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Genetic defects in a His-Purkinje system transcription factor, IRX3, cause lethal cardiac arrhythmias

Akiko Koizumi1, Tetsuo Sasano2, Wataru Kimura3

  • 1Department of Bio-Informational Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan.

European Heart Journal
|October 3, 2015
PubMed

Insights

Genetic defects in IRX3 cause idiopathic ventricular fibrillation (VF) by disrupting the His-Purkinje system. This finding identifies novel risk factors for sudden cardiac death (SCD) in healthy individuals.

Area of Science:

  • Cardiovascular Genetics
  • Cardiac Electrophysiology
  • Molecular Cardiology

Background:

  • Idiopathic ventricular fibrillation (VF) causes sudden cardiac death (SCD) in individuals without apparent heart disease.
  • The His-Purkinje system's role in idiopathic VF is suspected but mechanistically unclear.
  • IRX3 is a transcription factor crucial for His-Purkinje system function.

Purpose of the Study:

  • To investigate the link between His-Purkinje system dysfunction and idiopathic VF in Irx3-null mice.
  • To identify IRX3 genetic defects in human idiopathic VF patients.

Main Methods:

  • Telemetry ECG in Irx3-null mice to assess arrhythmias.
  • Genetic sequencing of IRX3 in idiopathic VF patients.
  • In vitro studies using HL-1 cells and neonatal mouse ventricular myocytes to assess IRX3 function.

Main Results:

  • Irx3-deleted mice exhibited frequent ventricular tachyarrhythmias, exacerbated by exercise and sympathetic stimulation.
  • Two novel IRX3 mutations were identified in idiopathic VF patients, associated with exercise-induced VF.
  • IRX3 influenced SCN5A and connexin-40 mRNA expression, with mutations impairing this regulation.

Conclusions:

  • IRX3 genetic defects are novel risk factors for idiopathic VF.
  • Perturbation of the His-Purkinje system by IRX3 dysfunction contributes to idiopathic VF.
  • These findings may enhance risk stratification and preventive strategies for SCD.
Abstract

Keywords:
Cardiac conduction systemSudden cardiac deathVentricular fibrillation

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