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Refaat MM, El Hage L, Steffensen AB, Hotait M, Schmitt N, Scheinman M, Badhwar N. Iron Overload Leading to Torsades de Pointes in β-Thalassemia and Long QT Syndrome. Card Electrophysiol Clin 2016; 8:247-256. [PMID: 26920202 DOI: 10.1016/j.ccep.2015.10.037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The authors present a unique case of torsades de pointes in a β-thalassemia patient with early iron overload in the absence of any structural abnormalities as seen in hemochromatosis. Genetic testing showed a novel KCNQ1 gene mutation 1591C>T [Gln531Ter(X)]. Testing of the gene mutation in Xenopus laevis oocytes showed loss of function of the IKs current. The authors hypothesize that iron overload combined with the KCNQ1 gene mutation leads to prolongation of QTc and torsades de pointes.
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Affiliation(s)
- Marwan M Refaat
- Cardiology Division, Department of Internal Medicine, American University of Beirut Medical Center, Beirut, Lebanon; Department of Biochemistry and Molecular Genetics, American University of Beirut Medical Center, Beirut, Lebanon; Cardiac Electrophysiology, Cardiology, Department of Internal Medicine, American University of Beirut Faculty of Medicine and Medical Center, 3 Dag Hammarskjold Plaza, 8th Floor, New York, NY 10017, USA; Department of Biochemistry and Molecular Genetics, American University of Beirut Faculty of Medicine and Medical Center, 3 Dag Hammarskjold Plaza, 8th Floor, New York, NY 10017, USA
| | - Lea El Hage
- Division of Cardiology, Department of Medicine, University of California San Francisco Medical Center, 500 Parnassus Avenue, MUE-431, San Francisco, CA 94143-1354, USA
| | - Annette Buur Steffensen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | - Mostafa Hotait
- Cardiology Division, Department of Internal Medicine, American University of Beirut Medical Center, Beirut, Lebanon
| | - Nicole Schmitt
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | - Melvin Scheinman
- Division of Cardiology, Department of Medicine, University of California San Francisco Medical Center, 500 Parnassus Avenue, MUE-431, San Francisco, CA 94143-1354, USA
| | - Nitish Badhwar
- Division of Cardiology, Department of Medicine, University of California San Francisco Medical Center, 500 Parnassus Avenue, MUE-431, San Francisco, CA 94143-1354, USA.
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de Villiers CP, van der Merwe L, Crotti L, Goosen A, George AL, Schwartz PJ, Brink PA, Moolman-Smook JC, Corfield VA. AKAP9 is a genetic modifier of congenital long-QT syndrome type 1. ACTA ACUST UNITED AC 2014; 7:599-606. [PMID: 25087618 DOI: 10.1161/circgenetics.113.000580] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Long-QT syndrome (LQTS), a cardiac arrhythmia disorder with variable phenotype, often results in devastating outcomes, including sudden cardiac death. Variable expression, independently from the primary disease-causing mutation, can partly be explained by genetic modifiers. This study investigates variants in a known LQTS-causative gene, AKAP9, for potential LQTS-type 1-modifying effects. METHODS AND RESULTS Members of a South African LQTS-type 1 founder population (181 noncarriers and 168 mutation carriers) carrying the identical-by-descent KCNQ1 p.Ala341Val (A341V) mutation were evaluated for modifying effects of AKAP9 variants on heart rate-corrected QT interval (QTc), cardiac events, and disease severity. Tag single nucleotide polymorphisms in AKAP9 rs11772585, rs7808587, rs2282972, and rs2961024 (order, 5'-3'positive strand) were genotyped. Associations between phenotypic traits and alleles, genotypes, and haplotypes were statistically assessed, adjusting for the degree of relatedness and confounding variables. The rs2961024 GG genotype, always represented by CGCG haplotype homozygotes, revealed an age-dependent heart rate-corrected QT interval increase (1% per additional 10 years) irrespective of A341V mutation status (P=0.006). The rs11772585 T allele, found uniquely in the TACT haplotype, more than doubled (218%) the risk of cardiac events (P=0.002) in the presence of A341V; additionally, it increased disease severity (P=0.025). The rs7808587 GG genotype was associated with a 74% increase in cardiac event risk (P=0.046), whereas the rs2282972 T allele, predominantly represented by the CATT haplotype, decreased risk by 53% (P=0.001). CONCLUSIONS AKAP9 has been identified as an LQTS-type 1-modifying gene. Variants investigated altered heart rate-corrected QT interval irrespective of mutation status, as well as cardiac event risk, and disease severity, in mutation carriers.
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Affiliation(s)
- Carin P de Villiers
- From the Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Medical Research Council (MRC) Centre for Molecular and Cellular Biology, (C.P.d.V., L.v.d.M., J.C.M.-S., V.A.C.), and Department of Internal Medicine (A.G., P.A.B.), Stellenbosch University, Stellenbosch, South Africa; Department of Statistics, University of Western Cape, Bellville, South Africa (L.v.d.M.); IRCCS Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Milan, Italy (L.C., P.J.S.); Department of Molecular Medicine, University of Pavia, Pavia, Italy (L.C.); Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany (L.C.); and Departments of Medicine and Pharmacology, and Institute for Integrative Genomics, Vanderbilt University, Nashville, TN (A.L.G.)
| | - Lize van der Merwe
- From the Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Medical Research Council (MRC) Centre for Molecular and Cellular Biology, (C.P.d.V., L.v.d.M., J.C.M.-S., V.A.C.), and Department of Internal Medicine (A.G., P.A.B.), Stellenbosch University, Stellenbosch, South Africa; Department of Statistics, University of Western Cape, Bellville, South Africa (L.v.d.M.); IRCCS Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Milan, Italy (L.C., P.J.S.); Department of Molecular Medicine, University of Pavia, Pavia, Italy (L.C.); Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany (L.C.); and Departments of Medicine and Pharmacology, and Institute for Integrative Genomics, Vanderbilt University, Nashville, TN (A.L.G.)
| | - Lia Crotti
- From the Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Medical Research Council (MRC) Centre for Molecular and Cellular Biology, (C.P.d.V., L.v.d.M., J.C.M.-S., V.A.C.), and Department of Internal Medicine (A.G., P.A.B.), Stellenbosch University, Stellenbosch, South Africa; Department of Statistics, University of Western Cape, Bellville, South Africa (L.v.d.M.); IRCCS Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Milan, Italy (L.C., P.J.S.); Department of Molecular Medicine, University of Pavia, Pavia, Italy (L.C.); Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany (L.C.); and Departments of Medicine and Pharmacology, and Institute for Integrative Genomics, Vanderbilt University, Nashville, TN (A.L.G.)
| | - Althea Goosen
- From the Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Medical Research Council (MRC) Centre for Molecular and Cellular Biology, (C.P.d.V., L.v.d.M., J.C.M.-S., V.A.C.), and Department of Internal Medicine (A.G., P.A.B.), Stellenbosch University, Stellenbosch, South Africa; Department of Statistics, University of Western Cape, Bellville, South Africa (L.v.d.M.); IRCCS Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Milan, Italy (L.C., P.J.S.); Department of Molecular Medicine, University of Pavia, Pavia, Italy (L.C.); Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany (L.C.); and Departments of Medicine and Pharmacology, and Institute for Integrative Genomics, Vanderbilt University, Nashville, TN (A.L.G.)
| | - Alfred L George
- From the Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Medical Research Council (MRC) Centre for Molecular and Cellular Biology, (C.P.d.V., L.v.d.M., J.C.M.-S., V.A.C.), and Department of Internal Medicine (A.G., P.A.B.), Stellenbosch University, Stellenbosch, South Africa; Department of Statistics, University of Western Cape, Bellville, South Africa (L.v.d.M.); IRCCS Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Milan, Italy (L.C., P.J.S.); Department of Molecular Medicine, University of Pavia, Pavia, Italy (L.C.); Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany (L.C.); and Departments of Medicine and Pharmacology, and Institute for Integrative Genomics, Vanderbilt University, Nashville, TN (A.L.G.)
| | - Peter J Schwartz
- From the Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Medical Research Council (MRC) Centre for Molecular and Cellular Biology, (C.P.d.V., L.v.d.M., J.C.M.-S., V.A.C.), and Department of Internal Medicine (A.G., P.A.B.), Stellenbosch University, Stellenbosch, South Africa; Department of Statistics, University of Western Cape, Bellville, South Africa (L.v.d.M.); IRCCS Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Milan, Italy (L.C., P.J.S.); Department of Molecular Medicine, University of Pavia, Pavia, Italy (L.C.); Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany (L.C.); and Departments of Medicine and Pharmacology, and Institute for Integrative Genomics, Vanderbilt University, Nashville, TN (A.L.G.)
| | - Paul A Brink
- From the Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Medical Research Council (MRC) Centre for Molecular and Cellular Biology, (C.P.d.V., L.v.d.M., J.C.M.-S., V.A.C.), and Department of Internal Medicine (A.G., P.A.B.), Stellenbosch University, Stellenbosch, South Africa; Department of Statistics, University of Western Cape, Bellville, South Africa (L.v.d.M.); IRCCS Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Milan, Italy (L.C., P.J.S.); Department of Molecular Medicine, University of Pavia, Pavia, Italy (L.C.); Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany (L.C.); and Departments of Medicine and Pharmacology, and Institute for Integrative Genomics, Vanderbilt University, Nashville, TN (A.L.G.)
| | - Johanna C Moolman-Smook
- From the Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Medical Research Council (MRC) Centre for Molecular and Cellular Biology, (C.P.d.V., L.v.d.M., J.C.M.-S., V.A.C.), and Department of Internal Medicine (A.G., P.A.B.), Stellenbosch University, Stellenbosch, South Africa; Department of Statistics, University of Western Cape, Bellville, South Africa (L.v.d.M.); IRCCS Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Milan, Italy (L.C., P.J.S.); Department of Molecular Medicine, University of Pavia, Pavia, Italy (L.C.); Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany (L.C.); and Departments of Medicine and Pharmacology, and Institute for Integrative Genomics, Vanderbilt University, Nashville, TN (A.L.G.)
| | - Valerie A Corfield
- From the Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Medical Research Council (MRC) Centre for Molecular and Cellular Biology, (C.P.d.V., L.v.d.M., J.C.M.-S., V.A.C.), and Department of Internal Medicine (A.G., P.A.B.), Stellenbosch University, Stellenbosch, South Africa; Department of Statistics, University of Western Cape, Bellville, South Africa (L.v.d.M.); IRCCS Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Milan, Italy (L.C., P.J.S.); Department of Molecular Medicine, University of Pavia, Pavia, Italy (L.C.); Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany (L.C.); and Departments of Medicine and Pharmacology, and Institute for Integrative Genomics, Vanderbilt University, Nashville, TN (A.L.G.)
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