Connexin30.2 containing gap junction channels decelerate impulse propagation through the atrioventricular node.
In the mammalian heart, gap junction channels between electrically coupled cardiomyocytes are necessary for impulse propagation and coordinated contraction of atria and ventricles. Recently, mouse connexin30.2 (Cx30.2) was shown to be expressed in the cardiac conduction system, predominantly in sinoatrial and atrioventricular (AV) nodes. The corresponding gap junctional channels expressed in HeLa cells exhibit the lowest unitary conductance (9 pS) of all connexin channels. Here we report that Cx30.2 slows down the propagation of excitation through the AV node. Mice expressing a LacZ reporter gene instead of the Cx30.2 coding region (Cx30.2(LacZ/LacZ)) exhibit a PQ interval that is approximately 25% shorter than in WT littermates. By recording atrial, His, and ventricular signals with intracardiac electrodes, we show that this decrease is attributed to significantly accelerated conduction above the His bundle (atrial-His interval: 27.9 +/- 5.1 ms in Cx30.2(LacZ/LacZ) versus 37.1 +/- 4.1 ms in Cx30.2(+/+) mice), whereas HV conduction is unaltered. Atrial stimulation revealed an elevated AV-nodal conduction capacity and faster ventricular response rates during induced episodes of atrial fibrillation in Cx30.2(LacZ/LacZ) mice. Our results show that Cx30.2 contributes to the slowdown of impulse propagation in the AV node and additionally limits the maximum number of beats conducted from atria to ventricles. Thus, it is likely to be involved in coordination of atrial and ventricular contraction and to fulfill a protective role toward pathophysiological states such as atrial tachyarrhythmias (e.g., atrial fibrillation) by preventing rapid conduction to the ventricles potentially associated with hemodynamic deterioration.
Institut für Genetik, Abteilung Molekulargenetik, Universität Bonn, Römerstrasse 164, 53117 Bonn, Germany.
Maria M
MM
Kreuzberg
Jan W
JW
Schrickel
Alexander
A
Ghanem
Jung-Sun
JS
Kim
Joachim
J
Degen
Ulrike
U
Janssen-Bienhold
Thorsten
T
Lewalter
Klaus
K
Tiemann
Klaus
K
Willecke
D000818:Animals; D001283:Atrioventricular Node / Q000502:physiology*; D017630:Connexins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D004562:Electrocardiography; D004594:Electrophysiology; D017629:Gap Junctions / Q000502:physiology*; D006339:Heart Rate; D007763:Lac Operon; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009200:Myocardial Contraction / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D017630:Connexins; C510757:connexin 30.2, mouse