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Rinné S, Oertli A, Nagel C, Tomsits P, Jenewein T, Kääb S, Kauferstein S, Loewe A, Beckmann BM, Decher N. Functional Characterization of a Spectrum of Novel Romano-Ward Syndrome KCNQ1 Variants. Int J Mol Sci 2023; 24:ijms24021350. [PMID: 36674868 PMCID: PMC9865342 DOI: 10.3390/ijms24021350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 12/20/2022] [Accepted: 12/23/2022] [Indexed: 01/13/2023] Open
Abstract
The KCNQ1 gene encodes the α-subunit of the cardiac voltage-gated potassium (Kv) channel KCNQ1, also denoted as Kv7.1 or KvLQT1. The channel assembles with the ß-subunit KCNE1, also known as minK, to generate the slowly activating cardiac delayed rectifier current IKs, a key regulator of the heart rate dependent adaptation of the cardiac action potential duration (APD). Loss-of-function variants in KCNQ1 cause the congenital Long QT1 (LQT1) syndrome, characterized by delayed cardiac repolarization and a QT interval prolongation in the surface electrocardiogram (ECG). Autosomal dominant loss-of-function variants in KCNQ1 result in the LQT syndrome called Romano-Ward syndrome (RWS), while autosomal recessive variants affecting function, lead to Jervell and Lange-Nielsen syndrome (JLNS), associated with deafness. The aim of this study was the characterization of novel KCNQ1 variants identified in patients with RWS to widen the spectrum of known LQT1 variants, and improve the interpretation of the clinical relevance of variants in the KCNQ1 gene. We functionally characterized nine human KCNQ1 variants using the voltage-clamp technique in Xenopus laevis oocytes, from which we report seven novel variants. The functional data was taken as input to model surface ECGs, to subsequently compare the functional changes with the clinically observed QTc times, allowing a further interpretation of the severity of the different LQTS variants. We found that the electrophysiological properties of the variants correlate with the severity of the clinically diagnosed phenotype in most cases, however, not in all. Electrophysiological studies combined with in silico modelling approaches are valuable components for the interpretation of the pathogenicity of KCNQ1 variants, but assessing the clinical severity demands the consideration of other factors that are included, for example in the Schwartz score.
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Affiliation(s)
- Susanne Rinné
- Institute of Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, 35037 Marburg, Germany
| | - Annemarie Oertli
- Institute of Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, 35037 Marburg, Germany
| | - Claudia Nagel
- Institute of Biomedical Engineering, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
| | - Philipp Tomsits
- Department of Medicine I, University Hospital, LMU Munich, 80802 Munich, Germany
- Deutsches Zentrum für Herz-Kreislauferkrankungen (DZHK), Partner Site Munich, 80636 Munich, Germany
- Member of the European Reference Network for Rare, Low Prevalance and Complex Diseases of the Heart (ERN GUARD-Heart), 81377 Munich, Germany
- Institute of Surgical Research at the Walter-Brendel-Centre of Experimental Medicine, University Hospital, LMU Munich, Marchioninistrasse 27, 81377 Munich, Germany
| | - Tina Jenewein
- Institute of Legal Medicine, Goethe University, University Hospital Frankfurt, 60590 Frankfurt, Germany
- Institute for Transfusion Medicine and Immunohematology, German Red Cross Blood Service Baden-Württemberg-Hessen, Goethe University Frankfurt, 60528 Frankfurt, Germany
| | - Stefan Kääb
- Department of Medicine I, University Hospital, LMU Munich, 80802 Munich, Germany
- Deutsches Zentrum für Herz-Kreislauferkrankungen (DZHK), Partner Site Munich, 80636 Munich, Germany
- Member of the European Reference Network for Rare, Low Prevalance and Complex Diseases of the Heart (ERN GUARD-Heart), 81377 Munich, Germany
| | - Silke Kauferstein
- Institute of Legal Medicine, Goethe University, University Hospital Frankfurt, 60590 Frankfurt, Germany
- Deutsches Zentrum für Herz-Kreislauferkrankungen (DZHK), Partner Site Frankfurt, 60596 Frankfurt, Germany
| | - Axel Loewe
- Institute of Biomedical Engineering, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
| | - Britt Maria Beckmann
- Department of Medicine I, University Hospital, LMU Munich, 80802 Munich, Germany
- Institute of Legal Medicine, Goethe University, University Hospital Frankfurt, 60590 Frankfurt, Germany
| | - Niels Decher
- Institute of Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, 35037 Marburg, Germany
- Correspondence: ; Tel.: +49-(0)6421-28-62148
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Dahlberg P, Axelsson K, Jensen SM, Lundahl G, Vahedi F, Perkins R, Gransberg L, Bergfeldt L. Accelerated QT adaptation following atropine-induced heart rate increase in LQT1 patients versus healthy controls: A sign of disturbed hysteresis. Physiol Rep 2022; 10:e15487. [PMID: 36324292 PMCID: PMC9630760 DOI: 10.14814/phy2.15487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 09/08/2022] [Accepted: 09/19/2022] [Indexed: 06/16/2023] Open
Abstract
Hysteresis, a ubiquitous regulatory phenomenon, is a salient feature of the adaptation of ventricular repolarization duration to heart rate (HR) change. We therefore compared the QT interval adaptation to rapid HR increase in patients with the long QT syndrome type 1 (LQT1) versus healthy controls because LQT1 is caused by loss-of-function mutations affecting the repolarizing potassium channel current IKs , presumably an important player in QT hysteresis. The study was performed in an outpatient hospital setting. HR was increased in LQT1 patients and controls by administering an intravenous bolus of atropine (0.04 mg/kg body weight) for 30 s. RR and QT intervals were recorded by continuous Frank vectorcardiography. Atropine induced transient expected side effects but no adverse arrhythmias. There was no difference in HR response (RR intervals) to atropine between the groups. Although atropine-induced ΔQT was 48% greater in 18 LQT1 patients than in 28 controls (p < 0.001), QT adaptation was on average 25% faster in LQT1 patients (measured as the time constant τ for the mono-exponential function and the time for 90% of ΔQT; p < 0.01); however, there was some overlap between the groups, possibly a beta-blocker effect. The shorter QT adaptation time to atropine-induced HR increase in LQT1 patients on the group level corroborates the importance of IKs in QT adaptation hysteresis in humans and shows that LQT1 patients have a disturbed ultra-rapid cardiac memory. On the individual level, the QT adaptation time possibly reflects the effect-size of the loss-of-function mutation, but its clinical implications need to be shown.
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Affiliation(s)
- Pia Dahlberg
- Department of Molecular and Clinical MedicineInstitute of Medicine, Sahlgrenska Academy, University of GothenburgGothenburgSweden
- Region Västra Götaland, Department of CardiologySahlgrenska University HospitalGothenburgSweden
| | - Karl‐Jonas Axelsson
- Department of Molecular and Clinical MedicineInstitute of Medicine, Sahlgrenska Academy, University of GothenburgGothenburgSweden
- Region Västra Götaland, Department of CardiologySahlgrenska University HospitalGothenburgSweden
| | - Steen M. Jensen
- Department of Public Health and Clinical Medicine, and Heart CentreUmeå UniversityUmeåSweden
| | - Gunilla Lundahl
- Department of Molecular and Clinical MedicineInstitute of Medicine, Sahlgrenska Academy, University of GothenburgGothenburgSweden
| | - Farzad Vahedi
- Department of Molecular and Clinical MedicineInstitute of Medicine, Sahlgrenska Academy, University of GothenburgGothenburgSweden
- Region Västra Götaland, Department of CardiologySahlgrenska University HospitalGothenburgSweden
| | - Rosie Perkins
- Department of Molecular and Clinical MedicineInstitute of Medicine, Sahlgrenska Academy, University of GothenburgGothenburgSweden
| | - Lennart Gransberg
- Department of Molecular and Clinical MedicineInstitute of Medicine, Sahlgrenska Academy, University of GothenburgGothenburgSweden
| | - Lennart Bergfeldt
- Department of Molecular and Clinical MedicineInstitute of Medicine, Sahlgrenska Academy, University of GothenburgGothenburgSweden
- Region Västra Götaland, Department of CardiologySahlgrenska University HospitalGothenburgSweden
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Kekenes-Huskey PM, Burgess DE, Sun B, Bartos DC, Rozmus ER, Anderson CL, January CT, Eckhardt LL, Delisle BP. Mutation-Specific Differences in Kv7.1 ( KCNQ1) and Kv11.1 ( KCNH2) Channel Dysfunction and Long QT Syndrome Phenotypes. Int J Mol Sci 2022; 23:7389. [PMID: 35806392 PMCID: PMC9266926 DOI: 10.3390/ijms23137389] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Revised: 06/22/2022] [Accepted: 06/24/2022] [Indexed: 11/16/2022] Open
Abstract
The electrocardiogram (ECG) empowered clinician scientists to measure the electrical activity of the heart noninvasively to identify arrhythmias and heart disease. Shortly after the standardization of the 12-lead ECG for the diagnosis of heart disease, several families with autosomal recessive (Jervell and Lange-Nielsen Syndrome) and dominant (Romano-Ward Syndrome) forms of long QT syndrome (LQTS) were identified. An abnormally long heart rate-corrected QT-interval was established as a biomarker for the risk of sudden cardiac death. Since then, the International LQTS Registry was established; a phenotypic scoring system to identify LQTS patients was developed; the major genes that associate with typical forms of LQTS were identified; and guidelines for the successful management of patients advanced. In this review, we discuss the molecular and cellular mechanisms for LQTS associated with missense variants in KCNQ1 (LQT1) and KCNH2 (LQT2). We move beyond the "benign" to a "pathogenic" binary classification scheme for different KCNQ1 and KCNH2 missense variants and discuss gene- and mutation-specific differences in K+ channel dysfunction, which can predispose people to distinct clinical phenotypes (e.g., concealed, pleiotropic, severe, etc.). We conclude by discussing the emerging computational structural modeling strategies that will distinguish between dysfunctional subtypes of KCNQ1 and KCNH2 variants, with the goal of realizing a layered precision medicine approach focused on individuals.
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Affiliation(s)
- Peter M. Kekenes-Huskey
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL 60153, USA
| | - Don E. Burgess
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40536, USA; (D.E.B.); (E.R.R.)
| | - Bin Sun
- Department of Pharmacology, Harbin Medical University, Harbin 150081, China;
| | | | - Ezekiel R. Rozmus
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40536, USA; (D.E.B.); (E.R.R.)
| | - Corey L. Anderson
- Cellular and Molecular Arrythmias Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, WI 53705, USA; (C.L.A.); (C.T.J.); (L.L.E.)
| | - Craig T. January
- Cellular and Molecular Arrythmias Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, WI 53705, USA; (C.L.A.); (C.T.J.); (L.L.E.)
| | - Lee L. Eckhardt
- Cellular and Molecular Arrythmias Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, WI 53705, USA; (C.L.A.); (C.T.J.); (L.L.E.)
| | - Brian P. Delisle
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40536, USA; (D.E.B.); (E.R.R.)
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Cócera-Ortega L, Wilders R, Kamps SC, Fabrizi B, Huber I, van der Made I, van den Bout A, de Vries DK, Gepstein L, Verkerk AO, Pinto YM, Tijsen AJ. shRNAs Targeting a Common KCNQ1 Variant Could Alleviate Long-QT1 Disease Severity by Inhibiting a Mutant Allele. Int J Mol Sci 2022; 23:ijms23074053. [PMID: 35409410 PMCID: PMC9000197 DOI: 10.3390/ijms23074053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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: 02/28/2022] [Revised: 03/31/2022] [Accepted: 04/04/2022] [Indexed: 12/02/2022] Open
Abstract
Long-QT syndrome type 1 (LQT1) is caused by mutations in KCNQ1. Patients heterozygous for such a mutation co-assemble both mutant and wild-type KCNQ1-encoded subunits into tetrameric Kv7.1 potassium channels. Here, we investigated whether allele-specific inhibition of mutant KCNQ1 by targeting a common variant can shift the balance towards increased incorporation of the wild-type allele to alleviate the disease in human-induced pluripotent stem-cell-derived cardiomyocytes (hiPSC-CMs). We identified the single nucleotide polymorphisms (SNP) rs1057128 (G/A) in KCNQ1, with a heterozygosity of 27% in the European population. Next, we determined allele-specificity of short-hairpin RNAs (shRNAs) targeting either allele of this SNP in hiPSC-CMs that carry an LQT1 mutation. Our shRNAs downregulated 60% of the A allele and 40% of the G allele without affecting the non-targeted allele. Suppression of the mutant KCNQ1 allele by 60% decreased the occurrence of arrhythmic events in hiPSC-CMs measured by a voltage-sensitive reporter, while suppression of the wild-type allele increased the occurrence of arrhythmic events. Furthermore, computer simulations based on another LQT1 mutation revealed that 60% suppression of the mutant KCNQ1 allele shortens the prolonged action potential in an adult cardiomyocyte model. We conclude that allele-specific inhibition of a mutant KCNQ1 allele by targeting a common variant may alleviate the disease. This novel approach avoids the need to design shRNAs to target every single mutation and opens up the exciting possibility of treating multiple LQT1-causing mutations with only two shRNAs.
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Affiliation(s)
- Lucía Cócera-Ortega
- Department of Experimental Cardiology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; (L.C.-O.); (S.C.K.); (B.F.); (I.v.d.M.); (A.v.d.B.); (D.K.d.V.); (A.O.V.); (Y.M.P.)
| | - Ronald Wilders
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands;
| | - Selina C. Kamps
- Department of Experimental Cardiology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; (L.C.-O.); (S.C.K.); (B.F.); (I.v.d.M.); (A.v.d.B.); (D.K.d.V.); (A.O.V.); (Y.M.P.)
| | - Benedetta Fabrizi
- Department of Experimental Cardiology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; (L.C.-O.); (S.C.K.); (B.F.); (I.v.d.M.); (A.v.d.B.); (D.K.d.V.); (A.O.V.); (Y.M.P.)
| | - Irit Huber
- The Sohnis Family Laboratory for Cardiac Electrophysiology and Regenerative Medicine, Rappaport Faculty of Medicine and Research Institute, Technion—Israel Institute of Technology, Haifa 3109601, Israel; (I.H.); (L.G.)
| | - Ingeborg van der Made
- Department of Experimental Cardiology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; (L.C.-O.); (S.C.K.); (B.F.); (I.v.d.M.); (A.v.d.B.); (D.K.d.V.); (A.O.V.); (Y.M.P.)
| | - Anouk van den Bout
- Department of Experimental Cardiology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; (L.C.-O.); (S.C.K.); (B.F.); (I.v.d.M.); (A.v.d.B.); (D.K.d.V.); (A.O.V.); (Y.M.P.)
| | - Dylan K. de Vries
- Department of Experimental Cardiology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; (L.C.-O.); (S.C.K.); (B.F.); (I.v.d.M.); (A.v.d.B.); (D.K.d.V.); (A.O.V.); (Y.M.P.)
| | - Lior Gepstein
- The Sohnis Family Laboratory for Cardiac Electrophysiology and Regenerative Medicine, Rappaport Faculty of Medicine and Research Institute, Technion—Israel Institute of Technology, Haifa 3109601, Israel; (I.H.); (L.G.)
| | - Arie O. Verkerk
- Department of Experimental Cardiology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; (L.C.-O.); (S.C.K.); (B.F.); (I.v.d.M.); (A.v.d.B.); (D.K.d.V.); (A.O.V.); (Y.M.P.)
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands;
| | - Yigal M. Pinto
- Department of Experimental Cardiology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; (L.C.-O.); (S.C.K.); (B.F.); (I.v.d.M.); (A.v.d.B.); (D.K.d.V.); (A.O.V.); (Y.M.P.)
| | - Anke J. Tijsen
- Department of Experimental Cardiology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; (L.C.-O.); (S.C.K.); (B.F.); (I.v.d.M.); (A.v.d.B.); (D.K.d.V.); (A.O.V.); (Y.M.P.)
- Correspondence: ; Tel.: +31-205668544
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Affiliation(s)
- Gea-Ny Tseng
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia.
| | - Yu Xu
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia
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Bartos DC, Giudicessi JR, Tester DJ, Ackerman MJ, Ohno S, Horie M, Gollob MH, Burgess DE, Delisle BP. A KCNQ1 mutation contributes to the concealed type 1 long QT phenotype by limiting the Kv7.1 channel conformational changes associated with protein kinase A phosphorylation. Heart Rhythm 2013; 11:459-68. [PMID: 24269949 DOI: 10.1016/j.hrthm.2013.11.021] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [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] [Received: 08/30/2013] [Indexed: 11/17/2022]
Abstract
BACKGROUND Type 1 long QT syndrome (LQT1) is caused by loss-of-function mutations in the KCNQ1-encoded Kv7.1 channel that conducts the slowly activating component of the delayed rectifier K(+) current (IKs). Clinically, the diagnosis of LQT1 is complicated by variable phenotypic expressivity, whereby approximately 25% of genotype-positive individuals present with concealed LQT1 (resting corrected QT [QTc] interval ≤460 ms). OBJECTIVE To determine whether a specific molecular mechanism contributes to concealed LQT1. METHODS We identified a multigenerational LQT1 family whereby 79% of the patients genotype-positive for p.Ile235Asn-KCNQ1 (I235N-Kv7.1) have concealed LQT1. We assessed the effect I235N-Kv7.1 has on IKs and the ventricular action potential (AP) by using in vitro analysis and computational simulations. RESULTS Clinical data showed that all 10 patients with I235N-Kv7.1 have normal resting QTc intervals but abnormal QTc interval prolongation during the recovery phase of an electrocardiographic treadmill stress test. Voltage-clamping HEK293 cells coexpressing wild-type Kv7.1 and I235N-Kv7.1 (to mimic the patients' genotypes) showed that I235N-Kv7.1 generated relatively normal functioning Kv7.1 channels but were insensitive to protein kinase A (PKA) activation. Phosphomimetic and quinidine sensitivity studies suggest that I235N-Kv7.1 limits the conformational changes in Kv7.1 channels, which are necessary to upregulate IKs after PKA phosphorylation. Computational ventricular AP simulations predicted that the PKA insensitivity of I235N-Kv7.1 is primarily responsible for prolonging the AP with β-adrenergic stimulation, especially at slower cycle lengths. CONCLUSIONS KCNQ1 mutations that generate relatively normal Kv7.1 channels, but limit the upregulation of IKs by PKA activation, likely contribute to concealed LQT1.
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Affiliation(s)
- Daniel C Bartos
- Department of Physiology, Center for Muscle Biology, University of Kentucky, Lexington, Kentucky
| | - John R Giudicessi
- Departments of Medicine, Pediatrics, and Molecular Pharmacology and Experimental Therapeutics, Divisions of Cardiovascular Diseases and Pediatric Cardiology, Mayo Clinic, Rochester, Minnesota
| | - David J Tester
- Departments of Medicine, Pediatrics, and Molecular Pharmacology and Experimental Therapeutics, Divisions of Cardiovascular Diseases and Pediatric Cardiology, Mayo Clinic, Rochester, Minnesota
| | - Michael J Ackerman
- Departments of Medicine, Pediatrics, and Molecular Pharmacology and Experimental Therapeutics, Divisions of Cardiovascular Diseases and Pediatric Cardiology, Mayo Clinic, Rochester, Minnesota
| | - Seiko Ohno
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Sciences, Seta-tsukinowa, Otsu, Japan
| | - Minoru Horie
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Sciences, Seta-tsukinowa, Otsu, Japan
| | - Michael H Gollob
- Division of Cardiology, University of Ottawa Heart Institute, Ottawa, Ontario, Canada
| | - Don E Burgess
- Department of Physiology, Center for Muscle Biology, University of Kentucky, Lexington, Kentucky
| | - Brian P Delisle
- Department of Physiology, Center for Muscle Biology, University of Kentucky, Lexington, Kentucky.
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Costa J, Lopes CM, Barsheshet A, Moss AJ, Migdalovich D, Ouellet G, McNitt S, Polonsky S, Robinson JL, Zareba W, Ackerman MJ, Benhorin J, Kaufman ES, Platonov PG, Shimizu W, Towbin JA, Vincent GM, Wilde AAM, Goldenberg I. Combined assessment of sex- and mutation-specific information for risk stratification in type 1 long QT syndrome. Heart Rhythm 2012; 9:892-8. [PMID: 22293141 DOI: 10.1016/j.hrthm.2012.01.020] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Indexed: 01/08/2023]
Abstract
BACKGROUND Men and women with type 1 long QT syndrome (LQT1) exhibit time-dependent differences in the risk for cardiac events. OBJECTIVE We hypothesized that sex-specific risk for LQT1 is related to the location and function of the disease-causing mutation in the KCNQ1 gene. METHODS The risk for life-threatening cardiac events (comprising aborted cardiac arrest [ACA] or sudden cardiac death [SCD]) from birth through age 40 years was assessed among 1051 individuals with LQT1 (450 men and 601 women) by the location and function of the LQT1-causing mutation (prespecified as mutations in the intracellular domains linking the membrane-spanning segments [ie, S2-S3 and S4-S5 cytoplasmic loops] involved in adrenergic channel regulation vs other mutations). RESULTS Multivariate analysis showed that during childhood (age group: 0-13 years) men had >2-fold (P < .003) increased risk for ACA/SCD than did women, whereas after the onset of adolescence the risk for ACA/SCD was similar between men and women (hazard ratio = 0.89 [P = .64]). The presence of cytoplasmic-loop mutations was associated with a 2.7-fold (P < .001) increased risk for ACA/SCD among women, but it did not affect the risk among men (hazard ratio 1.37; P = .26). Time-dependent syncope was associated with a more pronounced risk-increase among men than among women (hazard ratio 4.73 [P < .001] and 2.43 [P = .02], respectively), whereas a prolonged corrected QT interval (≥ 500 ms) was associated with a higher risk among women than among men. CONCLUSION Our findings suggest that the combined assessment of clinical and mutation location/functional data can be used to identify sex-specific risk factors for life-threatening events for patients with LQT1.
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Affiliation(s)
- Jason Costa
- Cardiology Division, University of Rochester Medical Center, Rochester, NY 14642, USA
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Moretti A, Bellin M, Welling A, Jung CB, Lam JT, Bott-Flügel L, Dorn T, Goedel A, Höhnke C, Hofmann F, Seyfarth M, Sinnecker D, Schömig A, Laugwitz KL. Patient-specific induced pluripotent stem-cell models for long-QT syndrome. N Engl J Med 2010; 363:1397-409. [PMID: 20660394 DOI: 10.1056/nejmoa0908679] [Citation(s) in RCA: 894] [Impact Index Per Article: 63.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
BACKGROUND Long-QT syndromes are heritable diseases associated with prolongation of the QT interval on an electrocardiogram and a high risk of sudden cardiac death due to ventricular tachyarrhythmia. In long-QT syndrome type 1, mutations occur in the KCNQ1 gene, which encodes the repolarizing potassium channel mediating the delayed rectifier I(Ks) current. METHODS We screened a family affected by long-QT syndrome type 1 and identified an autosomal dominant missense mutation (R190Q) in the KCNQ1 gene. We obtained dermal fibroblasts from two family members and two healthy controls and infected them with retroviral vectors encoding the human transcription factors OCT3/4, SOX2, KLF4, and c-MYC to generate pluripotent stem cells. With the use of a specific protocol, these cells were then directed to differentiate into cardiac myocytes. RESULTS Induced pluripotent stem cells maintained the disease genotype of long-QT syndrome type 1 and generated functional myocytes. Individual cells showed a “ventricular,” “atrial,” or “nodal” phenotype, as evidenced by the expression of cell-type–specific markers and as seen in recordings of the action potentials in single cells. The duration of the action potential was markedly prolonged in “ventricular” and “atrial” cells derived from patients with long-QT syndrome type 1, as compared with cells from control subjects. Further characterization of the role of the R190Q–KCNQ1 mutation in the pathogenesis of long-QT syndrome type 1 revealed a dominant negative trafficking defect associated with a 70 to 80% reduction in I(Ks) current and altered channel activation and deactivation properties. Moreover, we showed that myocytes derived from patients with long-QT syndrome type 1 had an increased susceptibility to catecholamine-induced tachyarrhythmia and that beta-blockade attenuated this phenotype. CONCLUSIONS We generated patient-specific pluripotent stem cells from members of a family affected by long-QT syndrome type 1 and induced them to differentiate into functional cardiac myocytes. The patient-derived cells recapitulated the electrophysiological features of the disorder. (Funded by the European Research Council and others.)
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Affiliation(s)
- Alessandra Moretti
- Cardiology Division, First Department of Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
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Vaglio M, Couderc JP, McNitt S, Xia X, Moss AJ, Zareba W. A quantitative assessment of T-wave morphology in LQT1, LQT2, and healthy individuals based on Holter recording technology. Heart Rhythm 2007; 5:11-8. [PMID: 18180017 DOI: 10.1016/j.hrthm.2007.08.026] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2006] [Accepted: 08/16/2007] [Indexed: 11/18/2022]
Abstract
BACKGROUND The clinical course and the precipitating risk factors in the congenital long QT syndrome (LQTS) are genotype specific. OBJECTIVES The goal of this study was to develop a computer algorithm allowing for electrocardiogram (ECG)-based identification and differentiation of LQT1 and LQT2 carriers. METHODS Twelve-lead ECG Holter monitor recordings were acquired in 49 LQT1 carriers, 25 LQT2 carriers, and 38 healthy subjects as controls. The cardiac beats were clustered based on heart-rate bin method. Scalar and vectorial repolarization parameters were compared for similar heart rates among study groups. The Q to Tpeak (QTpeak), the Tpeak to Tend interval, T-wave magnitude and T-loop morphology were automatically quantified using custom-made algorithms. RESULTS QTpeak from lead II and the right slope of the T-wave were the most discriminant parameters for differentiating the 3 groups using prespecified heart rate bin (75.0 to 77.5 beats/min). The predictive model utilizing these scalar parameters was validated using the entire spectrum of heart rates. Both scalar and vectorcardiographic models provided very effective identification of tested subjects in heart rates between 60 and 100 beats/min, whereas they had limited performance during tachycardia and slightly better discrimination in bradycardia. In the 60 to 100 beats/min heart rate range, the best 2-variable model identified correctly 89% of healthy subjects, 84% of LQT1 carriers, and 92% of LQT2 carriers. A model including 3 parameters based purely on scalar ECG parameters could correctly identify 90% of the population (89% of healthy subjects, 90% of LQT1 carriers, and 92% of LQT2 carriers). CONCLUSION Automatic algorithm quantifying T-wave morphology discriminates LQT1 and LQT2 carriers and healthy subjects with high accuracy. Such computerized ECG methodology could assist physicians evaluating subjects suspected for LQTS.
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Affiliation(s)
- Martino Vaglio
- Heart Research Follow-Up Program, University of Rochester Medical Center, Rochester, New York, USA
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14
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Pellegrino PL, Bafunno V, Ieva R, Brunetti ND, Mavilio G, Sessa F, Grimaldi M, Margaglione M, Di Biase M. A novel mutation in human ether-a-go-go-related gene, alanine to proline at position 490, found in a large family with autosomal dominant long QT syndrome. Am J Cardiol 2007; 99:1737-40. [PMID: 17560885 DOI: 10.1016/j.amjcard.2007.01.056] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2006] [Revised: 01/10/2007] [Accepted: 01/10/2007] [Indexed: 11/26/2022]
Abstract
Long-QT syndrome is a rare disease characterized by prolonged ventricular repolarization. The clinical presentation of long-QT syndrome is the occurrence of syncope, seizures, or cardiac arrest in young patients. Previous studies have demonstrated locus heterogeneity, with causative mutations reported in >or=8 different genes, including the human ether-a-go-go-related gene. This study was conducted in 26 members of a 4-generation family with long-QT syndrome. The proband was a 14-year-old female patient referred to the emergency department for the evaluation of recurrent syncope associated with a prolonged QT interval on electrocardiography at rest. There was a family history of sudden death in a 27-year-old woman. Sequencing of the entire coding regions of the human ether-a-go-go-related gene and the intron and exon boundaries of the proband identified a single base-pair substitution (guanine to cytosine at nucleotide 1468). This mutation resulted in a novel missense mutation, alanine to proline at position 490 (Ala490Pro), in the inner loop of the S2 and S3 domains. The proband was heterozygous for the Ala490Pro mutation. To address whether the mutational change detected in the patient would be a polymorphism, 100 control subjects from the same ethnical background were investigated. None showed the Ala490Pro substitution. Of 26 family members, 9 were mutation carriers, and none had normal electrocardiographic results. The penetrance of this pedigree was assumed to be 100%. In conclusion, the Ala490Pro mutation of the human ether-a-go-go-related gene is a rare, novel mutation that was inherited in this family, leading to Romano-Ward syndrome with complete penetrance.
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15
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Moss AJ, Shimizu W, Wilde AAM, Towbin JA, Zareba W, Robinson JL, Qi M, Vincent GM, Ackerman MJ, Kaufman ES, Hofman N, Seth R, Kamakura S, Miyamoto Y, Goldenberg I, Andrews ML, McNitt S. Clinical aspects of type-1 long-QT syndrome by location, coding type, and biophysical function of mutations involving the KCNQ1 gene. Circulation 2007; 115:2481-9. [PMID: 17470695 PMCID: PMC3332528 DOI: 10.1161/circulationaha.106.665406] [Citation(s) in RCA: 299] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BACKGROUND Type-1 long-QT syndrome (LQTS) is caused by loss-of-function mutations in the KCNQ1-encoded I(Ks) cardiac potassium channel. We evaluated the effect of location, coding type, and biophysical function of KCNQ1 mutations on the clinical phenotype of this disorder. METHODS AND RESULTS We investigated the clinical course in 600 patients with 77 different KCNQ1 mutations in 101 proband-identified families derived from the US portion of the International LQTS Registry (n=425), the Netherlands' LQTS Registry (n=93), and the Japanese LQTS Registry (n=82). The Cox proportional hazards survivorship model was used to evaluate the independent contribution of clinical and genetic factors to the first occurrence of time-dependent cardiac events from birth through age 40 years. The clinical characteristics, distribution of mutations, and overall outcome event rates were similar in patients enrolled from the 3 geographic regions. Biophysical function of the mutations was categorized according to dominant-negative (> 50%) or haploinsufficiency (< or = 50%) reduction in cardiac repolarizing I(Ks) potassium channel current. Patients with transmembrane versus C-terminus mutations (hazard ratio, 2.06; P<0.001) and those with mutations having dominant-negative versus haploinsufficiency ion channel effects (hazard ratio, 2.26; P<0.001) were at increased risk for cardiac events, and these genetic risks were independent of traditional clinical risk factors. CONCLUSIONS This genotype-phenotype study indicates that in type-1 LQTS, mutations located in the transmembrane portion of the ion channel protein and the degree of ion channel dysfunction caused by the mutations are important independent risk factors influencing the clinical course of this disorder.
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MESH Headings
- Adolescent
- Adrenergic beta-Antagonists/therapeutic use
- Adult
- Child
- Child, Preschool
- Codon, Nonsense
- Death, Sudden, Cardiac/epidemiology
- Death, Sudden, Cardiac/prevention & control
- Female
- Frameshift Mutation
- Genetic Predisposition to Disease
- Genotype
- Heart Arrest/epidemiology
- Humans
- Infant
- Infant, Newborn
- Ion Transport/genetics
- Japan/epidemiology
- KCNQ1 Potassium Channel/chemistry
- KCNQ1 Potassium Channel/genetics
- KCNQ1 Potassium Channel/physiology
- Kaplan-Meier Estimate
- Male
- Membrane Potentials
- Models, Molecular
- Mutagenesis, Insertional
- Mutation
- Mutation, Missense
- Netherlands/epidemiology
- Phenotype
- Potassium/metabolism
- Proportional Hazards Models
- Protein Structure, Tertiary
- Protein Transport
- RNA Splice Sites/genetics
- Registries
- Risk Factors
- Romano-Ward Syndrome/complications
- Romano-Ward Syndrome/drug therapy
- Romano-Ward Syndrome/genetics
- Romano-Ward Syndrome/mortality
- Sequence Deletion
- Syncope/epidemiology
- United States/epidemiology
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Affiliation(s)
- Arthur J Moss
- Cardiology Division, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.
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16
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Novotny T, Kadlecova J, Janousek J, Gaillyova R, Bittnerova A, Florianova A, Sisakova M, Toman O, Chroust K, Papousek I, Spinar J. The homozygous KCNQ1 gene mutation associated with recessive Romano-Ward syndrome. Pacing Clin Electrophysiol 2007; 29:1013-5. [PMID: 16981927 DOI: 10.1111/j.1540-8159.2006.00478.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In a 7-year-old boy with normal hearing suffering from repeated syncope an extremely prolonged QTc interval (up to 700 ms) was found. The mother was completely asymptomatic and the father had an intermittently borderline QTc interval (maximum 470 ms) but no symptoms. In the proband a mutation analysis of KCNQ1 gene revealed a homozygous 1893insC mutation. The parents were heterozygous for this mutation. There was no consanguineous marriage in the family. The clinical relevance of these findings is that apparently normal individuals may have a latent reduction of repolarizing currents, a "reduced repolarization reserve," because they are carriers of latent ion channel genes mutations.
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Affiliation(s)
- Tomas Novotny
- Department of Internal Medicine and Cardiology, University Hospital Brno, Brno, Czech Republic.
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17
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Heradien MJ, Goosen A, Crotti L, Durrheim G, Corfield V, Brink PA, Schwartz PJ. Does pregnancy increase cardiac risk for LQT1 patients with the KCNQ1-A341V mutation? J Am Coll Cardiol 2006; 48:1410-5. [PMID: 17010804 DOI: 10.1016/j.jacc.2006.05.060] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2006] [Revised: 04/21/2006] [Accepted: 05/31/2006] [Indexed: 11/15/2022]
Abstract
OBJECTIVES The purpose of this study was to assess the pregnancy-related cardiovascular risk in LQT1 patients. BACKGROUND Only 1 study addressed this issue in genotyped patients and reported that the highest risk is for LQT2 patients. METHODS This case-control study, performed in a cohort of patients from 22 families affected by LQT1 and all sharing the common KCNQ1-A341V mutation, involved 36 mutation carriers and 24 of their unaffected sisters for a total of 182 pregnancies. RESULTS There were 3 (2.6%) cardiac events (2 cardiac arrests) in the 115 LQT1 pregnancies. Because they occurred only among the 27 mothers with previous symptoms, all off-therapy, the risk for symptomatic patients is 11%, but decreases to 0 in symptomatic patients treated with beta-blockers. Carriers and control subjects did not differ for the incidence of miscarriage (10% vs. 15%). Cesarean sections (C-sections), elective or owing to fetal distress, were performed more often in carriers than in non-carriers (27% vs. 14%). Beta-blocker therapy did not influence the prevalence of fetal distress. Among the infants born to carriers, all those with fetal distress were carriers of the A341V mutation (10 of 10, 100%). Among the offspring of the carriers, 48 of 92 (52%) were mutation carriers, and of those, 15% died suddenly at age 14 +/- 6 years. CONCLUSIONS Women affected by the common KCNQ1-A341V mutation are at low risk for cardiac events during pregnancy and without excess risk of miscarriage; their infants delivered by C-section because of fetal distress are extremely likely to also be mutation carriers. Beta-blockers remain recommended. These conclusions likely apply to most LQT1 patients.
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Affiliation(s)
- Marshall J Heradien
- Department of Internal Medicine, University of Stellenbosch, Stellenbosch, South Africa
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18
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Siebrands CC, Binder S, Eckhoff U, Schmitt N, Friederich P. Long QT 1 Mutation KCNQ1A344VIncreases Local Anesthetic Sensitivity of the Slowly Activating Delayed Rectifier Potassium Current. Anesthesiology 2006; 105:511-20. [PMID: 16931984 DOI: 10.1097/00000542-200609000-00015] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Background
Anesthesia in patients with long QT syndrome (LQTS) is a matter of concern. Congenital LQTS is most frequently caused by mutations in KCNQ1 (Kv7.1), whereas drug-induced LQTS is a consequence of HERG (human ether-a-go-go-related gene) channel inhibition. The aim of this study was to investigate whether the LQT1 mutation A344V in the S6 region of KCNQ1, at a position corresponding to the local anesthetic binding site in HERG, may render drug insensitive KCNQ1 channels into a toxicologically relevant target of these pharmacologic agents. This may suggest that LQTS constitutes not only a nonspecific but also a specific pharmacogenetic risk factor for anesthesia.
Methods
The authors examined electrophysiologic and pharmacologic properties of wild-type and mutant KCNQ1 channels. The effects of bupivacaine, ropivacaine, and mepivacaine were investigated using two-electrode voltage clamp and whole cell patch clamp recordings.
Results
The mutation A344V induced voltage-dependent inactivation in homomeric KCNQ1 channels and shifted the voltage dependence of KCNQ1/KCNE1 channel activation by +30 mV. The mutation furthermore increased the sensitivity of KCNQ1/KCNE1 channels for bupivacaine 22-fold (KCNQ1wt/KCNE1: IC50 = 2,431 +/- 582 microM, n = 20; KCNQ1A344V/KCNE1: IC50 = 110 +/- 9 microM, n = 24). Pharmacologic effects of the mutant channels were dominant when mutant and wild-type channels were coexpressed. Simulation of cardiac action potentials with the Luo-Rudy model yielded a prolongation of the cardiac action potential duration and induction of early afterdepolarizations by the mutation A344V that were aggravated by local anesthetic intoxication.
Conclusions
The results indicate that certain forms of the LQTS may constitute a specific pharmacogenetic risk factor for regional anesthesia.
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Affiliation(s)
- Cornelia C Siebrands
- Department of Anesthesiology, University Medical Center Hamburg-Eppendorf, Germany
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19
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Strutz-Seebohm N, Seebohm G, Fedorenko O, Baltaev R, Engel J, Knirsch M, Lang F. Functional coassembly of KCNQ4 with KCNE-beta- subunits in Xenopus oocytes. Cell Physiol Biochem 2006; 18:57-66. [PMID: 16914890 DOI: 10.1159/000095158] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The KCNQ gene family comprises voltage-gated potassium channels expressed in epithelial tissues (KCNQ1, KCNQ5), inner ear structures (KCNQ1, KCNQ4) and the brain (KCNQ2-5). KCNQ4 is expressed in inner and outer hair cells of the inner ear where it influences electrical excitability and cell survival. Accordingly, loss of function mutations of the KCNQ4 gene cause hearing loss in humans and functional k.o.-mice show progressive degeneration of outer hair cells (OHCs). However, characteristic electrophysiological features of the native KCNQ4- carried current I(K,n) in OHCs are not recapitulated by expression of KCNQ4 channels in heterologous expression systems. This might suggest modulation of KCNQ4 by interacting KCNE Beta-subunits, which are known to modify the properties of the closely related KCNQ1. The present study explored whether transcripts of the KCNE isoforms could be identified in OHC mRNA and whether the subunits modulate KCNQ4 function. RT-PCR indeed yielded transcripts of all five KCNEs in OHCs. Coexpression of the KCNE- Beta-subunits with human KCNQ4 in the Xenopus laevis oocyte expression system revealed that all KCNEs modulate KCNQ4 voltage dependence, protein stability and ion selectivity of hKCNQ4 in Xenopus oocytes. The deafness-associated Jervell and Lange- Nielsen syndrome (JLNS) mutation KCNE1(D76N) impairs KCNQ4-function whereas the Romano-Ward syndrome (RWS) mutant KCNE1(S74L), which shows normal hearing in patients, does not impair KCNQ4 channel function. In conclusion, KCNEs are presumably coexpressed with KCNQ4 in hair cells from the organ of Corti and might regulate KCNQ4 functional properties, effects that could be important under physiological and pathophysiological conditions.
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20
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Abstract
Background—
A paradoxical increase in the uncorrected QT interval during infusion of low-dose epinephrine appears pathognomonic for type 1 long-QT syndrome (LQT1). We sought to determine the diagnostic accuracy of this response among patients referred for clinical evaluation of congenital long-QT syndrome (LQTS).
Methods and Results—
From 1999 to 2002, 147 genotyped patients (125 untreated and 22 undergoing β-blocker therapy) had an epinephrine QT stress test that involved a 25-minute infusion protocol (0.025 to 0.3 μg · kg
−1
· min
−1
). A 12-lead ECG was monitored continuously, and repolarization parameters were measured. The sensitivity, specificity, and positive and negative predictive values for the paradoxical QT response (defined as a ≥30-ms increase in QT during infusion of ≤0.1 μg · kg
−1
· min
−1
epinephrine) was determined. The 125 untreated patients (44 genotype negative, 40 LQT1, 30 LQT2, and 11 LQT3) constituted the primary analysis. The median baseline corrected QT intervals (QTc) were 444 ms (gene negative), 456 ms (LQT1), 486 ms (LQT2), and 473 ms (LQT3). The median change in QT interval during low-dose epinephrine infusion was −23 ms in the gene-negative group, 78 ms in LQT1, −4 ms in LQT2, and −58 ms in LQT3. The paradoxical QT response was observed in 37 (92%) of 40 patients with LQT1 compared with 18% (gene-negative), 13% (LQT2), and 0% (LQT3;
P
<0.0001) of the remaining patients. Overall, the paradoxical QT response had a sensitivity of 92.5%, specificity of 86%, positive predictive value of 76%, and negative predictive value of 96% for LQT1 status. Secondary analysis of the subset undergoing β-blocker therapy indicated inferior diagnostic utility in this setting.
Conclusions—
The epinephrine QT stress test can unmask concealed type 1 LQTS with a high level of accuracy.
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Affiliation(s)
- Himeshkumar Vyas
- Division of Pediatric Cardiology, Department of Pediatric and Adolescent Medicine, Mayo Clinic College of Medicine, Rochester, MN, USA
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21
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Thomas D, Wimmer AB, Karle CA, Licka M, Alter M, Khalil M, Ulmer HE, Kathöfer S, Kiehn J, Katus HA, Schoels W, Koenen M, Zehelein J. Dominant-negative I(Ks) suppression by KCNQ1-deltaF339 potassium channels linked to Romano-Ward syndrome. Cardiovasc Res 2006; 67:487-97. [PMID: 15950200 DOI: 10.1016/j.cardiores.2005.05.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2005] [Revised: 05/01/2005] [Accepted: 05/02/2005] [Indexed: 11/18/2022] Open
Abstract
OBJECTIVE Hereditary long QT syndrome (LQTS) is a genetically heterogeneous disease characterized by prolonged QT intervals and an increased risk for ventricular arrhythmias and sudden cardiac death. Mutations in the voltage-gated potassium channel subunit KCNQ1 induce the most common form of LQTS. KCNQ1 is associated with two different entities of LQTS, the autosomal-dominant Romano-Ward syndrome (RWS), and the autosomal-recessive Jervell and Lange-Nielsen syndrome (JLNS) characterized by bilateral deafness in addition to cardiac arrhythmias. In this study, we investigate and discuss dominant-negative I(Ks) current reduction by a KCNQ1 deletion mutation identified in a RWS family. METHODS Single-strand conformation polymorphism analysis and direct sequencing were used to screen LQTS genes for mutations. Mutant KCNQ1 channels were heterologously expressed in Xenopus oocytes, and potassium currents were recorded using the two-microelectrode voltage clamp technique. RESULTS A heterozygous deletion of three nucleotides (CTT) identified in the KCNQ1 gene caused the loss of a single phenylalanine residue at position 339 (KCNQ1-deltaF339). Electrophysiological measurements in the presence and absence of the regulatory beta-subunit KCNE1 revealed that mutant and wild type forms of an N-terminal truncated KCNQ1 subunit (isoform 2) caused much stronger dominant-negative current reduction than the mutant form of the full-length KCNQ1 subunit (isoform 1). CONCLUSION This study highlights the functional relevance of the truncated KCNQ1 splice variant (isoform 2) in establishment and mode of inheritance in long QT syndrome. In the RWS family presented here, the autosomal-dominant trait is caused by multiple dominant-negative effects provoked by heteromultimeric channels formed by wild type and mutant KCNQ1-isoforms in combination with KCNE1.
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Affiliation(s)
- Dierk Thomas
- Universitätsklinik Heidelberg, Innere Medizin III, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
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22
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Napolitano C, Priori SG, Schwartz PJ, Bloise R, Ronchetti E, Nastoli J, Bottelli G, Cerrone M, Leonardi S. Genetic testing in the long QT syndrome: development and validation of an efficient approach to genotyping in clinical practice. JAMA 2005; 294:2975-80. [PMID: 16414944 DOI: 10.1001/jama.294.23.2975] [Citation(s) in RCA: 339] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
CONTEXT In long QT syndrome (LQTS), disease severity and response to therapy vary according to the genetic loci. There exists a critical need to devise strategies to expedite genetic analysis. OBJECTIVE To perform genetic screening in patients with LQTS to determine the yield of genetic testing, as well as the type and the prevalence of mutations. DESIGN, PATIENTS, AND SETTING We investigated whether the detection of a set of frequently mutated codons in the KCNQ1, KCNH2, and SCN5A genes may translate in a novel strategy for rapid efficient genetic testing of 430 consecutive patients referred to our center between June 1996 and June 2004. The entire coding regions of KCNQ1, KCNH2, SCN5A, KCNE1, and KCNE2 were screened by denaturing high-performance liquid chromatography and DNA sequencing. The frequency and the type of mutations were defined to identify a set of recurring mutations. A separate cohort of 75 consecutive probands was used as a validation group to quantify prospectively the prevalence of the recurring mutations identified in the primary LQTS population. MAIN OUTCOME MEASURES Development of a novel approach to LQTS genotyping. RESULTS We identified 235 different mutations, 138 of which were novel, in 310 (72%) of 430 probands (49% KCNQ1, 39% KCNH2, 10% SCN5A, 1.7% KCNE1, and 0.7% KCNE2). Fifty-eight percent of probands carried nonprivate mutations in 64 codons of KCNQ1, KCNH2, and SCN5A genes. A similar occurrence of mutations at these codons (52%) was confirmed in the prospective cohort of 75 probands and in previously published LQTS cohorts. CONCLUSIONS We have developed an approach to improve the efficiency of genetic screening for LQTS. This novel method may facilitate wider access to genotyping resulting in better risk stratification and treatment of LQTS patients.
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Affiliation(s)
- Carlo Napolitano
- Molecular Cardiology, IRCCS Fondazione S. Maugeri Foundation, Pavia, Italy
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23
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24
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Viitasalo M, Oikarinen L, Swan H, Glatter KA, Väänänen H, Fodstad H, Chiamvimonvat N, Kontula K, Toivonen L, Scheinman MM. Ratio of late to early T-wave peak amplitude in 24-h electrocardiographic recordings as indicator of symptom history in patients with long-QT Syndrome types 1 and 2. J Am Coll Cardiol 2005; 47:112-20. [PMID: 16386673 DOI: 10.1016/j.jacc.2005.07.068] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2005] [Revised: 07/14/2005] [Accepted: 07/25/2005] [Indexed: 10/25/2022]
Abstract
UNLABELLED We reviewed 24-h electrocardiographic recordings from 214 genotyped subjects--97 with long-QT syndrome type 1 (LQT1), 62 with LQT2, and 55 unaffected--to record maximal diurnal amplitude ratios between late and early T-wave peaks. Maximal amplitude ratios between late and early T-wave peaks were higher in symptomatic than in asymptomatic patients both in LQT1 (3.2 +/- 1.0 vs. 2.3 +/- 0.8; p < 0.001) and in LQT2 patients (2.6 +/- 1.0 vs. 1.7 +/- 0.5; p < 0.001). The maximal amplitude ratio between late and early T-wave peaks was independently associated with symptom history in both LQT1 and LQT2 patients. OBJECTIVES We tested the hypothesis that in long-QT syndrome types 1 (LQT1) and 2 (LQT2), the diurnal maximal ratio between late and early T-wave peak amplitudes correlates with a history of symptoms better than QT interval durations. BACKGROUND Genotype and phenotype studies have delineated clinical profiles of the most prevalent LQT1 and LQT2 subtypes of inherited LQT, but prediction of arrhythmia risk remains uncertain, the baseline QTc interval being the best predictor. In experimental long-QT syndrome models, the ratio between late and early T-wave peak amplitude predicts onset of torsade de pointes. METHODS We reviewed 24-h electrocardiographic recordings from 214 genotyped subjects--97 with LQT1, 62 with LQT2, and 55 unaffected-to record maximal amplitude ratios between late and early T-wave peaks by use of a computer-assisted program. RESULTS Maximal amplitude ratios between late and early T-wave peaks were higher in symptomatic than in asymptomatic patients both in LQT1 (3.2 +/- 1.0 vs. 2.3 +/- 0.8; p < 0.001) and LQT2 patients (2.6 +/- 1.0 vs. 1.7 +/- 0.5; p < 0.001). Although the QTc interval also was longer in symptomatic patients, only the maximal amplitude ratio between late and early T-wave peaks was independently associated with symptoms in both LQT1 and LQT2 patients. CONCLUSIONS Maximal diurnal ratio between late and early T-wave peak amplitude improves noninvasive risk assessment both in LQT1 and LQT2 syndromes. We propose this new indicator in clinical evaluation of arrhythmia risk in LQT1 and LQT2.
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Affiliation(s)
- Matti Viitasalo
- Department of Cardiology, Helsinki University Central Hospital, Helsinki, Finland.
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25
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Wilson AJ, Quinn KV, Graves FM, Bitner-Glindzicz M, Tinker A. Abnormal KCNQ1 trafficking influences disease pathogenesis in hereditary long QT syndromes (LQT1). Cardiovasc Res 2005; 67:476-86. [PMID: 15935335 DOI: 10.1016/j.cardiores.2005.04.036] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2004] [Revised: 04/20/2005] [Accepted: 04/25/2005] [Indexed: 12/01/2022] Open
Abstract
OBJECTIVE In the hereditary long QT syndromes the commonest defect is in the K+ channel pore forming subunit, KCNQ1. In this study we investigated the role that abnormal KCNQ1 trafficking has in the pathogenesis of the hereditary long QT syndrome (LQT1). METHODS We introduced nine missense and nonsense mutations occurring in LQT1 into the cDNA encoding KCNQ1 fused in frame to the green fluorescent protein. These mutations occur in syndromes that are inherited in both autosomal dominant and recessive fashions. We used biochemistry, electrophysiology and cell imaging to examine the behaviour of wildtype and mutant channel subunits expressed together with the auxiliary subunit KCNE1 expressed in CHO-K1 and C2C12 cells. RESULTS We found that a number of mutations in KCNQ1 are retained in the endoplasmic reticulum and unable to translocate to the plasma membrane. Furthermore, some mutations act in a dominant negative fashion and have the ability to suppress the trafficking of wildtype channel. We use fluorescence resonance energy transfer microscopy to show that this occurs because of direct interaction between the mutant subunit and wildtype channel in the endoplasmic reticulum. Finally, a number of specific and nonspecific pharmacological tools are unable to promote the delivery of these mutants to the plasma membrane. CONCLUSIONS Our data revealed that channel trafficking may contribute to the pathogenesis of LQT1.
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Affiliation(s)
- Andrew J Wilson
- BHF Laboratories and Department of Medicine, University College London, 5 University Street, London, WC1E 6JJ, UK
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Du R, Ren FX, Yang JG, Yuan GH, Zhang SY, Kang CL, Li W, Gui L, Li J. [Relationship between congenital long QT syndrome and Brugada syndrome gene mutation]. Zhongguo Yi Xue Ke Xue Yuan Xue Bao 2005; 27:289-94. [PMID: 16038262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
OBJECTIVE To investigate the molecular pathology in families with long QT syndrome (LQTS) including Jervell-Longe-Nielsen syndrome (JLNS) and Romano-ward syndrome (RWS) and Brugada syndrome (BS) in Chinese population. METHODS Polymerase chain reaction and DNA sequencing were used to screen for KCNQ1, KCNH2, KCNE1, and SCN5A mutation. RESULTS We identified a novel mutation N1774S in the SCN5A gene of the BS family, a novel mutation G314S in a RWS family which had also been found in Europe, North America, and Japan, and a single nucleotide polymorphisms (SNPs) G643S in the KCNQ1 of the JLNS family. In this JLNS family, another heterozygous novel mutation in exon 2a was found in KCNQ1 of the patients. CONCLUSION New mutations were found in our experiment, which expand the spectrum of KCNQ1 and SCN5A mutations that cause LQTS and BS.
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Affiliation(s)
- Rong Du
- Institute of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
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27
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Casimiro MC, Knollmann BC, Yamoah EN, Nie L, Vary JC, Sirenko SG, Greene AE, Grinberg A, Huang SP, Ebert SN, Pfeifer K. Targeted point mutagenesis of mouse Kcnq1: phenotypic analysis of mice with point mutations that cause Romano-Ward syndrome in humans. Genomics 2005; 84:555-64. [PMID: 15498462 DOI: 10.1016/j.ygeno.2004.06.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2004] [Revised: 06/08/2004] [Accepted: 06/09/2004] [Indexed: 01/23/2023]
Abstract
Inherited long QT syndrome is most frequently associated with mutations in KCNQ1, which encodes the primary subunit of a potassium channel. Patients with mutations in KCNQ1 may show only the cardiac defect (Romano-Ward syndrome or RWS) or may also have severe deafness (Jervell and Lange-Nielsen syndrome or JLNS). Targeted disruption of mouse Kcnq1 models JLNS in that mice are deaf and show abnormal ECGs. However, the phenotype is broader than that seen in patients. Most dramatically, the inner ear defects result in a severe hyperactivity/circling behavior, which may influence cardiac function. To understand the etiology of the cardiac phenotype in these mice and to generate a potentially more useful model system, we generated new mouse lines by introducing point mutations associated with RWS. The A340E line phenocopies RWS: the repolarization phenotype is inherited in a dominant manner and is observed independent of any inner ear defect. The T311I line phenocopies JLNS, with deafness associated with inner hair cell malfunction.
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Affiliation(s)
- Mathew C Casimiro
- Laboratory of Mammalian Genes and Development, NICHD/National Institutes of Health, Building 6B Room 2B-206, Bethesda, MD 20892, USA
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28
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Wedekind H, Schwarz M, Hauenschild S, Djonlagic H, Haverkamp W, Breithardt G, Wülfing T, Pongs O, Isbrandt D, Schulze-Bahr E. Effective long-term control of cardiac events with beta-blockers in a family with a common LQT1 mutation. Clin Genet 2004; 65:233-41. [PMID: 14756674 DOI: 10.1111/j.0009-9163.2004.00221.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The congenital long QT syndrome (LQTS) is characterized by a prolonged QT interval on the surface electrocardiogram and an increased risk of recurrent syncope and sudden cardiac death. Mutations in seven genes have been identified as the molecular basis of LQTS. beta-blockers are the treatment of choice to reduce cardiac symptoms. However, long-term follow-up of genotyped families with LQTS has been rarely reported. We have clinically followed a four-generation family with LQTS being treated with beta-blocker therapy over a period of 23 years. Seven family members were carriers of two amino acid alterations in cis (V254M-V417M) in the cardiac potassium channel gene KCNQ1. Voltage-clamp recordings of mutant KCNQ1 protein in Xenopus oocytes showed that only the V254M mutation reduced the IKs current and that the effect of the V417M variant was negligible. The family exhibited the complete clinical spectrum of the disease, from asymptomatic patients to victims of sudden death before beta-blocker therapy. There was no significant reduction in QTc (556 +/- 40 ms(1/2) before therapy, 494 +/- 20 ms(1/2) during 17 years of treatment; n = 5 individuals). Of nine family members, one female died suddenly before treatment, three females of the second generation were asymptomatic, and four individuals of the third and fourth generation were symptomatic. All mutation carriers were treated with beta-blockers and remained asymptomatic for a follow-up up to 23 years. Long-term follow-up of a LQT1 family with a common mutation (V254M) being on beta-blocker therapy was effective and safe. This study underscores the importance of long-term follow-up in families with specific LQT mutations to provide valuable information for clinicians for an appropriate antiarrhythmic treatment.
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Affiliation(s)
- H Wedekind
- Departments of Cardiology and Angiology,University of Münster, Albert-Schweitzer-Strasse 33, D-48149 Münster, Germany.
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29
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Zehelein J, Thomas D, Khalil M, Wimmer AB, Koenen M, Licka M, Wu K, Kiehn J, Brockmeier K, Kreye VAW, Karle CA, Katus HA, Ulmer HE, Schoels W. Identification and characterisation of a novel KCNQ1 mutation in a family with Romano–Ward syndrome. Biochim Biophys Acta Mol Basis Dis 2004; 1690:185-92. [PMID: 15511625 DOI: 10.1016/j.bbadis.2004.06.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2004] [Revised: 06/16/2004] [Accepted: 06/16/2004] [Indexed: 12/29/2022]
Abstract
Romano-Ward syndrome (RWS), the autosomal dominant form of the congenital long QT syndrome, is characterised by prolongation of the cardiac repolarisation process associated with ventricular tachyarrhythmias of the torsades de pointes type. Genetic studies have identified mutations in six ion channel genes, KCNQ1, KCNH2, SCN5A, KCNE1 and KCNE2 and the accessory protein Ankyrin-B gene, to be responsible for this disorder. Single-strand conformation polymorphism (SSCP) analysis and subsequent DNA sequence analysis have identified a KCNQ1 mutation in a family that were clinically conspicuous due to several syncopes and prolonged QTc intervals in the ECG. The mutant subunit was expressed and functionally characterised in the Xenopus oocyte expression system. A novel heterozygous missense mutation with a C to T transition at the first position of codon 343 (CCA) of the KCNQ1 gene was identified in three concerned family members (QTc intervals: 500, 510 and 530 ms, respectively). As a result, proline 343 localised within the highly conserved transmembrane segment S6 of the KCNQ1 channel is replaced by a serine. Co-expression of mutant (KCNQ1-P343S) and wild-type (KCNQ1) cRNA in Xenopus oocytes produced potassium currents reduced by approximately 92%, while IKs reconstitution experiments with a combination of KCNQ1 mutant, wild-type and KCNE1 subunits yielded currents reduced by approximately 60%. A novel mutation (P343S) identified in the KCNQ1 subunit gene of three members of a RWS family showed a dominant-negative effect on native IKs currents leading to prolongation of the heart repolarisation and possibly increases the risk of malign arrhythmias with sudden cardiac death.
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Affiliation(s)
- J Zehelein
- Innere Medizin III, Universitätsklinik Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.
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30
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Abstract
Congenital long QT syndrome (LQTS) is a rare but potentially lethal disease, characterized by prolongation of QT interval, recurrent syncope, and sudden death. In the pregenomic era (1959-1991), sympathetic imbalance was thought to be responsible for this disease. Since 1991 (postgenomic era), 7 LQTS genes have been discovered and more than 300 mutations have been identified to account for approximately 70% of patients affected. Despite the advancement in molecular genetic knowledge, diagnosis of congenital LQTS is still based on electrocardiographic and clinical characteristics. Beta-blockers remain the mainstay treatment. For high-risk patients, the implantable cardioverter-defibrillator (ICD) offer an effective therapeutic option to reduce mortality. Gene-based specific therapy is still preliminary. Further studies are required to investigate new strategies for targeting the defective genes or mutant channels. For acquired LQTS, it is generally believed that the main issue is the blockade of the slow component of the delayed rectifier K+ current (IKr). These IKr blockers have a "reverse frequency-dependent" effect on the QTc interval and increase the dispersion in repolarization. In the presence of risk factors such as female gender, slow heart rate, and hypokalemia, these IKr blockers have a high propensity to induce torsades de pointes. For patients with a history of drug-induced LQTS, care must be taken to avoid further exposure to QT-prolonging drugs or conditions. Molecular genetic analysis could be useful to unravel subclinical mutations or polymorphisms. Physicians not only need to be aware of the pharmacodynamic and pharmacokinetic interactions of various important drugs, but also need to update their knowledge.
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Affiliation(s)
- Chern-En Chiang
- Division of Cardiology, Taipei Veterans General Hospital, National Yang-Ming University, Taipei, Taiwan.
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31
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Kovalev DV, Skibitskiĭ VV. [Romano-Ward syndrome initially diagnosed as epilepsy]. Kardiologiia 2003; 43:100-4. [PMID: 12891279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 03/04/2023]
Abstract
A report of a case of Romano-Ward syndrome presenting as epilepsy is accompanied with discussion of symptoms characteristic of the syndrome and possible causes of erroneous primary diagnosis.
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32
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Burton DY, Song C, Fishbein I, Hazelwood S, Li Q, DeFelice S, Connolly JM, Perlstein I, Coulter DA, Levy RJ. The incorporation of an ion channel gene mutation associated with the long QT syndrome (Q9E-hMiRP1) in a plasmid vector for site-specific arrhythmia gene therapy: in vitro and in vivo feasibility studies. Hum Gene Ther 2003; 14:907-22. [PMID: 12828861 DOI: 10.1089/104303403765701196] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The present studies investigated the cardiac potassium channel missense mutation, Q9E-hMiRP1, for potential use as a gene therapy construct for cardiac arrhythmias. This gene abnormality is one of a number of mutations that can cause the long QT syndrome (LQTS), a hereditary arrhythmia disorder that is associated with sudden death. However, individuals who carry the Q9E-hMiRP1 variant are predisposed to developing the LQTS only after clarithromycin administration. Because the electrophysiologic mechanism of action of Q9E-hMiRP1 (i.e., diminished potassium currents resulting in delayed myocardial repolarization) is comparable to that of class III antiarrhythmic agents, we examined Q9E-hMiRP1 as a candidate gene therapy construct for site-specific treatment of reentrant atrial cardiac arrhythmias. Our rationale was also based on the hypothetical safety of the atrial use of Q9E-hMiRP1 because LQTS characteristically causes ventricular but not atrial arrhythmias. Furthermore, the possible use of clarithromycin to control the conduction effects of overexpressed Q9E-hMiRP1 pharmacologically was another attractive feature. In our studies we investigated the use of two bicistronic plasmid DNA gene vectors with either hMiRP1 or Q9E-MiRP1 and green fluorescent protein (GFP), plus a C-terminus of the hMiRP1 or of the Q9E-hMiRP1 coding region for the FLAG (MDYKDDDDK) peptide. We generated two stable cell lines using HEK293 and SH-SY5Y (human cell lines), overexpressing the genes of interest, confirmed by real-time reverse transcription-polymerase chain reaction (RT-PCR) and Western blots. The expected plasma membrane localization of each overexpressed transgene was confirmed by immunofluorescent confocal fluorescent microscopy using anti-FLAG antibody. Patchclamp studies demonstrated that cells transfected with Q9E-hMiRP1 plasmid DNA exhibited significantly reduced potassium currents but only with clarithromycin administration. A novel plasmid DNA delivery system was formulated for use in our animal studies of the hMiRP1 vectors, which was composed of DNA-anti-DNA antibody-cationic lipid (DAC) heteroplexes. In vitro and in vivo studies using DAC heteroplexes containing anti-DNA antibodies with nuclear targeting capability demonstrated significantly increased transfection compared to naked DNA, and to DNA-cationic lipid complexes. Pig atrial myocardial injections of DAC heteroplexes demonstrated 16% of regional cardiac myocytes transfected using the Q9E-hMiRP1 plasmid, and 15% of cells with the hMiRP1 vector. It is concluded that the present studies support the view that site-specific gene therapy for atrial arrhythmias is feasible using plasmid vectors for overexpressing ion channel mutations that have electrophysiologic effects comparable to class III antiarrhythmic agents.
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Affiliation(s)
- Denise Y Burton
- Division of Cardiology, Children's Hospital of Philadelphia, Civic Center Boulevard, Philadelphia, PA 19104-4318, USA
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Shimizu W, Noda T, Takaki H, Kurita T, Nagaya N, Satomi K, Suyama K, Aihara N, Kamakura S, Sunagawa K, Echigo S, Nakamura K, Ohe T, Towbin JA, Napolitano C, Priori SG. Epinephrine unmasks latent mutation carriers with LQT1 form of congenital long-QT syndrome. J Am Coll Cardiol 2003; 41:633-42. [PMID: 12598076 DOI: 10.1016/s0735-1097(02)02850-4] [Citation(s) in RCA: 142] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
OBJECTIVES This study was designed to test the hypothesis that epinephrine infusion may be a provocative test able to unmask nonpenetrant KCNQ1 mutation carriers. BACKGROUND The LQT1 form of congenital long QT syndrome is associated with high vulnerability to sympathetic stimulation and appears with incomplete penetrance. METHODS The 12-lead electrocardiographic parameters before and after epinephrine infusion were compared among 19 mutation carriers with a baseline corrected QT interval (QTc) of > or =460 ms (Group I), 15 mutation carriers with a QTc of <460 ms (Group II), 12 nonmutation carriers (Group III), and 15 controls (Group IV). RESULTS The mean corrected Q-Tend (QTce), Q-Tpeak (QTcp), and Tpeak-end (Tcp-e) intervals among 12-leads before epinephrine were significantly larger in Group I than in the other three groups. Epinephrine (0.1 microg/kg/min) increased significantly the mean QTce, QTcp, Tcp-e, and the dispersion of QTcp in Groups I and II, but not in Groups III and IV. The sensitivity and specificity of QTce measurements to identify mutation carriers were 59% (20/34) and 100% (27/27), respectively, before epinephrine, and the sensitivity was substantially improved to 91% (31/34) without the expense of specificity (100%, 27/27) after epinephrine. The mean QTce, QTcp, and Tcp-e before and after epinephrine were significantly larger in 15 symptomatic than in 19 asymptomatic mutation carriers in Groups I and II, and the prolongation of the mean QTce with epinephrine was significantly larger in symptomatic patients. CONCLUSIONS Epinephrine challenge is a powerful test to establish electrocardiographic diagnosis in silent LQT1 mutation carriers, thus allowing implementation of prophylactic measures aimed at reducing sudden cardiac death.
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Affiliation(s)
- Wataru Shimizu
- Division of Cardiology, Department of Internal Medicine, National Cardiovascular Center, 5-7-1 Fujishiro-dai, Suita, Osaka 565-8565, Japan.
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34
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Abstract
Molecular genetics applied to the study of inherited arrhythmogenic diseases has profoundly modified our understanding of cardiac electrophysiology providing new information on the crucial pathophysiological role of cardiac ion channels. These data are now putting forth innovative strategies for clinical management of the affected patients. Among these conditions, long QT syndrome (LQTS) was the first to enter the "genetic era", and nowadays the availability of large population of patients with known mutation allows to draw meaningful genotype-phenotype correlation and genetic-based risk stratification. However, despite the remarkable impact on knowledge, several still poorly defined issues limit the translation of such information into more effective therapeutic stratigies. As an example, despite the evidence of a significant QT shortening potential, the gene-specific therapy of LQTS has still to prove its impact upon the risk of cardiac events. The present article reviews the most critical findings obtained in the last decade in the field of genetic of LQTS in the attempt of underlying its current applicability, limitations and the future perspectives of this knowledge in the management of affected patients.
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Affiliation(s)
- Raffaella Bloise
- Molecular Cardiology Laboratories, Fondazione Salvatore Maugeri IRCCS, Pavia, Italy
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35
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Swan H. [Long QT--a polymorphic syndrome]. Duodecim 1998; 114:1905-13. [PMID: 11717744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/17/2023]
Affiliation(s)
- H Swan
- HYKS, kardiologian toimiala Haartmaninkatu 4 00290 Helsinki.
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