title: SCN1Bb R214Q found in 3 patients: 1 with Brugada syndrome and 2 with lone atrial fibrillation.
abstract: BACKGROUND
  SCN1Bb encodes the β-subunit of the sodium channel. A mutation in SCN1Bb R214Q has recently been shown both to increase the Kv4.3 current and to decrease the sodium current. The variant was suggested to increase the susceptibility to Brugada syndrome (BrS).
  
  
  OBJECTIVE
  To sequence a population of BrS and early-onset lone atrial fibrillation (AF) patients for the R214Q mutation in the SCN1Bb gene.
  
  
  METHODS
  The coding sequence and splice junctions of SCN1Bb were bidirectionally sequenced by using Big Dye chemistry in 192 early-onset lone AF patients and 22 BrS patients.
  
  
  RESULTS
  Three probands carrying the R214Q variant were identified. No mutations were identified in genes previously associated with BrS or AF in these patients. Case 1 also had the onset of persistent lone AF at the age of 39 years. Case 2 was a lone AF case with onset at the age of 39 years and paroxysmal lone AF. Case 3 was a BrS patient with a type 1 electrocardiogram and onset of disease at the age of 54 years. Both lone AF patients had electrocardiograms that raised the suspicion of BrS, but intravenous flecainide testing was, in both cases, negative. R214Q was not present in the control group (n = 216) and has not previously been reported in conjunction to AF.
  
  
  CONCLUSIONS
  Three patients of 192 young lone AF and 22 BrS patients carried the nonsynonymous R214Q mutations in SCN1Bb, thereby indicating that this variant increases the susceptibility to both BrS and AF.
authors.affiliation: Danish National Research Foundation Centre for Cardiac Arrhythmia, Copenhagen, Denmark.
authors.forename: Morten S
authors.initials: MS
authors.lastname: Olesen
authors.forename: Anders G
authors.initials: AG
authors.lastname: Holst
authors.forename: Jesper Hastrup
authors.initials: JH
authors.lastname: Svendsen
authors.forename: Stig
authors.initials: S
authors.lastname: Haunsø
authors.forename: Jacob
authors.initials: J
authors.lastname: Tfelt-Hansen
mesh_terms: D000328:Adult; D001281:Atrial Fibrillation / Q000235:genetics*; D053840:Brugada Syndrome / Q000235:genetics; D004562:Electrocardiography; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D017422:Sequence Analysis, DNA; D062547:Voltage-Gated Sodium Channel beta-1 Subunit / Q000235:genetics*
chemical_list: C470379:SCN1B protein, human; D062547:Voltage-Gated Sodium Channel beta-1 Subunit