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Zeng D, Ford B, Doležel J, Karafiátová M, Hayden MJ, Rathjen TM, George TS, Brown LK, Ryan PR, Pettolino FA, Mathesius U, Delhaize E. A conditional mutation in a wheat (Triticum aestivum L.) gene regulating root morphology. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2024; 137:48. [PMID: 38345612 PMCID: PMC10861616 DOI: 10.1007/s00122-024-04555-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Accepted: 01/12/2024] [Indexed: 02/15/2024]
Abstract
KEY MESSAGE Characterisation and genetic mapping of a key gene defining root morphology in bread wheat. Root morphology is central to plants for the efficient uptake up of soil water and mineral nutrients. Here we describe a conditional mutant of hexaploid wheat (Triticum aestivum L.) that when grown in soil with high Ca2+ develops a larger rhizosheath accompanied with shorter roots than the wild type. In wheat, rhizosheath size is a reliable surrogate for root hair length and this was verified in the mutant which possessed longer root hairs than the wild type when grown in high Ca2+ soil. We named the mutant Stumpy and showed it to be due to a single semi-dominant mutation. The short root phenotype at high Ca2+ was due to reduced cellular elongation which might also explain the long root hair phenotype. Analysis of root cell walls showed that the polysaccharide composition of Stumpy roots is remodelled when grown at non-permissive (high) Ca2+ concentrations. The mutation mapped to chromosome 7B and sequencing of the 7B chromosomes in both wild type and Stumpy identified a candidate gene underlying the Stumpy mutation. As part of the process to determine whether the candidate gene was causative, we identified wheat lines in a Cadenza TILLING population with large rhizosheaths but accompanied with normal root length. This finding illustrates the potential of manipulating the gene to disconnect root length from root hair length as a means of developing wheat lines with improved efficiency of nutrient and water uptake. The Stumpy mutant will be valuable for understanding the mechanisms that regulate root morphology in wheat.
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Affiliation(s)
- Deying Zeng
- Department of Biological Science, College of Life Sciences, Sichuan Normal University, Chengdu, Sichuan, 610101, China
| | - Brett Ford
- Grains Research and Development Corporation, Barton, ACT, 2600, Australia
- CSIRO Agriculture & Food, PO Box 1700, Canberra, ACT, 2601, Australia
| | - Jaroslav Doležel
- Centre of Plant Structural and Functional Genomics, Institute of Experimental Botany of the Czech Academy of Sciences, Olomouc, Czech Republic
| | - Miroslava Karafiátová
- Centre of Plant Structural and Functional Genomics, Institute of Experimental Botany of the Czech Academy of Sciences, Olomouc, Czech Republic
| | - Mathew J Hayden
- Department of Jobs, Precincts and Regions, Agriculture Victoria Research, AgriBio, Bundoora, VIC, Australia
- School of Applied Systems Biology, La Trobe University, Bundoora, VIC, Australia
| | - Tina M Rathjen
- CSIRO Agriculture & Food, PO Box 1700, Canberra, ACT, 2601, Australia
| | | | - Lawrie K Brown
- James Hutton Institute, Invergowrie, Dundee, DD2 5DA, UK
| | - Peter R Ryan
- CSIRO Agriculture & Food, PO Box 1700, Canberra, ACT, 2601, Australia
| | | | - Ulrike Mathesius
- Research School of Biology, The Australian National University, Canberra, ACT, 2601, Australia
| | - Emmanuel Delhaize
- Research School of Biology, The Australian National University, Canberra, ACT, 2601, Australia.
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Mondejar-Parreño G, Perez-Vizcaino F, Cogolludo A. Kv7 Channels in Lung Diseases. Front Physiol 2020; 11:634. [PMID: 32676036 PMCID: PMC7333540 DOI: 10.3389/fphys.2020.00634] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 05/18/2020] [Indexed: 12/23/2022] Open
Abstract
Lung diseases constitute a global health concern causing disability. According to WHO in 2016, respiratory diseases accounted for 24% of world population mortality, the second cause of death after cardiovascular diseases. The Kv7 channels family is a group of voltage-dependent K+ channels (Kv) encoded by KCNQ genes that are involved in various physiological functions in numerous cell types, especially, cardiac myocytes, smooth muscle cells, neurons, and epithelial cells. Kv7 channel α-subunits are regulated by KCNE1–5 ancillary β-subunits, which modulate several characteristics of Kv7 channels such as biophysical properties, cell-location, channel trafficking, and pharmacological sensitivity. Kv7 channels are mainly expressed in two large groups of lung tissues: pulmonary arteries (PAs) and bronchial tubes. In PA, Kv7 channels are expressed in pulmonary artery smooth muscle cells (PASMCs); while in the airway (trachea, bronchus, and bronchioles), Kv7 channels are expressed in airway smooth muscle cells (ASMCs), airway epithelial cells (AEPs), and vagal airway C-fibers (VACFs). The functional role of Kv7 channels may vary depending on the cell type. Several studies have demonstrated that the impairment of Kv7 channel has a strong impact on pulmonary physiology contributing to the pathophysiology of different respiratory diseases such as cystic fibrosis, asthma, chronic obstructive pulmonary disease, chronic coughing, lung cancer, and pulmonary hypertension. Kv7 channels are now recognized as playing relevant physiological roles in many tissues, which have encouraged the search for Kv7 channel modulators with potential therapeutic use in many diseases including those affecting the lung. Modulation of Kv7 channels has been proposed to provide beneficial effects in a number of lung conditions. Therefore, Kv7 channel openers/enhancers or drugs acting partly through these channels have been proposed as bronchodilators, expectorants, antitussives, chemotherapeutics and pulmonary vasodilators.
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Affiliation(s)
- Gema Mondejar-Parreño
- Departamento de Farmacología y Toxicología, Facultad de Medicina, Universidad Complutense de Madrid, Madrid, Spain.,Ciber Enfermedades Respiratorias (Ciberes), Madrid, Spain.,Instituto de Investigación Sanitaria Gregorio Marañón (IISGM), Madrid, Spain
| | - Francisco Perez-Vizcaino
- Departamento de Farmacología y Toxicología, Facultad de Medicina, Universidad Complutense de Madrid, Madrid, Spain.,Ciber Enfermedades Respiratorias (Ciberes), Madrid, Spain.,Instituto de Investigación Sanitaria Gregorio Marañón (IISGM), Madrid, Spain
| | - Angel Cogolludo
- Departamento de Farmacología y Toxicología, Facultad de Medicina, Universidad Complutense de Madrid, Madrid, Spain.,Ciber Enfermedades Respiratorias (Ciberes), Madrid, Spain.,Instituto de Investigación Sanitaria Gregorio Marañón (IISGM), Madrid, Spain
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3
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Wei H, Wu J, Liu Z. Studying KCNQ1 Mutation and Drug Response in Type 1 Long QT Syndrome Using Patient-Specific Induced Pluripotent Stem Cell-Derived Cardiomyocytes. Methods Mol Biol 2018; 1684:7-28. [PMID: 29058180 DOI: 10.1007/978-1-4939-7362-0_2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Patient-specific human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (hiPSC-CMs) are becoming a valuable model for studying inherited cardiac arrhythmias. Type 1 long-QT syndrome is associated with the genetic variants of KCNQ1 gene that encodes Kv7.1, the α-subunit of the voltage-gated potassium channel QKT subfamily member 1 that channels the slow component of the outwardly rectifying K+ channel current in cardiac myocytes. Patient- or disease-specific hiPSC-CM model could facilitate the characterization of the genotype-phenotype relationships and testing of individualized drug responses.Here, we describe the methods in the generation of hiPSC-CMs, molecular and electrophysiological characterizations of their cellular phenotypes associated with KCNQ1/Kv7.1 defects, and evaluation of the effects of K+ channel-specific drugs.
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Affiliation(s)
- Heming Wei
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Republic of Singapore.
| | - Jianjun Wu
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Republic of Singapore
| | - Zhenfeng Liu
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Republic of Singapore
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4
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Donahue JK. Sequencing of uncertain significance. J Cardiovasc Electrophysiol 2017; 29:105-106. [PMID: 29120076 DOI: 10.1111/jce.13384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 11/06/2017] [Indexed: 11/30/2022]
Affiliation(s)
- J Kevin Donahue
- Division of Cardiology, University of Massachusetts Medical School, Worcester, MA, USA
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5
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Ma D, Wei H, Lu J, Huang D, Liu Z, Loh LJ, Islam O, Liew R, Shim W, Cook SA. Characterization of a novel KCNQ1 mutation for type 1 long QT syndrome and assessment of the therapeutic potential of a novel IKs activator using patient-specific induced pluripotent stem cell-derived cardiomyocytes. Stem Cell Res Ther 2015; 6:39. [PMID: 25889101 PMCID: PMC4396080 DOI: 10.1186/s13287-015-0027-z] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Revised: 02/27/2015] [Accepted: 02/27/2015] [Indexed: 12/14/2022] Open
Abstract
Introduction Type 1 long QT syndrome (LQT1) is a common type of cardiac channelopathy associated with loss-of-function mutations of KCNQ1. Currently there is a lack of drugs that target the defected slowly activating delayed rectifier potassium channel (IKs). With LQT1 patient-specific human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (hiPSC-CMs), we tested the effects of a selective IKs activator ML277 on reversing the disease phenotypes. Methods A LQT1 family with a novel heterozygous exon 7 deletion in the KCNQ1 gene was identified. Dermal fibroblasts from the proband and her healthy father were reprogrammed to hiPSCs and subsequently differentiated into hiPSC-CMs. Results Compared with the control, LQT1 patient hiPSC-CMs showed reduced levels of wild type KCNQ1 mRNA accompanied by multiple exon skipping mRNAs and a ~50% reduction of the full length Kv7.1 protein. Patient hiPSC-CMs showed reduced IKs current (tail current density at 30 mV: 0.33 ± 0.02 vs. 0.92 ± 0.21, P < 0.05) and prolonged action potential duration (APD) (APD 50 and APD90: 603.9 ± 39.2 vs. 319.3 ± 13.8 ms, P < 0.005; and 671.0 ± 41.1 vs. 372.9 ± 14.2 ms, P < 0.005). ML277, a small molecule recently identified to selectively activate KV7.1, reversed the decreased IKs and partially restored APDs in patient hiPSC-CMs. Conclusions From a LQT1 patient carrying a novel heterozygous exon7 deletion mutation of KCNQ1, we generated hiPSC-CMs that faithfully recapitulated the LQT1 phenotypes that are likely associated with haploinsufficiency and trafficking defect of KCNQ1/Kv7.1. The small molecule ML277 restored IKs function in hiPSC-CMs and could have therapeutic value for LQT1 patients. Electronic supplementary material The online version of this article (doi:10.1186/s13287-015-0027-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Dongrui Ma
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore.
| | - Heming Wei
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore. .,Cardiovascular & Metabolic Disorders Program, Duke-NUS Graduate Medical School Singapore, 8 College Road, Singapore, 169857, Singapore.
| | - Jun Lu
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore.
| | - Dou Huang
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore.
| | - Zhenfeng Liu
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore.
| | - Li Jun Loh
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore.
| | - Omedul Islam
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore.
| | - Reginald Liew
- Cardiovascular & Metabolic Disorders Program, Duke-NUS Graduate Medical School Singapore, 8 College Road, Singapore, 169857, Singapore.
| | - Winston Shim
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore. .,Cardiovascular & Metabolic Disorders Program, Duke-NUS Graduate Medical School Singapore, 8 College Road, Singapore, 169857, Singapore.
| | - Stuart A Cook
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore. .,Cardiovascular & Metabolic Disorders Program, Duke-NUS Graduate Medical School Singapore, 8 College Road, Singapore, 169857, Singapore. .,National Heart and Lung Institute, Imperial College, South Kensington Campus, London, SW7 2AZ, UK.
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Hedley PL, Durrheim GA, Hendricks F, Goosen A, Jespersgaard C, Støvring B, Pham TT, Christiansen M, Brink PA, Corfield VA. Long QT syndrome in South Africa: the results of comprehensive genetic screening. Cardiovasc J Afr 2014; 24:231-7. [PMID: 24217263 PMCID: PMC3772322 DOI: 10.5830/cvja-2013-032] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Accepted: 05/24/2013] [Indexed: 01/06/2023] Open
Abstract
Congenital long QT syndrome (cLQTS) is a genetic disorder predisposing to ventricular arrhythmia, syncope and sudden death. Over 700 different cLQTS-causing mutations in 13 genes are known. The genetic spectrum of LQTS in 44 South African cLQTS patients (23 known to carry the South African founder mutation p.A341V in KCNQ1) was established by screening for mutations in the coding regions of KCNQ1, KCNH2, KCNE1, KCNE2 and SCN5A, the most frequently implicated cLQTS-causing genes (five-gene screening). Fourteen disease-causing mutations were identified, eight (including the founder mutation) in KCNQ1, five in KCNH2 and one in KCNE1. Two mutations were novel. Two double heterozygotes were found among the 23 families (8.5%) carrying the founder mutation. In conclusion, cLQTS in South Africa reflects both a strong founder effect and a genetic spectrum similar to that seen in other populations. Consequently, five-gene screening should be offered as a standard screening option, as is the case internationally. This will disclose compound and double heterozygotes. Fivegene screening will most likely be even more informative in other South African sub-populations with a greater genetic diversity.
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Affiliation(s)
- Paula L Hedley
- US/MRC Centre for Molecular and Cellular Biology, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, University of Stellenbosch, South Africa
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Christiansen M, Hedley PL, Theilade J, Stoevring B, Leren TP, Eschen O, Sørensen KM, Tybjærg-Hansen A, Ousager LB, Pedersen LN, Frikke-Schmidt R, Aidt FH, Hansen MG, Hansen J, Bloch Thomsen PE, Toft E, Henriksen FL, Bundgaard H, Jensen HK, Kanters JK. Mutations in Danish patients with long QT syndrome and the identification of a large founder family with p.F29L in KCNH2. BMC MEDICAL GENETICS 2014; 15:31. [PMID: 24606995 PMCID: PMC4007532 DOI: 10.1186/1471-2350-15-31] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Accepted: 02/18/2014] [Indexed: 01/08/2023]
Abstract
Background Long QT syndrome (LQTS) is a cardiac ion channelopathy which presents clinically with palpitations, syncope or sudden death. More than 700 LQTS-causing mutations have been identified in 13 genes, all of which encode proteins involved in the execution of the cardiac action potential. The most frequently affected genes, covering > 90% of cases, are KCNQ1, KCNH2 and SCN5A. Methods We describe 64 different mutations in 70 unrelated Danish families using a routine five-gene screen, comprising KCNQ1, KCNH2 and SCN5A as well as KCNE1 and KCNE2. Results Twenty-two mutations were found in KCNQ1, 28 in KCNH2, 9 in SCN5A, 3 in KCNE1 and 2 in KCNE2. Twenty-six of these have only been described in the Danish population and 18 are novel. One double heterozygote (1.4% of families) was found. A founder mutation, p.F29L in KCNH2, was identified in 5 “unrelated” families. Disease association, in 31.2% of cases, was based on the type of mutation identified (nonsense, insertion/deletion, frameshift or splice-site). Functional data was available for 22.7% of the missense mutations. None of the mutations were found in 364 Danish alleles and only three, all functionally characterised, were recorded in the Exome Variation Server, albeit at a frequency of < 1:1000. Conclusion The genetic etiology of LQTS in Denmark is similar to that found in other populations. A large founder family with p.F29L in KCNH2 was identified. In 48.4% of the mutations disease causation was based on mutation type or functional analysis.
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Affiliation(s)
- Michael Christiansen
- Department of Clinical Biochemistry, Immunology and Genetics, Statens Serum Institut, Ørestads Boulevard 5, 2300S, Copenhagen, Denmark.
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Gao Y, Li C, Liu W, Wu R, Qiu X, Liang R, Li L, Zhang L, Hu D. Genotype-phenotype analysis of three Chinese families with Jervell and Lange-Nielsen syndrome. J Cardiovasc Dis Res 2012; 3:67-75. [PMID: 22629021 PMCID: PMC3354473 DOI: 10.4103/0975-3583.95357] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
BACKGROUND Long QT syndrome (LQTS) is characterized by QT prolongation, syncope and sudden death. This study aims to explore the causes, clinical manifestations and therapeutic outcomes of Jervell and Lange-Nielsen syndrome (JLNS), a rare form of LQTS with congenital sensorineural deafness, in Chinese individuals. MATERIALS AND METHODS Three JLNS kindreds from the Chinese National LQTS Registry were investigated. Mutational screening of KCNQ1 and KCNE1 genes was performed by polymerase chain reaction and direct DNA sequence analysis. LQTS phenotype and therapeutic outcomes were evaluated for all probands and family members. RESULTS We identified 7 KCNQ1 mutations. c.1032_1117dup (p.Ser373TrpfsX10) and c.1319delT (p.Val440AlafsX26) were novel, causing JLNS in a 16-year-old boy with a QTc (QT interval corrected for heart rate) of 620 ms and recurrent syncope. c.605-2A>G and c.815G>A (p.Gly272Asp) caused JLNS in a 12-year-old girl and her 5-year-old brother, showing QTc of 590 to 600 ms and recurrent syncope. The fourth JLNS case, a 46-year-old man carrying c.1032G>A (p.Ala344Alasp) and c.569G>A (p.Arg190Gln) and with QTc of 460 ms, has been syncope-free since age 30. His 16-year-old daughter carries novel missense mutation c.574C>T (p.Arg192Cys) and c.1032G>A(p.Ala344Alasp) and displayed a severe phenotype of Romano-Ward syndrome (RWS) characterized by a QTc of 530 ms and recurrent syncope with normal hearing. Both the father and daughter also carried c.253G>A (p.Asp85Asn; rs1805128), a rare single nucleotide polymorphism (SNP) on KCNE1. Bizarre T waves were seen in 3/4 JLNS patients. Symptoms were improved and T wave abnormalities became less abnormal after appropriate treatment. CONCLUSION This study broadens the mutation and phenotype spectrums of JLNS. Compound heterozygous KCNQ1 mutations can result in both JLNS and severe forms of RWS in Chinese individuals.
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Affiliation(s)
- Yuanfeng Gao
- Heart Center, Peking University People's Hospital, Beijing - 100 044, P. R. China
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Abstract
Phosphoinositides (PIs), a family of phosphorylated derivatives of the membrane lipid phosphatidylinositol, are established regulators of multiple cellular functions. An increasing amount of evidence has highlighted potential links between PI-mediated signaling pathways and the etiology of many human diseases, including cardiovascular pathologies. This chapter will provide a detailed overview of the peculiar functions of the major cardiovascular PIs in the pathogenesis of atherosclerosis, heart failure, and arrhythmias.
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Affiliation(s)
- Alessandra Ghigo
- Department of Genetics, Biology and Biochemistry, University of Torino, Molecular Biotechnology Center, Italy
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Tsuji-Wakisaka K, Akao M, Ishii TM, Ashihara T, Makiyama T, Ohno S, Toyoda F, Dochi K, Matsuura H, Horie M. Identification and functional characterization of KCNQ1 mutations around the exon 7-intron 7 junction affecting the splicing process. Biochim Biophys Acta Mol Basis Dis 2011; 1812:1452-9. [PMID: 21810471 DOI: 10.1016/j.bbadis.2011.07.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Revised: 06/28/2011] [Accepted: 07/18/2011] [Indexed: 10/18/2022]
Abstract
BACKGROUND KCNQ1 gene encodes the delayed rectifier K(+) channel in cardiac muscle, and its mutations cause long QT syndrome type 1 (LQT1). Especially exercise-related cardiac events predominate in LQT1. We previously reported that a KCNQ1 splicing mutation displays LQT1 phenotypes. METHODS AND RESULTS We identified novel mutation at the third base of intron 7 (IVS7 +3A>G) in exercise-induced LQT1 patients. Minigene assay in COS7 cells and RT-PCR analysis of patients' lymphocytes demonstrated the presence of exon 7-deficient mRNA in IVS7 +3A>G, as well as c.1032G>A, but not in c.1022C>T. Real-time RT-PCR demonstrated that both IVS7 +3A>G and c.1032G>A carrier expressed significant amounts of exon-skipping mRNAs (18.8% and 44.8% of total KCNQ1 mRNA). Current recordings from Xenopus oocytes injected cRNA by simulating its ratios of exon skipping displayed a significant reduction in currents to 64.8 ± 4.5% for IVS7 +3A>G and to 41.4 ± 9.5% for c.1032G>A carrier, respectively, compared to the condition without splicing error. Computer simulation incorporating these quantitative results revealed the pronounced QT prolongation under beta-adrenergic stimulation in IVS7 +3A>G carrier model. CONCLUSION Here we report a novel splicing mutation IVS7 +3A>G, identified in a family with mild form LQT1 phenotypes, and examined functional outcome in comparison with three other variants around the exon 7-intron 7 junction. In addition to c.1032G>A mutation, IVS7 +3A>G generates exon-skipping mRNAs, and thereby causing LQT1 phenotype. The severity of clinical phenotypes appeared to differ between the two splicing-related mutations and to result from the amount of resultant mRNAs and their functional consequences.
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Affiliation(s)
- Keiko Tsuji-Wakisaka
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan
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Huang K. A K+ channel that channels neurology to nephrology. Clin Genet 2010; 77:230-1. [DOI: 10.1111/j.1399-0004.2009.01322.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Hedley PL, Jørgensen P, Schlamowitz S, Wangari R, Moolman-Smook J, Brink PA, Kanters JK, Corfield VA, Christiansen M. The genetic basis of long QT and short QT syndromes: A mutation update. Hum Mutat 2009; 30:1486-511. [DOI: 10.1002/humu.21106] [Citation(s) in RCA: 318] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Affiliation(s)
- Dan M Roden
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232-0575, USA.
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Daneshi A, Ghassemi MM, Talee M, Hassanzadeh S. Cochlear implantation in children with Jervell, Lange-Nielsen syndrome. J Laryngol Otol 2007; 122:314-7. [PMID: 17498328 DOI: 10.1017/s0022215107007712] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Jervell, Lange-Nielsen syndrome is a condition that causes profound hearing loss and disruption of the normal cardiac rhythm. This disorder is a form of long QT syndrome, a cardiac disorder that causes the cardiac muscle to take longer than usual to recharge between beats. A retrospective case study was performed to document cochlear implantation in three profoundly deaf children (two of them siblings) with Jervell, Lange-Nielsen syndrome. We discuss diagnosis and management of this syndrome and also the long-term performance of cochlear implantation in these Iranian patients, referring especially to the role of the ENT specialist in diagnosis and treatment. The collected data show that cochlear implantation can be relatively safely performed in patients with Jervell, Lange-Nielsen syndrome and that these children received significant benefit from cochlear implantation.
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Affiliation(s)
- A Daneshi
- Head and Neck Surgery Department, Iran University of Medical Sciences, Tehran, Iran
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Tsuji K, Akao M, Ishii TM, Ohno S, Makiyama T, Takenaka K, Doi T, Haruna Y, Yoshida H, Nakashima T, Kita T, Horie M. Mechanistic basis for the pathogenesis of long QT syndrome associated with a common splicing mutation in KCNQ1 gene. J Mol Cell Cardiol 2007; 42:662-9. [PMID: 17292394 DOI: 10.1016/j.yjmcc.2006.12.015] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2006] [Revised: 12/15/2006] [Accepted: 12/28/2006] [Indexed: 01/06/2023]
Abstract
Mutations in KCNQ1, the gene encoding the delayed rectifier K(+) channel in cardiac muscle, cause long QT syndrome (LQTS). We studied 3 families with LQTS, in whom a guanine to adenine change in the last base of exon 7 (c.1032G>A), previously reported as a common splice-site mutation, was identified. We performed quantitative measurements of exon-skipping KCNQ1 mRNAs caused by this mutation using real-time reverse transcription polymerase chain reaction. Compared with normal individuals who have minor fractions of splicing variants (Delta7-8: 0.1%, Delta8: 6.9%, of total KCNQ1 transcripts), the affected individuals showed remarkable increases of exon-skipping mRNAs (Delta7: 23.5%, Delta7-8: 16.8%, Delta8: 4.5%). Current recordings from Xenopus laevis oocytes heterologously expressing channels of wild-type (WT) or exon-skipping KCNQ1 (Delta7, Delta7-8, or Delta8) revealed that none of the mutants produced any measurable currents, and moreover they displayed mutant-specific degree of dominant-negative effects on WT currents, when co-expressed with WT. Confocal microscopy analysis showed that fluorescent protein-tagged WT was predominantly expressed on the plasma membrane, whereas the mutants showed intracellular distribution. When WT was co-expressed with mutants, the majority of WT co-localized with the mutants in the intracellular space. Finally, we provide evidence showing direct protein-protein interactions between WT and the mutants, by using fluorescence resonance energy transfer. Thus, the mutants may exert their dominant-negative effects by trapping WT intracellularly and thereby interfering its translocation to the plasma membrane. In conclusion, our data provide a mechanistic basis for the pathogenesis of LQTS caused by a splicing mutation in KCNQ1.
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Affiliation(s)
- Keiko Tsuji
- Department of Cardiovascular Medicine, Kyoto University Graduate School of Medicine, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
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Anastasakis A, Kotta CM, Kyriakogonas S, Wollnik B, Theopistou A, Stefanadis C. Phenotype reveals genotype in a Greek long QT syndrome family. ACTA ACUST UNITED AC 2006; 8:241-4. [PMID: 16627448 DOI: 10.1093/europace/eul012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
We aimed to verify the long QT syndrome (LQTS) genotype in a family with strong evidence of LQTS type 1 (LQT1) on the basis of so far established genotype-phenotype correlations. Genetic testing for mutations in the KCNQ1 potassium channel gene revealed an A341V mutation in three generations of the family. Existing genotype-phenotype correlations were correctly predictive of the genotype in the case of this family, despite the fact that there are no previously reported data for the Greek LQTS genetic pool. Thus, genotype-phenotype correlations are often a helpful tool in the management of LQTS patients and their families.
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Affiliation(s)
- Aris Anastasakis
- Division of Inherited Cardiovascular Diseases, 1st Department of Cardiology, University of Athens Medical School, l99 Michalakopoulou Street, Athens 11528, Greece
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17
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Fodstad H, Bendahhou S, Rougier JS, Laitinen-Forsblom PJ, Barhanin J, Abriel H, Schild L, Kontula K, Swan H. Molecular characterization of two founder mutations causing long QT syndrome and identification of compound heterozygous patients. Ann Med 2006; 38:294-304. [PMID: 16754261 DOI: 10.1080/07853890600756065] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Mutations of at least six different genes have been found to cause long QT syndrome (LQTS), an inherited arrhythmic disorder characterized by a prolonged QT interval on the electrocardiogram (ECG), ventricular arrhythmias and risk of sudden death. AIM The aims were to define the yet undetermined phenotypic characteristics of two founder mutations and to study clinical features in compound heterozygotes identified during the course of the study. METHODS To maximize identification of the compound heterozygotes, we used an extended group of LQTS patients comprising 700 documented or suspected cases. Functional studies were carried out upon transient expression in COS-7 or HEK293 cells. RESULTS The KCNQ1 IVS7-2A>G (KCNQ1-FinB) mutation associated with a mean QTc interval of 464 ms and a complete loss-of-channel function. The HERG R176W (HERG-FinB) mutation caused a reduction in current density as well as slight acceleration of the deactivation kinetics in vitro, and its carriers had a mean QTc of 448 ms. The HERG R176W mutation was also present in 3 (0.9%) out of 317 blood donors. A total of six compound heterozygotes were identified who had the HERG R176W mutation in combination with a previously reported LQTS mutation (KCNQ1 G589D or IVS7-2A>G). When present simultaneously with an apparent LQTS-causing mutation, the HERG R176W mutation may exert an additional in vivo phenotypic effect. CONCLUSIONS The HERG R176W mutation represents a population-prevalent mutation predisposing to LQTS. Compound heterozygosity for mutant LQTS genes may modify the clinical picture in LQTS.
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Affiliation(s)
- Heidi Fodstad
- Biomedicum Helsinki and Department of Medicine, University of Helsinki, Finland, and Service of Cardiology, University Hospital, Lausanne, Switzerland.
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18
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Friedlander Y, Vatta M, Sotoodehnia N, Sinnreich R, Li H, Manor O, Towbin JA, Siscovick DS, Kark JD. Possible association of the human KCNE1 (minK) gene and QT interval in healthy subjects: evidence from association and linkage analyses in Israeli families. Ann Hum Genet 2005; 69:645-56. [PMID: 16266404 DOI: 10.1046/j.1529-8817.2005.00182.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
QT interval prolongation is associated with increased risk of sudden and non-sudden cardiac death. Potassium channel gene variants are associated with inherited long QT syndromes. Using linkage and association analyses, we investigated whether variants in the potassium channel subunit KCNE1 are associated with QTc intervals in an unselected population sample of 80 kindreds living in kibbutz settlements in Israel. Variance-component linkage analysis revealed weak evidence of linkage of KCNE1 polymorphisms with QTc intervals. Family-based association analysis showed a significant association between the G38S polymorphism and QTc interval. Further quantitative trait association analysis demonstrated a significant residual heritability component (h(2)= 0.33), and that the effect of the G38S variant allele is modified by gender. Estimated maximum likelihood parameters from these models indicated that male gender, age, hypertension, diabetes, hypercholesterolemia, fibrinogen and BMI were positively associated with QTc interval; level of education and cigarette smoking showed an inverse association. Both erythrocyte membrane n-6 and n-3 fatty acids showed a significant inverse association with QTc interval. While more than 15.8% of QTc variability was contributed by covariates, another 4.7% was explained by dietary factors, the G38S polymorphism explained 2.2%, and approximately 36% was explained by polygenes. An in silico analysis showed also that the novel V80 SNP, another KCNE1 synonymous variant, abolishes the recognition for a splicing enhancer, which may lead to an increased effect of the G38S mutation. These results demonstrate that, in addition to polygenic background, dietary factors and other covariables, the KCNE1 G38S variant is involved in determining QTc levels in this population-based sample of families.
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Affiliation(s)
- Y Friedlander
- Unit of Epidemiology, Hebrew University-Hadassah School of Public Health, POB 12272, Jerusalem 91120, Israel.
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19
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Tian W, Fu Y, Wang DH, Cohen DM. Regulation of TRPV1 by a novel renally expressed rat TRPV1 splice variant. Am J Physiol Renal Physiol 2005; 290:F117-26. [PMID: 16091583 DOI: 10.1152/ajprenal.00143.2005] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The capsaicin receptor and transient receptor potential channel TRPV1 senses heat, protons, and vanilloid agonists in peripheral sensory ganglia. Abundant data have suggested the presence of potentially novel splice variants in the kidney. We report a novel rat TRPV1 splice variant, TRPV1(VAR), cloned from kidney papilla. TRPV1(VAR) cDNA was identified in multiple kidney tissues. Its sequence was fully compatible with potential splice donor and acceptor sites in the rat TRPV1 gene. TRPV1(VAR) is predicted to encode a truncated form of TRPV1 consisting of the NH2-terminal 248 residues of TRPV1 (all within the NH2-terminal intracellular domain) followed by five nonconsensus amino acids (Arg-Glu-Ala-Met-Trp) and a stop codon. The variant utilizes the same consensus Kozak sequence as canonical TRPV1. A band of the appropriate molecular mass was identified in rat kidney papillary (but not medullary) lysates immunoblotted with an antibody directed against the NH2 terminus of TRPV1, whereas an antibody recognizing the TRPV1 COOH terminus failed to detect it. Upon heterologous expression in HEK 293 cells, TRPV1(VAR) potentiated the ability of cotransfected TRPV1 to confer calcium influx in response to resiniferatoxin. TRPV1(VAR) did not influence expression or cell surface localization of cotransfected TRPV1. TRPV1(VAR) protein product associated with the NH2 terminus of canonical TRPV1. Interestingly, when expressed in the COS-7 epithelial cell line, TRPV1(VAR) functioned in a dominant-negative acting capacity, partially blocking TRPV1-dependent resiniferatoxin responsiveness. We conclude that TRPV1(VAR) is one of perhaps several TRPV1 splice variants expressed in rat kidney and that it may serve to modulate TRPV1 responsiveness in some tissues.
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Affiliation(s)
- Wei Tian
- Division of Nephrology and Hypertension, Department of Medicine, Oregon Health & Science University and the Portland Veterans Affairs Medical Center, Portland, OR 97239, USA
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20
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Towbin JA, Vatta M, Wang Z, Bowles NE, Li H. Emerging targets in the long QT syndromes and Brugada syndrome. ACTA ACUST UNITED AC 2005. [DOI: 10.1517/14728222.3.3.423] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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21
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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] [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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22
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Abstract
This article outlines the up-to-date understanding of the molecular basis of disorders that cause sudden death. Several arrhythmic disorders that cause sudden death have been well-described at the molecular level, including the long QT syndromes and Brugada syndrome; this article reviews the current scientific knowledge of these diseases. Hypertrophic cardiomyopathy, a myocardial disorder that causes sudden death also has been well-studied. Finally, a disorder in which myocardial abnormalities and rhythm abnormalities coexist, arrhythmogenic right ventricular dysplasia, is described.
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MESH Headings
- Arrhythmias, Cardiac/genetics
- Arrhythmias, Cardiac/physiopathology
- Arrhythmogenic Right Ventricular Dysplasia/genetics
- Arrhythmogenic Right Ventricular Dysplasia/physiopathology
- Cardiomyopathy, Hypertrophic, Familial/genetics
- Cardiomyopathy, Hypertrophic, Familial/physiopathology
- Child
- Death, Sudden, Cardiac/etiology
- ERG1 Potassium Channel
- Ether-A-Go-Go Potassium Channels
- Humans
- KCNQ Potassium Channels
- KCNQ1 Potassium Channel
- Long QT Syndrome/complications
- Long QT Syndrome/genetics
- Long QT Syndrome/therapy
- NAV1.5 Voltage-Gated Sodium Channel
- Potassium Channels/physiology
- Potassium Channels, Voltage-Gated
- Sodium Channels/physiology
- Syndrome
- Tachycardia, Ventricular/genetics
- Wolff-Parkinson-White Syndrome/physiopathology
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Affiliation(s)
- Jeffrey A Towbin
- Department of Pediatrics (Cardiology), Texas Children's Hospital and Baylor College of Medicine, 6621 Fannin Street, FC. 430.09, Houston, TX 77030, USA.
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23
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Abstract
PURPOSE OF REVIEW The understanding of the etiology of congenital cardiac lesions is rapidly progressing from the recognition of embryologic origins to insight into the genetic basis for these disorders. Concurrently, in this era, great effort is being expended to gather data that will generate clinically useful genotype-phenotype correlation. This rapidly evolving area of inquiry, in which the clinical implications of mutation status are fully explored, makes available information applicable to those involved in all aspects of congenital cardiac disease. RECENT FINDINGS Three syndromes with cardiovascular phenotypes were selected for review. Each has received a great deal of attention in the recent past based on improved understanding of the range of mutations expressed and the relation of these mutations to clinical findings. These three syndromes--Noonan, Marfan, and long QT syndrome--span the range of congenital heart disease and provide examples of genotype-phenotype correlation. SUMMARY Better understanding of the clinical implications of specific mutations should allow not only for more sensitive and specific diagnoses to be made but also for improvements in therapeutic options and efficacy.
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Affiliation(s)
- Mark B Lewin
- Division of Pediatric Cardiology, Children's Hospital and Regional Medical Center, and Department of Pediatrics, University of Washington School of Medicine, Seattle, 98105, USA.
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24
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Kobori A, Sarai N, Shimizu W, Nakamura Y, Murakami Y, Makiyama T, Ohno S, Takenaka K, Ninomiya T, Fujiwara Y, Matsuoka S, Takano M, Noma A, Kita T, Horie M. Additional Gene Variants Reduce Effectiveness of Beta-Blockers in the LQT1 Form of Long QT Syndrome. J Cardiovasc Electrophysiol 2004; 15:190-9. [PMID: 15028050 DOI: 10.1046/j.1540-8167.2004.03212.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
INTRODUCTION Beta-blockers are widely used to prevent the lethal cardiac events associated with the long QT syndrome (LQTS), especially in KCNQ1-related LQTS (LQT1) patients. Some LQT1 patients, however, are refractory to this therapy. METHODS AND RESULTS Eighteen symptomatic LQTS patients (12 families) were genetically diagnosed as having heterozygous KCNQ1 variants and received beta-blocker therapy. Cardiac events recurred in 4 members (3 families) despite continued therapy during mean follow-up of 70 months. Three of these patients (2 families) had the same mutation [A341V (KCNQ1)]; and the other had R243H (KCNQ1). The latter patient took aprindine, which seemed to be responsible for the event. By functional assay using a heterologous mammalian expression system, we found that A341V (KCNQ1) is a loss-of-function type mutation (not dominant negative). Further genetic screening revealed that one A341V (KCNQ1) family cosegregated with S706C (KCNH2) and another with G144S (KCNJ2). Functional assay of the S706C (KCNH2) mutation was found to reduce the current density of expressed heterozygous KCNH2 channels with a positive shift (+8 mV) of the activation curve. Action potential simulation study was conducted based on the KYOTO model to estimate the influence of additional gene modifiers. In both models mimicking LQT1 plus 2 and LQT1 plus 7, the incidence of early afterdepolarization was increased compared with the LQT1 model under the setting of beta-adrenergic stimulation. CONCLUSION Multiple mutations in different LQTS-related genes may modify clinical characteristics. Expanded gene survey may be required in LQT1 patients who are resistant to beta-blocker therapy.
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Affiliation(s)
- Atsushi Kobori
- Department of Cardiovascular Medicine, Kyoto University Graduate School of Medicine, Kyoto, Japan
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25
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Chen R, Tsuji T, Ichida F, Bowles KR, Yu X, Watanabe S, Hirono K, Tsubata S, Hamamichi Y, Ohta J, Imai Y, Bowles NE, Miyawaki T, Towbin JA. Mutation analysis of the G4.5 gene in patients with isolated left ventricular noncompaction. Mol Genet Metab 2002; 77:319-25. [PMID: 12468278 DOI: 10.1016/s1096-7192(02)00195-6] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Mutations in the gene G4.5, originally associated with Barth syndrome, have been reported to result in a wide spectrum of severe infantile X-linked cardiomyopathies. The purpose of this study was to investigate patients with isolated left ventricular noncompaction (LVNC) for disease-causing mutations in G4.5. In 27 patients including 10 families with isolated LVNC, mutation analysis of G4.5 was performed using single-strand DNA conformation polymorphism (SSCP) analysis and DNA sequencing. A novel splice acceptor site mutation of intron 8 of G4.5 was identified in a family with severe infantile X-linked LVNC without the usual findings of Barth syndrome. This mutation results in deletion of exon 9 from the mRNA, and is predicted to significantly disrupt the protein product. Genotype-phenotype correlation of G4.5 mutations in all 38 cases reported in the literature to date revealed that there was no correlation between location or type of mutation and either cardiac phenotype or disease severity. We suggest that males presenting with cardiomyopathy, particularly during infancy, even in the absence of the typical signs of Barth syndrome, should be evaluated for mutations in G4.5.
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Affiliation(s)
- Rui Chen
- Department of Pediatrics, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194, Japan
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26
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Anderson ME, Al-Khatib SM, Roden DM, Califf RM. Cardiac repolarization: current knowledge, critical gaps, and new approaches to drug development and patient management. Am Heart J 2002; 144:769-81. [PMID: 12422144 DOI: 10.1067/mhj.2002.125804] [Citation(s) in RCA: 121] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Mark E Anderson
- Vanderbilt University Medical Center, Nashville, Tenn 37232-6300, USA.
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27
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Wang Z, Li H, Moss AJ, Robinson J, Zareba W, Knilans T, Bowles NE, Towbin JA. Compound heterozygous mutations in KvLQT1 cause Jervell and Lange-Nielsen syndrome. Mol Genet Metab 2002; 75:308-16. [PMID: 12051962 DOI: 10.1016/s1096-7192(02)00007-0] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Jervell and Lange-Nielsen syndrome (JLNS) is characterized by sensorineural deafness, QT prolongation, abnormal T waves, ventricular tachyarrhythmias, and autosomal recessive inheritance. Previously homozygous mutations in the potassium channel-encoding genes, KvLQT1 (alpha-subunit) and KCNE1 (beta-subunit), have been described in consanguineous families with JLNS. We screened two nonconsanguineous families with JLNS for mutations in KvLQT1, using single-strand conformation polymorphism analysis, denaturing high-performance liquid chromatography, and DNA sequencing. In one family, a missense mutation was identified in exon 6 of KvLQT1 on the maternal side, resulting in a glycine to aspartic acid substitution at codon 269 (G269D). The apparently normal father had an incompletely penetrant missense mutation in exon 3 of KvLQT1, introducing a premature stop codon at position 171. In the other family, a missense mutation resulting in the substitution of asparagine for aspartic acid at codon 202 (D202N) was identified in the mother and maternal grandmother, who had QTc prolongation (borderline in the mother), while the father and paternal grandfather, who were clinically normal, had a deletion of nucleotide 585, resulting in a frameshift and premature termination. In both families, the proband inherited both mutations. In this report we provide evidence that not only homozygous but also compound heterozygous mutations in KvLQT1 may cause JLNS in nonconsanguineous families. Incomplete penetrance in individuals with mutations appears to be frequent, indicating a higher prevalence of mutations than estimated previously. Interestingly, mutations resulting in truncation of the protein appear to be benign, with heterozygous carriers being asymptomatic.
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Affiliation(s)
- Zhiqing Wang
- Department of Medicine (Cardiovascular Sciences), Baylor College of Medicine, Houston, TX 77030, USA
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28
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Abstract
In this review, the up-to-date understanding of the molecular basis of disorders causing sudden death will be described. Two arrhythmic disorders causing sudden death have recently been well described at the molecular level, the long QT syndromes (LQTS) and Brugada syndrome, and in this article we will review the current scientific knowledge of each disease. A third disorder, hypertrophic cardiomyopathy (HCM), a myocardial disorder causing sudden death, has also been well studied. Finally, a disorder in which both myocardial abnormalities and rhythm abnormalities coexist, arrhythmogenic right ventricular dysplasia (ARVD) will also be described. The role of the pathologist in these studies will be highlighted.
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MESH Headings
- Animals
- Arrhythmogenic Right Ventricular Dysplasia/genetics
- Arrhythmogenic Right Ventricular Dysplasia/pathology
- Arrhythmogenic Right Ventricular Dysplasia/physiopathology
- Cardiomyopathy, Hypertrophic, Familial/genetics
- Cardiomyopathy, Hypertrophic, Familial/pathology
- Cardiomyopathy, Hypertrophic, Familial/physiopathology
- Death, Sudden, Cardiac/etiology
- Death, Sudden, Cardiac/pathology
- Dogs
- Genetic Predisposition to Disease
- Humans
- Ion Channels
- Long QT Syndrome/genetics
- Long QT Syndrome/pathology
- Long QT Syndrome/physiopathology
- Molecular Biology
- Ventricular Fibrillation/genetics
- Ventricular Fibrillation/pathology
- Ventricular Fibrillation/physiopathology
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Affiliation(s)
- J A Towbin
- Department of Pediatrics (Cardiology), Texas Children's Hospital and Baylor College of Medicine, One Baylor Plaza, Room 333E, Houston, TX 77030, USA.
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29
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Lawson K, Dunne MJ. Peripheral channelopathies as targets for potassium channel openers. Expert Opin Investig Drugs 2001; 10:1345-59. [PMID: 11772256 DOI: 10.1517/13543784.10.7.1345] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Potassium channel openers (KCOs) are important tools that are often used to gain a greater understanding of K(+) channels. Agents that can induce or maintain the opening of K(+) channels also offer a therapeutic approach to controlling of cell excitability and offer a means of producing stability in biological systems. The pathogenesis of a broad range of peripheral disorders (e.g., LQT syndrome, hypokalemic periodic paralysis, hyperinsulinism in infancy and erectile dysfunction) are associated with dysfunctional K(+) channels due to mutations in genes encoding channel proteins. The therapeutic potential of KCOs in peripheral K(+) channelopathies is discussed. The identification of K(+) channel subtype-specific openers offers discrete modulation of cellular systems creating a realistic therapeutic advance in the treatment of K(+) channelopathies.
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Affiliation(s)
- K Lawson
- Division of Biomedical Sciences, Sheffield Hallam University, School of Science and Mathematics, City Campus, Sheffield, S1 1WB, UK.
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30
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Towbin JA, Vatta M, Li H. Genetics of brugada, long QT, and arrhythmogenic right ventricular dysplasia syndromes. J Electrocardiol 2001; 33 Suppl:11-22. [PMID: 11265709 DOI: 10.1054/jelc.2000.20361] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
This article outlines the up-to-date understanding of the molecular basis of primary ventricular arrhythmias. Two disorders have recently been well described at the molecular level, the long QT syndromes and Brugada syndrome, and this article reviews the current scientific knowledge of each disease. A third disorder, arrhythmogenic right ventricular dysplasia, which is on the cusp of understanding, will also be described.
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Affiliation(s)
- J A Towbin
- Department of Pediatrics (Cardiology), Texas Children's Hospital and Baylor College of Medicine, Houston 77030, USA.
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31
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Abstract
The prolonged QT syndromes are characterized by prolongation of the QT interval corrected for heart rate (QTc) on the surface electrocardiogram associated with T-wave abnormalities, relative bradycardia, and ventricular tachyarrhythmias, including polymorphic ventricular tachycardia and torsades de pointes. These patients tend to present with episodes of syncope, seizures, or sudden death typically triggered by exercise, emotion, noise, or, in some cases, sleep. These disorders of cardiac repolarization are commonly inherited, with the autosomal dominant form, Romano-Ward syndrome, most common. A rare autosomal recessive form associated with sensorineural deafness, Jervell and Lange-Nielsen syndrome, in which the cardiac disorder is autosomal dominant and deafness is a recessive trait, also occurs. The underlying genetic causes of these forms of prolonged QT interval syndromes are heterogeneous, with at least seven genes responsible for the clinical syndromes. All of the five genes identified to date encode ion channel proteins, suggesting this to be an ion channelopathy. In this review, the genetic basis of the prolonged QT interval syndromes will be discussed, genotype-phenotype correlations identified, and the approaches to genetic testing and treatments will be outlined.
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Affiliation(s)
- J A Towbin
- Department of Pediatrics (Cardiology), Baylor College of Medicine, Houston, Texas 77030, USA
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32
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Yamashita F, Horie M, Kubota T, Yoshida H, Yumoto Y, Kobori A, Ninomiya T, Kono Y, Haruna T, Tsuji K, Washizuka T, Takano M, Otani H, Sasayama S, Aizawa Y. Characterization and subcellular localization of KCNQ1 with a heterozygous mutation in the C terminus. J Mol Cell Cardiol 2001; 33:197-207. [PMID: 11162126 DOI: 10.1006/jmcc.2000.1300] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Numerous mutations in KCNQ1, a gene encoding the alpha -subunit of cardiac delayed rectifier potassium channels, have been found in long QT syndrome (LQTS). Among them, several mutations in the C terminus have been shown to cause autosomal recessive or subclinical autosomal dominant LQTS. Here, we report a heterozygous mutation, T587M, which is also in the KCNQ1 C-terminal domain. The same mutation was found in three independent probands that were clearly symptomatic with family history of cardiac sudden death. Functional assay using a heterologous expression system with a mammalian cell line (COS7 cells) revealed that the mutant displayed neither functional channels when expressed alone nor dominant-negative effect when co-expressed with wild-type (WT) KCNQ1. To examine the cellular trafficking of KCNQ1, green fluorescent protein (GFP) was tagged to the cytoplasmic C terminus of WT or mutant KCNQ1. This procedure did not affect the essential properties of expressed WT KCNQ1 channels. On confocal microscopic images, GFP-tagged WT KCNQ1 showed a plasma membrane fluorescence pattern, whereas the GFP-tagged mutant showed a perinuclear fluorescence pattern. Co-expression of the mutant with GFP-tagged WT KCNQ1 did not influence its normal cellular transport. Therefore, the T587M mutant cannot traffic to the plasma membrane and may form no subunit assembly with WT KCNQ1. These findings provide a novel molecular basis for the clinical finding that this C-terminal mutation produced a severe form of RWS-type LQTS.
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Affiliation(s)
- F Yamashita
- First Department of Internal Medicine, Niigata University School of Medicine, Niigata, 951-8510, Japan
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33
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Abstract
OBJECTIVES To describe the state of the art of our understanding of the long QT syndromes and to provide the genetic correlation of clinical severity of patients with this disorder. DATE SOURCES In this review, we outline data that were obtained from work in our laboratory, as well as information reported in the literature. STUDY SELECTION The information in this review spans the last decade; data were obtained from the studies that had the most impact, as well as from recent work at our laboratory. DATA EXTRACTION The data reported herein were extracted from the world literature on sudden death and the clinical aspects of long QT syndrome. The genes identified to date, mutations in these genes, and the biophysical perturbations in the mutated ion channels, as well as the severity of disease, are detailed. DATA SYNTHESIS The extracted data are described as a state-of-the-art review. CONCLUSIONS The long QT syndromes, genetically heterogeneous disorders due to mutations in genes encoding ion channels, are relatively common causes of syncope and sudden death. The affected genes, along with the genetic background of individuals, determine the clinical severity of disease. An understanding of the mechanisms responsible for long QT syndrome is expected to enable development of specific therapies.
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Affiliation(s)
- J A Towbin
- Department of Pediatrics, Texas Children's Hospital and Baylor College of Medicine, Houston 77030, USA
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Bianchi L, Priori SG, Napolitano C, Surewicz KA, Dennis AT, Memmi M, Schwartz PJ, Brown AM. Mechanisms of I(Ks) suppression in LQT1 mutants. Am J Physiol Heart Circ Physiol 2000; 279:H3003-11. [PMID: 11087258 DOI: 10.1152/ajpheart.2000.279.6.h3003] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mutations in the cardiac potassium ion channel gene KCNQ1 (voltage-gated K(+) channel subtype KvLQT1) cause LQT1, the most common type of hereditary long Q-T syndrome. KvLQT1 mutations prolong Q-T by reducing the repolarizing cardiac current [slow delayed rectifier K(+) current (I(Ks) )], but, for reasons that are not well understood, the clinical phenotypes may vary considerably even for carriers of the same mutation, perhaps explaining the mode of inheritance. At present, only currents expressed by LQT1 mutants have been studied, and it is unknown whether abnormal subunits are transported to the cell surface. Here, we have examined for the first time trafficking of KvLQT1 mutations and correlated the results with the I(Ks) currents that were expressed. Two missense mutations, S225L and A300T, produced abnormal currents, and two others, Y281C and Y315C, produced no currents. However, all four KvLQT1 mutations were detected at the cell surface. S225L, Y281C, and Y315C produced dominant negative effects on wild-type I(Ks) current, whereas the mutant with the mildest dysfunction, A300T, did not. We examined trafficking of a severe insertion deletion mutant Delta544 and detected this protein at the cell surface as well. We compared the cellular and clinical phenotypes and found a poor correlation for the severely dysfunctional mutations.
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Affiliation(s)
- L Bianchi
- The Rammelkamp Center for Education and Research, MetroHealth Campus, Case Western Reserve University, Cleveland, Ohio 44109-1998, USA
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Kubota T, Shimizu W, Kamakura S, Horie M. Hypokalemia-induced long QT syndrome with an underlying novel missense mutation in S4-S5 linker of KCNQ1. J Cardiovasc Electrophysiol 2000; 11:1048-54. [PMID: 11021476 DOI: 10.1111/j.1540-8167.2000.tb00178.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Congenital long QT syndrome (LQTS) is caused by mutations in at least five genes coding for cardiac potassium or sodium channels that regulate the duration of ventricular action potentials. Acquired LQTS often is associated with drugs or metabolic abnormalities. A 47-year-old woman who presented with marked QT prolongation (QTc = 620 msec(1/2)) and repeated episodes of torsades de pointes associated with hypokalemia (2.6 mEq/L) was screened for mutations in LQTS genes using polymerase chain reaction/single-strand conformation polymorphism (PCR/SSCP). We identified a novel missense mutation in the intracellular linker of S4-S5 domains of KCNQ1, resulting in an amino acid substitution of cysteine for arginine at position 259 (R259C). Whole cell, patch clamp experiments were conducted on COS7 cells transfected with wild-type and/or R259C KCNQ1 with or without KCNE1. Functional analyses of the mutant KCNQ1 subunit on COS7 cells revealed its functional channels in the homozygous state, producing a significantly smaller current than the KCNQ1 channels and a less severe dominant-negative effect on I(Ks). The novel KCNQ1 mutation R259C is the molecular basis for I(Ks) dysfunction underlying an apparently sporadic case of hypokalemia-induced LQTS, consistent with a mild mutation likely to disclose the clinical manifestation of LQTS in a context of severe hypokalemia. Our findings suggest that gene carriers with such mild mutations might not be so rare as commonly expected in patients with acquired LQTS, and stress the importance of mutational analysis for detecting either "silent" forms of congenital LQTS or de novo mutations.
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Affiliation(s)
- T Kubota
- Department of Internal Medicine, National Cardiovascular Center, Suita, Osaka, Japan
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Affiliation(s)
- R Warth
- Physiologisches Institut, Abt. II, Freiburg, Germany
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37
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Abstract
It is becoming clear that mutations in the KVLQT1, human "ether-a-go-go" related gene, cardiac voltage-dependent sodium channel gene, minK and MiRP1 genes, respectively, are responsible for the LQT1, LQT2, LQT3, LQT5 and LQT6 variants of the Romano-Ward syndrome, characterized by autosomal dominant transmission and no deafness. The much rarer Jervell-Lange-Nielsen syndrome (with marked QT prolongation and sensorineural deafness) arises when a child inherits mutant KVLQT1 or minK alleles from both parents. In addition, some families are not linked to the known genetic loci. Cardiac voltage-dependent sodium channel gene encodes the cardiac sodium channel, and long QT syndrome (LQTS) mutations prolong action potentials by increasing inward plateau sodium current. The other mutations cause a decrease in net repolarizing current by reducing potassium currents through "dominant negative" or "loss of function" mechanisms. Polymorphic ventricular tachycardia (torsade de pointes) is thought to be initiated by early after-depolarizations in the Purkinje system and maintained by reentry in the myocardium. Clinical presentations vary with the specific gene affected and the specific mutation. Nevertheless, patients with identical mutations can also present differently, and some patients with LQTS mutations may have no manifest baseline phenotype. The question of whether the latter situation is one of high risk for administration of QT prolonging drugs or during myocardial ischemia is under active investigation. More generally, the identification of LQTS genes has provided tremendous new insights for our understanding of normal cardiac electrophysiology and its perturbation in a wide range of conditions associated with sudden death. It seems likely that the approach of applying information from the genetics of uncommon congenital syndromes to the study of common acquired diseases will be an increasingly important one in the next millennium.
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Affiliation(s)
- C E Chiang
- Department of Medicine, Taipei Veterans General Hospital and National Yang-Ming University School of Medicine, Taiwan.
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Larsen LA, Christiansen M, Vuust J, Andersen PS. High-throughput single-strand conformation polymorphism analysis by automated capillary electrophoresis: robust multiplex analysis and pattern-based identification of allelic variants. Hum Mutat 2000; 13:318-27. [PMID: 10220146 DOI: 10.1002/(sici)1098-1004(1999)13:4<318::aid-humu9>3.0.co;2-f] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Genetic diagnosis of an inherited disease or cancer often involves analysis for unknown point mutations in several genes; therefore, rapid and automated techniques that can process a large number of samples are needed. We describe a method for high-throughput single-strand conformation polymorphism (SSCP) analysis using automated capillary electrophoresis. The operating temperature of a commercially available capillary electrophoresis instrument (ABI PRISM 310) was expanded by installation of a cheap in-house designed cooling system, thereby allowing us to perform automated SSCP analysis at 14-45 degrees C. We have used the method for detection of point mutations associated with the inherited cardiac disorders long QT syndrome (LQTS) and hypertrophic cardiomyopathy (HCM). The sensitivity of the method was 100% when 34 different point mutations were analyzed, including two previously unpublished LQTS-associated mutations (F157C in KVLQT1 and G572R in HERG), as well as eight novel normal variants in HERG and MYH7. The analyzed polymerase chain reaction (PCR) fragments ranged in size from 166 to 1,223 bp. Seventeen different sequence contexts were analyzed. Three different electrophoresis temperatures were used to obtain 100% sensitivity. Two mutants could not be detected at temperatures greater than 20 degrees C. The method has a high resolution and good reproducibility and is very robust, making multiplex SSCP analysis and pattern-based identification of known allelic variants as single nucleotide polymorphisms (SNPs) possible. These possibilities, combined with automation and short analysis time, make the method suitable for high-throughput tasks, such as genetic screening.
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Affiliation(s)
- L A Larsen
- Department of Clinical Biochemistry, Statens Serum Institut, Copenhagen, Denmark
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Jongbloed RJ, Wilde AA, Geelen JL, Doevendans P, Schaap C, Van Langen I, van Tintelen JP, Cobben JM, Beaufort-Krol GC, Geraedts JP, Smeets HJ. Novel KCNQ1 and HERG missense mutations in Dutch long-QT families. Hum Mutat 2000; 13:301-10. [PMID: 10220144 DOI: 10.1002/(sici)1098-1004(1999)13:4<301::aid-humu7>3.0.co;2-v] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Congenital long QT syndrome (cLQTS) is electrocardiographically characterized by a prolonged QT interval and polymorphic ventricular arrhythmias (torsade de pointes). These cardiac arrhythmias may result in recurrent syncopes, seizure, or sudden death. LQTS can occur either as an autosomal dominant (Romano Ward) or as an autosomal recessive disorder (Jervell and Lange-Nielsen syndrome). Mutations in at least five genes have been associated with the LQTS. Four genes, encoding cardiac ion channels, have been identified. The most common forms of LQTS are due to mutations in the potassium-channel genes KCNQ1 and HERG. We have screened 24 Dutch LQTS families for mutations in KCNQ1 and HERG. Fourteen missense mutations were identified. Eight of these missense mutations were novel: three in KCNQ1 and five in HERG. Novel missense mutations in KCNQ1 were Y184S, S373P, and W392R and novel missense mutations in HERG were A558P, R582C, G604S, T613M, and F640L. The KCNQ1 mutation G189R and the HERG mutation R582C were detected in two families. The pathogenicity of the mutations was based on segregation in families, absence in control individuals, the nature of the amino acid substitution, and localization in the protein. Genotype-phenotype studies indicated that auditory stimuli as trigger of cardiac events differentiate LQTS2 and LQTS1. In LQTS1, exercise was the predominant trigger. In addition, a number of asymptomatic gene defect carriers were identified. Asymptomatic carriers are still at risk of the development of life-threatening arrhythmias, underlining the importance of DNA analyses for unequivocal diagnosis of patients with LQTS.
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Affiliation(s)
- R J Jongbloed
- Department of Molecular Cell Biology and Genetics, Cardiovascular Research Institute Maastricht, University of Maastricht, The Netherlands.
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Schmitt N, Schwarz M, Peretz A, Abitbol I, Attali B, Pongs O. A recessive C-terminal Jervell and Lange-Nielsen mutation of the KCNQ1 channel impairs subunit assembly. EMBO J 2000; 19:332-40. [PMID: 10654932 PMCID: PMC305570 DOI: 10.1093/emboj/19.3.332] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/1999] [Revised: 11/30/1999] [Accepted: 11/30/1999] [Indexed: 01/08/2023] Open
Abstract
The LQT1 locus (KCNQ1) has been correlated with the most common form of inherited long QT (LQT) syndrome. LQT patients suffer from syncopal episodes and high risk of sudden death. The KCNQ1 gene encodes KvLQT1 alpha-subunits, which together with auxiliary IsK (KCNE1, minK) subunits form IK(s) K(+) channels. Mutant KvLQT1 subunits may be associated either with an autosomal dominant form of inherited LQT, Romano-Ward syndrome, or an autosomal recessive form, Jervell and Lange-Nielsen syndrome (JLNS). We have identified a small domain between residues 589 and 620 in the KvLQT1 C-terminus, which may function as an assembly domain for KvLQT1 subunits. KvLQT1 C-termini do not assemble and KvLQT1 subunits do not express functional K(+) channels without this domain. We showed that a JLN deletion-insertion mutation at KvLQT1 residue 544 eliminates important parts of the C-terminal assembly domain. Therefore, JLN mutants may be defective in KvLQT1 subunit assembly. The results provide a molecular basis for the clinical observation that heterozygous JLN carriers show slight cardiac dysfunctions and that the severe JLNS phenotype is characterized by the absence of KvLQT1 channel.
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Affiliation(s)
- N Schmitt
- Institut fuer Neurale Signalverarbeitung, ZMNH, Martinistrasse 52, 20246 Hamburg, Germany
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41
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Affiliation(s)
- J A Towbin
- Department of Pediatrics (Cardiology), Baylor College of Medicine, Texas Children's Hospital, Houston, USA.
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42
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Abstract
The inherited long QT syndrome (LQTS) is a familial disease characterized by QT interval changes that often are labile, syncope, and sudden death due to arrhythmias, predominantly in young people. Multiple mutations in five genes encoding structural subunits of cardiac ion channels now have been identified in families with LQTS. Correlations are being described between genotype and specific clinical features in LQTS. However, increasing screening of affected families and sporadic cases has identified incomplete penetrance with highly variable clinical manifestations, even among individuals carrying the same mutations. The identification of LQTS disease genes represents a crucial first step in developing an understanding of the molecular basis for normal cardiac repolarization. This information will be important not only for identifying new therapies in LQTS, but also in further understanding arrhythmias, and their potential therapies, in situations such as heart failure, cardiac hypertrophy, myocardial infarction, or sudden infant death syndrome, where abnormal repolarization has been linked to sudden death. LQTS thus presents a new paradigm to cardiac electrophysiology, in which new molecular information is being brought to bear both on clinical management of patients and on development of a new framework to study the fundamental causes of arrhythmias and new approaches to therapy.
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Affiliation(s)
- D M Roden
- Department of Medicine and Pharmacology, Vanderbilt University, Nashville, Tennessee, USA
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Ackerman MJ, Tester DJ, Porter CJ. Swimming, a gene-specific arrhythmogenic trigger for inherited long QT syndrome. Mayo Clin Proc 1999; 74:1088-94. [PMID: 10560595 DOI: 10.4065/74.11.1088] [Citation(s) in RCA: 187] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
OBJECTIVE To determine the genetic basis for long QT syndrome (LQTS) in a cohort of patients with a personal history or an extended family history of a swimming-triggered cardiac event. PATIENTS AND METHODS After review of the Mayo Clinic unit medical record system, blood samples or archived autopsy tissue samples were obtained from a retrospective cohort of 35 cases diagnosed as having autosomal dominant LQTS. Exon-specific amplification by polymerase chain reaction and direct sequence analyses were performed on the entire KVLQT1 gene. RESULTS Six cases had a personal history or an extended family history of a near drowning or drowning. In all 6 cases, LQTS-causing mutations in KVLQT1 gene were identified: 3 deletion mutations, 2 donor splice site mutations, and 1 missense mutation. One of the mutations, a novel donor splicing defect, was determined by postmortem molecular analysis of a paraffin-embedded tissue block from a 12-year-old girl who died in 1976. Distinct KVLQT1 mutations were demonstrated in 3 of the remaining 29 cases. The overall frequency of KVLQT1 defects in LQTS was 100% (6/6) in those with and 10% (3/29) in those without a personal history or an extended family history of drowning or near drowning (P<.001). CONCLUSION Swimming appears to be a gene-specific (KVLQT1) arrhythmogenic trigger for LQTS. This study provides proof of principle that an unexplained drowning or near drowning may have a genetic basis.
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Affiliation(s)
- M J Ackerman
- Department of Pediatric and Adolescent Medicine, Mayo Clinic Rochester, Minn 55905, USA
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44
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Wattanasirichaigoon D, Vesely MR, Duggal P, Levine JC, Blume ED, Wolff GS, Edwards SB, Beggs AH. Sodium channel abnormalities are infrequent in patients with long QT syndrome: identification of two novel SCN5A mutations. AMERICAN JOURNAL OF MEDICAL GENETICS 1999; 86:470-6. [PMID: 10508990 DOI: 10.1002/(sici)1096-8628(19991029)86:5<470::aid-ajmg13>3.0.co;2-y] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Long QT syndrome (LQTS) is a heterogeneous disorder caused by mutations of at least five different loci. Three of these, LQT1, LQT2, and LQT5, encode potassium channel subunits. LQT3 encodes the cardiac-specific sodium channel, SCN5A. Previously reported LQTS-associated mutations of SCN5A include a recurring three amino acid deletion (DeltaKPQ1505-1507) in four different families, and four different missense mutations. We have examined the SCN5A gene in 88 index cases with LQTS, including four with Jervell and Lange-Nielsen syndrome and the remainder with Romano-Ward syndrome. Screening portions of DIII-DIV, where mutations have previously been found, showed that none of these patients has the three amino acid deletion, DeltaKPQ1505-1507, or the other four known mutations. We identified a novel missense mutation, T1645M, in the DIV; S4 voltage sensor immediately adjacent to the previously reported mutation R1644H. We also examined all of the additional pore-forming regions and voltage-sensing regions and discovered another novel mutation, T1304M, at the voltage-sensing region DIII; S4. Neither T1645M nor T1304M were seen in a panel of unaffected control individuals. Five of six T1304M gene carriers were symptomatic. In contrast to previous studies, QT(onset-c) was not a sensitive indicator of SCN5A-associated LQTS, at least in this family. These data suggest that mutations of SCN5A are responsible for only a small proportion of LQTS cases.
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Abstract
By the introduction of technological advancement in methods of structural analysis, electronics, and recombinant DNA techniques, research in physiology has become molecular. Additionally, focus of interest has been moving away from classical physiology to become increasingly centered on mechanisms of disease. A wonderful example for this development, as evident by this review, is the field of ion channel research which would not be nearly as advanced had it not been for human diseases to clarify. It is for this reason that structure-function relationships and ion channel electrophysiology cannot be separated from the genetic and clinical description of ion channelopathies. Unique among reviews of this topic is that all known human hereditary diseases of voltage-gated ion channels are described covering various fields of medicine such as neurology (nocturnal frontal lobe epilepsy, benign neonatal convulsions, episodic ataxia, hemiplegic migraine, deafness, stationary night blindness), nephrology (X-linked recessive nephrolithiasis, Bartter), myology (hypokalemic and hyperkalemic periodic paralysis, myotonia congenita, paramyotonia, malignant hyperthermia), cardiology (LQT syndrome), and interesting parallels in mechanisms of disease emphasized. Likewise, all types of voltage-gated ion channels for cations (sodium, calcium, and potassium channels) and anions (chloride channels) are described together with all knowledge about pharmacology, structure, expression, isoforms, and encoding genes.
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Affiliation(s)
- F Lehmann-Horn
- Department of Applied Physiology, University of Ulm, Ulm, Germany.
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Mohammad-Panah R, Demolombe S, Neyroud N, Guicheney P, Kyndt F, van den Hoff M, Baró I, Escande D. Mutations in a dominant-negative isoform correlate with phenotype in inherited cardiac arrhythmias. Am J Hum Genet 1999; 64:1015-23. [PMID: 10090886 PMCID: PMC1377825 DOI: 10.1086/302346] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The long QT syndrome is characterized by prolonged cardiac repolarization and a high risk of sudden death. Mutations in the KCNQ1 gene, which encodes the cardiac KvLQT1 potassium ion (K+) channel, cause both the autosomal dominant Romano-Ward (RW) syndrome and the recessive Jervell and Lange-Nielsen (JLN) syndrome. JLN presents with cardiac arrhythmias and congenital deafness, and heterozygous carriers of JLN mutations exhibit a very mild cardiac phenotype. Despite the phenotypic differences between heterozygotes with RW and those with JLN mutations, both classes of variant protein fail to produce K+ currents in cultured cells. We have shown that an N-terminus-truncated KvLQT1 isoform endogenously expressed in the human heart exerts strong dominant-negative effects on the full-length KvLQT1 protein. Because RW and JLN mutations concern both truncated and full-length KvLQT1 isoforms, we investigated whether RW or JLN mutations would have different impacts on the dominant-negative properties of the truncated KvLQT1 splice variant. In a mammalian expression system, we found that JLN, but not RW, mutations suppress the dominant-negative effects of the truncated KvLQT1. Thus, in JLN heterozygous carriers, the full-length KvLQT1 protein encoded by the unaffected allele should not be subject to the negative influence of the mutated truncated isoform, leaving some cardiac K+ current available for repolarization. This is the first report of a genetic disease in which the impact of a mutation on a dominant-negative isoform correlates with the phenotype.
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Affiliation(s)
- R Mohammad-Panah
- Laboratoire de Physiopathologie et de Pharmacologie Cellulaires et Moléculaires, INSERM CJF96-01, Hôpital Hotel-Dieu, Nantes, France
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Fritzsch B, Beisel K. Development and maintenance of ear innervation and function: lessons from mutations in mouse and man. Am J Hum Genet 1998; 63:1263-70. [PMID: 9792853 PMCID: PMC1377536 DOI: 10.1086/302126] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Affiliation(s)
- B Fritzsch
- Department of Biomedical Sciences, Creigton University, Omaha, NE 68178, USA.
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49
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Wang Q, Bowles NE, Towbin JA. The molecular basis of long QT syndrome and prospects for therapy. MOLECULAR MEDICINE TODAY 1998; 4:382-8. [PMID: 9791861 DOI: 10.1016/s1357-4310(98)01320-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Long QT syndrome (LQT) is a cardiac disorder that causes sudden death from ventricular tachyarrhythmias, specifically torsade de pointes. Two types of LQT have been reported, autosomal-dominant LQT (Romano-Ward syndrome) and autosomal-recessive LQT (Jervell and Lange-Nielsen syndrome); Jervell and Lange-Nielsen syndrome is also associated with deafness. Four LQT genes have been identified for autosomal-dominant LQT: K+ channel genes KVLQT1 on chromosome 11p15.5, HERG on 7q35-36 and minK on 21q22, and the cardiac Na+ channel gene SCN5A on chromosome 3p21-24. Two genes, KVLQT1 and minK, have been identified for Jervell and Lange-Nielsen syndrome. Genetic testing and gene-specific therapies are available for some LQT patients.
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Affiliation(s)
- Q Wang
- Lillie Frank Abercrombie Section of Pediatric Cardiology, Baylor College of Medicine, Texas Children's Hospital, Houston 77030, USA
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50
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Ackerman MJ, Schroeder JJ, Berry R, Schaid DJ, Porter CJ, Michels VV, Thibodeau SN. A novel mutation in KVLQT1 is the molecular basis of inherited long QT syndrome in a near-drowning patient's family. Pediatr Res 1998; 44:148-53. [PMID: 9702906 DOI: 10.1203/00006450-199808000-00002] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
After identifying a 10-year-old boy with inherited long QT syndrome (LQTS) after a near-drowning that required defibrillation from torsades de pointes, evaluation of first degree relatives revealed a four-generation kindred comprising 26 individuals with four additional symptomatic and eight asymptomatic members harboring an abnormally prolonged QTc (defined as > or =0.46 s1/2). We set out to determine the molecular basis of their LQTS. The inherited LQTS represents a collection of genetically distinct ion channelopathies with over 40 mutations in four fundamental cardiac ion channels identified. Molecular studies, including linkage analysis and identification of the disease-associated mutation, were performed on genomic DNA isolated from peripheral blood samples from 29 available family members. Genetic linkage analysis excluded the regions for LQT2, LQT3, and LQT5. However, the chromosome 11p15.5 region (LQT1) showed evidence of linkage with a maximum lod score of 3.36. Examination of the KVLQT1 gene revealed a novel 3-bp deletion resulting in an in-frame deltaF339 (phenylalanine) deletion in the proband. This deltaF339 mutation was confirmed in nine additional family members who shared both an assigned affected phenotype and the disease-associated linked haplotype. Importantly, three asymptomatic family members, with a tentative clinical diagnosis based on their QTc, did not have this mutation and could be reclassified as unaffected. It is noteworthy that the proband's ECG suggested the sodium channel-based LQT3 genotype. These findings show the potential importance of establishing a molecular diagnosis rather than initiating genotype-specific interventions based upon inspection of a patient's ECG.
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Affiliation(s)
- M J Ackerman
- Department of Pediatrics and Adolescent Medicine, Mayo Clinic/Foundation, Rochester, Minnesota 55905, USA
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