies in HEK293 cells showed that both mutations alter the inactivation of Na+ current and cause a sustained Na+ current upon depolarisation. In this paper, a nine state Markov model was used to simulate the Na+ current in wild-type Na+ cardiac channel and the current alterations observed in Y1795C and Y1795H mutant channels. The model includes three distinct closed states, a conducting open state and five inactivation states (one fast-, two intermediate- and two closed-inactivation). Transition rates between these states were identified on the basis of previously published voltage-clamp experiments. The model was able to reproduce the experimental Na+ current in mutant channels just by altering the assignment of model parameters with respect to wild-type case. Parameter assignment was validated by performing action potential clamp experiments and comparing experimental and simulated I(Na) current. The Markov model was subsequently introduced in the Luo-Rudy model of ventricular myocyte to investigate "in silico" the consequences on the ventricular cell action potential of the two mutations. Coherently with their phenotypes, the Y1795C mutation prolongs the action potential, while the Y1795H mutation causes only negligible changes in action potential morphology.
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Affiliation(s)
- Stefania Vecchietti
- Cellular and Molecular Engineering Laboratory, DEIS, University of Bologna, via Venezia 52, 47023 Cesena (FC), Italy.
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Abstract
This review examines the role of spatial electrical heterogeneity within the ventricular myocardium on the function of the heart in health and disease. The cellular basis for transmural dispersion of repolarization (TDR) is reviewed, and the hypothesis that amplification of spatial dispersion of repolarization underlies the development of life-threatening ventricular arrhythmias associated with inherited ion channelopathies is evaluated. The role of TDR in long QT, short QT, and Brugada syndromes, as well as catecholaminergic polymorphic ventricular tachycardia (VT), is critically examined. In long QT syndrome, amplification of TDR is often secondary to preferential prolongation of the action potential duration (APD) of M cells; in Brugada syndrome, however, it is thought to be due to selective abbreviation of the APD of the right ventricular epicardium. Preferential abbreviation of APD of the endocardium or epicardium appears to be responsible for the amplification of TDR in short QT syndrome. In catecholaminergic polymorphic VT, reversal of the direction of activation of the ventricular wall is responsible for the increase in TDR. In conclusion, long QT, short QT, Brugada, and catecholaminergic polymorphic VT syndromes are pathologies with very different phenotypes and etiologies, but they share a common final pathway in causing sudden cardiac death.
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Affiliation(s)
- Charles Antzelevitch
- Masonic Medical Research Laboratory, 2150 Bleecker St., Utica, NY 13501-1787, USA.
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Shimizu W, Matsuo K, Kokubo Y, Satomi K, Kurita T, Noda T, Nagaya N, Suyama K, Aihara N, Kamakura S, Inamoto N, Akahoshi M, Tomoike H. Sex Hormone and Gender Difference?Role of Testosterone on Male Predominance in Brugada Syndrome. J Cardiovasc Electrophysiol 2007; 18:415-21. [PMID: 17394456 DOI: 10.1111/j.1540-8167.2006.00743.x] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
INTRODUCTION The clinical phenotype is 8 to 10 times more prevalent in males than in females in patients with Brugada syndrome. Brugada syndrome has been reported to be thinner than asymptomatic normal controls. We tested the hypothesis that higher testosterone level associated with lower visceral fat may relate to Brugada phenotype and male predominance. METHODS AND RESULTS We measured body-mass index (BMI), body fat percentage (BF%), and several hormonal levels, including testosterone, in 48 Brugada males and compared with those in 96 age-matched control males. Brugada males had significantly higher testosterone (631 +/- 176 vs 537 +/- 158 ng/dL; P = 0.002), serum sodium, potassium, and chloride levels than those in control males by univariate analysis, and even after adjusting for age, exercise, stress, smoking, and medication of hypertension, diabetes, and hyperlipidemia, whereas there were no significant differences in other sex and thyroid hormonal levels. Brugada males had significantly lower BMI (22.1 +/- 2.9 vs 24.6 +/- 2.6 kg/m(2); P < 0.001) and BF% (19.6 +/- 4.9 vs 23.1 +/- 4.7%; P < 0.001) than control males. Testosterone level was inversely correlated with BMI and BF% in both groups, even after adjusting for the confounding variables. Conditional logistic regression models analysis showed significant positive and inverse association between Brugada syndrome and hypertestosteronemia (OR:3.11, 95% CI:1.22-7.93, P = 0.017) and BMI (OR:0.72, 95% CI:0.61-0.85, P < 0.001), respectively. CONCLUSIONS Higher testosterone level associated with lower visceral fat may have a significant role in the Brugada phenotype and male predominance in Brugada syndrome.
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Affiliation(s)
- Wataru Shimizu
- Division of Cardiology, Department of Internal Medicine, National Cardiovascular Center, Suita, Osaka, Japan.
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Abstract
This report describes a Brugada electrocardiographic pattern after tricyclic antidepressant intoxication that fails to resolve following sodium bicarbonate treatment. A 50-year-old male ingested 13.6 grams of amitriptyline and presented in cardiopulmonary arrest. After initial resuscitation, the patient developed a Brugada electrocardiographic pattern. The pattern persisted despite intravenous administration of 700 mEq of sodium bicarbonate. Five hours after the last dose of sodium bicarbonate and 18 hours after initial presentation, the Brugada pattern resolved. No co-ingestants were ingested and an ischemic pattern was not seen on electrocardiogram. The serum amitriptyline level was >1000 ng/ml. Response of the tricyclic-induced Brugada pattern to sodium bicarbonate has not been previously reported.
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Affiliation(s)
- Vikhyat S Bebarta
- Director of Medical Toxicology, Department of Emergency Medicine, Wilford Hall Medical Center, University of Texas Health Sciences Center at San Antonio, San Antonio, Texas, USA.
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Nakano Y, Tashiro S, Kinoshita E, Kinoshita-Kikuta E, Takenaka S, Miyoshi M, Ogi H, Sakoda E, Oda N, Suenari K, Tonouchi Y, Okimoto T, Hirai Y, Miura F, Yamaoka K, Koike T, Chayama K. Non-SCN5A Related Brugada Syndromes: Verification of Normal Splicing and Trafficking of SCN5A Without Exonic Mutations. Ann Hum Genet 2007; 71:8-17. [PMID: 17227473 DOI: 10.1111/j.1469-1809.2006.00297.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Recently, it has been reported that under 20% of Brugada syndrome cases are linked to SCN5A mutations. The purpose of this study was to clarify whether abnormalities other than exonic mutations, such as splicing disorders, decreased mRNA expression levels, or membrane transport abnormalities of SCN5A, play a role in the pathogenesis of Brugada syndrome. We analyzed all SCN5A exons and splice sites using genomic DNA from 23 Brugada syndrome patients. We also analyzed the mRNA obtained from RV cardiomyocytes using real time PCR and sequencing, to study the expression levels and splicing patterns of SCN5A. The localization of SCN5A was examined by immunofluorescence analysis. A de novo heterozygous G to A transversion in a 5' splice junction of the intron between exons 21 and 22 was detected in 1 patient. In the mRNA analysis of Brugada syndrome patients without a mutation of SCN5A no splicing abnormalities were detected, and the SCN5A mRNA levels were similar to those of normal controls. Immunofluorescence analyses revealed that SCN5A is located on the surface membrane not only in the RV cardiomyocytes of normal controls but also in those with Brugada syndrome. We can confirm that some Brugada syndrome patients without exonic mutations in SCN5A had no other SCN5A abnormalities, including any involving the location of the SCN5A protein. These results suggest the involvement of other proteins in the pathogenesis in Brugada syndrome.
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Affiliation(s)
- Yukiko Nakano
- Department of Medicine and Molecular Science, Graduate School of Biomedical Sciences, Hiroshima University [corrected] Japan.
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Cordeiro JM, Barajas-Martinez H, Hong K, Burashnikov E, Pfeiffer R, Orsino AM, Wu YS, Hu D, Brugada J, Brugada P, Antzelevitch C, Dumaine R, Brugada R. Compound heterozygous mutations P336L and I1660V in the human cardiac sodium channel associated with the Brugada syndrome. Circulation 2006; 114:2026-33. [PMID: 17075016 PMCID: PMC1989773 DOI: 10.1161/circulationaha.106.627489] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
BACKGROUND Loss-of-function mutations in SCN5A have been associated with the Brugada syndrome. We report the first Brugada syndrome family with compound heterozygous mutations in SCN5A. The proband inherited 1 mutation from each parent and transmitted 1 to each daughter. METHODS AND RESULTS The effects of the mutations on the function of the sodium channel were evaluated with heterologous expression in TSA201 cells, patch-clamp study, and confocal microscopy. Genetic analysis revealed that the proband carried 2 heterozygous missense mutations (P336L and I1660V) on separate alleles. He displayed a coved-type ST-segment elevation and a prolonged PR interval (280 ms). One daughter inherited P336L and exhibited a prolonged PR (210 ms). The other daughter inherited mutation I1660V and displayed a normal PR interval. Both daughters had a slightly elevated, upsloping ST-segment elevation. The parents had normal ECGs. Patch-clamp analysis showed that the P336L mutation reduced I(Na) by 85% relative to wild type. The I1660V mutation produced little measurable current, which was rescued by room temperature incubation for 48 hours. Sodium channel blockers also rescued the I1660V current, with mexiletine proving to be the most effective. Confocal immunofluorescence showed that I1660V channels conjugated to green fluorescent protein remained trapped in intracellular organelles. CONCLUSIONS Mutation P336L produced a reduction in cardiac I(Na), whereas I1660V abolished it. Only the proband carrying both mutations displayed the Brugada syndrome phenotype, whereas neither mutation alone produced the clinical phenotype. I1660V channels could be rescued pharmacologically and by incubation at room temperature. The present data highlight the role of compound heterozygosity in modulating the phenotypic expression and penetrance of Brugada syndrome.
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Affiliation(s)
- Jonathan M Cordeiro
- Department of Experimental Cardiology, Masonic Medical Research Laboratory, 2150 Bleecker St, Utica, NY 13501, USA.
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Keller DI, Huang H, Zhao J, Frank R, Suarez V, Delacrétaz E, Brink M, Osswald S, Schwick N, Chahine M. A novel SCN5A mutation, F1344S, identified in a patient with Brugada syndrome and fever-induced ventricular fibrillation. Cardiovasc Res 2006; 70:521-9. [PMID: 16616735 DOI: 10.1016/j.cardiores.2006.02.030] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2006] [Revised: 02/03/2006] [Accepted: 02/18/2006] [Indexed: 11/21/2022] Open
Abstract
OBJECTIVE Brugada syndrome (BS) is an inherited electrical cardiac disorder characterized by right bundle branch block pattern and ST segment elevation in leads V1 to V3 on surface electrocardiogram that can potentially lead to malignant ventricular tachycardia and sudden cardiac death. About 20% of patients have mutations in the only so far identified gene, SCN5A, which encodes the alpha-subunit of the human cardiac voltage-dependent sodium channel (hNa(v)1.5). Fever has been shown to unmask or trigger the BS phenotype, but the associated molecular and the biophysical mechanisms are still poorly understood. We report on the identification and biophysical characterization of a novel heterozygous missense mutation in SCN5A, F1344S, in a 42-year-old male patient showing the BS phenotype leading to ventricular fibrillation during fever. METHODS The mutation was reproduced in vitro using site-directed mutagenesis and characterized using the patch clamp technique in the whole-cell configuration. RESULTS The biophysical characterization of the channels carrying the F1344S mutation revealed a 10 mV mid-point shift of the G/V curve toward more positive voltages during activation. Raising the temperature to 40.5 degrees C further shifted the mid-point activation by 18 mV and significantly changed the slope factor in Na(v)1.5/F1344S mutant channels from -6.49 to -10.27 mV. CONCLUSIONS Our findings indicate for the first time that the shift in activation and change in the slope factor at a higher temperature mimicking fever could reduce sodium currents' amplitude and trigger the manifestation of the BS phenotype.
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Affiliation(s)
- Dagmar I Keller
- Cardiology Department, University Hospital Basel, Switzerland
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