1
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Schwartz PJ, Sala L. The impact of genetics on the long QT syndrome: myth or reality? Curr Opin Cardiol 2023; 38:149-156. [PMID: 36789771 DOI: 10.1097/hco.0000000000001027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
PURPOSE OF REVIEW To summarize and critically assess the contribution of genetics to the Long QT Syndrome (LQTS), with specific reference to the unraveling of its underlying mechanisms and to its impact on clinical practice. RECENT FINDINGS The evolution towards our current approach to therapy for LQTS patients is examined in terms of risk stratification, gene-specific management, and assessment of the clinical impact that genetic modifiers may have in modulating the natural history of the patients. Glimpses are provided on the newest multidisciplinary approaches to study disease mechanisms, test new candidate drugs and identify precision treatments. SUMMARY It is undeniable that genetics has revolutionized our mechanistic understanding of cardiac channelopathies. Its impact has been enormous but, curiously, the way LQTS patients are being treated today is largely the same that was used in the pregenetic era, even though management has been refined and gene-specific differences allow a more individually tailored antiarrhythmic protection. The synergy of genetic findings with modern in vitro and in silico tools may expand precision treatments; however, they will need to prove more effective than the current therapeutic approaches and equally safe.
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Affiliation(s)
- Peter J Schwartz
- Istituto Auxologico Italiano IRCCS, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics
| | - Luca Sala
- Istituto Auxologico Italiano IRCCS, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics.,Department of Biotechnology and Biosciences, University of Milano - Bicocca, Milan, Italy
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2
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Song Y, Zheng Z, Lian J. Deciphering Common Long QT Syndrome Using CRISPR/Cas9 in Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes. Front Cardiovasc Med 2022; 9:889519. [PMID: 35647048 PMCID: PMC9136094 DOI: 10.3389/fcvm.2022.889519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Accepted: 04/22/2022] [Indexed: 11/13/2022] Open
Abstract
From carrying potentially pathogenic genes to severe clinical phenotypes, the basic research in the inherited cardiac ion channel disease such as long QT syndrome (LQTS) has been a significant challenge in explaining gene-phenotype heterogeneity. These have opened up new pathways following the parallel development and successful application of stem cell and genome editing technologies. Stem cell-derived cardiomyocytes and subsequent genome editing have allowed researchers to introduce desired genes into cells in a dish to replicate the disease features of LQTS or replace causative genes to normalize the cellular phenotype. Importantly, this has made it possible to elucidate potential genetic modifiers contributing to clinical heterogeneity and hierarchically manage newly identified variants of uncertain significance (VUS) and more therapeutic options to be tested in vitro. In this paper, we focus on and summarize the recent advanced application of human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) combined with clustered regularly interspaced short palindromic repeats/CRISPR-associated system 9 (CRISPR/Cas9) in the interpretation for the gene-phenotype relationship of the common LQTS and presence challenges, increasing our understanding of the effects of mutations and the physiopathological mechanisms in the field of cardiac arrhythmias.
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Affiliation(s)
- Yongfei Song
- Department of Cardiovascular, Ningbo Institute of Innovation for Combined Medicine and Engineering, Ningbo, China
- Yongfei Song
| | - Zequn Zheng
- Department of Cardiovascular, Medical College, Ningbo University, Ningbo, China
- Department of Cardiovascular, Lihuili Hospital Affiliated to Ningbo University, Ningbo, China
| | - Jiangfang Lian
- Department of Cardiovascular, Ningbo Institute of Innovation for Combined Medicine and Engineering, Ningbo, China
- Department of Cardiovascular, Medical College, Ningbo University, Ningbo, China
- Department of Cardiovascular, Lihuili Hospital Affiliated to Ningbo University, Ningbo, China
- *Correspondence: Jiangfang Lian
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3
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van den Brink L, Brandão KO, Yiangou L, Blanch-Asensio A, Mol MPH, Mummery CL, Verkerk AO, Davis RP. The Linkage Phase of the Polymorphism KCNH2-K897T Influences the Electrophysiological Phenotype in hiPSC Models of LQT2. Front Physiol 2022; 12:755642. [PMID: 34992545 PMCID: PMC8726482 DOI: 10.3389/fphys.2021.755642] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 11/10/2021] [Indexed: 12/29/2022] Open
Abstract
While rare mutations in ion channel genes are primarily responsible for inherited cardiac arrhythmias, common genetic variants are also an important contributor to the clinical heterogeneity observed among mutation carriers. The common single nucleotide polymorphism (SNP) KCNH2-K897T is associated with QT interval duration, but its influence on the disease phenotype in patients with long QT syndrome type 2 (LQT2) remains unclear. Human induced pluripotent stem cells (hiPSCs), coupled with advances in gene editing technologies, are proving an invaluable tool for modeling cardiac genetic diseases and identifying variants responsible for variability in disease expressivity. In this study, we have used isogenic hiPSC-derived cardiomyocytes (hiPSC-CMs) to establish the functional consequences of having the KCNH2-K897T SNP in cis- or trans-orientation with LQT2-causing missense variants either within the pore-loop domain (KCNH2A561T/WT) or tail region (KCNH2N996I/WT) of the potassium ion channel, human ether-a-go-go-related gene (hERG). When KCNH2-K897T was on the same allele (cis) as the primary mutation, the hERG channel in hiPSC-CMs exhibited faster activation and deactivation kinetics compared to their trans-oriented counterparts. Consistent with this, hiPSC-CMs with KCNH2-K897T in cis orientation had longer action and field potential durations. Furthermore, there was an increased occurrence of arrhythmic events upon pharmacological blocking of hERG. Collectively, these results indicate that the common polymorphism KCNH2-K897T differs in its influence on LQT2-causing KCNH2 mutations depending on whether it is present in cis or trans. This study corroborates hiPSC-CMs as a powerful platform to investigate the modifying effects of common genetic variants on inherited cardiac arrhythmias and aids in unraveling their contribution to the variable expressivity of these diseases.
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Affiliation(s)
- Lettine van den Brink
- Department of Anatomy and Embryology, Leiden University Medical Center, Leiden, Netherlands
| | - Karina O Brandão
- Department of Anatomy and Embryology, Leiden University Medical Center, Leiden, Netherlands
| | - Loukia Yiangou
- Department of Anatomy and Embryology, Leiden University Medical Center, Leiden, Netherlands
| | - Albert Blanch-Asensio
- Department of Anatomy and Embryology, Leiden University Medical Center, Leiden, Netherlands
| | - Mervyn P H Mol
- Department of Anatomy and Embryology, Leiden University Medical Center, Leiden, Netherlands
| | - Christine L Mummery
- Department of Anatomy and Embryology, Leiden University Medical Center, Leiden, Netherlands.,Department of Applied Stem Cell Technologies, University of Twente, Enschede, Netherlands
| | - Arie O Verkerk
- Department of Medical Biology, Amsterdam UMC, Amsterdam, Netherlands
| | - Richard P Davis
- Department of Anatomy and Embryology, Leiden University Medical Center, Leiden, Netherlands
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4
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Glinge C, Lahrouchi N, Jabbari R, Tfelt-Hansen J, Bezzina CR. Genome-wide association studies of cardiac electrical phenotypes. Cardiovasc Res 2021; 116:1620-1634. [PMID: 32428210 PMCID: PMC7341169 DOI: 10.1093/cvr/cvaa144] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 04/24/2020] [Accepted: 05/14/2020] [Indexed: 12/19/2022] Open
Abstract
The genetic basis of cardiac electrical phenotypes has in the last 25 years been the subject of intense investigation. While in the first years, such efforts were dominated by the study of familial arrhythmia syndromes, in recent years, large consortia of investigators have successfully pursued genome-wide association studies (GWAS) for the identification of single-nucleotide polymorphisms that govern inter-individual variability in electrocardiographic parameters in the general population. We here provide a review of GWAS conducted on cardiac electrical phenotypes in the last 14 years and discuss the implications of these discoveries for our understanding of the genetic basis of disease susceptibility and variability in disease severity. Furthermore, we review functional follow-up studies that have been conducted on GWAS loci associated with cardiac electrical phenotypes and highlight the challenges and opportunities offered by such studies.
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Affiliation(s)
- Charlotte Glinge
- Department of Clinical and Experimental Cardiology, Amsterdam University Medical Center, University of Amsterdam, Heart Center, Amsterdam Cardiovascular Sciences, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands.,Department of Cardiology, The Heart Centre, Copenhagen University Hospital, Rigshospitalet, Inge Lehmanns Vej 7, 2100 Copenhagen, Denmark
| | - Najim Lahrouchi
- Department of Clinical and Experimental Cardiology, Amsterdam University Medical Center, University of Amsterdam, Heart Center, Amsterdam Cardiovascular Sciences, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
| | - Reza Jabbari
- Department of Cardiology, The Heart Centre, Copenhagen University Hospital, Rigshospitalet, Inge Lehmanns Vej 7, 2100 Copenhagen, Denmark
| | - Jacob Tfelt-Hansen
- Department of Cardiology, The Heart Centre, Copenhagen University Hospital, Rigshospitalet, Inge Lehmanns Vej 7, 2100 Copenhagen, Denmark.,Department of Forensic Medicine, Faculty of Medical Sciences, University of Copenhagen, Frederik V's Vej, 2100 Copenhagen, Denmark
| | - Connie R Bezzina
- Department of Clinical and Experimental Cardiology, Amsterdam University Medical Center, University of Amsterdam, Heart Center, Amsterdam Cardiovascular Sciences, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
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5
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Santori M, Gil R, Blanco-Verea A, Riuró H, Díaz-Castro Ó, López-Abel B, Brugada R, Carracedo Á, Pérez GJ, Scornik FS, Brion M. Sudden infant death as the most severe phenotype caused by genetic modulation in a family with atrial fibrillation. Forensic Sci Int Genet 2019; 43:102159. [PMID: 31522018 DOI: 10.1016/j.fsigen.2019.102159] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 08/26/2019] [Accepted: 08/29/2019] [Indexed: 12/29/2022]
Abstract
AIMS To assess the functional impact of two combined KCNH2 variants involved in atrial fibrillation, syncope and sudden infant death syndrome. METHODS AND RESULTS Genetic testing of a 4-month old SIDS victim identified a rare missense heterozygous in KCNH2 variant (V483I) and a missense homozygous polymorphism (K897T) which is often described as a genetic modifier. Electrophysiological characterisation of heterologous HERG channels representing two different KCNH2 genotypes within the family, showed significant differences in both voltage and time dependence of activation and inactivation with a global gain-of-function effect of mutant versus wild type channels and, also, differences between both types of recombinant channels. CONCLUSIONS The rare variant V483I in combination with K897T produces a gain-of-function effect that represents a pathological substrate for atrial fibrillation, syncope and sudden infant death syndrome events in this family. Ascertaining the genotype-phenotype correlation of genetic variants is imperative for the correct assessment of genetic testing and counselling. TRANSLATIONAL PERSPECTIVE According to the current guidelines for clinical interpretation of sequence variants, functional studies are an essential tool for the ascertainment of variant pathogenicity. They are especially relevant in the context of sudden infant death syndrome and sudden cardiac death, where individuals cannot be clinically evaluated. The patch-clamp technique is a gold-standard for analysis of the biophysical mechanisms of ion channels.
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Affiliation(s)
- Montserrat Santori
- Xenética Cardiovascular, Instituto de Investigación Sanitaria de Santiago de Compostela, Spain; Grupo de Medicina Xenómica, Universidade de Santiago de Compostela, Spain.
| | - Rocío Gil
- Xenética Cardiovascular, Instituto de Investigación Sanitaria de Santiago de Compostela, Spain; Grupo de Medicina Xenómica, Universidade de Santiago de Compostela, Spain
| | - Alejandro Blanco-Verea
- Xenética Cardiovascular, Instituto de Investigación Sanitaria de Santiago de Compostela, Spain; Grupo de Medicina Xenómica, Universidade de Santiago de Compostela, Spain
| | - Helena Riuró
- Cardiovascular Genetics Center, Institut d'Investigació Biomèdica de Girona, Spain; Department of Medical Sciences, Medical School, Universitat de Girona, Spain
| | - Óscar Díaz-Castro
- Servizo de Cardioloxía, Hospital de Pontevedra, Servizo Galego de Saúde, Pontevedra, Spain
| | - Bernardo López-Abel
- Xenética Cardiovascular, Instituto de Investigación Sanitaria de Santiago de Compostela, Spain; Servizo de Pediatría, Hospital Clínico Universitario de Santiago de Compostela, Spain
| | - Ramón Brugada
- Cardiovascular Genetics Center, Institut d'Investigació Biomèdica de Girona, Spain; Department of Medical Sciences, Medical School, Universitat de Girona, Spain; Red de Enfermedades Cardiovasculares (CIBERCV), Spain
| | - Ángel Carracedo
- Grupo de Medicina Xenómica, Universidade de Santiago de Compostela, Spain; Fundación Pública Galega de Medicina Xenómica, Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, Santiago de Compostela, Spain
| | - Guillermo J Pérez
- Department of Medical Sciences, Medical School, Universitat de Girona, Spain; Red de Enfermedades Cardiovasculares (CIBERCV), Spain
| | - Fabiana S Scornik
- Department of Medical Sciences, Medical School, Universitat de Girona, Spain; Red de Enfermedades Cardiovasculares (CIBERCV), Spain
| | - María Brion
- Xenética Cardiovascular, Instituto de Investigación Sanitaria de Santiago de Compostela, Spain; Grupo de Medicina Xenómica, Universidade de Santiago de Compostela, Spain; Red de Enfermedades Cardiovasculares (CIBERCV), Spain
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6
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Giudicessi JR, Roden DM, Wilde AAM, Ackerman MJ. Classification and Reporting of Potentially Proarrhythmic Common Genetic Variation in Long QT Syndrome Genetic Testing. Circulation 2019; 137:619-630. [PMID: 29431662 DOI: 10.1161/circulationaha.117.030142] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The acquired and congenital forms of long QT syndrome represent 2 distinct but clinically and genetically intertwined disorders of cardiac repolarization characterized by the shared final common pathway of QT interval prolongation and risk of potentially life-threatening arrhythmias. Over the past 2 decades, our understanding of the spectrum of genetic variation that (1) perturbs the function of cardiac ion channel macromolecular complexes and intracellular calcium-handling proteins, (2) underlies acquired/congenital long QT syndrome susceptibility, and (3) serves as a determinant of QT interval duration in the general population has grown exponentially. In turn, these molecular insights led to the development and increased utilization of clinically impactful genetic testing for congenital long QT syndrome. However, the widespread adoption and potential misinterpretation of the 2015 American College of Medical Genetics and Genomics variant classification and reporting guidelines may have contributed unintentionally to the reduced reporting of common genetic variants, with compelling epidemiological and functional evidence to support a potentially proarrhythmic role in patients with congenital and acquired long QT syndrome. As a result, some genetic testing reports may fail to convey the full extent of a patient's genetic susceptibility for a potentially life-threatening arrhythmia to the ordering healthcare professional. In this white paper, we examine the current classification and reporting (or lack thereof) of potentially proarrhythmic common genetic variants and investigate potential mechanisms to facilitate the reporting of these genetic variants without increasing the risk of diagnostic miscues.
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Affiliation(s)
- John R Giudicessi
- Departments of Cardiovascular Medicine and Internal Medicine, Clinician-Investigator Training Program, Mayo Clinic, Rochester, MN (J.R.G)
| | - Dan M Roden
- Departments of Biomedical Informatics, Medicine, and Pharmacology, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN (D.M.R.)
| | - Arthur A M Wilde
- Department of Clinical and Experimental Cardiology, Academic Medical Center, University of Amsterdam, The Netherlands (A.A.M.W.)
| | - Michael J Ackerman
- Departments of Cardiovascular Diseases, Pediatrics, and Molecular Pharmacology and Experimental Therapeutics, Divisions of Heart Rhythm Services and Pediatric Cardiology, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, MN (M.J.A.)
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7
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Crotti L, Ghidoni A, Dagradi F. Genetics of Adult and Fetal Forms of Long QT Syndrome. GENETIC CAUSES OF CARDIAC DISEASE 2019. [DOI: 10.1007/978-3-030-27371-2_1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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8
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Schwartz PJ, Crotti L, George AL. Modifier genes for sudden cardiac death. Eur Heart J 2018; 39:3925-3931. [PMID: 30215713 PMCID: PMC6247660 DOI: 10.1093/eurheartj/ehy502] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 08/28/2018] [Indexed: 01/07/2023] Open
Abstract
Genetic conditions, even those associated with identical gene mutations, can present with variable clinical manifestations. One widely accepted explanation for this phenomenon is the existence of genetic factors capable of modifying the consequences of disease-causing mutations (modifier genes). Here, we address the concepts and principles by which genetic factors may be involved in modifying risk for cardiac arrhythmia, then discuss the current knowledge and interpretation of their contribution to clinical heterogeneity. We illustrate these concepts in the context of two important clinical conditions associated with risk for sudden cardiac death including a monogenic disorder (congenital long QT syndrome) in which the impact of modifier genes has been established, and a complex trait (life-threatening arrhythmias in acute myocardial infarction) for which the search for genetic modifiers of arrhythmic risk is more challenging. Advances in understanding the contribution of modifier genes to a higher or lower propensity towards sudden death should improve patient-specific risk stratification and be a major step towards precision medicine.
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Affiliation(s)
- Peter J Schwartz
- Istituto Auxologico Italiano, IRCCS, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Via Pier Lombardo, 22, Milan, Italy
- Corresponding author. Tel: +39 02 55000408, Fax: +39 02 55000411, ;
| | - Lia Crotti
- Istituto Auxologico Italiano, IRCCS, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Via Pier Lombardo, 22, Milan, Italy
- Department of Medicine and Surgery, University of Milano-Bicocca, Via Cadore, 48, Monza, Italy
- Istituto Auxologico Italiano, IRCCS, Department of Cardiovascular, Neural and Metabolic Sciences, San Luca Hospital, Piazzale Brescia 20, Milan, Italy
| | - Alfred L George
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Searle 8-510, East Superior Street, Chicago, IL, USA
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9
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Sicouri S, Antzelevitch C. Mechanisms Underlying the Actions of Antidepressant and Antipsychotic Drugs That Cause Sudden Cardiac Arrest. Arrhythm Electrophysiol Rev 2018; 7:199-209. [PMID: 30416734 PMCID: PMC6141916 DOI: 10.15420/aer.2018.29.2] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 06/19/2018] [Indexed: 12/18/2022] Open
Abstract
A number of antipsychotic and antidepressant drugs are known to increase the risk of ventricular arrhythmias and sudden cardiac death. Based largely on a concern over the development of life-threatening arrhythmias, a number of antipsychotic drugs have been temporarily or permanently withdrawn from the market or their use restricted. While many antidepressants and antipsychotics have been linked to QT prolongation and the development of torsade de pointes arrhythmias, some have been associated with a Brugada syndrome phenotype and the development of polymorphic ventricular arrhythmias. This article examines the arrhythmic liability of antipsychotic and antidepressant drugs capable of inducing long QT and/or Brugada syndrome phenotypes. The goal of this article is to provide an update on the ionic and cellular mechanisms thought to be involved in, and the genetic and environmental factors that predispose to, the development of cardiac arrhythmias and sudden cardiac death among patients taking antidepressant and antipsychotic drugs that are in clinical use.
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Affiliation(s)
- Serge Sicouri
- Lankenau Institute for Medical ResearchWynnewood, PA, USA
| | - Charles Antzelevitch
- Lankenau Institute for Medical ResearchWynnewood, PA, USA
- Lankenau Heart InstituteWynnewood, PA
- Sidney Kimmel Medical College of Thomas Jefferson UniversityPhiladelphia, PA, USA
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10
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Engelbrechtsen L, Mahendran Y, Jonsson A, Gjesing AP, Weeke PE, Jørgensen ME, Færch K, Witte DR, Holst JJ, Jørgensen T, Grarup N, Pedersen O, Vestergaard H, Torekov S, Kanters JK, Hansen T. Common variants in the hERG (KCNH2) voltage-gated potassium channel are associated with altered fasting and glucose-stimulated plasma incretin and glucagon responses. BMC Genet 2018; 19:15. [PMID: 29548277 PMCID: PMC5857134 DOI: 10.1186/s12863-018-0602-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 03/13/2018] [Indexed: 01/29/2023] Open
Abstract
Background Patients with long QT syndrome due to rare loss-of-function mutations in the human ether-á-go-go-related gene (hERG) have prolonged QT interval, risk of arrhythmias, increased secretion of insulin and incretins and impaired glucagon response to hypoglycemia. This is caused by a dysfunctional Kv11.1 voltage-gated potassium channel. Based on these findings in patients with rare variants in hERG, we hypothesized that common variants in hERG may also lead to alterations in glucose homeostasis. Subsequently, we aimed to evaluate the effect of two common gain-of-function variants in hERG (rs36210421 and rs1805123) on QT interval and plasma levels of glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), insulin and glucagon during an oral glucose tolerance test (OGTT). We used two population-based cohorts for evaluation of the effect of common variants in hERG on QT-interval and circulation levels of incretins, insulin and glucagon. The Danish population-based Inter99 cohort (n = 5895) was used to assess the effect of common variants on QT-interval. The Danish ADDITION-PRO cohort was used (n = 1329) to study genetic associations with levels of GLP-1, GIP, insulin and glucagon during an OGTT. Results Carriers of either the minor A-allele of rs36210421 or the minor G-allele of rs1805123 had ~ 2 ms shorter QT interval per risk allele (p = 0.025 and p = 1.9 × 10− 7). Additionally, both variants were associated with alterations in pancreatic and gut hormone release among carriers. The minor A- allele of rs36210421 was associated with increased GLP-1 and decreased GIP response to oral glucose stimulation, whereas the minor G-allele of rs1805123 is associated with decreased fasting plasma insulin and glucagon release. A genetic risk score combining the two gene variants revealed reductions in glucose-stimulated GIP, as well as suppressed glucagon response to increased glucose levels during an OGTT. Conclusions Two common missense polymorphisms of the Kv11.1 voltage-gated hERG potassium channel are associated with alterations in circulating levels of GIP and glucagon, suggesting that hERG potassium channels play a role in fasting and glucose-stimulated release of GIP and glucagon. Trial registration ClinicalTrials.gov (NCT00289237). Trial retrospectively registered at February 9, 2006. Studies were approved by the Ethical Committee of the Central Denmark Region (journal no. 20080229) and by the Copenhagen County Ethical Committee (KA 98155). Electronic supplementary material The online version of this article (10.1186/s12863-018-0602-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Line Engelbrechtsen
- Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, University of Copenhagen, Faculty of Health and Medical Sciences, Blegdamsvej 3B, Maersk Tower 8. floor, -2200, Copenhagen, DK, Denmark. .,Danish Diabetes Academy, Odense, Denmark.
| | - Yuvaraj Mahendran
- Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, University of Copenhagen, Faculty of Health and Medical Sciences, Blegdamsvej 3B, Maersk Tower 8. floor, -2200, Copenhagen, DK, Denmark.,Danish Diabetes Academy, Odense, Denmark
| | - Anna Jonsson
- Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, University of Copenhagen, Faculty of Health and Medical Sciences, Blegdamsvej 3B, Maersk Tower 8. floor, -2200, Copenhagen, DK, Denmark
| | - Anette Prior Gjesing
- Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, University of Copenhagen, Faculty of Health and Medical Sciences, Blegdamsvej 3B, Maersk Tower 8. floor, -2200, Copenhagen, DK, Denmark
| | - Peter E Weeke
- Department of Cardiology, Rigshospitalet, Copenhagen, Denmark
| | - Marit E Jørgensen
- National Institute of Public Health, University of Southern Denmark, Odense, Denmark.,Steno Diabetes Center, Gentofte, Denmark
| | | | - Daniel R Witte
- Section of General Practice, Department of Public Health, Aarhus University, Aarhus, Denmark
| | - Jens J Holst
- Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, University of Copenhagen, Faculty of Health and Medical Sciences, Blegdamsvej 3B, Maersk Tower 8. floor, -2200, Copenhagen, DK, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Torben Jørgensen
- Research Centre for Prevention and Health, The Capital Region of Denmark, Hillerød, Denmark.,Department of Public health, Faculty of Health Science, University of Copenhagen, Copenhagen, Denmark.,Faculty of Medicine, Aalborg University, Aalborg, Denmark
| | - Niels Grarup
- Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, University of Copenhagen, Faculty of Health and Medical Sciences, Blegdamsvej 3B, Maersk Tower 8. floor, -2200, Copenhagen, DK, Denmark
| | - Oluf Pedersen
- Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, University of Copenhagen, Faculty of Health and Medical Sciences, Blegdamsvej 3B, Maersk Tower 8. floor, -2200, Copenhagen, DK, Denmark
| | - Henrik Vestergaard
- Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, University of Copenhagen, Faculty of Health and Medical Sciences, Blegdamsvej 3B, Maersk Tower 8. floor, -2200, Copenhagen, DK, Denmark.,Steno Diabetes Center, Gentofte, Denmark
| | - Signe Torekov
- Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, University of Copenhagen, Faculty of Health and Medical Sciences, Blegdamsvej 3B, Maersk Tower 8. floor, -2200, Copenhagen, DK, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jørgen K Kanters
- Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, University of Copenhagen, Faculty of Health and Medical Sciences, Blegdamsvej 3B, Maersk Tower 8. floor, -2200, Copenhagen, DK, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Torben Hansen
- Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, University of Copenhagen, Faculty of Health and Medical Sciences, Blegdamsvej 3B, Maersk Tower 8. floor, -2200, Copenhagen, DK, Denmark
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11
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Allelic Complexity in Long QT Syndrome: A Family-Case Study. Int J Mol Sci 2017; 18:ijms18081633. [PMID: 28749435 PMCID: PMC5578023 DOI: 10.3390/ijms18081633] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Revised: 07/13/2017] [Accepted: 07/21/2017] [Indexed: 12/17/2022] Open
Abstract
Congenital long QT syndrome (LQTS) is associated with high genetic and allelic heterogeneity. In some cases, more than one genetic variant is identified in the same (compound heterozygosity) or different (digenic heterozygosity) genes, and subjects with multiple pathogenic mutations may have a more severe disease. Standard-of-care clinical genetic testing for this and other arrhythmia susceptibility syndromes improves the identification of complex genotypes. Therefore, it is important to distinguish between pathogenic mutations and benign rare variants. We identified four genetic variants (KCNQ1-p.R583H, KCNH2-p.C108Y, KCNH2-p.K897T, and KCNE1-p.G38S) in an LQTS family. On the basis of in silico analysis, clinical data from our family, and the evidence from previous studies, we analyzed two mutated channels, KCNQ1-p.R583H and KCNH2-p.C108Y, using the whole-cell patch clamp technique. We found that KCNQ1-p.R583H was not associated with a severe functional impairment, whereas KCNH2-p.C108Y, a novel variant, encoded a non-functional channel that exerts dominant-negative effects on the wild-type. Notably, the common variants KCNH2-p.K897T and KCNE1-p.G38S were previously reported to produce more severe phenotypes when combined with disease-causing alleles. Our results indicate that the novel KCNH2-C108Y variant can be a pathogenic LQTS mutation, whereas KCNQ1-p.R583H, KCNH2-p.K897T, and KCNE1-p.G38S could be LQTS modifiers.
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J E, T D, M S, M KN, J D, M NW. Mutation analysis for the detection of long QT-syndrome (LQTS) associated SNPs. Int J Legal Med 2016; 131:333-338. [PMID: 27613431 DOI: 10.1007/s00414-016-1446-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Accepted: 08/26/2016] [Indexed: 02/06/2023]
Abstract
Congenital long QT-syndrome (LQTS) is an inherited cardiac arrhythmia, which is characterized by a prolonged QT interval which predisposes to sudden cardiac death due to ventricular arrhythmias. The altered functions are based on different mutations in LQTS-associated genes. In this study, we performed a mutation analysis for the detection of 125 LQTS-associated single nucleotide polymorphisms (SNPs) focused on the genes KCNQ1, KCNH2, and SCN5A by using the SNaPshot multiplex minisequencing technique. Furthermore, we investigated 152 autopsy-negative cases from younger adults and infants, as well as samples from patients with clinically suspicion for LQTS, in which we found two types of variations.
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Affiliation(s)
- Edelmann J
- Institute of Legal Medicine, University of Leipzig, Leipzig, Germany.
| | - Dobosz T
- Department of Forensic Medicine, Wroclaw Medical University, Wroclaw, Poland
| | - Sobieszczanska M
- Department of Pathophysiology, Division of Electrocardiology and Cardiovascular Diseases Prevention, Wroclaw Medical University, Wroclaw, Poland
| | - Kawecka-Negrusz M
- Department and Clinic of Cardiology, Wroclaw Medical University, Wroclaw, Poland
| | - Dreßler J
- Institute of Legal Medicine, University of Leipzig, Leipzig, Germany
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Vlachos K, Georgopoulos S, Efremidis M, Sideris A, Letsas KP. An update on risk factors for drug-induced arrhythmias. Expert Rev Clin Pharmacol 2015; 9:117-27. [DOI: 10.1586/17512433.2016.1100073] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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Genetic modulators of the phenotype in the long QT syndrome: state of the art and clinical impact. Curr Opin Genet Dev 2015; 33:17-24. [DOI: 10.1016/j.gde.2015.06.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 06/23/2015] [Accepted: 06/29/2015] [Indexed: 12/22/2022]
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Erdem M, Tekiner TA, Fejzullahu A, Akan G, Anak S, Saribeyoglu ET, Ozbek U, Atalar F. herg1b expression as a potential specific marker in pediatric acute myeloid leukemia patients with HERG 897K/K genotype. Pediatr Hematol Oncol 2015; 32:182-92. [PMID: 25247487 DOI: 10.3109/08880018.2014.949941] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Human ether-a-go-go related gene (herg) encoding HERG K(+) channel has been demonstrated in many previous studies with its association to cell cycle progression and growth in tumor cells. The upregulated expression of HERG K+ channels was determined in different tumor types. Furthermore, not only full-length transcript herg1 but also a truncated isoform herg1b was shown to be expressed in cancer cells. In this study, the expression levels of herg1 and herg1b and the impact of K897T mutation on their expressions were investigated in pediatric acute myeloid leukemia (pAML). Expression levels of herg1 and herg1b isoforms were analyzed by quantitative real time polymerase chain reaction (PCR) in pAML patients together with healthy donors, and their expressions were confirmed by western blotting. The 2690 A>C nucleotide variation in KCNH2 gene corresponding to K897T amino acid change was analyzed by PCR followed by restriction enzyme digestion. herg1b overexpression was observed in tumor cells compared to healthy controls (P = .0024). However, herg1 expression was higher in healthy control cells than tumor cells (P = .001). The prevalence of polymorphic allele 897T was 26% in our patient group and 897T carriers showed increased herg1b expression compared to wild-type allele carriers. Our results demonstrate the presence of the increased levels of herg1b expression in pAML. In addition, we report for the first time that, pAML subgroup with HERG 897K/K genotype compared to 897K/T and T/T genotypes express increased levels of herg1b. In conclusion, HERG 897K/K genotype with increased level of herg1b expression might well be a prognostic marker for pAML.
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Affiliation(s)
- Merve Erdem
- Department of Growth-Development and Pediatric Endocrinology, Child Health Institute, Istanbul University , Capa, Istanbul , Turkey
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Hasegawa K, Ohno S, Itoh H, Makiyama T, Aiba T, Nakano Y, Shimizu W, Matsuura H, Makita N, Horie M. A rare KCNE1 polymorphism, D85N, as a genetic modifier of long QT syndrome. J Arrhythm 2014. [DOI: 10.1016/j.joa.2013.08.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Andreasen L, Nielsen JB, Christophersen IE, Holst AG, Sajadieh A, Tveit A, Haunsø S, Svendsen JH, Schmitt N, Olesen MS. Genetic modifier of the QTc interval associated with early-onset atrial fibrillation. Can J Cardiol 2013; 29:1234-40. [PMID: 24074973 DOI: 10.1016/j.cjca.2013.06.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Revised: 06/14/2013] [Accepted: 06/14/2013] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Both shortening and prolongation of the QTc interval have been associated with atrial fibrillation (AF). We investigated whether 8 single nucleotide polymorphisms (SNPs) at loci previously shown to affect QTc interval duration were associated with lone AF. METHODS We included 358 patients diagnosed with lone AF (defined as onset of AF at < 50 years of age in the absence of traditional cardiovascular risk factors) and a control group consisting of 751 individuals free of AF. The 8 loci were genotyped using TaqMan assays. Genotype frequencies in lone AF cases and controls were compared using an additive logistic regression model. RESULTS Risk of the development of early-onset lone AF in individuals homozygous for the variant rs2968863 (7q36.1) was higher than in individuals with no copies of the risk allele (odds ratio [OR], 2.40; P = 0.001). The association was also significant after Bonferroni correction (P = 0.016). This polymorphism has been shown to decrease the QTc interval by 1.4 ms in genome-wide association studies (GWAS). The genetic variant is situated close to the long QT syndrome (LQTS) type 2 gene KCNH2 that encodes the potassium channel Kv11.1 (hERG). Sanger sequencing of KCNH2 confirmed the known high linkage disequilibrium between rs2968863 and the nonsynonymous variant K897T in KCNH2. No novel mutations were found in the gene. CONCLUSIONS The variant rs2968863 (7q36.1), reported in GWAS to shorten the QTc interval, was found to be associated with early-onset lone AF. This may have implications for the pathophysiological understanding of AF.
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Affiliation(s)
- Laura Andreasen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, Copenhagen, Denmark; Laboratory for Molecular Cardiology, Rigshospitalet, Copenhagen, Denmark; The Ion Channel Group, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
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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: 161] [Impact Index Per Article: 14.6] [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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Liu C, Zhao Q, Su T, Tang S, Lv G, Liu H, Quan L, Cheng J. Postmortem molecular analysis of KCNQ1, KCNH2, KCNE1 and KCNE2 genes in sudden unexplained nocturnal death syndrome in the Chinese Han population. Forensic Sci Int 2013; 231:82-7. [PMID: 23890619 DOI: 10.1016/j.forsciint.2013.04.020] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Revised: 03/15/2013] [Accepted: 04/17/2013] [Indexed: 10/26/2022]
Abstract
The etiology of sudden unexplained nocturnal death syndrome (SUNDS) remains unclear. Previous studies have implicated that SUNDS is probably allelic to cardiac sodium channel diseases such as Brugada syndrome. The variation in cardiac potassium channels is the main genetic cause of inherited long QT syndrome (LQTS), which may manifest as syncope and sudden cardiac death without structural disease. We hypothesized that cardiac potassium channel disease may be responsible for certain Chinese SUNDS cases. Genotyping of 4 main LQTS-susceptibility genes (KCNQ1, KCNH2, KCNE1, and KCNE2) was performed here for the first time in SUNDS victims from the Chinese Han population to address the pathogenic cause of some SUNDS using polymerase chain reaction and direct DNA sequencing. 120 sporadic SUNDS cases were enrolled. Genomic DNA was extracted from blood samples. A total of 2 novel non-synonymous mutations and 3 previously reported arrhythmia susceptibility polymorphisms were identified in KCNQ1, KCNH2, KCNE1, and KCNE2. We concluded that the variants in KCNQ1, KCNH2, KCNE1 and KCNE2 genes may be correlated with the occurrence of part of SUNDS cases in southern China.
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Affiliation(s)
- Chao Liu
- Guangzhou Institute of Criminal Sciences and Technology, Guangzhou 510030, China
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Vandenberg JI, Perry MD, Perrin MJ, Mann SA, Ke Y, Hill AP. hERG K+ Channels: Structure, Function, and Clinical Significance. Physiol Rev 2012; 92:1393-478. [DOI: 10.1152/physrev.00036.2011] [Citation(s) in RCA: 463] [Impact Index Per Article: 38.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The human ether-a-go-go related gene (hERG) encodes the pore-forming subunit of the rapid component of the delayed rectifier K+ channel, Kv11.1, which are expressed in the heart, various brain regions, smooth muscle cells, endocrine cells, and a wide range of tumor cell lines. However, it is the role that Kv11.1 channels play in the heart that has been best characterized, for two main reasons. First, it is the gene product involved in chromosome 7-associated long QT syndrome (LQTS), an inherited disorder associated with a markedly increased risk of ventricular arrhythmias and sudden cardiac death. Second, blockade of Kv11.1, by a wide range of prescription medications, causes drug-induced QT prolongation with an increase in risk of sudden cardiac arrest. In the first part of this review, the properties of Kv11.1 channels, including biogenesis, trafficking, gating, and pharmacology are discussed, while the second part focuses on the pathophysiology of Kv11.1 channels.
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Affiliation(s)
- Jamie I. Vandenberg
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Matthew D. Perry
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Mark J. Perrin
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Stefan A. Mann
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Ying Ke
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Adam P. Hill
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
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Genetic marker of torsades de pointes risk following myocardial infarction. Heart Rhythm 2012; 9:1113-4. [DOI: 10.1016/j.hrthm.2012.05.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Indexed: 11/21/2022]
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Kolder ICRM, Tanck MWT, Bezzina CR. Common genetic variation modulating cardiac ECG parameters and susceptibility to sudden cardiac death. J Mol Cell Cardiol 2012; 52:620-9. [PMID: 22248531 DOI: 10.1016/j.yjmcc.2011.12.014] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Revised: 12/23/2011] [Accepted: 12/31/2011] [Indexed: 01/19/2023]
Abstract
Sudden cardiac death (SCD) is a prevalent cause of death in Western societies. Genome-wide association studies (GWAS) conducted over the last few years have uncovered common genetic variants modulating risk of SCD. Furthermore, GWAS studies uncovered several loci impacting on heart rate and ECG indices of conduction and repolarization, as measures of cardiac electrophysiological function and likely intermediate phenotypes of SCD risk. We here review these recent developments and their implications for the identification of novel molecular pathways underlying normal electrophysiological function and susceptibility to SCD.
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Affiliation(s)
- Iris C R M Kolder
- Heart Failure Research Center, Department of Experimental Cardiology, Academic Medical Center, Meibergdreef 15, 1105 AZ, Amsterdam, The Netherlands
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Cordeiro JM, Perez GJ, Schmitt N, Pfeiffer R, Nesterenko VV, Burashnikov E, Veltmann C, Borggrefe M, Wolpert C, Schimpf R, Antzelevitch C. Overlapping LQT1 and LQT2 phenotype in a patient with long QT syndrome associated with loss-of-function variations in KCNQ1 and KCNH2. Can J Physiol Pharmacol 2011; 88:1181-90. [PMID: 21164565 DOI: 10.1139/y10-094] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Long QT syndrome (LQTS) is an inherited disorder characterized by prolonged QT intervals and potentially life-threatening arrhythmias. Mutations in 12 different genes have been associated with LQTS. Here we describe a patient with LQTS who has a mutation in KCNQ1 as well as a polymorphism in KCNH2. The proband (MMRL0362), a 32-year-old female, exhibited multiple ventricular extrasystoles and one syncope. Her ECG (QT interval corrected for heart rate (QTc) = 518ms) showed an LQT2 morphology in leads V4-V6 and LQT1 morphology in leads V1-V2. Genomic DNA was isolated from lymphocytes. All exons and intron borders of 7 LQTS susceptibility genes were amplified and sequenced. Variations were detected predicting a novel missense mutation (V110I) in KCNQ1, as well as a common polymorphism in KCNH2 (K897T). We expressed wild-type (WT) or V110I Kv7.1 channels in CHO-K1 cells cotransfected with KCNE1 and performed patch-clamp analysis. In addition, WT or K897T Kv11.1 were also studied by patch clamp. Current-voltage (I-V) relations for V110I showed a significant reduction in both developing and tail current densities compared with WT at potentials >+20 mV (p < 0.05; n = 8 cells, each group), suggesting a reduction in IKs currents. K897T- Kv11.1 channels displayed a significantly reduced tail current density compared with WT-Kv11.1 at potentials >+10 mV. Interestingly, channel availability assessed using a triple-pulse protocol was slightly greater for K897T compared with WT (V0.5 = -53.1 ± 1.13 mV and -60.7 ± 1.15 mV for K897T and WT, respectively; p < 0.05). Comparison of the fully activated I-V revealed no difference in the rectification properties between WT and K897T channels. We report a patient with a loss-of-function mutation in KCNQ1 and a loss-of-function polymorphism in KCNH2. Our results suggest that a reduction of both IKr and IKs underlies the combined LQT1 and LQT2 phenotype observed in this patient.
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NAPOLITANO CARLO. The Slow Pace of the Heart and the Objectives of Molecular Cardiology. J Cardiovasc Electrophysiol 2010; 21:1373-4. [DOI: 10.1111/j.1540-8167.2010.01879.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Grilo LS, Carrupt PA, Abriel H. Stereoselective Inhibition of the hERG1 Potassium Channel. Front Pharmacol 2010; 1:137. [PMID: 21833176 PMCID: PMC3153011 DOI: 10.3389/fphar.2010.00137] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Accepted: 11/03/2010] [Indexed: 12/11/2022] Open
Abstract
A growing number of drugs have been shown to prolong cardiac repolarization, predisposing individuals to life-threatening ventricular arrhythmias known as Torsades de Pointes. Most of these drugs are known to interfere with the human ether à-gogo related gene 1 (hERG1) channel, whose current is one of the main determinants of action potential duration. Prolonged repolarization is reflected by lengthening of the QT interval of the electrocardiogram, as seen in the suitably named drug-induced long QT syndrome. Chirality (presence of an asymmetric atom) is a common feature of marketed drugs, which can therefore exist in at least two enantiomers with distinct three-dimensional structures and possibly distinct biological fates. Both the pharmacokinetic and pharmacodynamic properties can differ between enantiomers, as well as also between individuals who take the drug due to metabolic polymorphisms. Despite the large number of reports about drugs reducing the hERG1 current, potential stereoselective contributions have only been scarcely investigated. In this review, we present a non-exhaustive list of clinically important molecules which display chiral toxicity that may be related to hERG1-blocking properties. We particularly focus on methadone cardiotoxicity, which illustrates the importance of the stereoselective effect of drug chirality as well as individual variations resulting from pharmacogenetics. Furthermore, it seems likely that, during drug development, consideration of chirality in lead optimization and systematic assessment of the hERG1 current block with all enantiomers could contribute to the reduction of the risk of drug-induced LQTS.
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Affiliation(s)
- Liliana Sintra Grilo
- School of Pharmaceutical Sciences, University of Geneva, University of LausanneGeneva, Switzerland
- Department of Clinical Research, University of BernBern, Switzerland
| | - Pierre-Alain Carrupt
- School of Pharmaceutical Sciences, University of Geneva, University of LausanneGeneva, Switzerland
| | - Hugues Abriel
- Department of Clinical Research, University of BernBern, Switzerland
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Torsades de pointes during complete atrioventricular block: Genetic factors and electrocardiogram correlates. Can J Cardiol 2010; 26:208-12. [PMID: 20386770 DOI: 10.1016/s0828-282x(10)70369-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
INTRODUCTION Atrioventricular (AV) block is infrequently associated with QT prolongation and torsades de pointes (TdP). It was hypothesized that patients with AV block-mediated QT-related arrhythmia may have latent congenital long QT syndrome or a vulnerable genetic polymorphism. METHODS Eleven patients with complete AV block and TdP were prospectively identified. Patients underwent assessment, resting electrocardiography and telemetry at baseline, during AV block and pre-TdP. Genetic testing of KCNH2, KCNQ1, KCNE1, KCNE2 and SCN5A was performed. Thirty-three patients with AV block without TdP were included for comparison. RESULTS Genetic variants were identified in 36% of patients with AV block and TdP. Patients with AV block who developed TdP had significantly longer mean (+/- SD) corrected QT intervals (440+/-93 ms versus 376+/-40 ms, P=0.048) and Tpeak to Tend (Tp-Te) intervals (147+/-25 ms versus 94+/-25 ms, P=0.0001) than patients with AV block alone. In patients with a genetic variant, there was a significant increase in Tp-Te intervals at baseline, in AV block and pre-TdP compared with those who were genotype negative. A personal or family history of syncope or sudden death was more likely observed in patients with a genetic variant. CONCLUSIONS TdP in the setting of AV block may be a marker of an underlying genetic predisposition to reduced repolarization reserve. The Tp-Te interval at baseline, in AV block and pre-TdP may predict a genetic mutation or polymorphism compromising repolarization reserve. Patients with TdP in the setting of AV block represent a phenotypic manifestation of latent congenital long QT syndrome.
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Porthan K, Marjamaa A, Viitasalo M, Väänänen H, Jula A, Toivonen L, Nieminen MS, Newton-Cheh C, Salomaa V, Kontula K, Oikarinen L. Relationship of common candidate gene variants to electrocardiographic T-wave peak to T-wave end interval and T-wave morphology parameters. Heart Rhythm 2010; 7:898-903. [PMID: 20215044 DOI: 10.1016/j.hrthm.2010.03.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2009] [Accepted: 03/01/2010] [Indexed: 12/31/2022]
Abstract
BACKGROUND Single-nucleotide polymorphisms (SNPs) in genes encoding cardiac ion channels and nitric oxide synthase-1 adaptor protein (NOS1AP) are associated with electrocardiographic (ECG) QT-interval duration, but the association of these SNPs with new, prognostically important ECG measures of ventricular repolarization is unknown. OBJECTIVE The purpose of this study was to examine the relationship of SNPs to ECG T-wave peak to T-wave end (TPE) interval and T-wave morphology parameters. METHODS We studied 5,890 adults attending the Health 2000 Study, a Finnish epidemiologic survey. TPE interval and four T-wave morphology parameters were measured from digital 12-lead ECGs and related to the seven SNPs showing a phenotypic effect on QT-interval duration in the Health 2000 Study population. RESULTS In multivariable analyses, the KCNH2 K897T minor allele was associated with a 1.2-ms TPE-interval shortening (P = .00005) and the KCNH2 intronic rs3807375 minor allele was associated with a 0.8-ms TPE-interval prolongation (P = .001), whereas the KCNE1 D85N variant had no TPE-interval effect (P = .20). NOS1AP minor alleles (rs2880058, rs4657139, rs10918594, rs10494366) were associated with a shorter TPE interval (effects from 0.5 to 0.8 ms, P from .032 to .002), which resulted from their stronger effects on QT(peak) than QT(end) interval. None of the SNPs showed a consistent association with T-wave morphology parameters. CONCLUSION KCNH2 K897T and rs3807375 as well as the four studied NOS1AP variants have modest effects on ECG TPE interval but are not related to T-wave morphology measures. The previously observed prognostic value of T-wave morphology parameters likely is not based on these SNPs.
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Affiliation(s)
- Kimmo Porthan
- Department of Cardiology, Helsinki University Central Hospital, Helsinki, Finland.
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Nakajima T, Kaneko Y, Saito A, Irie T, Kato T, Iso T, Kurabayashi M. Post myocardial ischemia-associated torsades de pointes in a patient carrying a KCNQ1 G643S variant. Intern Med 2010; 49:2587-91. [PMID: 21139297 DOI: 10.2169/internalmedicine.49.4245] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Polymorphic ventricular tachycardia, which occurs during the subacute phase of myocardial infarction (MI) or ischemia and is not related to ongoing ischemia, has recently been reported. It has characteristics of typical pause-dependent torsades de pointes (TdP) following excessive QT prolongation (post MI/ischemia-associated TdP). We describe a male patient with post MI/ischemia-associated TdP. The patient experienced recurrent TdP with excessive QT prolongation 2 days after transient myocardial ischemia. Genetic screening of the major LQTS-causing genes identified a KCNQ1 G643S variant. This gene variant could be a genetic predisposition to the development of TdP during the subacute phase of MI/ischemia.
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Affiliation(s)
- Tadashi Nakajima
- Department of Medicine and Biological Science, Gunma University Graduate School of Medicine, Maebashi.
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30
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Abstract
Evidence from family history, twin studies and molecular studies of rare inherited arrhythmia predisposition syndromes indicate that genetic factors are important contributors to determining risk for sudden cardiac death (SCD). More recent evidence indicates that common genetic variants in several genes can explain part of this risk at the population level. Here, the genetic risks for SCD are reviewed along with explanations of basic concepts relevant to understanding genetic contributions to common diseases. Also reviewed are two categories of genetic studies that have led to important discoveries about the genetic basis for SCD in general populations. Candidate gene studies focusing mainly on genes responsible for rare inherited arrhythmia susceptibility syndromes or on determinants of autonomic nervous system function will be highlighted first followed by more recent data from genome wide association studies that have identified previously unrecognized genomic intervals that explain inter-individual differences in QT interval duration possibly accounting for a proportion of the population-attributable risk for SCD.
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Affiliation(s)
- Alfred L George
- Division of Genetic Medicine, Department of Medicine, Vanderbilt University, Nashville, Tennessee 37232-0275, USA.
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31
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Männikkö R, Overend G, Perrey C, Gavaghan CL, Valentin JP, Morten J, Armstrong M, Pollard CE. Pharmacological and electrophysiological characterization of nine, single nucleotide polymorphisms of the hERG-encoded potassium channel. Br J Pharmacol 2009; 159:102-14. [PMID: 19673885 DOI: 10.1111/j.1476-5381.2009.00334.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND AND PURPOSE Potencies of compounds blocking K(V)11.1 [human ether-ago-go-related gene (hERG)] are commonly assessed using cell lines expressing the Caucasian wild-type (WT) variant. Here we tested whether such potencies would be different for hERG single nucleotide polymorphisms (SNPs). EXPERIMENTAL APPROACH SNPs (R176W, R181Q, Del187-189, P347S, K897T, A915V, P917L, R1047L, A1116V) and a binding-site mutant (Y652A) were expressed in Tet-On CHO-K1 cells. Potencies [mean IC(50); lower/upper 95% confidence limit (CL)] of 48 hERG blockers was estimated by automated electrophysiology [IonWorks HT (IW)]. In phase one, rapid potency comparison of each WT-SNP combination was made for each compound. In phase two, any compound-SNP combinations from phase one where the WT upper/lower CL did not overlap with those of the SNPs were re-examined. Electrophysiological WT and SNP parameters were determined using conventional electrophysiology. KEY RESULTS IW detected the expected sixfold potency decrease for propafenone in Y652A. In phase one, the WT lower/upper CL did not overlap with those of the SNPs for 77 compound-SNP combinations. In phase two, 62/77 cases no longer yielded IC(50) values with non-overlapping CLs. For seven of the remaining 15 cases, there were non-overlapping CLs but in the opposite direction. For the eight compound-SNP combinations with non-overlapping CLs in the same direction as for phase 1, potencies were never more than twofold apart. The only statistically significant electrophysiological difference was the voltage dependence of activation of R1047L. CONCLUSION AND IMPLICATIONS Potencies of hERG channel blockers defined using the Caucasian WT sequence, in this in vitro assay, were representative of potencies for common SNPs.
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32
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Millat G, Kugener B, Chevalier P, Chahine M, Huang H, Malicier D, Rodriguez-Lafrasse C, Rousson R. Contribution of long-QT syndrome genetic variants in sudden infant death syndrome. Pediatr Cardiol 2009; 30:502-9. [PMID: 19322600 DOI: 10.1007/s00246-009-9417-2] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2008] [Revised: 01/21/2009] [Accepted: 03/11/2009] [Indexed: 11/27/2022]
Abstract
A cohort of 52 French unrelated infant cases who died unexpectedly before they reached 12 months of age was blindly investigated to better quantify the contribution of long-QT syndrome (LQTS) genetic variants in French cases of sudden infant death syndrome (SIDS). After a standardized autopsy protocol, a blinded molecular screening of the KCNQ1, KCNH2, SCN5A, KCNE1, and KCNE2 genes was performed on each case. These postmortem investigations enabled us to reclassify 18 as non-SIDS cases, 32 as SIDS cases, and 2 as suspected SIDS cases. Among the 18 non-SIDS cases, no LQTS mutation was identified. In contrast, our results led to a possible explanation for the death of at least three infants in the SIDS cohort. Half of the LQTS gene variants identified were located on the SCN5A gene. This study confirms that LQTS mutations may represent one of the leading genetic causes of SIDS. If autopsy fails to provide an explanation for an unexplained infant death, medicolegal investigation should be extended with a molecular screening of major LQTS genes. Identification of more LQTS mutations in SIDS cases could provide new insights into the pathophysiology of SIDS and, consequently, reduce the number of unexplained sudden infant deaths.
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Affiliation(s)
- Gilles Millat
- Laboratoire de Cardiogénétique Moléculaire, Centre de Biologie et Pathologie Est, Hospices Civils de Lyon, Lyon, Bron Cedex, France.
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33
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Lehtinen AB, Daniel KR, Shah SA, Nelson MR, Ziegler JT, Freedman BI, Carr JJ, Herrington DM, Langefeld CD, Bowden DW. Relationship between genetic variants in myocardial sodium and potassium channel genes and QT interval duration in diabetics: the Diabetes Heart Study. Ann Noninvasive Electrocardiol 2009; 14:72-9. [PMID: 19149796 DOI: 10.1111/j.1542-474x.2008.00276.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Genetic variants in myocardial sodium and potassium channel genes are associated with prolonged QT interval and increased risk of sudden death. It is unclear whether these genetic variants remain relevant in subjects with underlying conditions such as diabetes that are associated with prolonged QT interval. METHODS We tested single nucleotide polymorphisms (SNPs) in five candidate genes for association with QT interval in a family-based study of subjects with type 2 diabetes mellitus (T2DM). Thirty-six previously reported SNPs were genotyped in KCNQ1, HERG, SCN5A, KCNE1, and KCNE2 in 901 European Americans from 366 families. The heart rate-corrected (QTc) durations were determined using the Marquette 12SL program. Associations between the QTc interval and the genotypes were evaluated using SOLAR adjusting for age, gender, T2DM status, and body mass index. RESULTS Within KCNQ1 there was weak evidence for association between the minor allele of IVS12 +14T>C and increased QTc (P = 0.02). The minor allele of rs2236609 in KCNE1 trended toward significance with longer QTc (P = 0.06), while the minor allele of rs1805123 in HERG trended toward significance with shorter QTc (P = 0.07). However, no statistically significant associations were observed between the remaining SNPs and QTc variation. CONCLUSIONS We found weak evidence of association between three previously reported SNPs and QTc interval duration. While it appears as though genetic variants in previously identified candidate genes may be associated with QT duration in subjects with diabetes, the clinical implications of these associations in diabetic subjects at high risk for sudden death remain to be determined.
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Affiliation(s)
- Allison B Lehtinen
- Department of Biochemistry, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA
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34
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Marjamaa A, Newton-Cheh C, Porthan K, Reunanen A, Lahermo P, Väänänen H, Jula A, Karanko H, Swan H, Toivonen L, Nieminen MS, Viitasalo M, Peltonen L, Oikarinen L, Palotie A, Kontula K, Salomaa V. Common candidate gene variants are associated with QT interval duration in the general population. J Intern Med 2009; 265:448-58. [PMID: 19019189 PMCID: PMC2668713 DOI: 10.1111/j.1365-2796.2008.02026.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
OBJECTIVES QT interval prolongation is associated with increased risk of sudden cardiac death at the population level. As 30-40% of the QT-interval variability is heritable, we tested the association of common LQTS and NOS1AP gene variants with QT interval in a Finnish population-based sample. METHODS We genotyped 12 common LQTS and NOS1AP genetic variants in Health 2000, an epidemiological sample of 5043 Finnish individuals, using Sequenom MALDI-TOF mass spectrometry. ECG parameters were measured from digital 12-lead ECGs and QT intervals were adjusted for age, gender and heart rate with a nomogram (Nc) method derived from the present study population. RESULTS The KCNE1 D85N minor allele (frequency 1.4%) was associated with a 10.5 ms (SE 1.6) or 0.57 SD prolongation of the adjusted QT(Nc) interval (P=3.6 x 10(-11)) in gender-pooled analysis. In agreement with previous studies, we replicated the association with QT(Nc) interval with minor alleles of KCNH2 intronic SNP rs3807375 [1.6 ms (SE 0.4) or 0.08 SD, P=4.7 x 10(-5)], KCNH2 K897T [-2.6 ms (SE 0.5) or -0.14 SD, P=2.1 x 10(-7)] and NOSA1P variants including rs2880058 [4.0 ms (SE 0.4) or 0.22 SD, P=3.2 x 10(-24)] under additive models. CONCLUSIONS We demonstrate that each additional copy of the KCNE1 D85N minor allele is associated with a considerable 10.5 ms prolongation of the age-, gender- and heart rate-adjusted QT interval and could thus modulate repolarization-related arrhythmia susceptibility at the population level. In addition, we robustly confirm the previous findings that three independent KCNH2 and NOSA1P variants are associated with adjusted QT interval.
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Affiliation(s)
- A Marjamaa
- Research Program in Molecular Medicine, Biomedicum Helsinki, University of Helsinki, Helsinki, Finland
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35
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Schulze-Bahr E. Susceptibility genes & modifiers for cardiac arrhythmias. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 98:289-300. [DOI: 10.1016/j.pbiomolbio.2009.01.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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36
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The human ERG1 channel polymorphism, K897T, creates a phosphorylation site that inhibits channel activity. Proc Natl Acad Sci U S A 2008; 105:14704-8. [PMID: 18791070 DOI: 10.1073/pnas.0802250105] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Single-nucleotide polymorphisms (SNPs) in the human ether-a-go-go-related gene 1, hERG1, are associated with cardiac arrhythmias. The Kv11.1 channels encoded by hERG1 are also essential for rhythmic excitability of the pituitary, where they are regulated by thyroid hormone through a signal transduction cascade involving the phosphatidylinositol 3-kinase (PI3K) and the Ser/Thr-directed protein phosphatase, PP5. Here, we show that the hERG1 polymorphism at codon 897, which is read as a Thr instead of a Lys, creates a phosphorylation site for the Akt protein kinase on the Kv11.1 channel protein. Consequently, hormonal signaling through the PI3K signaling cascade, which normally stimulates K897 channels through PP5-mediated dephosphorylation, inhibits T897 channels through Akt-mediated phosphorylation. Thus, hormonal regulation of Kv11.1 in humans with the T897 polymorphism is predicted to prolong the QT interval of cardiac myocytes. A systematic bioinformatics search for SNPs in human ion channel genes identified 15 additional candidates for such "phosphorylopathies," which are predicted to create or destroy putative phosphorylation sites. Changes in protein phosphorylation might represent a general mechanism for the interaction of genetic variation and environment on human health.
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37
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Sicouri S, Antzelevitch C. Sudden cardiac death secondary to antidepressant and antipsychotic drugs. Expert Opin Drug Saf 2008; 7:181-94. [PMID: 18324881 DOI: 10.1517/14740338.7.2.181] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
A number of antipsychotic and antidepressant drugs are known to increase the risk of ventricular arrhythmias and sudden cardiac death. Based largely on a concern over QT prolongation and the development of life-threatening arrhythmias, a number of antipsychotic drugs have been temporarily or permanently withdrawn from the market or their use restricted. Some antidepressants and antipsychotics have been linked to QT prolongation and the development of Torsade de pointes arrhythmias, whereas others have been associated with a Brugada syndrome phenotype and the development of polymorphic ventricular arrhythmias. This review examines the mechanisms and predisposing factors underlying the development of cardiac arrhythmias, and sudden cardiac death, associated with antidepressant and antipsychotic drugs in clinical use.
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Affiliation(s)
- Serge Sicouri
- Masonic Medical Research Laboratory, 2150 Bleecker Street, Utica, New York, NY 13501-1787, USA
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38
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Koskela J, Laiho J, KäHönen M, Rontu R, Lehtinen R, Viik J, Niemi M, Niemelä K, Kööbi T, Turjanmaa V, Pörsti I, Lehtimäki T, Nieminen T. Potassium channel KCNH2 K897T polymorphism and cardiac repolarization during exercise test: The Finnish Cardiovascular Study. Scandinavian Journal of Clinical and Laboratory Investigation 2008; 68:31-8. [PMID: 17852802 DOI: 10.1080/00365510701496488] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
OBJECTIVE Cardiac repolarization is regulated, in part, by the KCNH2 gene, which encodes a rapidly activating component of the delayed rectifier potassium channel. The gene expresses a functional single nucleotide polymorphism, K897T, which changes the biophysical properties of the channel. The objective of this study was to evaluate whether this polymorphism influences two indices of repolarization--the QT interval and T-wave alternans (TWA)--during different phases of a physical exercise test. MATERIAL AND METHODS The cohort consisted of 1,975 patients undergoing an exercise test during which on-line electrocardiographic data were registered. Information on coronary risk factors and medication was recorded. The 2690A>C nucleotide variation in the KCNH2 gene corresponding to the K897T amino acid change was analysed after polymerase chain reaction with allele-specific TaqMan probes. RESULTS Among all subjects, the QTc intervals did not differ between the three genotype groups (p> or =0.31, RANOVA). Women with the CC genotype tended to have longer QT intervals during the exercise test, but the difference was statistically significant only at rest (p = 0.011, ANOVA). This difference was also detected when the analysis was adjusted for several factors influencing the QT interval. No statistically significant effects of the K897T polymorphism on TWA were observed among all subjects (p = 0.16, RANOVA), nor in men and women separately. CONCLUSIONS The K897T polymorphism of the KCNH2 gene may not be a major genetic determinant for the TWA, but the influence of the CC genotype on QT interval deserves further research among women.
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Affiliation(s)
- J Koskela
- Internal Medicine, Tampere University Hospital and Tampere University Medical School, Tampere, Finland.
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39
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SCICLUNA BRENDONP, WILDE ARTHURW, BEZZINA CONNIER. The Primary Arrhythmia Syndromes: Same Mutation, Different Manifestations. Are We Starting to Understand Why? J Cardiovasc Electrophysiol 2008; 19:445-52. [DOI: 10.1111/j.1540-8167.2007.01073.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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40
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Lin MCA, Papazian DM. Differences between ion binding to eag and HERG voltage sensors contribute to differential regulation of activation and deactivation gating. Channels (Austin) 2008; 1:429-37. [PMID: 18690045 DOI: 10.4161/chan.1.6.5760] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
HERG (KCNH2) and ether-à-go-go (eag) (KCNH1) are members of the same subfamily of voltage-gated K+ channels. In eag, voltage-dependent activation is significantly slowed by extracellular divalent cations. To exert this effect, ions bind to a site located between transmembrane segments S2 and S3 in the voltage sensor domain where they interact with acidic residues that are conserved only among members of the eag subfamily. In HERG channels, extracellular divalent ions significantly accelerate deactivation. To investigate the ionbinding site in HERG, acidic residues in S2 and S3 were neutralized singly or in pairs to alanine, and the functional effects of extracellular Mg(2+) were characterized in Xenopus oocytes. To modulate deactivation kinetics in HERG, divalent cations interact with eag subfamily-specific acidic residues (D460 and D509) and also with an acidic residue in S2 (D456) that is widely conserved in the voltage-gated channel superfamily. In contrast, the analogous widely-conserved residue does not contribute to the ion-binding site that modulates activation kinetics in eag. We propose that structural differences between the ion-binding sites in the eag and HERG voltage sensors contribute to the differential regulation of activation and deactivation gating in these channels. A previously proposed model for S4 conformational changes during voltagedependent activation can account for the differential regulation of gating seen in eag and HERG.
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Affiliation(s)
- Meng Chin A Lin
- Department of Physiology and Molecular Biology Institute, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90095-1751, USA
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41
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Sinner MF, Pfeufer A, Akyol M, Beckmann BM, Hinterseer M, Wacker A, Perz S, Sauter W, Illig T, Näbauer M, Schmitt C, Wichmann HE, Schömig A, Steinbeck G, Meitinger T, Kääb S. The non-synonymous coding IKr-channel variant KCNH2-K897T is associated with atrial fibrillation: results from a systematic candidate gene-based analysis of KCNH2 (HERG). Eur Heart J 2008; 29:907-14. [PMID: 18222980 DOI: 10.1093/eurheartj/ehm619] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
AIMS Atrial fibrillation (AF) is the most frequent arrhythmia in humans. Rare familial forms exist. Recent evidence indicates a genetic susceptibility to common forms of AF. The alpha-subunit of the myocardial I(Kr)-channel, encoded by the KCNH2 gene, is crucial to ventricular and atrial repolarization. Patients with mutations in KCNH2 present with higher incidence of AF. Common variants in KCNH2 have been shown to modify ventricular repolarization. We intended to investigate, whether such variants may also modulate atrial repolarization and predispose to AF. METHODS AND RESULTS In a two-stage association study we analysed 1207 AF-cases and 2475 controls. In stage I 40 tagSNPs (single nucleotide polymorphisms) from the KCNH2 genomic region were genotyped in 671 AF-cases and 694 controls. Of five associated variants, the common K897-allele of the KCNH2-K897T variant was replicated in n = 536 independent AF cases and n = 1781 controls in stage II [overall odds ratio 1.25, 95% confidence interval 1.11-1.41, P = 0.00033]. This association remained significant after adjustment for gender and age. CONCLUSION We report a genetic association finding including positive replication between the K897-allele and higher incidence of AF. This provides a molecular correlate for complex genetic predispositions to AF. The consequences of the K897T variant at the atrial level will require further functional investigations.
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Affiliation(s)
- Moritz F Sinner
- Department of Medicine I, Ludwig-Maximilians-University Munich, Klinikum Grosshadern, Marchioninistr. 15, Munich D-81377, Germany
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42
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Bankston JR, Yue M, Chung W, Spyres M, Pass RH, Silver E, Sampson KJ, Kass RS. A novel and lethal de novo LQT-3 mutation in a newborn with distinct molecular pharmacology and therapeutic response. PLoS One 2007; 2:e1258. [PMID: 18060054 PMCID: PMC2082660 DOI: 10.1371/journal.pone.0001258] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2007] [Accepted: 11/10/2007] [Indexed: 11/18/2022] Open
Abstract
Background SCN5A encodes the α-subunit (Nav1.5) of the principle Na+ channel in the human heart. Genetic lesions in SCN5A can cause congenital long QT syndrome (LQTS) variant 3 (LQT-3) in adults by disrupting inactivation of the Nav1.5 channel. Pharmacological targeting of mutation-altered Na+ channels has proven promising in developing a gene-specific therapeutic strategy to manage specifically this LQTS variant. SCN5A mutations that cause similar channel dysfunction may also contribute to sudden infant death syndrome (SIDS) and other arrhythmias in newborns, but the prevalence, impact, and therapeutic management of SCN5A mutations may be distinct in infants compared with adults. Methods and Results Here, in a multidisciplinary approach, we report a de novo SCN5A mutation (F1473C) discovered in a newborn presenting with extreme QT prolongation and differential responses to the Na+ channel blockers flecainide and mexiletine. Our goal was to determine the Na+ channel phenotype caused by this severe mutation and to determine whether distinct effects of different Na+ channel blockers on mutant channel activity provide a mechanistic understanding of the distinct therapeutic responsiveness of the mutation carrier. Sequence analysis of the proband revealed the novel missense SCN5A mutation (F1473C) and a common variant in KCNH2 (K897T). Patch clamp analysis of HEK 293 cells transiently transfected with wild-type or mutant Na+ channels revealed significant changes in channel biophysics, all contributing to the proband's phenotype as predicted by in silico modeling. Furthermore, subtle differences in drug action were detected in correcting mutant channel activity that, together with both the known genetic background and age of the patient, contribute to the distinct therapeutic responses observed clinically. Significance The results of our study provide further evidence of the grave vulnerability of newborns to Na+ channel defects and suggest that both genetic background and age are particularly important in developing a mutation-specific therapeutic personalized approach to manage disorders in the young.
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Affiliation(s)
- John R. Bankston
- Department of Pharmacology, College of Physicians and Surgeons, Columbia University Medical Center, New York, New York, United States of America
| | - Minerva Yue
- Department of Pharmacology, College of Physicians and Surgeons, Columbia University Medical Center, New York, New York, United States of America
| | - Wendy Chung
- Department of Pediatrics, College of Physicians and Surgeons, Columbia University Medical Center, New York, New York, United States of America
| | - Meghan Spyres
- College of Physicians and Surgeons, Columbia University Medical Center, New York, New York, United States of America
| | - Robert H. Pass
- Department of Pediatrics, College of Physicians and Surgeons, Columbia University Medical Center, New York, New York, United States of America
| | - Eric Silver
- Department of Pediatrics, College of Physicians and Surgeons, Columbia University Medical Center, New York, New York, United States of America
| | - Kevin J. Sampson
- Department of Pharmacology, College of Physicians and Surgeons, Columbia University Medical Center, New York, New York, United States of America
| | - Robert S. Kass
- Department of Pharmacology, College of Physicians and Surgeons, Columbia University Medical Center, New York, New York, United States of America
- * To whom correspondence should be addressed. E-mail:
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43
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Newton-Cheh C, Guo CY, Larson MG, Musone SL, Surti A, Camargo AL, Drake JA, Benjamin EJ, Levy D, D'Agostino RB, Hirschhorn JN, O'donnell CJ. Common Genetic Variation in
KCNH2
Is Associated With QT Interval Duration. Circulation 2007; 116:1128-36. [PMID: 17709632 DOI: 10.1161/circulationaha.107.710780] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background—
QT prolongation is associated with increased risk of sudden cardiac death in the general population and in people exposed to QT-prolonging drugs. Mutations in the
KCNH2
gene encoding the HERG potassium channel cause 30% of long-QT syndrome, and binding to this channel leads to drug-induced QT prolongation. We tested common
KCNH2
variants for association with continuous QT interval duration.
Methods and Results—
We selected 17 single nucleotide polymorphisms and rs1805123, a previously associated missense single nucleotide polymorphism, for genotyping in 1730 unrelated men and women from the Framingham Heart Study. rs3807375 genotypes were associated with continuous QT interval duration in men and women (2-
df
P
=0.002), with a dominant model suggested (
P
=0.0004). An independent sample of 871 Framingham Heart Study men and women replicated the association (1-sided dominant
P
=0.02). On combined analysis of 2123 subjects, individuals with AA or AG genotypes had a 0.14-SD (SE, 0.04) or 3.9-ms higher age-, sex- and RR-adjusted QT interval compared with GG individuals (
P
=0.00006). The previously reported association of rs1805123 (K897T) replicated under a dominant (AA/AC, 0.12 SD [SE, 0.07] or 3.1 ms higher versus CC; 1-sided
P
=0.04) or additive model (0.06 SD [SE, 0.03] or 1.6 ms higher per A allele; 1-sided
P
=0.01).
Conclusions—
Two common genetic variants at the
KCNH2
locus are associated with continuous QT interval duration in an unselected community-based sample. Studies to determine the influence of these variants on risk of sudden cardiac death and drug-induced arrhythmias should be considered.
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44
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Newton-Cheh C, Shah R. Genetic determinants of QT interval variation and sudden cardiac death. Curr Opin Genet Dev 2007; 17:213-21. [PMID: 17467978 DOI: 10.1016/j.gde.2007.04.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2007] [Accepted: 04/17/2007] [Indexed: 12/19/2022]
Abstract
Electrocardiographic QT interval prolongation or shortening is a risk factor for sudden cardiac death. The study of Mendelian syndromes in families with extreme long and short QT interval duration and ventricular arrhythmias has led to the identification of genes encoding ion channel proteins important in myocardial repolarization. Rare mutations in such ion channel genes do not individually contribute substantially to the population burden of ventricular arrhythmias and sudden cardiac death. Only now are studies systematically testing the relationship between common variants in these genes--or elsewhere in the genome--and QT interval variation and sudden cardiac death. Identification of genetic variation underlying myocardial repolarization could have important implications for the prevention of both sporadic and drug-induced arrhythmias.
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Affiliation(s)
- Christopher Newton-Cheh
- Program in Medical and Population Genetics, Broad Institute of Harvard and MIT, NHLBI's Framingham Heart Study, Cardiology Division, Massachusetts General Hospital, Boston, MA 02114, USA.
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45
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Mank-Seymour AR, Richmond JL, Wood LS, Reynolds JM, Fan YT, Warnes GR, Milos PM, Thompson JF. Association of torsades de pointes with novel and known single nucleotide polymorphisms in long QT syndrome genes. Am Heart J 2006; 152:1116-22. [PMID: 17161064 DOI: 10.1016/j.ahj.2006.08.020] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2006] [Accepted: 08/23/2006] [Indexed: 01/08/2023]
Abstract
BACKGROUND Reduction of drug-induced adverse events may be achievable through a better understanding of the underlying causes of such events. Identifying phenotypes and genotypes that allow event prediction would provide greater safety margins for new therapeutics. Torsades de pointes (TdP) is one such life-threatening adverse event and can arise from excessive lengthening of the QT interval. This study was designed to better understand the role of genetics in the development of TdP and to determine whether genotypes can be used to predict susceptibility and thus reduce adverse events. METHODS Seven known familial long QT syndrome genes were scanned for sequence variations in 34 patients with TdP. This group of patients is the largest such cohort ever assembled for this type of analysis. The allele frequencies for novel and known polymorphisms in these patients were compared with those in healthy control subjects. RESULTS Six novel mutations--4 in ANK2, 1 in KCNQ1, and 1 in SCN5A--were found in the patients with TdP. Two mutations were also found in 595 healthy control subjects, whereas the others were unique to patients with TdP. Two common single nucleotide polymorphisms may be associated with the risk of TdP. The entire ANK2 gene had not been screened in a population this large previously. CONCLUSIONS Genotypes alone could not be used to completely predict susceptibility to TdP, even when used with phenotypes. The best model using genotypic and phenotypic variables was unable to predict all events. It is unclear what other risk genes or environmental effects might be necessary to predict such cases.
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Chapman H, Pasternack M. The action of the novel gastrointestinal prokinetic prucalopride on the HERG K+ channel and the common T897 polymorph. Eur J Pharmacol 2006; 554:98-105. [PMID: 17109852 DOI: 10.1016/j.ejphar.2006.10.019] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2006] [Revised: 10/03/2006] [Accepted: 10/06/2006] [Indexed: 01/08/2023]
Abstract
The human ether-à-go-go related gene (HERG) encodes the alpha-subunit of a delayed rectifier potassium channel important in the repolarisation of the cardiac action potential. Excessive action potential prolongation through HERG channel inhibition is associated with a risk of torsade de pointes arrhythmias and is a major challenge for drug development. The acute effects of the novel prokinetic prucalopride were examined on heterologously expressed HERG channels in human embryonic kidney (HEK) 293 cells using the whole-cell patch-clamp technique. Prucalopride inhibited HERG channels in a concentration-dependent manner with an IC(50) of 4.1 microM. Prucalopride significantly slowed channel deactivation and recovery from inactivation, accelerated and altered the extent of inactivation. Similar concentration-dependency and kinetic changes were observed with the minor T897 polymorphic HERG variant. Prucalopride block was frequency-independent due to rapid state-dependent block, with binding occurring in the open and inactivated states. Though prucalopride blocks HERG channels this is unlikely to be significant at clinically relevant concentrations.
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Affiliation(s)
- Hugh Chapman
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland.
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Koo SH, Ho WF, Lee EJD. Genetic polymorphisms in KCNQ1, HERG, KCNE1 and KCNE2 genes in the Chinese, Malay and Indian populations of Singapore. Br J Clin Pharmacol 2006; 61:301-8. [PMID: 16487223 PMCID: PMC1885019 DOI: 10.1111/j.1365-2125.2005.02545.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
AIMS To determine the genetic variability of long QT syndrome (LQTS)-associated genes (KCNQ1, HERG, KCNE1 and KCNE2) among three distinct ethnic groups in the Singapore population. METHODS Genomic DNA samples from up to 265 normal healthy Chinese, 118 Malay and 139 Indian volunteer subjects were screened for genetic variations in the coding region of the LQTS-associated genes using denaturing high-performance liquid chromatography and sequencing analyses. RESULTS In total, 37 single nucleotide polymorphisms (SNPs) were identified in the coding exons of the LQTS-associated potassium ion channel genes, seven of which were novel nonsynonymous polymorphisms. SNPs 356G-->A (exon 1 of KCNQ1), 2624C-->T and 2893G-->A (exon 11 of HERG), 3164G-->A, 3322C-->G and 3460G-->A (exon 14 of HERG), and 79C-->T (exon 3 of KCNE2) resulted in Gly119Asp, Thr875Met, Gly965Arg, Arg1055Gln, Leu1108Val, Gly1154Ser and Arg27Cys amino acid substitutions, respectively. In addition, 16 intronic variants were detected. The functional consequence of these variants has not been studied and their association with risk of LQTS is unclear. CONCLUSIONS There exist multiple genetic polymorphisms of the LQTS-associated genes in the three distinct Asian populations. Though the functional significance of many of these SNPs is unknown, this interindividual and interethnic genetic variability may underlie the different susceptibilities of individuals to developing LQTS.
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Affiliation(s)
- Seok Hwee Koo
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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Millat G, Chevalier P, Restier-Miron L, Da Costa A, Bouvagnet P, Kugener B, Fayol L, Gonzàlez Armengod C, Oddou B, Chanavat V, Froidefond E, Perraudin R, Rousson R, Rodriguez-Lafrasse C. Spectrum of pathogenic mutations and associated polymorphisms in a cohort of 44 unrelated patients with long QT syndrome. Clin Genet 2006; 70:214-27. [PMID: 16922724 DOI: 10.1111/j.1399-0004.2006.00671.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Long QT syndrome (LQTS) is a rare and clinically heterogeneous inherited disorder characterized by a long QT interval on the electrocardiogram, increased risk of syncope and sudden death caused by arrhythmias. This syndrome is mostly caused by mutations in genes encoding various cardiac ion channels. The clinical heterogeneity is usually attributed to variable penetrance. One of the reasons for this variability in expression could be the coexistence of common single nucleotide polymorphisms (SNPs) on LQTS-causing genes and/or unknown genes. Some synonymous and nonsynonymous exonic SNPs identified in LQTS-causing genes may have an effect on the cardiac repolarization process and modulate the clinical expression of a latent LQTS pathogenic mutation. We report the molecular pattern of 44 unrelated patients with LQTS using denaturing high-performance liquid chromatography analysis of the KCNQ1, KCNH2, SCN5A, KCNE1 and KCNE2 genes. Forty-five disease-causing mutations (including 24 novel ones) were identified in this cohort. Most of our patients (84%) showed complex molecular pattern with one mutation (and even two for four patients) associated with several SNPs located in several LQTS genes.
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Affiliation(s)
- G Millat
- Laboratoire de Biochimie et Biologie Moléculaire, Hopital CardioVasculaire et Pneumologique L Pradel, Bron, France, and Unidad de neonatología Servicio de pediatría, Hospital Universitario Río Hortega, Valladolid, Spain.
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Linna EH, Perkiömäki JS, Karsikas M, Seppänen T, Savolainen M, Kesäniemi YA, Mäkikallio T, Huikuri HV. Functional significance of KCNH2 (HERG) K897T polymorphism for cardiac repolarization assessed by analysis of T-wave morphology. Ann Noninvasive Electrocardiol 2006; 11:57-62. [PMID: 16472284 PMCID: PMC6932664 DOI: 10.1111/j.1542-474x.2006.00083.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND Although KCNH2 (HERG) K897T polymorphism has been shown to be associated with the QT interval measured from 12-lead electrocardiogram (ECG), the functional significance of K897T polymorphism has been debated. The aim of this study was to test whether the K897T polymorphism of the KCNH2 (HERG) gene coding for the rapidly activating delayed rectifier K+ channel influences cardiac repolarization assessed by principal component analysis (PCA) of T-wave morphology. METHODS Twelve-lead ECGs were digitized and T-wave morphology was analyzed with a PCA method in a population consisting of 228 healthy middle-aged subjects (121 women and 107 men). DNA samples were genotyped for the nucleotide 2690 A>C variation of the KCNH2 gene, corresponding to the KCNH2 K(lysine)897T(threonine) amino acid polymorphism. RESULTS The allele frequencies were 0.86 (K) and 0.14 (T). The KCNH2 K897T polymorphism was associated with the total cosine R-to-T (TCRT), which reflects the wave front direction between depolarization and repolarization. TCRT was 0.421 in the genotype KK and 0.300 in the genotypes KT and TT (P = 0.04). The difference of TCRT was more marked between the KCNH2 K897T genotypes in women (P = 0.03) than in men (P = 0.52). CONCLUSIONS The common K897T polymorphism of the cardiac potassium channel KCNH2 has functional significance for cardiac electrical properties. Subjects with a less common genotype, KT or TT, have smaller TCRT, which reflects dyssynchrony between depolarization and repolarization and is associated with an increased risk of cardiac mortality.
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Affiliation(s)
- Eeva H Linna
- Division of Cardiology, Department of Medicine, University of Oulu, Finland.
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