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LI GUOLIANG, SHI RUI, WU JINE, HAN WENQI, ZHANG AIFENG, CHENG GONG, XUE XIAOLIN, SUN CHAOFENG. Association of the hERG mutation with long-QT syndrome type 2, syncope and epilepsy. Mol Med Rep 2016; 13:2467-75. [PMID: 26847485 PMCID: PMC4768985 DOI: 10.3892/mmr.2016.4859] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 08/04/2015] [Indexed: 01/08/2023] Open
Abstract
Mutations in the human ether‑à‑go‑go‑related gene (hERG) are responsible for long‑QT syndrome (LQTS) type 2 (LQT2). In the present study, a heterozygous missense mutation (A561V) linked to LQT2, syncope and epilepsy was identified in the S5/pore region of the hERG protein. The mutation, A561V, was prepared and subcloned into hERG‑pcDNA3.0. Mutant plasmids were co‑transfected into HEK‑293 cells, which stably express wild‑type (WT) hERG, in order to mimic a heterozygous genotype, and the whole‑cell current was recorded using a patch‑clamp technique. Confocal microscopy was performed to evaluate the membrane distribution of the hERG channel protein using a green fluorescent protein tagged to the N‑terminus of hERG. A561V‑hERG decreased the amplitude of the WT‑hERG currents in a concentration‑dependent manner. In addition, A561V‑hERG resulted in alterations to activation, inactivation and recovery from inactivation in the hERG protein channels. Further evaluation of hERG membrane localization indicated that the A561V‑hERG mutant protein was unable to travel to the plasma membrane, which resulted in a trafficking‑deficient WT‑hERG protein. In conclusion, A561V‑hERG exerts a potent dominant‑negative effect on WT‑hERG channels, resulting in decreased hERG currents and impairment of hERG membrane localization. This may partially elucidate the clinical manifestations of LQTS patients who carry the A561V mutation.
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Affiliation(s)
- GUOLIANG LI
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi 710061, P.R. China
| | - RUI SHI
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi 710061, P.R. China
| | - JINE WU
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi 710061, P.R. China
| | - WENQI HAN
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi 710061, P.R. China
| | - AIFENG ZHANG
- Department of Cardiovascular Medicine, The Second Affiliated Hospital of Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi 710004, P.R. China
| | - GONG CHENG
- Department of Cardiovascular Medicine, Shaanxi Provincial People's Hospital, Xi'an, Shaanxi 710068, P.R. China
| | - XIAOLIN XUE
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi 710061, P.R. China
| | - CHAOFENG SUN
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi 710061, P.R. China
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Phan DQ, Silka MJ, Lan YT, Chang RKR. Comparison of formulas for calculation of the corrected QT interval in infants and young children. J Pediatr 2015; 166:960-4.e1-2. [PMID: 25648293 PMCID: PMC4380641 DOI: 10.1016/j.jpeds.2014.12.037] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Revised: 10/27/2014] [Accepted: 12/15/2014] [Indexed: 01/08/2023]
Abstract
OBJECTIVE To compare 4 heart rate correction formulas for calculation of the rate corrected QT (QTc) interval among infants and young children. STUDY DESIGN R-R and QT intervals were measured from digital electrocardiograms. QTc were calculated with the Bazett, Fridericia, Hodges, and Framingham formulas. QTc vs R-R graphs were plotted, and slopes of the regression lines compared. Slopes of QTc-R-R regression lines close to zero indicate consistent QT corrections over the range of heart rates. RESULTS We reviewed electrocardiograms from 702 children, with 233 (33%) <1 year of age and 567 (81%) <2 years. The average heart rate was 122 ± 20 bpm (median 121 bpm). The slopes of the QTc-R-R regression lines for the 4 correction formulas were -0.019 (Bazett); 0.1028 (Fridericia); -0.1241 (Hodges); and 0.2748 (Framingham). With the Bazett formula, a QTc >460 ms was 2 SDs above the mean, compared with "prolonged" QTc values of 414, 443, and 353 ms for the Fridericia, Hodges, and Framingham formulas, respectively. CONCLUSIONS The Bazett formula calculated the most consistent QTc; 460 ms is the best threshold for prolonged QTc. The study supports continued use of the Bazett formula for infants and children and differs from the use of the Fridericia correction during clinical trials of new medications.
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Affiliation(s)
- Derek Q. Phan
- Division of Pediatric Cardiology, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA
| | - Michael J. Silka
- Division of Cardiology, Children’s Hospital Los Angeles, University of Southern California, Los Angeles, CA
| | - Yueh-Tze Lan
- Division of Pediatric Cardiology, Santa Clara Valley Medical Center, San Jose, CA
| | - Ruey-Kang R. Chang
- Division of Pediatric Cardiology, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA
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Leslie LK, Cohen JT, Newburger JW, Alexander ME, Wong JB, Sherwin ED, Rodday AM, Parsons SK, Triedman JK. Costs and benefits of targeted screening for causes of sudden cardiac death in children and adolescents. Circulation 2012; 125:2621-9. [PMID: 22556340 PMCID: PMC3365629 DOI: 10.1161/circulationaha.111.087940] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
BACKGROUND Sudden cardiac death in children is a rare but devastating event. Experts have debated the merits of community-based screening programs using an ECG and targeting 2 potential high-risk groups: school-aged children initiating stimulant medications to treat attention-deficit/hyperactivity disorder and adolescents participating in sports. METHODS AND RESULTS Simulation models incorporating detailed prevalence, sensitivity and specificity, and treatment algorithms were built to determine the cost-effectiveness of targeted sudden cardiac death screening. Clinical care algorithms were constructed for asymptomatic children initiating stimulants for attention-deficit/hyperactivity disorder (8 years of age) or participating in sports (14 years of age) and presenting with a positive ECG finding suggestive of 1 of the 3 most common pediatric disorders causing sudden cardiac death and identifiable by ECG. Information to develop simulation model assumptions was drawn from the existing literature, Medicaid fees, and expert judgment. Sensitivity analyses examined parameter ranges to identify influential sources of uncertainty. Outcomes included costs and lost life-years caused by condition-related mortality. Our models estimate that screening for all 3 conditions simultaneously would reduce sudden death risk by 3.6 to 7.5 × 10(-5) with projected life expectancy increases of 0.8 to 1.6 days per screened individual. The incremental cost-effectiveness of screening is $91,000 to $204,000 per life-year. Sensitivity analysis showed that assumed disease prevalence, baseline mortality, and the relative risk of mortality resulting from stimulant medication use and sports participation had the greatest impact on estimated cost-effectiveness. CONCLUSION Results based on assumptions favoring sudden cardiac death screening indicated that its cost is high relative to its health benefits.
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Affiliation(s)
- Laurel K Leslie
- Institute for Clinical Research and Health Policy Studies at Tufts Medical Center, Boston, MA 02111, USA.
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Affiliation(s)
- David J Tester
- Long QT Syndrome Clinic and the Mayo Clinic Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, MN 55905, USA
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Cheng J, Van Norstrand DW, Medeiros-Domingo A, Valdivia C, Tan BH, Ye B, Kroboth S, Vatta M, Tester DJ, January CT, Makielski JC, Ackerman MJ. Alpha1-syntrophin mutations identified in sudden infant death syndrome cause an increase in late cardiac sodium current. Circ Arrhythm Electrophysiol 2009; 2:667-76. [PMID: 20009079 PMCID: PMC2810855 DOI: 10.1161/circep.109.891440] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
BACKGROUND Sudden infant death syndrome (SIDS) is a leading cause of death during the first 6 months after birth. About 5% to 10% of SIDS may stem from cardiac channelopathies such as long-QT syndrome. We recently implicated mutations in alpha1-syntrophin (SNTA1) as a novel cause of long-QT syndrome, whereby mutant SNTA1 released inhibition of associated neuronal nitric oxide synthase by the plasma membrane Ca-ATPase PMCA4b, causing increased peak and late sodium current (I(Na)) via S-nitrosylation of the cardiac sodium channel. This study determined the prevalence and functional properties of SIDS-associated SNTA1 mutations. METHODS AND RESULTS Using polymerase chain reaction, denaturing high-performance liquid chromatography, and DNA sequencing of SNTA1's open reading frame, 6 rare (absent in 800 reference alleles) missense mutations (G54R, P56S, T262P, S287R, T372M, and G460S) were identified in 8 (approximately 3%) of 292 SIDS cases. These mutations were engineered using polymerase chain reaction-based overlap extension and were coexpressed heterologously with SCN5A, neuronal nitric oxide synthase, and PMCA4b in HEK293 cells. I(Na) was recorded using the whole-cell method. A significant 1.4- to 1.5-fold increase in peak I(Na) and 2.3- to 2.7-fold increase in late I(Na) compared with controls was evident for S287R-, T372M-, and G460S-SNTA1 and was reversed by a neuronal nitric oxide synthase inhibitor. These 3 mutations also caused a significant depolarizing shift in channel inactivation, thereby increasing the overlap of the activation and inactivation curves to increase window current. CONCLUSIONS Abnormal biophysical phenotypes implicate mutations in SNTA1 as a novel pathogenic mechanism for the subset of channelopathic SIDS. Functional studies are essential to distinguish pathogenic perturbations in channel interacting proteins such as alpha1-syntrophin from similarly rare but innocuous ones.
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Affiliation(s)
- Jianding Cheng
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison, WI 53792, USA
| | - David W. Van Norstrand
- Departments of Medicine, Pediatrics, and Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, USA
| | - Argelia Medeiros-Domingo
- Departments of Medicine, Pediatrics, and Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, USA
| | - Carmen Valdivia
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison, WI 53792, USA
| | - Bi-hua Tan
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison, WI 53792, USA
| | - Bin Ye
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison, WI 53792, USA
| | - Stacie Kroboth
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison, WI 53792, USA
| | - Matteo Vatta
- Section of Pediatric Cardiology, Texas Children's Hospital/Baylor College of Medicine, Houston, TX 77030, USA
| | - David J. Tester
- Departments of Medicine, Pediatrics, and Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, USA
| | - Craig T. January
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison, WI 53792, USA
| | - Jonathan C. Makielski
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison, WI 53792, USA
| | - Michael J. Ackerman
- Departments of Medicine, Pediatrics, and Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, USA
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Ocorr K, Reeves NL, Wessells RJ, Fink M, Chen HSV, Akasaka T, Yasuda S, Metzger JM, Giles W, Posakony JW, Bodmer R. KCNQ potassium channel mutations cause cardiac arrhythmias in Drosophila that mimic the effects of aging. Proc Natl Acad Sci U S A 2007; 104:3943-8. [PMID: 17360457 PMCID: PMC1820688 DOI: 10.1073/pnas.0609278104] [Citation(s) in RCA: 167] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2006] [Indexed: 12/13/2022] Open
Abstract
Population profiles of industrialized countries show dramatic increases in cardiovascular disease with age, but the molecular and genetic basis of disease progression has been difficult to study because of the lack of suitable model systems. Our studies of Drosophila show a markedly elevated incidence of cardiac dysfunction and arrhythmias in aging fruit fly hearts and a concomitant decrease in the expression of the Drosophila homolog of human KCNQ1-encoded K(+) channel alpha subunits. In humans, this channel is involved in myocardial repolarization, and alterations in the function of this channel are associated with an increased risk for Torsades des Pointes arrhythmias and sudden death. Hearts from young KCNQ1 mutant fruit flies exhibit prolonged contractions and fibrillations reminiscent of Torsades des Pointes arrhythmias, and they exhibit severely increased susceptibility to pacing-induced cardiac dysfunction at young ages, characteristics that are observed only at advanced ages in WT flies. The fibrillations observed in mutant flies correlate with delayed relaxation of the myocardium, as revealed by increases in the duration of phasic contractions, extracellular field potentials, and in the baseline diastolic tension. These results suggest that K(+) currents, mediated by a KCNQ channel, contribute to the repolarization reserve of fly hearts, ensuring normal excitation-contraction coupling and rhythmical contraction. That arrhythmias in both WT and KCNQ1 mutants become worse as flies age suggests that additional factors are also involved.
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Affiliation(s)
- Karen Ocorr
- *Center for Neuroscience and Aging, Burnham Institute for Medical Research, La Jolla, CA 92037
| | - Nick L. Reeves
- Division of Biological Sciences/Section of Cell and Developmental Biology and
| | - Robert J. Wessells
- *Center for Neuroscience and Aging, Burnham Institute for Medical Research, La Jolla, CA 92037
| | | | - H.-S. Vincent Chen
- *Center for Neuroscience and Aging, Burnham Institute for Medical Research, La Jolla, CA 92037
- **Cardiology, University of California at San Diego, La Jolla, CA 92093-0349; and
| | - Takeshi Akasaka
- *Center for Neuroscience and Aging, Burnham Institute for Medical Research, La Jolla, CA 92037
| | - Soichiro Yasuda
- Departments of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109
| | - Joseph M. Metzger
- Departments of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109
| | | | - James W. Posakony
- Division of Biological Sciences/Section of Cell and Developmental Biology and
| | - Rolf Bodmer
- *Center for Neuroscience and Aging, Burnham Institute for Medical Research, La Jolla, CA 92037
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Abstract
Body surface electrocardiograms and electrograms recorded from the surfaces of the heart are the basis for diagnosis and treatment of cardiac electrophysiological disorders and arrhythmias. Given recent advances in understanding the molecular mechanisms of arrhythmia, it is important to relate these electrocardiographic waveforms to cellular electrophysiological processes. This modeling study establishes the following principles: (1) voltage gradients created by heterogeneities of the slow-delayed rectifier (I(Ks)) and transient outward (I(to)) potassium current inscribe the T wave and J wave, respectively; T-wave polarity and width are strongly influenced by the degree of intercellular coupling through gap-junctions. (2) Changes in [K+]o modulate the T wave through their effect on the rapid-delayed rectifier, I(Kr). (3) Alterations of I(Ks), I(Kr), and I(Na) (fast sodium current) in long-QT syndrome (LQT1, LQT2, and LQT3, respectively) are reflected in characteristic QT-interval and T-wave changes; LQT1 prolongs QT without widening the T wave. (4) Accelerated inactivation of I(Na) on the background of large epicardial I(to) results in ST elevation (Brugada phenotype) that reflects the degree of severity. (5) Activation of the ATP-sensitive potassium current, I(K(ATP)), is sufficient to cause ST elevation during acute ischemia. These principles provide a mechanistic cellular basis for interpretation of electrocardiographic waveforms.
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Affiliation(s)
- Kazutaka Gima
- Cardiac Bioelectricity Research and Training Center, Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio 44106-7207, USA
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Abstract
BACKGROUND Complex physiological interactions determine the functional consequences of gene abnormalities and make mechanistic interpretation of phenotypes extremely difficult. A recent example is a single mutation in the C terminus of the cardiac Na(+) channel, 1795insD. The mutation causes two distinct clinical syndromes, long QT (LQT) and Brugada, leading to life-threatening cardiac arrhythmias. Coexistence of these syndromes is seemingly paradoxical; LQT is associated with enhanced Na(+) channel function, and Brugada with reduced function. METHODS AND RESULTS Using a computational approach, we demonstrate that the 1795insD mutation exerts variable effects depending on the myocardial substrate. We develop Markov models of the wild-type and 1795insD cardiac Na(+) channels. By incorporating the models into a virtual transgenic cell, we elucidate the mechanism by which 1795insD differentially disrupts cellular electrical behavior in epicardial and midmyocardial cell types. We provide a cellular mechanistic basis for the ECG abnormalities observed in patients carrying the 1795insD gene mutation. CONCLUSIONS We demonstrate that the 1795insD mutation can cause both LQT and Brugada syndromes through interaction with the heterogeneous myocardium in a rate-dependent manner. The results highlight the complexity and multiplicity of genotype-phenotype relationships, and the usefulness of computational approaches in establishing a mechanistic link between genetic defects and functional abnormalities.
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Affiliation(s)
- Colleen E Clancy
- Cardiac Bioelectricity Research and Training Center, Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio 44106-7207, USA
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