title: A novel trafficking-defective HCN4 mutation is associated with early-onset atrial fibrillation.
abstract: BACKGROUND
  Atrial fibrillation (AF) is the most common arrhythmia, and a recent genome-wide association study identified the hyperpolarization-activated cyclic nucleotide-gated channel 4 (HCN4) as a novel AF susceptibility locus. HCN4 encodes for the cardiac pacemaker channel, and HCN4 mutations are associated with familial sinus bradycardia and AF.
  
  
  OBJECTIVE
  The purpose of this study was to determine whether novel variants in the coding region of HCN4 contribute to the susceptibility for AF.
  
  
  METHODS
  We sequenced the coding region of HCN4 for novel variants from 527 cases with early-onset AF from the Massachusetts General Hospital AF Study and 443 referents from the Framingham Heart Study. We used site-directed mutagenesis, cellular electrophysiology, immunocytochemistry, and confocal microscopy to functionally characterize novel variants.
  
  
  RESULTS
  We found the frequency of novel coding HCN4 variants was 2-fold greater for individuals with AF (7 variants) compared to the referents (3 variants). We determined that of the 7 novel HCN4 variants in our AF cases, 1 (p.Pro257Ser, located in the amino-terminus adjacent to the first transmembrane spanning domain) did not traffic to cell membrane, whereas the remaining 6 were not functionally different from wild type. In addition, the 3 novel variants in our referents did not alter function compared to wild-type. Coexpression studies showed that the p.Pro257Ser mutant channel failed to colocalize with the wild-type HCN4 channel on the cell membrane.
  
  
  CONCLUSIONS
  Our findings are consistent with HCN4 haploinsufficiency as the likely mechanism for early-onset AF in the p.Pro257Ser carrier.
authors.affiliation: Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts, USA.|Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Macri
authors.affiliation: Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts, USA.|Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Saagar N
authors.initials: SN
authors.lastname: Mahida
authors.affiliation: Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts, USA.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Zhang
authors.affiliation: Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts, USA.|Department of Medicine I, University Hospital Grosshadern, Ludwig-Maximilians University, Munich, Germany.|National Heart, Lung, and Blood Institute's and Boston University's Framingham Heart Study, Framingham, Massachusetts, USA.
authors.forename: Moritz F
authors.initials: MF
authors.lastname: Sinner
authors.affiliation: Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts, USA.|Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Elena V
authors.initials: EV
authors.lastname: Dolmatova
authors.affiliation: Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts, USA.|Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Nathan R
authors.initials: NR
authors.lastname: Tucker
authors.affiliation: Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts, USA.
authors.forename: Micheal
authors.initials: M
authors.lastname: McLellan
authors.affiliation: Cardiac Arrhythmia Service, Massachusetts General Hospital, Boston, Massachusetts, USA.
authors.forename: Marisa A
authors.initials: MA
authors.lastname: Shea
authors.affiliation: Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts, USA.|Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Milan
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, Massachusetts, USA.|Department of Biostatistics, Boston University School of Public Health, Boston, Massachusetts, USA.|National Heart, Lung, and Blood Institute's and Boston University's Framingham Heart Study, Framingham, Massachusetts, USA.
authors.forename: Kathryn L
authors.initials: KL
authors.lastname: Lunetta
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, Massachusetts, USA.|Department of Biostatistics, Boston University School of Public Health, Boston, Massachusetts, USA.|National Heart, Lung, and Blood Institute's and Boston University's Framingham Heart Study, Framingham, Massachusetts, USA.|Preventive Medicine Section, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, USA.|Cardiology Section, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, USA.
authors.forename: Emelia J
authors.initials: EJ
authors.lastname: Benjamin
authors.affiliation: Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts, USA.|Harvard Medical School, Boston, Massachusetts, USA.|Cardiac Arrhythmia Service, Massachusetts General Hospital, Boston, Massachusetts, USA.
authors.forename: Patrick T
authors.initials: PT
authors.lastname: Ellinor
mesh_terms: D017668:Age of Onset; D000818:Animals; D001281:Atrial Fibrillation / Q000453:epidemiology / Q000235:genetics*; D016466:CHO Cells; D003412:Cricetulus; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D057895:Haploinsufficiency; D006801:Humans; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels / Q000235:genetics* / Q000378:metabolism; D008297:Male; D018613:Microscopy, Confocal; D008875:Middle Aged; D009124:Muscle Proteins / Q000235:genetics* / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D015221:Potassium Channels / Q000235:genetics* / Q000378:metabolism; D021381:Protein Transport
chemical_list: C119587:HCN4 protein, human; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D009124:Muscle Proteins; D015221:Potassium Channels
keywords: Atrial fibrillation; Electrophysiology; HCN4; Mutation