1
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Ukachukwu CU, Jimenez-Vazquez EN, Jain A, Jones DK. hERG1 channel subunit composition mediates proton inhibition of rapid delayed rectifier potassium current (I Kr) in cardiomyocytes derived from hiPSCs. J Biol Chem 2023; 299:102778. [PMID: 36496073 PMCID: PMC9867984 DOI: 10.1016/j.jbc.2022.102778] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 11/29/2022] [Accepted: 12/04/2022] [Indexed: 12/13/2022] Open
Abstract
The voltage-gated channel, hERG1, conducts the rapid delayed rectifier potassium current (IKr) and is critical for human cardiac repolarization. Reduced IKr causes long QT syndrome and increases the risk for cardiac arrhythmia and sudden death. At least two subunits form functional hERG1 channels, hERG1a and hERG1b. Changes in hERG1a/1b abundance modulate IKr kinetics, magnitude, and drug sensitivity. Studies from native cardiac tissue suggest that hERG1 subunit abundance is dynamically regulated, but the impact of altered subunit abundance on IKr and its response to external stressors is not well understood. Here, we used a substrate-driven human-induced pluripotent stem cell-derived cardiomyocyte (hiPSC-CM) maturation model to investigate how changes in relative hERG1a/1b subunit abundance impact the response of native IKr to extracellular acidosis, a known component of ischemic heart disease and sudden infant death syndrome. IKr recorded from immatured hiPSC-CMs displays a 2-fold greater inhibition by extracellular acidosis (pH 6.3) compared with matured hiPSC-CMs. Quantitative RT-PCR and immunocytochemistry demonstrated that hERG1a subunit mRNA and protein were upregulated and hERG1b subunit mRNA and protein were downregulated in matured hiPSC-CMs compared with immatured hiPSC-CMs. The shift in subunit abundance in matured hiPSC-CMs was accompanied by increased IKr. Silencing hERG1b's impact on native IKr kinetics by overexpressing a polypeptide identical to the hERG1a N-terminal Per-Arnt-Sim domain reduced the magnitude of IKr proton inhibition in immatured hiPSC-CMs to levels comparable to those observed in matured hiPSC-CMs. These data demonstrate that hERG1 subunit abundance is dynamically regulated and determines IKr proton sensitivity in hiPSC-CMs.
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Affiliation(s)
- Chiamaka U Ukachukwu
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Eric N Jimenez-Vazquez
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Abhilasha Jain
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - David K Jones
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA; Department of Internal Medicine, University of Michigan Medical School.
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2
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KCNH2 encodes a nuclear-targeted polypeptide that mediates hERG1 channel gating and expression. Proc Natl Acad Sci U S A 2023; 120:e2214700120. [PMID: 36626562 PMCID: PMC9934303 DOI: 10.1073/pnas.2214700120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
KCNH2 encodes hERG1, the voltage-gated potassium channel that conducts the rapid delayed rectifier potassium current (IKr) in human cardiac tissue. hERG1 is one of the first channels expressed during early cardiac development, and its dysfunction is associated with intrauterine fetal death, sudden infant death syndrome, cardiac arrhythmia, and sudden cardiac death. Here, we identified a hERG1 polypeptide (hERG1NP) that is targeted to the nuclei of immature cardiac cells, including human stem cell-derived cardiomyocytes (hiPSC-CMs) and neonatal rat cardiomyocytes. The nuclear hERG1NP immunofluorescent signal is diminished in matured hiPSC-CMs and absent from adult rat cardiomyocytes. Antibodies targeting distinct hERG1 channel epitopes demonstrated that the hERG1NP signal maps to the hERG1 distal C-terminal domain. KCNH2 deletion using CRISPR simultaneously abolished IKr and the hERG1NP signal in hiPSC-CMs. We then identified a putative nuclear localization sequence (NLS) within the distal hERG1 C-terminus, 883-RQRKRKLSFR-892. Interestingly, the distal C-terminal domain was targeted almost exclusively to the nuclei when overexpressed HEK293 cells. Conversely, deleting the NLS from the distal peptide abolished nuclear targeting. Similarly, blocking α or β1 karyopherin activity diminished nuclear targeting. Finally, overexpressing the putative hERG1NP peptide in the nuclei of HEK cells significantly reduced hERG1a current density, compared to cells expressing the NLS-deficient hERG1NP or GFP. These data identify a developmentally regulated polypeptide encoded by KCNH2, hERG1NP, whose presence in the nucleus indirectly modulates hERG1 current magnitude and kinetics.
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3
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Crotti L, Odening KE, Sanguinetti MC. Heritable arrhythmias associated with abnormal function of cardiac potassium channels. Cardiovasc Res 2021; 116:1542-1556. [PMID: 32227190 DOI: 10.1093/cvr/cvaa068] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 02/24/2020] [Accepted: 03/26/2020] [Indexed: 12/16/2022] Open
Abstract
Cardiomyocytes express a surprisingly large number of potassium channel types. The primary physiological functions of the currents conducted by these channels are to maintain the resting membrane potential and mediate action potential repolarization under basal conditions and in response to changes in the concentrations of intracellular sodium, calcium, and ATP/ADP. Here, we review the diversity and functional roles of cardiac potassium channels under normal conditions and how heritable mutations in the genes encoding these channels can lead to distinct arrhythmias. We briefly review atrial fibrillation and J-wave syndromes. For long and short QT syndromes, we describe their genetic basis, clinical manifestation, risk stratification, traditional and novel therapeutic approaches, as well as insights into disease mechanisms provided by animal and cellular models.
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Affiliation(s)
- Lia Crotti
- Center for Cardiac Arrhythmias of Genetic Origin, Istituto Auxologico Italiano, IRCCS, Milan, Italy.,Laboratory of Cardiovascular Genetics, Istituto Auxologico Italiano, IRCCS, Milan, Italy.,Department of Cardiovascular, Neural and Metabolic Sciences, Istituto Auxologico Italiano, IRCCS, San Luca Hospital, Milan, Italy.,Department of Medicine and Surgery, University of Milano-Bicocca, Milan, Italy
| | - Katja E Odening
- Department of Cardiology and Angiology I, Heart Center University of Freiburg, Medical Faculty, Freiburg, Germany.,Institute of Experimental Cardiovascular Medicine, Heart Center University of Freiburg, Medical Faculty, Freiburg, Germany.,Department of Cardiology, Translational Cardiology, Inselspital, Bern University Hospital, and Institute of Physiology, University of Bern, Bern, Switzerland
| | - Michael C Sanguinetti
- Department of Internal Medicine, Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, USA
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4
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Naffaa MM, Al-Ewaidat OA. Ligand modulation of KCNQ-encoded (K V7) potassium channels in the heart and nervous system. Eur J Pharmacol 2021; 906:174278. [PMID: 34174270 DOI: 10.1016/j.ejphar.2021.174278] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 06/06/2021] [Accepted: 06/18/2021] [Indexed: 10/21/2022]
Abstract
KCNQ-encoded (KV7) potassium channels are diversely distributed in the human tissues, associated with many physiological processes and pathophysiological conditions. These channels are increasingly used as drug targets for treating diseases. More selective and potent molecules on various types of the KV7 channels are desirable for appropriate therapies. The recent knowledge of the structure and function of human KCNQ-encoded channels makes it more feasible to achieve these goals. This review discusses the role and mechanism of action of many molecules in modulating the function of the KCNQ-encoded potassium channels in the heart and nervous system. The effects of these compounds on KV7 channels help to understand their involvement in many diseases, and to search for more selective and potent ligands to be used in the treatment of many disorders such as various types of cardiac arrhythmias, epilepsy, and pain.
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Affiliation(s)
- Moawiah M Naffaa
- Department of Cell Biology, Duke University School of Medicine, Durham, NC, 27710, USA; Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA.
| | - Ola A Al-Ewaidat
- Faculty of Medicine, The University of Jordan, Amman, 11942, Jordan
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5
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Huang H, Chamness LM, Vanoye CG, Kuenze G, Meiler J, George AL, Schlebach JP, Sanders CR. Disease-linked supertrafficking of a potassium channel. J Biol Chem 2021; 296:100423. [PMID: 33600800 PMCID: PMC7988323 DOI: 10.1016/j.jbc.2021.100423] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 02/04/2021] [Accepted: 02/12/2021] [Indexed: 12/21/2022] Open
Abstract
Gain-of-function (GOF) mutations in the voltage-gated potassium channel subfamily Q member 1 (KCNQ1) can induce cardiac arrhythmia. In this study, it was tested whether any of the known human GOF disease mutations in KCNQ1 act by increasing the amount of KCNQ1 that reaches the cell surface-"supertrafficking." Seven of the 15 GOF mutants tested were seen to surface traffic more efficiently than the WT channel. Among these, we found that the levels of R231C KCNQ1 in the plasma membrane were fivefold higher than the WT channel. This was shown to arise from the combined effects of enhanced efficiency of translocon-mediated membrane integration of the S4 voltage-sensor helix and from enhanced post-translational folding/trafficking related to the energetic linkage of C231 with the V129 and F166 side chains. Whole-cell electrophysiology recordings confirmed that R231C KCNQ1 in complex with the voltage-gated potassium channel-regulatory subfamily E member 1 not only exhibited constitutive conductance but also revealed that the single-channel activity of this mutant is only 20% that of WT. The GOF phenotype associated with R231C therefore reflects the effects of supertrafficking and constitutive channel activation, which together offset reduced channel activity. These investigations show that membrane protein supertrafficking can contribute to human disease.
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Affiliation(s)
- Hui Huang
- Department of Biochemistry, Vanderbilt University, Nashville, Tennessee, USA; Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, USA
| | - Laura M Chamness
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
| | - Carlos G Vanoye
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Georg Kuenze
- Departments of Chemistry and Pharmacology, Vanderbilt University, Nashville, Tennessee, USA; Department of Bioinformatics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Jens Meiler
- Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, USA; Departments of Chemistry and Pharmacology, Vanderbilt University, Nashville, Tennessee, USA; Department of Bioinformatics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Alfred L George
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | | | - Charles R Sanders
- Department of Biochemistry, Vanderbilt University, Nashville, Tennessee, USA; Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, USA; Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA.
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6
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Vanoye CG, Desai RR, Fabre KL, Gallagher SL, Potet F, DeKeyser JM, Macaya D, Meiler J, Sanders CR, George AL. High-Throughput Functional Evaluation of KCNQ1 Decrypts Variants of Unknown Significance. CIRCULATION-GENOMIC AND PRECISION MEDICINE 2019; 11:e002345. [PMID: 30571187 DOI: 10.1161/circgen.118.002345] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
BACKGROUND The explosive growth in known human gene variation presents enormous challenges to current approaches for variant classification that have implications for diagnosis and treatment of many genetic diseases. For disorders caused by mutations in cardiac ion channels as in congenital arrhythmia syndromes, in vitro electrophysiological evidence has high value in discriminating pathogenic from benign variants, but these data are often lacking because assays are cost, time, and labor intensive. METHODS We implemented a strategy for performing high-throughput functional evaluations of ion channel variants that repurposed an automated electrophysiological recording platform developed previously for drug discovery. RESULTS We demonstrated the success of this approach by evaluating 78 variants in KCNQ1, a major gene involved in genetic disorders of cardiac arrhythmia susceptibility. We benchmarked our results with traditional electrophysiological approaches and observed a high level of concordance. This strategy also enabled studies of dominant-negative behavior of variants exhibiting severe loss-of-function. Overall, our results provided functional data useful for reclassifying >65% of the studied KCNQ1 variants. CONCLUSIONS Our results illustrate an efficient and high-throughput paradigm linking genotype to function for a human cardiac ion channel that will enable data-driven classification of large numbers of variants and create new opportunities for precision medicine.
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Affiliation(s)
- Carlos G Vanoye
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL (C.G.V., R.R.D., K.L.F., S.L.G., F.P., J.-M.D., A.L.G.)
| | - Reshma R Desai
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL (C.G.V., R.R.D., K.L.F., S.L.G., F.P., J.-M.D., A.L.G.)
| | - Katarina L Fabre
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL (C.G.V., R.R.D., K.L.F., S.L.G., F.P., J.-M.D., A.L.G.)
| | - Shannon L Gallagher
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL (C.G.V., R.R.D., K.L.F., S.L.G., F.P., J.-M.D., A.L.G.)
| | - Franck Potet
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL (C.G.V., R.R.D., K.L.F., S.L.G., F.P., J.-M.D., A.L.G.)
| | - Jean-Marc DeKeyser
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL (C.G.V., R.R.D., K.L.F., S.L.G., F.P., J.-M.D., A.L.G.)
| | | | - Jens Meiler
- Department of Chemistry, Vanderbilt University School of Medicine, Nashville, TN (J.M.).,the Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN (J.M.,C.R.S.)
| | - Charles R Sanders
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN (C.R.S.).,the Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN (J.M.,C.R.S.)
| | - Alfred L George
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL (C.G.V., R.R.D., K.L.F., S.L.G., F.P., J.-M.D., A.L.G.)
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7
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Rico-Mesa JS, Al Qaysi M, Sovic W, Endo-Carvajal M, Badin A. Rare but lethal short QT syndrome: most recent understanding of the disease. ELECTRONIC JOURNAL OF GENERAL MEDICINE 2019. [DOI: 10.29333/ejgm/108495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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8
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Functional significance of channelopathy gene variants in unexplained death. Forensic Sci Med Pathol 2018; 15:437-444. [DOI: 10.1007/s12024-018-0063-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/20/2018] [Indexed: 02/06/2023]
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9
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10
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Davis AM, Glengarry J, Skinner JR. Sudden Infant Death: QT or Not QT? That Is No Longer the Question. Circ Arrhythm Electrophysiol 2018; 9:CIRCEP.115.003859. [PMID: 27217342 DOI: 10.1161/circep.115.003859] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 03/11/2016] [Indexed: 02/07/2023]
Affiliation(s)
- Andrew M Davis
- From the Department of Cardiology, Royal Children's Hospital Melbourne, Melbourne, VIC, Australia (A.M.D.); Department of Paediatrics, University of Melbourne, Melbourne, VIC, Australia (A.M.D.); The Murdoch Childrens Research Institute, Melbourne, VIC, Australia (A.M.D.); Department of Forensic Pathology, LabPlus, Auckland City Hospital, Auckland, New Zealand (J.G.); Green Lane Paediatric and Congenital Cardiac Services, Starship Children's Hospital, Auckland, New Zealand (J.R.S.); and Department of Paediatrics, Child and Youth Health, The University of Auckland, Auckland, New Zealand (J.R.S.)
| | - Joanna Glengarry
- From the Department of Cardiology, Royal Children's Hospital Melbourne, Melbourne, VIC, Australia (A.M.D.); Department of Paediatrics, University of Melbourne, Melbourne, VIC, Australia (A.M.D.); The Murdoch Childrens Research Institute, Melbourne, VIC, Australia (A.M.D.); Department of Forensic Pathology, LabPlus, Auckland City Hospital, Auckland, New Zealand (J.G.); Green Lane Paediatric and Congenital Cardiac Services, Starship Children's Hospital, Auckland, New Zealand (J.R.S.); and Department of Paediatrics, Child and Youth Health, The University of Auckland, Auckland, New Zealand (J.R.S.)
| | - Jonathan R Skinner
- From the Department of Cardiology, Royal Children's Hospital Melbourne, Melbourne, VIC, Australia (A.M.D.); Department of Paediatrics, University of Melbourne, Melbourne, VIC, Australia (A.M.D.); The Murdoch Childrens Research Institute, Melbourne, VIC, Australia (A.M.D.); Department of Forensic Pathology, LabPlus, Auckland City Hospital, Auckland, New Zealand (J.G.); Green Lane Paediatric and Congenital Cardiac Services, Starship Children's Hospital, Auckland, New Zealand (J.R.S.); and Department of Paediatrics, Child and Youth Health, The University of Auckland, Auckland, New Zealand (J.R.S.).
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11
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Tuveng JM, Berling BM, Bunford G, Vanoye CG, Welch RC, Leren TP, George AL, Rognum TO. Long QT syndrome KCNH2 mutation with sequential fetal and maternal sudden death. Forensic Sci Med Pathol 2018; 14:367-371. [PMID: 29881912 DOI: 10.1007/s12024-018-9989-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/02/2018] [Indexed: 11/26/2022]
Abstract
We report a case of a woman who experienced intrauterine fetal death at full term pregnancy, and then died suddenly soon after learning about the death of her fetus. At autopsy, previously undiagnosed neurofibromatosis and an adrenal gland pheochromocytoma were discovered in the mother. Genetic screening also revealed a novel KCNH2mutation in both fetus and mother indicating type 2 congenital long-QT syndrome (LQTS). A catecholamine surge was suspected as the precipitating event of fetal cardiac arrhythmia and sudden fetal death, while the addition of emotional stress provoked a lethal cardiac event in the mother. This case illustrates the potential for lethal interactions between two occult diseases (pheochromocytoma, LQTS).
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Affiliation(s)
| | | | | | - Carlos G Vanoye
- Department of Medicine, Vanderbilt University, Nashville, TN, 37232-0275, USA
| | - Richard C Welch
- Department of Medicine, Vanderbilt University, Nashville, TN, 37232-0275, USA
| | - Trond P Leren
- Section of Laboratory Diagnostics, Oslo University Hospital, Oslo, Norway
| | - Alfred L George
- Department of Medicine, Vanderbilt University, Nashville, TN, 37232-0275, USA
| | - Torleiv Ole Rognum
- Section of Forensic Pediatric Medicine, Clinic of Laboratory Medicine, Oslo University Hospital, Oslo, Norway.
- Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
- Avdeling for Rettsmedisinske Fag, Seksjon for Rettsmedisinske Undersøkelser av Barn, Oslo Universitetssykehus HF, Postboks 4950 Nydalen, 0424, Oslo, Norway.
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12
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Ocorr K, Zambon A, Nudell Y, Pineda S, Diop S, Tang M, Akasaka T, Taylor E. Age-dependent electrical and morphological remodeling of the Drosophila heart caused by hERG/seizure mutations. PLoS Genet 2017; 13:e1006786. [PMID: 28542428 PMCID: PMC5459509 DOI: 10.1371/journal.pgen.1006786] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 06/05/2017] [Accepted: 04/30/2017] [Indexed: 12/03/2022] Open
Abstract
Understanding the cellular-molecular substrates of heart disease is key to the development of cardiac specific therapies and to the prevention of off-target effects by non-cardiac targeted drugs. One of the primary targets for therapeutic intervention has been the human ether a go-go (hERG) K+ channel that, together with the KCNQ channel, controls the rate and efficiency of repolarization in human myocardial cells. Neither of these channels plays a major role in adult mouse heart function; however, we show here that the hERG homolog seizure (sei), along with KCNQ, both contribute significantly to adult heart function as they do in humans. In Drosophila, mutations in or cardiac knockdown of sei channels cause arrhythmias that become progressively more severe with age. Intracellular recordings of semi-intact heart preparations revealed that these perturbations also cause electrical remodeling that is reminiscent of the early afterdepolarizations seen in human myocardial cells defective in these channels. In contrast to KCNQ, however, mutations in sei also cause extensive structural remodeling of the myofibrillar organization, which suggests that hERG channel function has a novel link to sarcomeric and myofibrillar integrity. We conclude that deficiency of ion channels with similar electrical functions in cardiomyocytes can lead to different types or extents of electrical and/or structural remodeling impacting cardiac output. We have used the fruit fly cardiac model to show that seizure, the fly homolog of the human ether a go-go K+ channel hERG, is functional in the fly heart. This channel plays a major role in cardiac repolarization in humans but not in adult rodent hearts. Loss of channel function in the fly causes bradycardia, electrical arrhythmia and altered myofibrillar structure. Gene expression analysis indicates that Wnt signaling is affected and we show a genetic interaction between sei and pygopus, a Wnt pathway component, on heart function.
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Affiliation(s)
- Karen Ocorr
- Development, Aging and Regeneration Program, Sanford-Burnham-Prebys Medical Discovery Institute, La Jolla, California, United States of America
- * E-mail:
| | - Alexander Zambon
- Development, Aging and Regeneration Program, Sanford-Burnham-Prebys Medical Discovery Institute, La Jolla, California, United States of America
| | - Yoav Nudell
- Development, Aging and Regeneration Program, Sanford-Burnham-Prebys Medical Discovery Institute, La Jolla, California, United States of America
| | - Santiago Pineda
- Development, Aging and Regeneration Program, Sanford-Burnham-Prebys Medical Discovery Institute, La Jolla, California, United States of America
| | - Soda Diop
- Development, Aging and Regeneration Program, Sanford-Burnham-Prebys Medical Discovery Institute, La Jolla, California, United States of America
| | - Min Tang
- Development, Aging and Regeneration Program, Sanford-Burnham-Prebys Medical Discovery Institute, La Jolla, California, United States of America
| | - Takeshi Akasaka
- Development, Aging and Regeneration Program, Sanford-Burnham-Prebys Medical Discovery Institute, La Jolla, California, United States of America
| | - Erika Taylor
- Development, Aging and Regeneration Program, Sanford-Burnham-Prebys Medical Discovery Institute, La Jolla, California, United States of America
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13
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Gando I, Morganstein J, Jana K, McDonald TV, Tang Y, Coetzee WA. Infant sudden death: Mutations responsible for impaired Nav1.5 channel trafficking and function. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2017; 40:703-712. [PMID: 28370132 DOI: 10.1111/pace.13087] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 03/20/2017] [Accepted: 03/27/2017] [Indexed: 01/10/2023]
Abstract
BACKGROUND Two genetic variants in SCN5A, encoding the Nav1.5 Na+ channel α-subunit, were found in a 5-month-old girl who died suddenly in her sleep. The first variant is a missense mutation, resulting in an amino acid change (Q1832E), which has been described (but not characterized) in a patient with Brugada syndrome. The second is a nonsense mutation that produces a premature stop codon and a C-terminal truncation (R1944Δ). METHODS AND RESULTS To investigate their functional relevance with patch clamp experiments in transfected HEK-293 cells. The Q1832E mutation drastically reduced Nav1.5 current density. The R1944Δ C-terminal truncation had negligible effects on Nav1.5 current density. Neither of the mutations affected the voltage dependence of steady activation and inactivation or influenced the late Na+ current or the recovery from inactivation. Biochemical and immunofluorescent approaches demonstrated that the Q1832E mutation caused severe trafficking defects. Polymerase chain reaction cloning and sequencing the victim's genomic DNA allowed us to determine that the two variants were in trans. We investigated the functional consequences by coexpressing Nav1.5(Q1832E) and Nav1.5(R1944Δ), which led to a significantly reduced current amplitude relative to wild-type. CONCLUSIONS These sudden infant death syndrome (SIDS)-related variants caused a severely dysfunctional Nav1.5 channel, which was mainly due to trafficking defects caused by the Q1832E mutation. The decreased current density is likely to be a major contributing factor to arrhythmogenesis in Brugada syndrome and the sudden death of this SIDS victim.
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Affiliation(s)
- Ivan Gando
- Pediatrics, NYU School of Medicine, New York, NY
| | | | - Kundan Jana
- Pediatrics, NYU School of Medicine, New York, NY
| | - Thomas V McDonald
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY
| | - Yingying Tang
- Molecular Genetics Laboratory, Office of Chief Medical Examiner, New York, NY
| | - William A Coetzee
- Pediatrics, NYU School of Medicine, New York, NY.,Physiology & Neuroscience, NYU School of Medicine, New York, NY.,Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, NY
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14
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Taylor KC, Sanders CR. Regulation of KCNQ/Kv7 family voltage-gated K + channels by lipids. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1859:586-597. [PMID: 27818172 DOI: 10.1016/j.bbamem.2016.10.023] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 10/24/2016] [Accepted: 10/31/2016] [Indexed: 12/19/2022]
Abstract
Many years of studies have established that lipids can impact membrane protein structure and function through bulk membrane effects, by direct but transient annular interactions with the bilayer-exposed surface of protein transmembrane domains, and by specific binding to protein sites. Here, we focus on how phosphatidylinositol 4,5-bisphosphate (PIP2) and polyunsaturated fatty acids (PUFAs) impact ion channel function and how the structural details of the interactions of these lipids with ion channels are beginning to emerge. We focus on the Kv7 (KCNQ) subfamily of voltage-gated K+ channels, which are regulated by both PIP2 and PUFAs and play a variety of important roles in human health and disease. This article is part of a Special Issue entitled: Lipid order/lipid defects and lipid-control of protein activity edited by Dirk Schneider.
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Affiliation(s)
- Keenan C Taylor
- Department of Biochemistry, Vanderbilt University, Nashville, TN, USA; Center for Structural Biology, Vanderbilt University, Nashville, TN, USA
| | - Charles R Sanders
- Department of Biochemistry, Vanderbilt University, Nashville, TN, USA; Center for Structural Biology, Vanderbilt University, Nashville, TN, USA; Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA.
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15
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Nakajo K, Kubo Y. Steric hindrance between S4 and S5 of the KCNQ1/KCNE1 channel hampers pore opening. Nat Commun 2014; 5:4100. [PMID: 24920132 DOI: 10.1038/ncomms5100] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Accepted: 05/13/2014] [Indexed: 01/06/2023] Open
Abstract
In voltage-gated K(+) channels, membrane depolarization induces an upward movement of the voltage-sensing domains (VSD) that triggers pore opening. KCNQ1 is a voltage-gated K(+) channel and its gating behaviour is substantially modulated by auxiliary subunit KCNE proteins. KCNE1, for example, markedly shifts the voltage dependence of KCNQ1 towards the positive direction and slows down the activation kinetics. Here we identify two phenylalanine residues on KCNQ1, Phe232 on S4 (VSD) and Phe279 on S5 (pore domain) to be responsible for the gating modulation by KCNE1. Phe232 collides with Phe279 during the course of the VSD movement and hinders KCNQ1 channel from opening in the presence of KCNE1. This steric hindrance caused by the bulky amino-acid residues destabilizes the open state and thus shifts the voltage dependence of KCNQ1/KCNE1 channel.
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Affiliation(s)
- Koichi Nakajo
- 1] Division of Biophysics and Neurobiology, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan [2] Department of Physiological Sciences, Hayama, Kanagawa 240-0193, Japan
| | - Yoshihiro Kubo
- 1] Division of Biophysics and Neurobiology, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan [2] Department of Physiological Sciences, Hayama, Kanagawa 240-0193, Japan
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16
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Terrenoire C, Wang K, Tung KWC, Chung WK, Pass RH, Lu JT, Jean JC, Omari A, Sampson KJ, Kotton DN, Keller G, Kass RS. Induced pluripotent stem cells used to reveal drug actions in a long QT syndrome family with complex genetics. ACTA ACUST UNITED AC 2013; 141:61-72. [PMID: 23277474 PMCID: PMC3536519 DOI: 10.1085/jgp.201210899] [Citation(s) in RCA: 147] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Understanding the basis for differential responses to drug therapies remains a challenge despite advances in genetics and genomics. Induced pluripotent stem cells (iPSCs) offer an unprecedented opportunity to investigate the pharmacology of disease processes in therapeutically and genetically relevant primary cell types in vitro and to interweave clinical and basic molecular data. We report here the derivation of iPSCs from a long QT syndrome patient with complex genetics. The proband was found to have a de novo SCN5A LQT-3 mutation (F1473C) and a polymorphism (K897T) in KCNH2, the gene for LQT-2. Analysis of the biophysics and molecular pharmacology of ion channels expressed in cardiomyocytes (CMs) differentiated from these iPSCs (iPSC-CMs) demonstrates a primary LQT-3 (Na+ channel) defect responsible for the arrhythmias not influenced by the KCNH2 polymorphism. The F1473C mutation occurs in the channel inactivation gate and enhances late Na+ channel current (INaL) that is carried by channels that fail to inactivate completely and conduct increased inward current during prolonged depolarization, resulting in delayed repolarization, a prolonged QT interval, and increased risk of fatal arrhythmia. We find a very pronounced rate dependence of INaL such that increasing the pacing rate markedly reduces INaL and, in addition, increases its inhibition by the Na+ channel blocker mexiletine. These rate-dependent properties and drug interactions, unique to the proband’s iPSC-CMs, correlate with improved management of arrhythmias in the patient and provide support for this approach in developing patient-specific clinical regimens.
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Affiliation(s)
- Cecile Terrenoire
- Department of Pharmacology, College of Physicians and Surgeons, Columbia University Medical Center, New York, NY 10032, USA
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17
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Wilders R. Cardiac ion channelopathies and the sudden infant death syndrome. ISRN CARDIOLOGY 2012; 2012:846171. [PMID: 23304551 PMCID: PMC3529486 DOI: 10.5402/2012/846171] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Accepted: 10/23/2012] [Indexed: 12/13/2022]
Abstract
The sudden infant death syndrome (SIDS) causes the sudden death of an apparently healthy infant, which remains unexplained despite a thorough investigation, including the performance of a complete autopsy. The triple risk model for the pathogenesis of SIDS points to the coincidence of a vulnerable infant, a critical developmental period, and an exogenous stressor. Primary electrical diseases of the heart, which may cause lethal arrhythmias as a result of dysfunctioning cardiac ion channels (“cardiac ion channelopathies”) and are not detectable during a standard postmortem examination, may create the vulnerable infant and thus contribute to SIDS. Evidence comes from clinical correlations between the long QT syndrome and SIDS as well as genetic analyses in cohorts of SIDS victims (“molecular autopsy”), which have revealed a large number of mutations in ion channel-related genes linked to inheritable arrhythmogenic syndromes, in particular the long QT syndrome, the short QT syndrome, the Brugada syndrome, and catecholaminergic polymorphic ventricular tachycardia. Combining data from population-based cohort studies, it can be concluded that at least one out of five SIDS victims carries a mutation in a cardiac ion channel-related gene and that the majority of these mutations are of a known malignant phenotype.
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Affiliation(s)
- Ronald Wilders
- Department of Anatomy, Embryology and Physiology, Heart Failure Research Center, Academic Medical Center, University of Amsterdam, P.O. Box 22700, 1100 DE Amsterdam, The Netherlands
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18
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Abstract
PURPOSE OF REVIEW Sudden cardiac death (SCD) is a major public health burden, and evidence from family history and from molecular studies on inherited arrhythmogenic syndromes indicates that genetic factors are important contributors to the risk of SCD. This review discusses recent advances on the genetic predisposition to SCD, with a specific focus on primary ventricular fibrillation and channelopathies. RECENT FINDINGS Coronary artery disease is the major determinant of SCD, and its predisposing genetic background is complex. Very recently, a first genome-wide association study on primary ventricular fibrillation was published but the results are not conclusive and further studies with greater numbers are needed. Among channelopathies, long QT syndrome and Brugada syndrome are those in which more significant advances have been reported in the last year. Of note is the recently described early repolarization syndrome and the proposed classification of J wave syndromes. Revision of current guidelines for autopsy investigation has introduced molecular autopsy as a standard requirement for adequate assessment of SCD. SUMMARY Interesting data on the genetic basis of sudden cardiac death have been published in the past year, and, whereas in the field of channelopathies research findings have been partially recognized by current guidelines and translated into clinical practice, in the field of coronary artery disease further advances are still needed.
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19
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Ackerman MJ, Priori SG, Willems S, Berul C, Brugada R, Calkins H, Camm AJ, Ellinor PT, Gollob M, Hamilton R, Hershberger RE, Judge DP, Le Marec H, McKenna WJ, Schulze-Bahr E, Semsarian C, Towbin JA, Watkins H, Wilde A, Wolpert C, Zipes DP. HRS/EHRA expert consensus statement on the state of genetic testing for the channelopathies and cardiomyopathies this document was developed as a partnership between the Heart Rhythm Society (HRS) and the European Heart Rhythm Association (EHRA). Heart Rhythm 2012; 8:1308-39. [PMID: 21787999 DOI: 10.1016/j.hrthm.2011.05.020] [Citation(s) in RCA: 729] [Impact Index Per Article: 60.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Indexed: 10/18/2022]
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20
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Electrophysiological study of V535M hERG mutation of LQT2. ACTA ACUST UNITED AC 2011; 31:741-748. [DOI: 10.1007/s11596-011-0670-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Indexed: 10/14/2022]
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21
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Ackerman MJ, Priori SG, Willems S, Berul C, Brugada R, Calkins H, Camm AJ, Ellinor PT, Gollob M, Hamilton R, Hershberger RE, Judge DP, Le Marec H, McKenna WJ, Schulze-Bahr E, Semsarian C, Towbin JA, Watkins H, Wilde A, Wolpert C, Zipes DP. HRS/EHRA expert consensus statement on the state of genetic testing for the channelopathies and cardiomyopathies: this document was developed as a partnership between the Heart Rhythm Society (HRS) and the European Heart Rhythm Association (EHRA). Europace 2011; 13:1077-109. [PMID: 21810866 DOI: 10.1093/europace/eur245] [Citation(s) in RCA: 569] [Impact Index Per Article: 43.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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22
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Cardiac ion channel mutations in the sudden infant death syndrome. Int J Cardiol 2011; 152:162-70. [DOI: 10.1016/j.ijcard.2010.12.051] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Revised: 11/27/2010] [Accepted: 12/08/2010] [Indexed: 12/19/2022]
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23
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Tfelt-Hansen J, Winkel BG, Grunnet M, Jespersen T. Cardiac channelopathies and sudden infant death syndrome. Cardiology 2011; 119:21-33. [PMID: 21778721 DOI: 10.1159/000329047] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2011] [Accepted: 04/24/2011] [Indexed: 12/19/2022]
Abstract
Sudden infant death syndrome (SIDS) is always a devastating and unexpected occurrence. SIDS is the leading cause of death in the first 6 months after birth in the industrialized world. Since the discovery in 1998 of long QT syndrome as an underlying substrate for SIDS, around 10-20% of SIDS cases have been proposed as being caused by genetic variants in either ion channel or ion channel-associated proteins. Until now, 10 cardiac channelopathy susceptibility genes have been found to be implicated in the pathogenesis of SIDS. Four of the genes encode cardiac ion channel α-subunits, 3 genes encode ion channel β-subunits, and 3 genes encode other channel-interacting proteins. All 10 genes have been associated with primary electrical heart diseases. SIDS may hereby be the initial symptom of rare primary electric channelopathies such as long QT, short QT and Brugada syndrome, as well as catecholaminergic polymorphic ventricular tachycardia. In this review we describe the functional role of sodium, potassium and calcium channels in propagation, depolarization and repolarization in the context of the 4 arrhythmogenic diseases reported to be associated with SIDS. Lastly, the possibility of postmortem genetic testing and potential recommendations on how to deal with family members are discussed.
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Affiliation(s)
- Jacob Tfelt-Hansen
- Danish National Research Foundation Centre for Cardiac Arrhythmia (DARC), Copenhagen, Denmark.
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24
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Shimizu W, Horie M. Phenotypic Manifestations of Mutations in Genes Encoding Subunits of Cardiac Potassium Channels. Circ Res 2011; 109:97-109. [DOI: 10.1161/circresaha.110.224600] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Since 1995, when a potassium channel gene,
hERG
(human ether-à-go-go-related gene), now referred to as
KCNH2
, encoding the rapid component of cardiac delayed rectifier potassium channels was identified as being responsible for type 2 congenital long-QT syndrome, a number of potassium channel genes have been shown to cause different types of inherited cardiac arrhythmia syndromes. These include congenital long-QT syndrome, short-QT syndrome, Brugada syndrome, early repolarization syndrome, and familial atrial fibrillation. Genotype-phenotype correlations have been investigated in some inherited arrhythmia syndromes, and as a result, gene-specific risk stratification and gene-specific therapy and management have become available, particularly for patients with congenital long-QT syndrome. In this review article, the molecular structure and function of potassium channels, the clinical phenotype due to potassium channel gene mutations, including genotype-phenotype correlations, and the diverse mechanisms underlying the potassium channel gene–related diseases will be discussed.
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Affiliation(s)
- Wataru Shimizu
- From the Division of Arrhythmia and Electrophysiology, Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Center (W.S.), Suita, Japan, and the Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science (M.H.), Otsu, Japan
| | - Minoru Horie
- From the Division of Arrhythmia and Electrophysiology, Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Center (W.S.), Suita, Japan, and the Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science (M.H.), Otsu, Japan
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25
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Abstract
Sudden infant death syndrome (SIDS) is a major contributor to postneonatal infant death, and is the third leading cause of infant mortality in the USA. While public health efforts have reduced these deaths in recent years, the pathogenesis of SIDS remains unclear. Epidemiological data on SIDS-related deaths have suggested genetic factors, and many studies have attempted to identify SIDS-associated genes. This has resulted in a large body of literature implicating various genes and their encoded proteins and signaling pathways in numerous cohorts of various sizes and ethnicities. This review has undertaken a systematic evaluation of these studies, identifying the pathways that have been implicated in these studies, including central nervous system pathways, cardiac channelopathies, immune dysfunction, metabolism/energy pathways, and nicotine response. This review also explores how new genomic techniques will aid in advancing our knowledge of the genomic risk factors associated with SIDS, including SNPs and copy number variation. Last, this review explores how the current information can be applied to aid in our assessment of the at risk infant population.
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Affiliation(s)
- David W Van Norstrand
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, USA.
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26
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Nof E, Cordeiro JM, Pérez GJ, Scornik FS, Calloe K, Love B, Burashnikov E, Caceres G, Gunsburg M, Antzelevitch C. A common single nucleotide polymorphism can exacerbate long-QT type 2 syndrome leading to sudden infant death. ACTA ACUST UNITED AC 2010; 3:199-206. [PMID: 20181576 DOI: 10.1161/circgenetics.109.898569] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BACKGROUND Identification of infants at risk for sudden arrhythmic death remains one of the leading challenges of modern medicine. We present a family in which a common polymorphism (single nucleotide polymorphism) inherited from the father, combined with a stop codon mutation inherited from the mother (both asymptomatic), led to 2 cases of sudden infant death. METHODS AND RESULTS KCNQ1, KCNH2, SCN5A, KCNE1, KCNE2, CACNA1c, CACNB2b, and KCNJ2 genes were amplified and analyzed by direct sequencing. Functional electrophysiological studies were performed with the single nucleotide polymorphism and mutation expressed singly and in combination in Chinese ovary (CHO-K1) and COS-1 cells. An asymptomatic woman presenting after the death of her 2-day-old infant and spontaneous abortion of a second baby in the first trimester was referred for genetic analysis. The newborn infant had nearly incessant ventricular tachycardia while in utero and a prolonged QTc (560 ms). The mother was asymptomatic but displayed a prolonged QTc. Genetic screening of the mother revealed a heterozygous nonsense mutation (P926AfsX14) in KCNH2, predicting a stop codon. The father was asymptomatic with a normal QTc but had a heterozygous polymorphism (K897T) in KCNH2. The baby who died at 2 days of age and the aborted fetus inherited both K897T and P926AfsX14. Heterologous coexpression of K897T and P926AfsX14 led to loss of function of HERG current much greater than expression of K897T or P926AfsX14 alone. CONCLUSIONS Our data suggest that a common polymorphism (K897T) can markedly accentuate the loss of function of mildly defective HERG channels, leading to long-QT syndrome-mediated arrhythmias and sudden infant death.
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Affiliation(s)
- Eyal Nof
- Masonic Medical Research Laboratory, Utica, NY 13501, USA
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27
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Crotti L, Taravelli E, Girardengo G, Schwartz PJ. Congenital short QT syndrome. Indian Pacing Electrophysiol J 2010; 10:86-95. [PMID: 20126594 PMCID: PMC2811207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
The Short QT Syndrome is a recently described new genetic disorder, characterized by abnormally short QT interval, paroxysmal atrial fibrillation and life threatening ventricular arrhythmias. This autosomal dominant syndrome can afflict infants, children, or young adults; often a remarkable family background of cardiac sudden death is elucidated. At electrophysiological study, short atrial and ventricular refractory periods are found, with atrial fibrillation and polymorphic ventricular tachycardia easily induced by programmed electrical stimulation. Gain of function mutations in three genes encoding K(+) channels have been identified, explaining the abbreviated repolarization seen in this condition: KCNH2 for I(kr) (SQT1), KCNQ1 for I(ks) (SQT2) and KCNJ2 for I(k1) (SQT3). The currently suggested therapeutic strategy is an ICD implantation, although many concerns exist for asymptomatic patients, especially in pediatric age. Pharmacological treatment is still under evaluation; quinidine has shown to prolong QT and reduce the inducibility of ventricular arrhythmias, but awaits additional confirmatory clinical data.
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Affiliation(s)
- Lia Crotti
- Section of Cardiology, Department of Lung, Blood and Heart, University of Pavia, Pavia, Italy ,Department of Cardiology, IRCCS Fondazione Policlinico S. Matteo, Pavia, Italy,Molecular Cardiology Laboratory, IRCCS Fondazione Policlinico S. Matteo, Pavia, Italy
| | - Erika Taravelli
- Section of Cardiology, Department of Lung, Blood and Heart, University of Pavia, Pavia, Italy ,Department of Cardiology, IRCCS Fondazione Policlinico S. Matteo, Pavia, Italy
| | - Giulia Girardengo
- Section of Cardiology, Department of Lung, Blood and Heart, University of Pavia, Pavia, Italy ,Department of Cardiology, IRCCS Fondazione Policlinico S. Matteo, Pavia, Italy
| | - Peter J Schwartz
- Section of Cardiology, Department of Lung, Blood and Heart, University of Pavia, Pavia, Italy ,Department of Cardiology, IRCCS Fondazione Policlinico S. Matteo, Pavia, Italy,Molecular Cardiology Laboratory, IRCCS Fondazione Policlinico S. Matteo, Pavia, Italy,Laboratory of Cardiovascular Genetics, IRCCS Istituto Auxologico, Milan, Italy,Cardiovascular Genetics Laboratory, Hatter Institute for Cardiovascular Research, University of Cape Town, Cape Town, South Africa,Sudden Death Chair, King Saud University, Riyadh, Saudi Arabia
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28
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Mathur N, Sood S, Wang S, van Oort RJ, Sarma S, Li N, Skapura DG, Bayle JH, Valderrábano M, Wehrens XHT. Sudden infant death syndrome in mice with an inherited mutation in RyR2. Circ Arrhythm Electrophysiol 2010; 2:677-85. [PMID: 20009080 DOI: 10.1161/circep.109.894683] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Mutations in the cardiac ryanodine receptor gene (RyR2) have been recently identified in victims of sudden infant death syndrome. The aim of this study was to determine whether a gain-of-function mutation in RyR2 increases the propensity to cardiac arrhythmias and sudden death in young mice. METHODS AND RESULTS Incidence of sudden death was monitored prospectively in heterozygous knock-in mice with mutation R176Q in RyR2 (R176Q/+). Young R176Q/+ mice exhibited a higher incidence of sudden death compared with wild-type littermates. Optical mapping of membrane potentials and intracellular calcium in 1- to 7-day-old R176Q/+ and wild-type mice revealed an increased incidence of ventricular ectopy and spontaneous calcium releases in neonatal R176Q/+ mice. Surface ECGs in 3- to 10-day-old mice showed that R176Q/+ mice developed more ventricular arrhythmias after provocation with epinephrine and caffeine. Intracardiac pacing studies in 12- to 18-day-old mice revealed the presence of an arrhythmogenic substrate in R176Q/+ compared with wild-type mice. Reverse transcription-polymerase chain reaction and Western blotting showed that expression levels of other calcium handling proteins were unaltered, suggesting that calcium leak through mutant RyR2 underlies arrhythmogenesis and sudden death in young R176Q/+ mice. CONCLUSIONS Our findings demonstrate that a gain-of-function mutation in RyR2 confers an increased risk of cardiac arrhythmias and sudden death in young mice and that young R176Q/+ mice may be used as a model for elucidating the complex interplay between genetic and environmental risk factors associated with sudden infant death syndrome.
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Affiliation(s)
- Nitin Mathur
- Department of Molecular Physiology and Biophysics, Division of Cardiology, Baylor College of Medicine, Houston, TX 77030, USA
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29
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Winbo A, Diamant UB, Stattin EL, Jensen SM, Rydberg A. Low Incidence of Sudden Cardiac Death in a Swedish Y111C Type 1 Long-QT syndrome Population. ACTA ACUST UNITED AC 2009; 2:558-64. [DOI: 10.1161/circgenetics.108.825547] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background—
A 10% cumulative incidence and a 0.3% per year incidence rate of sudden cardiac death in patients younger than 40 years and without therapy have been reported in type 1 long-QT syndrome. The Y111C-KCNQ1 mutation causes a severe phenotype in vitro, suggesting a high-risk mutation. This study investigated the phenotype among Y111C-KCNQ1 mutation carriers in the Swedish population with a focus on life-threatening cardiac events.
Methods and Results—
We identified 80 mutation carriers in 15 index families, segregating the Y111C-KCNQ1 mutation during a national inventory of mutations causing the long-QT syndrome. Twenty-four mutation carriers <40 years experienced syncope (30%). One mutation carrier had an aborted cardiac arrest (1.25%). No case of sudden cardiac death was reported during a mean nonmedicated follow-up of 25�20 years. This corresponds to a low incidence rate of life-threatening cardiac events (0.05%/year versus 0.3%/year,
P
=0.025). In 8 Y111C families connected by a common ancestor, the natural history of the mutation was assessed by investigating the survival over the age of 40 years for 107 nonmedicated ascertained mutation carriers (n=24) and family members (n=83) born between 1873 and 1968. In total, 4 deaths in individuals younger than 40 years were noted: 1 case of noncardiac death and 3 infant deaths between 1873 and 1915.
Conclusions—
The dominant-negative Y111C-KCNQ1 mutation, associated with a severe phenotype in vitro, presents with a low incidence of life-threatening cardiac events in a Swedish population. This finding of discrepancy emphasizes the importance of clinical observations in the risk stratification of long-QT syndrome.
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Affiliation(s)
- Annika Winbo
- From the Division of Pediatrics, Department of Clinical Sciences (A.W., A.R.), Cardiology Heart Centre and the Division of Medicine, Department of Public Health and Clinical Medicine (U.-B.D., S.M.J.) and Medical and Clinical Genetics, Department of Medical Biosciences (E.-L.S.), Umeå University Hospital, Umeå, Sweden
| | - Ulla-Britt Diamant
- From the Division of Pediatrics, Department of Clinical Sciences (A.W., A.R.), Cardiology Heart Centre and the Division of Medicine, Department of Public Health and Clinical Medicine (U.-B.D., S.M.J.) and Medical and Clinical Genetics, Department of Medical Biosciences (E.-L.S.), Umeå University Hospital, Umeå, Sweden
| | - Eva-Lena Stattin
- From the Division of Pediatrics, Department of Clinical Sciences (A.W., A.R.), Cardiology Heart Centre and the Division of Medicine, Department of Public Health and Clinical Medicine (U.-B.D., S.M.J.) and Medical and Clinical Genetics, Department of Medical Biosciences (E.-L.S.), Umeå University Hospital, Umeå, Sweden
| | - Steen M. Jensen
- From the Division of Pediatrics, Department of Clinical Sciences (A.W., A.R.), Cardiology Heart Centre and the Division of Medicine, Department of Public Health and Clinical Medicine (U.-B.D., S.M.J.) and Medical and Clinical Genetics, Department of Medical Biosciences (E.-L.S.), Umeå University Hospital, Umeå, Sweden
| | - Annika Rydberg
- From the Division of Pediatrics, Department of Clinical Sciences (A.W., A.R.), Cardiology Heart Centre and the Division of Medicine, Department of Public Health and Clinical Medicine (U.-B.D., S.M.J.) and Medical and Clinical Genetics, Department of Medical Biosciences (E.-L.S.), Umeå University Hospital, Umeå, Sweden
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30
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Hedley PL, Jørgensen P, Schlamowitz S, Wangari R, Moolman-Smook J, Brink PA, Kanters JK, Corfield VA, Christiansen M. The genetic basis of long QT and short QT syndromes: A mutation update. Hum Mutat 2009; 30:1486-511. [DOI: 10.1002/humu.21106] [Citation(s) in RCA: 318] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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31
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Kaufman ES. Mechanisms and clinical management of inherited channelopathies: Long QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia, and short QT syndrome. Heart Rhythm 2009; 6:S51-5. [DOI: 10.1016/j.hrthm.2009.02.009] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2008] [Indexed: 10/21/2022]
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32
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Abraham RL, Yang T, Blair M, Roden DM, Darbar D. Augmented potassium current is a shared phenotype for two genetic defects associated with familial atrial fibrillation. J Mol Cell Cardiol 2009; 48:181-90. [PMID: 19646991 DOI: 10.1016/j.yjmcc.2009.07.020] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Revised: 07/10/2009] [Accepted: 07/23/2009] [Indexed: 12/19/2022]
Abstract
Mutations in multiple genes have been implicated in familial atrial fibrillation (AF), but the underlying mechanisms, and thus implications for therapy, remain ill-defined. Among 231 participants in the Vanderbilt AF Registry, we found a mutation in KCNQ1 (encoding the alpha-subunit of slow delayed rectifier potassium current [I(Ks)]) and separately a mutation in natriuretic peptide precursor A (NPPA) gene (encoding atrial natriuretic peptide, ANP), both segregating with early onset lone AF in different kindreds. The functional effects of these mutations yielded strikingly similar I(Ks) "gain-of-function." In Chinese Hamster Ovary (CHO) cells, coexpression of mutant KCNQ1 with its ancillary subunit KCNE1 generated approximately 3-fold larger currents that activated much faster than wild-type (WT)-I(Ks). Application of the WT NPPA peptide fragment produced similar changes in WT-I(Ks), and these were exaggerated with the mutant NPPA S64R peptide fragment. Anantin, a competitive ANP receptor antagonist, completely inhibited the changes in I(Ks) gating observed with NPPA S64R. Computational simulations identified accelerated transitions into open states as the mechanism for variant I(Ks) gating. Incorporating these I(Ks) changes into computed human atrial action potentials (AP) resulted in 37% shortening (120 vs. 192 ms at 300 ms cycle length), reflecting loss of the phase II dome which is dependent on L-type calcium channel current. We found striking functional similarities due to mutations in KCNQ1 and NPPA genes which led to I(Ks) "gain-of-function", atrial AP shortening, and consequently altered calcium current as a common mechanism between diverse familial AF syndromes.
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Affiliation(s)
- Robert L Abraham
- Division of Cardiovascular Medicine, Vanderbilt University School of Medicine, 1285A MRB IV, 2311 Pierce Avenue, Nashville, TN 37232-6602, USA
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33
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Wang DW, Crotti L, Shimizu W, Pedrazzini M, Cantu F, De Filippo P, Kishiki K, Miyazaki A, Ikeda T, Schwartz PJ, George AL. Malignant perinatal variant of long-QT syndrome caused by a profoundly dysfunctional cardiac sodium channel. Circ Arrhythm Electrophysiol 2008; 1:370-8. [PMID: 19808432 DOI: 10.1161/circep.108.788349] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
BACKGROUND Inherited cardiac arrhythmia susceptibility contributes to sudden death during infancy and may contribute to perinatal and neonatal mortality, but the molecular basis of this risk and the relationship to genetic disorders presenting later in life is unclear. We studied the functional and pharmacological properties of a novel de novo cardiac sodium channel gene (SCN5A) mutation associated with an extremely severe perinatal presentation of long-QT syndrome in unrelated probands of different ethnicity. METHODS AND RESULTS Two subjects exhibiting severe fetal and perinatal ventricular arrhythmias were screened for SCN5A mutations, and the functional properties of a novel missense mutation (G1631D) were determined by whole-cell patch clamp recording. In vitro electrophysiological studies revealed a profound defect in sodium channel function characterized by approximately 10-fold slowing of inactivation, increased persistent current, slowing of recovery from inactivation, and depolarized voltage dependence of activation and inactivation. Single-channel recordings demonstrated increased frequency of late openings, prolonged mean open time, and increased latency to first opening for the mutant. Subjects carrying this mutation responded clinically to the combination of mexiletine with propranolol and survived. Pharmacologically, the mutant exhibited 2-fold greater tonic and use-dependent mexiletine block than wild-type channels. The mutant also exhibited enhanced tonic (2.4-fold) and use-dependent block ( approximately 5-fold) by propranolol, and we observed additive effects of the 2 drugs on the mutant. CONCLUSIONS Our study demonstrates the molecular basis for a malignant perinatal presentation of long-QT syndrome, illustrates novel functional and pharmacological properties of SCN5A-G1631D, which caused the disorder, and reveals therapeutic benefits of propranolol block of mutant sodium channels in this setting.
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Affiliation(s)
- Dao W Wang
- Department of Medicine, Vanderbilt University, Nashville, TN 37232-0275, USA
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Abstract
Over the past decade, molecular genetic studies have established a link between a number of inherited cardiac arrhythmias, including congenital long QT syndrome (LQTS) and Brugada syndrome (BrS), and mutations in genes encoding for ion channels or other membrane components. Twelve forms of LQTS have been identified in 50-70% of clinically affected patients. Genotype-phenotype correlations have been rigorously investigated in LQT1, LQT2 and LQT3 syndromes, which constitute more than 90% of genotyped LQTS patients, enabling stratification of risk and effective treatment of genotyped patients. Genotype-specific triggers for both the cardiac events and the clinical course have been reported, and genotype-specific therapy has been already introduced. More recently, mutation site-specific differences in the clinical phenotype have been reported in LQT1 and LQT2 patients, indicating the possibility of mutation site-specific management or treatment. In contrast, only one-third of BrS patients can be genotyped, and data on genotype-phenotype relationships in clinical studies are limited. A Haplotype B consisting of 6 individual DNA polymorphisms within the proximal promoter region of the SCN5A gene was recently identified only in Asians (frequency 22%). Individuals with Haplotype B show significantly longer duration of both PQ and QRS than those without Haplotype B, indicating that Haplotype B likely contributes to the higher incidence of BrS in Asian populations.
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Affiliation(s)
- Wataru Shimizu
- Division of Cardiology, Department of Internal Medicine, National Cardiovascular Center, Suita, Japan.
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Sale H, Wang J, O'Hara TJ, Tester DJ, Phartiyal P, He JQ, Rudy Y, Ackerman MJ, Robertson GA. Physiological properties of hERG 1a/1b heteromeric currents and a hERG 1b-specific mutation associated with Long-QT syndrome. Circ Res 2008; 103:e81-95. [PMID: 18776039 DOI: 10.1161/circresaha.108.185249] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cardiac I Kr is a critical repolarizing current in the heart and a target for inherited and acquired long-QT syndrome (LQTS). Biochemical and functional studies have demonstrated that I Kr channels are heteromers composed of both hERG 1a and 1b subunits, yet our current understanding of I Kr functional properties derives primarily from studies of homooligomers of the original hERG 1a isolate. Here, we examine currents produced by hERG 1a and 1a/1b channels expressed in HEK-293 cells at near-physiological temperatures. We find that heteromeric hERG 1a/1b currents are much larger than hERG 1a currents and conduct 80% more charge during an action potential. This surprising difference corresponds to a 2-fold increase in the apparent rates of activation and recovery from inactivation, thus reducing rectification and facilitating current rebound during repolarization. Kinetic modeling shows these gating differences account quantitatively for the differences in current amplitude between the 2 channel types. Drug sensitivity was also different. Compared to homomeric 1a channels, heteromeric 1a/1b channels were inhibited by E-4031 with a slower time course and a corresponding 4-fold shift in the IC50. The importance of hERG 1b in vivo is supported by the identification of a 1b-specific A8V missense mutation in 1/269 unrelated genotype-negative LQTS patients that was absent in 400 control alleles. Mutant 1bA8V expressed alone or with hERG 1a in HEK-293 cells dramatically reduced 1b protein levels. Thus, mutations specifically disrupting hERG 1b function are expected to reduce cardiac I Kr and enhance drug sensitivity, and represent a potential mechanism underlying inherited or acquired LQTS.
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Affiliation(s)
- Harinath Sale
- Department of Physiology, University of Wisconsin, Madison, WI, USA
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Cellular properties of C-terminal KCNH2 long QT syndrome mutations: Description and divergence from clinical phenotypes. Heart Rhythm 2008; 5:1159-67. [DOI: 10.1016/j.hrthm.2008.04.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2008] [Accepted: 04/15/2008] [Indexed: 11/22/2022]
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Van Norstrand DW, Ackerman MJ. Sudden infant death syndrome: do ion channels play a role? Heart Rhythm 2008; 6:272-8. [PMID: 18823823 DOI: 10.1016/j.hrthm.2008.07.028] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2008] [Indexed: 12/19/2022]
Affiliation(s)
- David W Van Norstrand
- Mayo Clinic, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minnesota 55905, USA
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Crotti L, Celano G, Dagradi F, Schwartz PJ. Congenital long QT syndrome. Orphanet J Rare Dis 2008; 3:18. [PMID: 18606002 PMCID: PMC2474834 DOI: 10.1186/1750-1172-3-18] [Citation(s) in RCA: 175] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2008] [Accepted: 07/07/2008] [Indexed: 12/15/2022] Open
Abstract
Congenital long QT syndrome (LQTS) is a hereditary cardiac disease characterized by a prolongation of the QT interval at basal ECG and by a high risk of life-threatening arrhythmias. Disease prevalence is estimated at close to 1 in 2,500 live births. The two cardinal manifestations of LQTS are syncopal episodes, that may lead to cardiac arrest and sudden cardiac death, and electrocardiographic abnormalities, including prolongation of the QT interval and T wave abnormalities. The genetic basis of the disease was identified in the mid-nineties and all the LQTS genes identified so far encode cardiac ion channel subunits or proteins involved in modulating ionic currents. Mutations in these genes (KCNQ1, KCNH2, KCNE1, KCNE2, CACNA1c, CAV3, SCN5A, SCN4B) cause the disease by prolonging the duration of the action potential. The most prevalent LQTS variant (LQT1) is caused by mutations in the KCNQ1 gene, with approximately half of the genotyped patients carrying KCNQ1 mutations. Given the characteristic features of LQTS, the typical cases present no diagnostic difficulties for physicians aware of the disease. However, borderline cases are more complex and require the evaluation of various electrocardiographic, clinical, and familial findings, as proposed in specific diagnostic criteria. Additionally, molecular screening is now part of the diagnostic process. Treatment should always begin with beta-blockers, unless there are valid contraindications. If the patient has one more syncope despite a full dose beta-blockade, left cardiac sympathetic denervation (LCSD) should be performed without hesitation and implantable cardioverter defibrillator (ICD) therapy should be considered with the final decision being based on the individual patient characteristics (age, sex, clinical history, genetic subgroup including mutation-specific features in some cases, presence of ECG signs - including 24-hour Holter recordings - indicating high electrical instability). The prognosis of the disease is usually good in patients that are correctly diagnosed and treated. However, there are a few exceptions: patients with Timothy syndrome, patients with Jervell Lange-Nielsen syndrome carrying KCNQ1 mutations and LQT3 patients with 2:1 atrio-ventricular block and very early occurrence of cardiac arrhythmias.
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Affiliation(s)
- Lia Crotti
- Section of Cardiology, Department of Lung, Blood and Heart, University of Pavia, Pavia, Italy
- Department of Cardiology, IRCCS Fondazione Policlinico S. Matteo, Pavia, Italy
- Molecular Cardiology Laboratory, IRCCS Fondazione Policlinico S. Matteo, Pavia, Italy
| | - Giuseppe Celano
- Section of Cardiology, Department of Lung, Blood and Heart, University of Pavia, Pavia, Italy
- Department of Cardiology, IRCCS Fondazione Policlinico S. Matteo, Pavia, Italy
| | - Federica Dagradi
- Section of Cardiology, Department of Lung, Blood and Heart, University of Pavia, Pavia, Italy
- Department of Cardiology, IRCCS Fondazione Policlinico S. Matteo, Pavia, Italy
| | - Peter J Schwartz
- Section of Cardiology, Department of Lung, Blood and Heart, University of Pavia, Pavia, Italy
- Department of Cardiology, IRCCS Fondazione Policlinico S. Matteo, Pavia, Italy
- Molecular Cardiology Laboratory, IRCCS Fondazione Policlinico S. Matteo, Pavia, Italy
- Laboratory of Cardiovascular Genetics, IRCCS Istituto Auxologico, Milan, Italy
- Department of Medicine, University of Stellenbosch, South Africa
- Cardiovascular Genetics Laboratory, Hatter Institute for Cardiovascular Research, Department of Medicine, University of Cape Town, South Africa
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Shimizu W. Genetics of congenital long QT syndrome and Brugada syndrome. Future Cardiol 2008; 4:379-89. [PMID: 19804318 DOI: 10.2217/14796678.4.4.379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The inherited cardiac arrhythmias including congenital and acquired long QT syndrome (LQTS), Brugada syndrome, progressive cardiac conduction defect, catecholaminergic polymorphic ventricular tachycardia, arrhythmogenic right ventricular cardiomyopathy, familial atrial fibrillation, familial sick sinus syndrome and short QT syndrome, are linked to mutations in genes encoding for ion channels or other membrane components. Eleven forms of congenital LQTS have been identified and these are caused by mutations in genes of the potassium, sodium and calcium channels or membrane adapter. Genotype-phenotype correlations have been rigorously investigated, especially in the LQT1, LQT2 and LQT3 forms, which constitute more than 90% of genotyped patients. On the other hand, causative mutations were identified much less in patients with Brugada syndrome, therefore data on genotype-phenotype relationships are limited.
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Affiliation(s)
- Wataru Shimizu
- National Cardiovascular Center, Division of Cardiology, Department of Internal Medicine, 5-7-1 Fujishiro-dai, Suita, Osaka, 565-8565 Japan.
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