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Abbott GW. Kv Channel Ancillary Subunits: Where Do We Go from Here? Physiology (Bethesda) 2022; 37:0. [PMID: 35797055 PMCID: PMC9394777 DOI: 10.1152/physiol.00005.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 04/29/2022] [Accepted: 04/29/2022] [Indexed: 01/10/2023] Open
Abstract
Voltage-gated potassium (Kv) channels each comprise four pore-forming α-subunits that orchestrate essential duties such as voltage sensing and K+ selectivity and conductance. In vivo, however, Kv channels also incorporate regulatory subunits-some Kv channel specific, others more general modifiers of protein folding, trafficking, and function. Understanding all the above is essential for a complete picture of the role of Kv channels in physiology and disease.
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Affiliation(s)
- Geoffrey W Abbott
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, California
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Izumi G, Hayama E, Yamazawa H, Inai K, Shimada M, Furutani M, Nishizawa T, Furutani Y, Matsuoka R, Nakanishi T. Compound Mutations Cause Increased Cardiac Events in Children with Long QT Syndrome: Can the Sequence Homology-Based Tools be Applied for Prediction of Phenotypic Severity? Pediatr Cardiol 2016; 37:962-70. [PMID: 27041096 DOI: 10.1007/s00246-016-1378-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 03/21/2016] [Indexed: 11/29/2022]
Abstract
Long QT syndrome (LQTS) can cause syncope, ventricular fibrillation, and death. Recently, several disease-causing mutations in ion channel genes have been identified, and compound mutations have also been detected. It is unclear whether children who are carriers of compound mutations exhibit a more severe phenotype than those with single mutations. Although predicting phenotypic severity is clinically important, the availability of prediction tools for LQTS is unknown. To determine whether the severity of the LQTS phenotype can be predicted by the presence of compound mutations in children is needed. We detected 97 single mutations (Group S) and 13 compound mutations (Group C) between 1998 and 2012, age at diagnosis ranging 0-19 years old (median age is 9.0) and 18.0 years of follow-up period. The phenotypes and Kaplan-Meier event-free rates of the two groups were compared for cardiac events. This study investigated phenotypic severity in relation to the location of mutations in the protein sequence, which was analyzed using two sequence homology-based tools. In results, compound mutations in children were associated with a high incidence of syncope within the first decade (Group S: 32 % vs. Group C: 61 %), requiring an ICD in the second decade (Group S: 3 % vs. Group C: 56 %). Mortality in these patients was high within 5 years of birth (23 %). Phenotypic prediction tools correctly predicted the phenotypic severity in both Groups S and C, especially by using their coupling method. The coupling prediction method is useful in the initial evaluation of phenotypes both with single and compound mutations of LQTS patients. However, it should be noted that the compound mutation makes more severe phenotype.
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Affiliation(s)
- Gaku Izumi
- Department of Pediatric Cardiology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, 162-8666, Japan. .,Department of Pediatrics, Hokkaido University Graduate School of Medicine, North-15 West-7, Sapporo, 060-8638, Japan.
| | - Emiko Hayama
- Department of Pediatric Cardiology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, 162-8666, Japan
| | - Hirokuni Yamazawa
- Department of Pediatrics, Hokkaido University Graduate School of Medicine, North-15 West-7, Sapporo, 060-8638, Japan
| | - Kei Inai
- Department of Pediatric Cardiology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, 162-8666, Japan
| | - Mitsuyo Shimada
- Department of Pediatric Cardiology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, 162-8666, Japan
| | - Michiko Furutani
- Department of Pediatric Cardiology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, 162-8666, Japan
| | - Tsutomu Nishizawa
- Department of Pediatric Cardiology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, 162-8666, Japan
| | - Yoshiyuki Furutani
- Department of Pediatric Cardiology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, 162-8666, Japan
| | - Rumiko Matsuoka
- Department of Pediatric Cardiology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, 162-8666, Japan
| | - Toshio Nakanishi
- Department of Pediatric Cardiology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, 162-8666, Japan
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Guo Q, Ren L, Chen X, Hou C, Chu J, Pu J, Zhang S. A novel mutation in the SCN5A gene contributes to arrhythmogenic characteristics of early repolarization syndrome. Int J Mol Med 2016; 37:727-33. [PMID: 26820605 PMCID: PMC4771109 DOI: 10.3892/ijmm.2016.2468] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Accepted: 01/13/2016] [Indexed: 12/17/2022] Open
Abstract
Several genetic variants have been associated with early repolarization syndrome (ERS). However, the lack of functional validations of the mutant effects has limited the interpretation of genetic tests. In the present study, we identified and characterized a novel sodium channel, voltage gated, type V alpha subunit (SCN5A) mutation that was associated with ERS. A 67-year-old male proband suffering from recurrent syncope underwent a documented electrocardiogram (ECG) for polymorphic ventricular tachycardia (VT). It was noted that baseline 12-lead ECG exhibited a predominantly elevated ST-segment which mimicked acute myocardial ischemia in lead V2-V6, and the ECG also demonstrated J waves in lead Ⅱ, Ⅲ, aVF and V2-V6. Using genetic analysis, we noted that the proband carried a novel heterozygous missense mutation of A1055G in the SCN5A gene. Whole-cell configuration of patch-clamp analysis revealed that the mutation significantly decreased peak sodium current (INa) density and shifted the steady-state inactivation curve of INa to a more negative potential. Confocal imaging suggested that in the mutant channel a defect of protein expression both on the cell membrane and in cytoplasm was present. The present study demonstrated that a novel heterozygous missense mutation of A1055G in SCN5A led to 'loss-of function' of the sodium channels, and we suggest that it accounts for the arrhythmogenic characteristics of ERS.
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Affiliation(s)
- Qi Guo
- State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, P.R. China
| | - Lan Ren
- State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, P.R. China
| | - Xuhua Chen
- State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, P.R. China
| | - Cuihong Hou
- State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, P.R. China
| | - Jianmin Chu
- State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, P.R. China
| | - Jielin Pu
- State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, P.R. China
| | - Shu Zhang
- State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, P.R. China
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Mousavi Nik A, Gharaie S, Jeong Kim H. Cellular mechanisms of mutations in Kv7.1: auditory functions in Jervell and Lange-Nielsen syndrome vs. Romano-Ward syndrome. Front Cell Neurosci 2015; 9:32. [PMID: 25705178 PMCID: PMC4319400 DOI: 10.3389/fncel.2015.00032] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2014] [Accepted: 01/19/2015] [Indexed: 01/06/2023] Open
Abstract
As a result of cell-specific functions of voltage-activated K+ channels, such as Kv7.1, mutations in this channel produce profound cardiac and auditory defects. At the same time, the massive diversity of K+ channels allows for compensatory substitution of mutant channels by other functional channels of their type to minimize defective phenotypes. Kv7.1 represents a clear example of such functional dichotomy. While several point mutations in the channel result in a cardio-auditory syndrome called Jervell and Lange-Nielsen syndrome (JLNS), about 100-fold mutations result in long QT syndrome (LQTS) denoted as Romano–Ward syndrome (RWS), which has an intact auditory phenotype. To determine whether the cellular mechanisms for the diverse phenotypic outcome of Kv7.1 mutations, are dependent on the tissue-specific function of the channel and/or specialized functions of the channel, we made series of point mutations in hKv7.1 ascribed to JLNS and RWS. For JLNS mutations, all except W248F yielded non-functional channels when expressed alone. Although W248F at the end of the S4 domain yielded a functional current, it underwent marked inactivation at positive voltages, rendering the channel non-functional. We demonstrate that by definition, none of the JLNS mutants operated in a dominant negative (DN) fashion. Instead, the JLNS mutants have impaired membrane trafficking, trapped in the endoplasmic reticulum (ER) and Cis-Golgi. The RWS mutants exhibited varied functional phenotypes. However, they can be summed up as exhibiting DN effects. Phenotypic differences between JLNS and RWS may stem from tissue-specific functional requirements of cardiac vs. inner ear non-sensory cells.
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Affiliation(s)
- Atefeh Mousavi Nik
- Department of Anesthesiology and Pain Medicine, Center for Neuroscience, School of Medicine, University of California, Davis Davis, CA, USA
| | - Somayeh Gharaie
- Department of Anesthesiology and Pain Medicine, Center for Neuroscience, School of Medicine, University of California, Davis Davis, CA, USA
| | - Hyo Jeong Kim
- Department of Anesthesiology and Pain Medicine, Center for Neuroscience, School of Medicine, University of California, Davis Davis, CA, USA
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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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Liu F, Struchalin MV, Duijn KV, Hofman A, Uitterlinden AG, Duijn CV, Aulchenko YS, Kayser M. Detecting low frequent loss-of-function alleles in genome wide association studies with red hair color as example. PLoS One 2011; 6:e28145. [PMID: 22140526 PMCID: PMC3226656 DOI: 10.1371/journal.pone.0028145] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Accepted: 11/02/2011] [Indexed: 11/18/2022] Open
Abstract
Multiple loss-of-function (LOF) alleles at the same gene may influence a phenotype not only in the homozygote state when alleles are considered individually, but also in the compound heterozygote (CH) state. Such LOF alleles typically have low frequencies and moderate to large effects. Detecting such variants is of interest to the genetics community, and relevant statistical methods for detecting and quantifying their effects are sorely needed. We present a collapsed double heterozygosity (CDH) test to detect the presence of multiple LOF alleles at a gene. When causal SNPs are available, which may be the case in next generation genome sequencing studies, this CDH test has overwhelmingly higher power than single SNP analysis. When causal SNPs are not directly available such as in current GWA settings, we show the CDH test has higher power than standard single SNP analysis if tagging SNPs are in linkage disequilibrium with the underlying causal SNPs to at least a moderate degree (r²>0.1). The test is implemented for genome-wide analysis in the publically available software package GenABEL which is based on a sliding window approach. We provide the proof of principle by conducting a genome-wide CDH analysis of red hair color, a trait known to be influenced by multiple loss-of-function alleles, in a total of 7,732 Dutch individuals with hair color ascertained. The association signals at the MC1R gene locus from CDH were uniformly more significant than traditional GWA analyses (the most significant P for CDH = 3.11×10⁻¹⁴² vs. P for rs258322 = 1.33×10⁻⁶⁶). The CDH test will contribute towards finding rare LOF variants in GWAS and sequencing studies.
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Affiliation(s)
- Fan Liu
- Department of Forensic Molecular Biology, Erasmus University Medical Center, Rotterdam, The Netherlands.
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