title: Functional Characterization of Rare Variants Implicated in Susceptibility to Lone Atrial Fibrillation.
abstract: BACKGROUND
  Few rare variants in atrial fibrillation (AF)-associated genes have been functionally characterized to identify a causal relationship between these variants and development of AF. We here sought to determine the clinical effect of rare variants in AF-associated genes in patients with lone AF and characterized these variants electrophysiologically and bioinformatically.
  
  
  RESULTS
  We screened all coding regions in 12 AF-associated genes in 90 patients with lone AF, with an onset of 47±11 years (66 men; mean age, 56±13 years) by high-resolution melting curve analysis and DNA sequencing. The potassium and sodium currents were analyzed using whole-cell patch clamping. In addition to using 4 individual in silico prediction tools, we extended those predictions to an integrated tool (Combined Annotation Dependent Depletion). We identified 7 rare variants in KCNA5, KCNQ1, KCNH2, SCN5A, and SCN1B genes in 8 patients: 2 of 8 probands had a family history of AF. Electrophysiological studies revealed that 2 variants showed a loss-of-function, and 4 variants showed a gain-of-function. Five of 6 variants with electrophysiological abnormalities were predicted as pathogenic by Combined Annotation Dependent Depletion scores.
  
  
  CONCLUSIONS
  In our cohort of patients with lone AF, 7 rare variants in cardiac ion channels were identified in 8 probands. A combination of electrophysiological studies and in silico predictions showed that these variants could contribute to the development of lone AF, although further in vivo study is necessary to confirm these results. More than half of AF-associated rare variants showed gain-of-function behavior, which may be targeted using genotype-specific pharmacological therapy.
authors.affiliation: From the Division of Cardiovascular Medicine, Kanazawa University Graduate School of Medicine, Kanazawa, Japan (K.H., T.K., H.T., S.T., L.L., N.F., A.N., A.H., T.T., Y.T., M.K., M.Y.); Department of Cardiology, Komatsu Municipal Hospital, Komatsu, Japan (H.I.); and Department of Molecular Physiology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan (N.M.). kenshi@med.kanazawa-u.ac.jp.
authors.forename: Kenshi
authors.initials: K
authors.lastname: Hayashi
authors.affiliation: From the Division of Cardiovascular Medicine, Kanazawa University Graduate School of Medicine, Kanazawa, Japan (K.H., T.K., H.T., S.T., L.L., N.F., A.N., A.H., T.T., Y.T., M.K., M.Y.); Department of Cardiology, Komatsu Municipal Hospital, Komatsu, Japan (H.I.); and Department of Molecular Physiology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan (N.M.).
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Konno
authors.affiliation: From the Division of Cardiovascular Medicine, Kanazawa University Graduate School of Medicine, Kanazawa, Japan (K.H., T.K., H.T., S.T., L.L., N.F., A.N., A.H., T.T., Y.T., M.K., M.Y.); Department of Cardiology, Komatsu Municipal Hospital, Komatsu, Japan (H.I.); and Department of Molecular Physiology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan (N.M.).
authors.forename: Hayato
authors.initials: H
authors.lastname: Tada
authors.affiliation: From the Division of Cardiovascular Medicine, Kanazawa University Graduate School of Medicine, Kanazawa, Japan (K.H., T.K., H.T., S.T., L.L., N.F., A.N., A.H., T.T., Y.T., M.K., M.Y.); Department of Cardiology, Komatsu Municipal Hospital, Komatsu, Japan (H.I.); and Department of Molecular Physiology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan (N.M.).
authors.forename: Satoyuki
authors.initials: S
authors.lastname: Tani
authors.affiliation: From the Division of Cardiovascular Medicine, Kanazawa University Graduate School of Medicine, Kanazawa, Japan (K.H., T.K., H.T., S.T., L.L., N.F., A.N., A.H., T.T., Y.T., M.K., M.Y.); Department of Cardiology, Komatsu Municipal Hospital, Komatsu, Japan (H.I.); and Department of Molecular Physiology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan (N.M.).
authors.forename: Li
authors.initials: L
authors.lastname: Liu
authors.affiliation: From the Division of Cardiovascular Medicine, Kanazawa University Graduate School of Medicine, Kanazawa, Japan (K.H., T.K., H.T., S.T., L.L., N.F., A.N., A.H., T.T., Y.T., M.K., M.Y.); Department of Cardiology, Komatsu Municipal Hospital, Komatsu, Japan (H.I.); and Department of Molecular Physiology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan (N.M.).
authors.forename: Noboru
authors.initials: N
authors.lastname: Fujino
authors.affiliation: From the Division of Cardiovascular Medicine, Kanazawa University Graduate School of Medicine, Kanazawa, Japan (K.H., T.K., H.T., S.T., L.L., N.F., A.N., A.H., T.T., Y.T., M.K., M.Y.); Department of Cardiology, Komatsu Municipal Hospital, Komatsu, Japan (H.I.); and Department of Molecular Physiology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan (N.M.).
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nohara
authors.affiliation: From the Division of Cardiovascular Medicine, Kanazawa University Graduate School of Medicine, Kanazawa, Japan (K.H., T.K., H.T., S.T., L.L., N.F., A.N., A.H., T.T., Y.T., M.K., M.Y.); Department of Cardiology, Komatsu Municipal Hospital, Komatsu, Japan (H.I.); and Department of Molecular Physiology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan (N.M.).
authors.forename: Akihiko
authors.initials: A
authors.lastname: Hodatsu
authors.affiliation: From the Division of Cardiovascular Medicine, Kanazawa University Graduate School of Medicine, Kanazawa, Japan (K.H., T.K., H.T., S.T., L.L., N.F., A.N., A.H., T.T., Y.T., M.K., M.Y.); Department of Cardiology, Komatsu Municipal Hospital, Komatsu, Japan (H.I.); and Department of Molecular Physiology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan (N.M.).
authors.forename: Toyonobu
authors.initials: T
authors.lastname: Tsuda
authors.affiliation: From the Division of Cardiovascular Medicine, Kanazawa University Graduate School of Medicine, Kanazawa, Japan (K.H., T.K., H.T., S.T., L.L., N.F., A.N., A.H., T.T., Y.T., M.K., M.Y.); Department of Cardiology, Komatsu Municipal Hospital, Komatsu, Japan (H.I.); and Department of Molecular Physiology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan (N.M.).
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Tanaka
authors.affiliation: From the Division of Cardiovascular Medicine, Kanazawa University Graduate School of Medicine, Kanazawa, Japan (K.H., T.K., H.T., S.T., L.L., N.F., A.N., A.H., T.T., Y.T., M.K., M.Y.); Department of Cardiology, Komatsu Municipal Hospital, Komatsu, Japan (H.I.); and Department of Molecular Physiology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan (N.M.).
authors.forename: Masa-aki
authors.initials: MA
authors.lastname: Kawashiri
authors.affiliation: From the Division of Cardiovascular Medicine, Kanazawa University Graduate School of Medicine, Kanazawa, Japan (K.H., T.K., H.T., S.T., L.L., N.F., A.N., A.H., T.T., Y.T., M.K., M.Y.); Department of Cardiology, Komatsu Municipal Hospital, Komatsu, Japan (H.I.); and Department of Molecular Physiology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan (N.M.).
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Ino
authors.affiliation: From the Division of Cardiovascular Medicine, Kanazawa University Graduate School of Medicine, Kanazawa, Japan (K.H., T.K., H.T., S.T., L.L., N.F., A.N., A.H., T.T., Y.T., M.K., M.Y.); Department of Cardiology, Komatsu Municipal Hospital, Komatsu, Japan (H.I.); and Department of Molecular Physiology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan (N.M.).
authors.forename: Naomasa
authors.initials: N
authors.lastname: Makita
authors.affiliation: From the Division of Cardiovascular Medicine, Kanazawa University Graduate School of Medicine, Kanazawa, Japan (K.H., T.K., H.T., S.T., L.L., N.F., A.N., A.H., T.T., Y.T., M.K., M.Y.); Department of Cardiology, Komatsu Municipal Hospital, Komatsu, Japan (H.I.); and Department of Molecular Physiology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan (N.M.).
authors.forename: Masakazu
authors.initials: M
authors.lastname: Yamagishi
mesh_terms: D001281:Atrial Fibrillation / Q000235:genetics* / Q000503:physiopathology; D000072237:ERG1 Potassium Channel; D022062:Electrophysiologic Techniques, Cardiac; D051638:Ether-A-Go-Go Potassium Channels / Q000235:genetics; D005260:Female; D020022:Genetic Predisposition to Disease; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D007473:Ion Channels / Q000235:genetics; D051657:KCNQ1 Potassium Channel / Q000235:genetics; D051666:Kv1.5 Potassium Channel / Q000235:genetics; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000235:genetics; D062554:NAV1.5 Voltage-Gated Sodium Channel / Q000235:genetics; D018408:Patch-Clamp Techniques; D062547:Voltage-Gated Sodium Channel beta-1 Subunit / Q000235:genetics
chemical_list: D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D007473:Ion Channels; C000606913:KCNH2 protein, human; D051657:KCNQ1 Potassium Channel; D051666:Kv1.5 Potassium Channel; D062554:NAV1.5 Voltage-Gated Sodium Channel; D062547:Voltage-Gated Sodium Channel beta-1 Subunit
keywords: analysis of variance; atrial fibrillation; genetic association studies; genetic variation; ion channels