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Connexin30.2 containing gap junction channels decelerate impulse propagation through the atrioventricular node

Maria M Kreuzberg1, Jan W Schrickel, Alexander Ghanem

  • 1Institut für Genetik, Abteilung Molekulargenetik, Universität Bonn, Römerstrasse 164, 53117 Bonn, Germany.

Proceedings of the National Academy of Sciences of the United States of America
|March 31, 2006
PubMed

Insights

Connexin30.2 (Cx30.2) slows cardiac impulse propagation in the atrioventricular node, preventing rapid ventricular responses during atrial fibrillation. This protein is crucial for coordinated heartbeats and protecting against arrhythmias.

Area of Science:

  • Cardiovascular Physiology
  • Molecular Cardiology
  • Electrophysiology

Background:

  • Gap junctions composed of connexins facilitate electrical coupling in cardiomyocytes, essential for coordinated heart function.
  • Connexin30.2 (Cx30.2) is a recently identified connexin expressed in the cardiac conduction system, particularly the sinoatrial and atrioventricular (AV) nodes.
  • Cx30.2 forms gap junction channels with exceptionally low unitary conductance (9 pS).

Purpose of the Study:

  • To investigate the functional role of Cx30.2 in cardiac impulse propagation within the AV node.
  • To determine the impact of Cx30.2 deficiency on heart rhythm and response to arrhythmias.

Main Methods:

  • Utilized Cx30.2 knockout mice (Cx30.2(LacZ/LacZ)) and wild-type littermates (Cx30.2(+/+)).
  • Recorded intracardiac electrograms to measure atrial, His bundle, and ventricular activation intervals (PQ, atrial-His, and HV intervals).
  • Assessed AV nodal conduction capacity and ventricular response rates during induced atrial fibrillation.

Main Results:

  • Cx30.2 knockout mice exhibited a significantly shorter PQ interval (approx. 25%) compared to wild-type mice.
  • Accelerated conduction was observed above the His bundle (shorter atrial-His interval) in knockout mice, while HV conduction remained unchanged.
  • Knockout mice displayed enhanced AV nodal conduction capacity and faster ventricular rates during induced atrial fibrillation.

Conclusions:

  • Cx30.2 significantly contributes to slowing impulse propagation through the AV node.
  • Cx30.2 limits the maximum conduction rate from atria to ventricles, playing a role in coordinating atrial and ventricular contraction.
  • Cx30.2 likely provides a protective mechanism against rapid ventricular rates during atrial tachyarrhythmias, preventing hemodynamic compromise.

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