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Wang C, Lu Y, Cheng J, Zhang L, Liu W, Peng W, Zhang D, Duan H, Han D, Yuan H. Identification of KCNQ1 compound heterozygous mutations in three Chinese families with Jervell and Lange-Nielsen Syndrome. Acta Otolaryngol 2017; 137:522-528. [PMID: 27917693 DOI: 10.1080/00016489.2016.1260156] [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] [Indexed: 10/20/2022]
Abstract
CONCLUSION Besides expanding the spectrum of KCNQ1 mutations causing Jervell and Lange-Nielsen Syndrome (JLNS), the results showed diversity of its phenotypes, and emphasized the importance of molecular genetic analysis in confirming clinical diagnosis and making diagnosis possible before the emergency symptoms for deaf individuals. OBJECTIVES This study aimed to investigate four patients from three Chinese families with congenital hearing loss clinically and genetically. METHOD Genetic analysis of previously reported deafness genes based on massively parallel sequencing was conducted in more than five thousand Chinese hearing loss patients. Detailed clinical features of the patients with compound heterozygous or homozygous mutations of KCNQ1 gene were collected and analyzed. RESULTS Compound mutations of KCNQ1 were found to be the genetic etiology of four patients from three families. Among the six KCNQ1 mutations, c.546C > A was identified as a novel mutation, c.965C > T had been reported in JLNS, while c.683 + 5G > A, c.1484_1485delCT, c.905C > T and c.1831G > A were previously reported in LQT1. In addition to congenital profound hearing loss in all subjects, two sibling subjects showed typical JLNS cardiac phenotype of prolonged QTc and recurrent syncopal episodes. One subject presented not only JLNS, but also iron-deficiency anemia and epilepsy. The other subject did not present any cardiac phenotype.
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Affiliation(s)
- Cuicui Wang
- Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, PR China
- School of Medicine, Nankai University, Tianjin, PR China
| | - Yu Lu
- Medical Genetics Center, Southwest Hospital, Third Military Medical University, Chongqing, PR China
| | - Jing Cheng
- Medical Genetics Center, Southwest Hospital, Third Military Medical University, Chongqing, PR China
| | - Lei Zhang
- Medical Genetics Center, Southwest Hospital, Third Military Medical University, Chongqing, PR China
| | - Wei Liu
- Department of Otolaryngology, Ordos Central Hospital, Ordos, Inner Mongolia Province, PR China
| | - Weihua Peng
- Medical Genetics Center, Southwest Hospital, Third Military Medical University, Chongqing, PR China
| | - Di Zhang
- Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, PR China
| | - Hong Duan
- Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, PR China
| | - Dongyi Han
- Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, PR China
| | - Huijun Yuan
- Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, PR China
- Medical Genetics Center, Southwest Hospital, Third Military Medical University, Chongqing, PR China
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2
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Liin SI, Larsson JE, Barro-Soria R, Bentzen BH, Larsson HP. Fatty acid analogue N-arachidonoyl taurine restores function of I Ks channels with diverse long QT mutations. eLife 2016; 5. [PMID: 27690226 PMCID: PMC5081249 DOI: 10.7554/elife.20272] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Accepted: 09/28/2016] [Indexed: 01/08/2023] Open
Abstract
About 300 loss-of-function mutations in the IKs channel have been identified in patients with Long QT syndrome and cardiac arrhythmia. How specific mutations cause arrhythmia is largely unknown and there are no approved IKs channel activators for treatment of these arrhythmias. We find that several Long QT syndrome-associated IKs channel mutations shift channel voltage dependence and accelerate channel closing. Voltage-clamp fluorometry experiments and kinetic modeling suggest that similar mutation-induced alterations in IKs channel currents may be caused by different molecular mechanisms. Finally, we find that the fatty acid analogue N-arachidonoyl taurine restores channel gating of many different mutant channels, even though the mutations are in different domains of the IKs channel and affect the channel by different molecular mechanisms. N-arachidonoyl taurine is therefore an interesting prototype compound that may inspire development of future IKs channel activators to treat Long QT syndrome caused by diverse IKs channel mutations. DOI:http://dx.doi.org/10.7554/eLife.20272.001 Every heartbeat relies on an electric wave that travels through the heart. This wave must reach different parts of the heart in a specific sequence to ensure that the heart muscle cells contract in a coordinated manner. Such coordinated contractions enable the heart to pump enough blood around the body. By allowing specific ions to flow into or out of the heart muscle cell, proteins called ion channels in the cell membrane generate the electric wave, keep it going and stop it. One such protein called the IKs channel controls the flow of potassium ions, and in doing so stops the electric wave in heart muscle cells. About 300 different mutations in the IKs channel have been shown to cause abnormal heart rhythms in individuals with a disorder called long QT syndrome. People with this condition may suddenly black out because their heart develops prolonged electric waves that prevent blood from being pumped properly. To investigate how mutations in the IKs channel produce heart rhythm abnormalities, Liin et al. genetically engineered the egg cells of African clawed frogs to have one of eight mutant forms of the human IKs channel. Studying these channels revealed that the mutations reduce how well the channels work in a wide variety of ways. However, treating the cells with a particular fatty acid helped to normalize how each of the mutant channels worked. Therefore, variants of the fatty acid could potentially form a useful treatment for people with heart rhythm problems caused by mutations in the IKs channel. More studies are needed to confirm whether the fatty acid is as effective at combating the effects of the mutations in whole hearts and animals. As ion channels related to the IKs channel are found in many types of cells, it is also important to investigate whether treatment with the fatty acid could cause any side effects that affect other organs. DOI:http://dx.doi.org/10.7554/eLife.20272.002
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Affiliation(s)
- Sara I Liin
- Department of Physiology and Biophysics, University of Miami, Miami, United States.,Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
| | - Johan E Larsson
- Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
| | - Rene Barro-Soria
- Department of Physiology and Biophysics, University of Miami, Miami, United States
| | - Bo Hjorth Bentzen
- The Danish Arrhythmia Research Centre, University of Copenhagen, Copenhagen, Denmark.,Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - H Peter Larsson
- Department of Physiology and Biophysics, University of Miami, Miami, United States
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3
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Rothenberg I, Piccini I, Wrobel E, Stallmeyer B, Müller J, Greber B, Strutz-Seebohm N, Schulze-Bahr E, Schmitt N, Seebohm G. Structural interplay of K V7.1 and KCNE1 is essential for normal repolarization and is compromised in short QT syndrome 2 (K V7.1-A287T). HeartRhythm Case Rep 2016; 2:521-529. [PMID: 28491751 PMCID: PMC5420010 DOI: 10.1016/j.hrcr.2016.08.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Affiliation(s)
- Ina Rothenberg
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, Münster, Germany
| | - Ilaria Piccini
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, Münster, Germany
| | - Eva Wrobel
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, Münster, Germany
| | - Birgit Stallmeyer
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, Münster, Germany
| | - Jovanca Müller
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, Münster, Germany
| | - Boris Greber
- Human Stem Cell Pluripotency Laboratory, Max Planck Institute for Molecular Biomedicine, Münster, Germany
- Chemical Genomics Centre of the Max Planck Society, Dortmund, Germany
| | - Nathalie Strutz-Seebohm
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, Münster, Germany
| | - Eric Schulze-Bahr
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, Münster, Germany
- Interdisziplinäres Zentrum für Klinische Forschung Münster (IZKF Münster) and Innovative Medizinische Forschung (IMF Münster), Faculty of Medicine, University of Münster, Münster, Germany
| | - Nicole Schmitt
- Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Guiscard Seebohm
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, Münster, Germany
- Interdisziplinäres Zentrum für Klinische Forschung Münster (IZKF Münster) and Innovative Medizinische Forschung (IMF Münster), Faculty of Medicine, University of Münster, Münster, Germany
- Address reprint requests and correspondence: Dr Guiscard Seebohm, Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, D48149 Münster, Germany.Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, D48149MünsterGermany
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4
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Genotype-based clinical manifestation and treatment of Chinese long QT syndrome patients with KCNQ1 mutations - R380S and W305L. Cardiol Young 2016; 26:754-63. [PMID: 26344792 DOI: 10.1017/s1047951115001304] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
UNLABELLED Aim Most long QT syndrome patients are associated with genetic mutations. We aimed to investigate the clinical and biochemical characteristics and look for genotype-based preventive implications in Chinese long QT syndrome patients. Methods and results We identified two missense mutations of the KCNQ1 gene in two independent Chinese families, including a previously reported mutation R380S in the C-terminus and a novel mutation W305L in the P-loop domain of the Kv7.1 channel, respectively. The proband with R380S was an 11-year-old girl who suffered a prolonged corrected QT interval of 660 ms, recurrent syncope, and sudden cardiac death, whose father was an asymptomatic carrier. The mutation W305L was detected in a 36-year-old woman with long QT syndrome and her immediate family members including the proband's younger sister with an unexplained syncope, her son, and her elder daughter without symptoms. Metoprolol appeared to be effective in preventing arrhythmias and syncope in long QT syndrome patients with mutation W305L. Both R380S and W305L mutations led to "loss-of-function" of the Kv7.1 channel accounting for the clinical phenotypes. CONCLUSIONS We first show two missense KCNQ1 mutations - R380S and W305L - in Chinese long QT syndrome patients, resulting in the loss of protein function. Mutation W305L in the P-loop domain of the Kv7.1 may derive a pronounced benefit from β-blocker therapy in symptomatic long QT syndrome patients, whereas mutation R380S located in the C-terminus may be associated with a high risk of sudden cardiac death.
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5
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Structural analysis of the S4-S5 linker of the human KCNQ1 potassium channel. Biochem Biophys Res Commun 2015; 456:410-4. [PMID: 25475720 DOI: 10.1016/j.bbrc.2014.11.097] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 11/24/2014] [Indexed: 11/23/2022]
Abstract
KCNQ1 plays important roles in the cardiac action potential and consists of an N-terminal domain, a voltage-sensor domain, a pore domain and a C-terminal domain. KCNQ1 is a voltage-gated potassium channel and its channel activity is regulated by membrane potentials. The linker between transmembrane helices 4 and 5 (S4-S5 linker) is important for transferring the conformational changes from the voltage-sensor domain to the pore domain. In this study, the structure of the S4-S5 linker of KCNQ1 was investigated by solution NMR, circular dichroism and fluorescence spectroscopic studies. The S4-S5 linker adopted a helical structure in detergent micelles. The W248 may interact with the cell membrane.
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6
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Pravdic D. "Who" can be found in and beyond of an electrocardiographic strip. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2013; 37:265-78. [PMID: 24313927 DOI: 10.1111/pace.12313] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Revised: 10/07/2013] [Accepted: 10/09/2013] [Indexed: 12/26/2022]
Abstract
Over the years, an electrocardiogram had become the basic tool to study the heart physiology and pathophysiology. Many authors gave a substantial contribution in understanding the electrophysiological basis for numerous electrocardiographic changes. Some of them were named after authors themselves, or others used the names of scientists who first discovered or explained the nature of a particular electrocardiographic finding. In this article, electrocardiographic phenomena and eponyms used in today's electrocardiography are described.
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Affiliation(s)
- Danijel Pravdic
- From the Departments of Physiology and Internal Medicine, University of Mostar School of Medicine and Clinical Hospital Mostar, Mostar, Bosnia and Herzegovina
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7
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Al-Aama J, Al-Ghamdi S, Bdier A, Wilde A, Bhuiyan ZA. De novomutation in theKCNQ1gene causal to Jervell and Lange-Nielsen syndrome. Clin Genet 2013; 86:492-5. [DOI: 10.1111/cge.12300] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 10/02/2013] [Accepted: 10/09/2013] [Indexed: 11/27/2022]
Affiliation(s)
- J.Y. Al-Aama
- Department of Genetic Medicine; King Abdulaziz University Hospital; Jeddah Saudi Arabia
- Princess Al Jawhara Albrahim Center of Excellence in Research of Hereditary Disorders; King Abdulaziz University; Jeddah Saudi Arabia
| | - S. Al-Ghamdi
- Department of Pediatric Cardiology; Prince Sultan Cardiac Center; Riyadh Saudi Arabia
| | - A.Y. Bdier
- Princess Al Jawhara Albrahim Center of Excellence in Research of Hereditary Disorders; King Abdulaziz University; Jeddah Saudi Arabia
| | - A.A.M. Wilde
- Princess Al Jawhara Albrahim Center of Excellence in Research of Hereditary Disorders; King Abdulaziz University; Jeddah Saudi Arabia
- Department of Cardiology, Academic Medical Center; University of Amsterdam; Amsterdam the Netherlands
| | - Zahurul A. Bhuiyan
- Laboratoire de Génétique Moléculaire, Service de Génétique Médicale; CHUV; Lausanne Switzerland
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8
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Novel mutations of KCNQ1 in Long QT syndrome. Indian Heart J 2013; 65:552-60. [PMID: 24206879 DOI: 10.1016/j.ihj.2013.08.025] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Revised: 03/30/2013] [Accepted: 08/09/2013] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Autosomal recessive Long QT syndrome is characterized by prolonged QTc along with congenital bilateral deafness depends on mutations in K(+) channel genes. A family of a Long QT syndrome proband from India has been identified with novel indel variations. METHODS The molecular study of the proband revealed 4 novel indel variations in KCNQ1. In-silico analysis revealed the intronic variations has led to a change in the secondary structure of mRNA and splice site variations. The exonic variations leads to frameshift mutations. DNA analysis of the available family members revealed a carrier status. RESULTS AND CONCLUSION It is thus predicted that the variations may lead to a change in the position of the splicing enhancer/inhibitor in KCNQ1 leading to the formation of a truncated S2-S3 fragment of KCNQ1 transmembrane protein in cardiac cells as well as epithelial cells of inner ear leading to deafness and aberrant repolarization causing prolonged QTc.
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9
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Jackson HA, McIntosh S, Whittome B, Asuri S, Casey B, Kerr C, Tang A, Arbour LT. LQTS in Northern BC: homozygosity for KCNQ1 V205M presents with a more severe cardiac phenotype but with minimal impact on auditory function. Clin Genet 2013; 86:85-90. [PMID: 23844633 DOI: 10.1111/cge.12235] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Revised: 07/03/2013] [Accepted: 07/08/2013] [Indexed: 01/02/2023]
Abstract
Long QT syndrome (LQTS), a rare congenital cardiac condition associated with life-threatening ventricular arrhythmias is characterized by a prolonged QT interval on electrocardiograph corrected for heart rate [corrected QT (QTc)]. LQTS has been historically categorized into the autosomal dominant Romano-Ward syndrome (RWS) and the autosomal recessive Jervell and Lange-Nielsen syndrome (JLNS). JLNS is associated with prelingual sensorineural deafness. Both types of LQTS can be caused by mutations in channel genes (e.g. KCNQ1) responsible for potassium homeostasis in cardiac myocytes and cochlea. Autosomal dominant mutations often cause the RWS phenotype and homozygous or compound heterozygous mutations contribute to JLNS. Two First Nations communities in northern British Columbia are affected disproportionately with LQTS largely due to the V205M mutation in KCNQ1, however, the pathology and phenotypic expression for those V205M homozygous has been unknown. Here, we show that four V205M homozygous individuals have a significantly higher 'peak' QTc, and a more severe cardiac phenotype compared with 41 V205M heterozygous carriers and 57 first to third degree relatives without mutations. Given the lack of prelingual deafness the homozygous V205M LQTS patients present with a phenotype more typical of RWS than JLNS.
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Affiliation(s)
- H A Jackson
- Department of Medical Genetics and the Island Medical program, University of British Columbia, Victoria, British Columbia, Canada
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10
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Gao Y, Li C, Liu W, Wu R, Qiu X, Liang R, Li L, Zhang L, Hu D. Genotype-phenotype analysis of three Chinese families with Jervell and Lange-Nielsen syndrome. J Cardiovasc Dis Res 2012; 3:67-75. [PMID: 22629021 PMCID: PMC3354473 DOI: 10.4103/0975-3583.95357] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
BACKGROUND Long QT syndrome (LQTS) is characterized by QT prolongation, syncope and sudden death. This study aims to explore the causes, clinical manifestations and therapeutic outcomes of Jervell and Lange-Nielsen syndrome (JLNS), a rare form of LQTS with congenital sensorineural deafness, in Chinese individuals. MATERIALS AND METHODS Three JLNS kindreds from the Chinese National LQTS Registry were investigated. Mutational screening of KCNQ1 and KCNE1 genes was performed by polymerase chain reaction and direct DNA sequence analysis. LQTS phenotype and therapeutic outcomes were evaluated for all probands and family members. RESULTS We identified 7 KCNQ1 mutations. c.1032_1117dup (p.Ser373TrpfsX10) and c.1319delT (p.Val440AlafsX26) were novel, causing JLNS in a 16-year-old boy with a QTc (QT interval corrected for heart rate) of 620 ms and recurrent syncope. c.605-2A>G and c.815G>A (p.Gly272Asp) caused JLNS in a 12-year-old girl and her 5-year-old brother, showing QTc of 590 to 600 ms and recurrent syncope. The fourth JLNS case, a 46-year-old man carrying c.1032G>A (p.Ala344Alasp) and c.569G>A (p.Arg190Gln) and with QTc of 460 ms, has been syncope-free since age 30. His 16-year-old daughter carries novel missense mutation c.574C>T (p.Arg192Cys) and c.1032G>A(p.Ala344Alasp) and displayed a severe phenotype of Romano-Ward syndrome (RWS) characterized by a QTc of 530 ms and recurrent syncope with normal hearing. Both the father and daughter also carried c.253G>A (p.Asp85Asn; rs1805128), a rare single nucleotide polymorphism (SNP) on KCNE1. Bizarre T waves were seen in 3/4 JLNS patients. Symptoms were improved and T wave abnormalities became less abnormal after appropriate treatment. CONCLUSION This study broadens the mutation and phenotype spectrums of JLNS. Compound heterozygous KCNQ1 mutations can result in both JLNS and severe forms of RWS in Chinese individuals.
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Affiliation(s)
- Yuanfeng Gao
- Heart Center, Peking University People's Hospital, Beijing - 100 044, P. R. China
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11
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Zumhagen S, Stallmeyer B, Friedrich C, Eckardt L, Seebohm G, Schulze-Bahr E. Inherited long QT syndrome: clinical manifestation, genetic diagnostics, and therapy. Herzschrittmacherther Elektrophysiol 2012; 23:211-219. [PMID: 22996910 DOI: 10.1007/s00399-012-0232-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Accepted: 07/20/2012] [Indexed: 06/01/2023]
Abstract
Inherited long QT syndrome (LQTS) is characterized by a prolonged ventricular repolarization (QTc interval) and symptoms (syncope, sudden cardiac arrest) due to polymorphic ventricular arrhythmias. As of today, 13 different cardiac ion channel genes have been associated with congenital LQTS. The most common ones are due to KCNQ1 (LQT-1), KCNH2 (LQT-2), and SCN5A (LQT-3) gene mutations and account for up to 75 % of cases. Typical clinical findings are an increased QT interval on the surface electrocardiogram, specifically altered T wave morphologies, polymorphic ventricular arrhythmias, or an indicative family history. Recently, in the HRS/EHRA expert consensus statement, comprehensive genetic testing of major LQTS genes was recommended for index patients for whom there is a strong clinical suspicion of LQTS. Overall, antiadrenergic therapy, in particular β-receptor blockers, has been the mainstay of therapy and has significantly reduced cardiac events. For high-risk patients, an implantable cardioverter defibrillator (ICD) is recommended. Importantly, lifestyle modification and avoidance of arrhythmia triggers are additional important approaches.
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Affiliation(s)
- Sven Zumhagen
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, Albert-Schweitzer-Campus 1, Gebäude D3, 48149, Münster, Germany.
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12
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Kharche S, Adeniran I, Stott J, Law P, Boyett MR, Hancox JC, Zhang H. Pro-arrhythmogenic effects of the S140G KCNQ1 mutation in human atrial fibrillation - insights from modelling. J Physiol 2012; 590:4501-14. [PMID: 22508963 DOI: 10.1113/jphysiol.2012.229146] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Functional analysis has shown that the missense gain-in-function KCNQ1 S140G mutation associated with familial atrial fibrillation produces an increase of the slow delayed rectifier potassium current (I(Ks)). Through computer modelling, this study investigated mechanisms by which the KCNQ1 S140G mutation promotes and perpetuates atrial fibrillation. In simulations, Courtemanche et al.'s model of human atrial cell action potentials (APs) was modified to incorporate experimental data on changes of I(Ks) induced by the KCNQ1 S140G mutation. The cell models for wild type (WT) and mutant type (MT) I(Ks) were incorporated into homogeneous multicellular 2D and 3D tissue models. Effects of the mutation were quantified on AP profile, AP duration (APD) restitution, effective refractory period (ERP) restitution, and conduction velocity (CV) restitution.Temporal and spatial vulnerabilities of atrial tissue to genesis of re-entry were computed. Dynamic behaviours of re-entrant excitation waves (lifespan (LS), tip meandering patterns and dominant frequency) in 2D and 3D models were characterised. It was shown that the KCNQ1 S140G mutation abbreviated atrial APD and ERP and flattened APD and ERP restitution curves. It reduced atrial CV at low excitation rates, but increased it at high excitation rates that facilitated the conduction of high rate atrial excitation waves. Although it increased slightly tissue temporal vulnerability for initiating re-entry, it reduced markedly the minimal substrate size necessary for sustaining re-entry (increasing the tissue spatial vulnerability). In the 2D and 3D models, the mutation also stabilized and accelerated re-entrant excitation waves, leading to rapid and sustained re-entry. In the 3D model, scroll waves under the mutation condition MT conditions also degenerated into persistent and erratic wavelets, leading to fibrillation. In conclusion, increased I(Ks) due to the KCNQ1 S140G mutation increases atrial susceptibility to arrhythmia due to increased tissue vulnerability, shortened ERP and altered atrial conduction velocity, which, in combination, facilitate initiation and maintenance of re-entrant excitation waves.
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Affiliation(s)
- Sanjay Kharche
- Biological Physics Group, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK
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13
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Beacham DW, Blackmer T, O' Grady M, Hanson GT. Cell-based potassium ion channel screening using the FluxOR assay. ACTA ACUST UNITED AC 2010; 15:441-6. [PMID: 20208034 DOI: 10.1177/1087057109359807] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
FluxOR technology is a cell-based assay used for high-throughput screening measurements of potassium channel activity. Using thallium influx as a surrogate indicator of potassium ion channel activity, the FluxOR Potassium Ion Channel Assay is based on the activation of a novel fluorescent dye. This indicator reports channel activity with a large fluorogenic response and is proportional to the number of open potassium channels on the cell, making it extremely useful for studying K(+) channel targets. In contrast to BTC-AM ester, FluxOR dye is roughly 10-fold more thallium sensitive, requiring much lower thallium for a larger signal window. This also means that the assay is carried out in a physiological, normal-chloride saline. In this article, the authors describe how they used BacMam gene delivery to express Kv7.2 and 7.3 (KCNQ), Kir2.1, or Kv11.1 (hERG) potassium ion channels in U2-OS cells. Using these cells, they ran the FluxOR assay to identify and characterize channel-specific inhibitory compounds discovered within the library (Tocriscreen Mini 1200 and Sigma Sodium/Potassium Modulators Ligand set). The FluxOR assay was able to identify several known specific inhibitors of Kv7.2/7.3 or hERG, highlighting its potential to identify novel and more efficacious small-molecule modulators.
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Affiliation(s)
- Daniel W Beacham
- Cellular Systems Division, Invitrogen Molecular Probes, Life Technologies Corporation, Eugene, Oregon 97402, USA
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