A novel trafficking-defective HCN4 mutation is associated with early-onset atrial fibrillation

Heart Rhythm. 2014 Jun;11(6):1055-1062. doi: 10.1016/j.hrthm.2014.03.002. Epub 2014 Mar 4.


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.

Conclusion: Our findings are consistent with HCN4 haploinsufficiency as the likely mechanism for early-onset AF in the p.Pro257Ser carrier.

Keywords: Atrial fibrillation; Electrophysiology; HCN4; Mutation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Age of Onset
  • Animals
  • Atrial Fibrillation / epidemiology
  • Atrial Fibrillation / genetics*
  • CHO Cells
  • Cricetulus
  • Electrophysiologic Techniques, Cardiac
  • Female
  • Haploinsufficiency
  • Humans
  • Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels / genetics*
  • Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels / metabolism
  • Male
  • Microscopy, Confocal
  • Middle Aged
  • Muscle Proteins / genetics*
  • Muscle Proteins / metabolism
  • Mutagenesis, Site-Directed
  • Potassium Channels / genetics*
  • Potassium Channels / metabolism
  • Protein Transport


  • HCN4 protein, human
  • Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels
  • Muscle Proteins
  • Potassium Channels