title: Deficiency of cyclase-associated protein 2 promotes arrhythmias associated with connexin43 maldistribution and fibrosis.
abstract: BACKGROUND
  Cyclase-associated protein 2 (CAP2) plays a major role in regulating the actin cytoskeleton. Since inactivation of CAP2 in a mouse model by a gene trap approach (Cap2 (gt/gt) ) results in cardiomyopathy and increased mortality, we hypothesized that CAP2 has a major impact on arrhythmias and electrophysiological parameters.
  
  
  METHODS
  We performed long-term-ECG recordings in transgenic CAP2 deficient mice (C57BL/6) to detect spontaneous arrhythmias. In vivo electrophysiological studies by right heart catheterization and ex vivo epicardial mapping were used to analyze electrophysiological parameters, the inducibility of arrhythmias, and conduction velocities. Expression and distribution of cardiac connexins and the amount of cardiac fibrosis were evaluated.
  
  
  RESULTS
  Spontaneous ventricular arrhythmias could be detected in Cap2 (gt/gt) during the long-term-ECG recording. Cap2 (gt/gt) showed marked conduction delays at atrial and ventricular levels, including a reduced heart rate (421.0 ±40.6 bpm vs. 450.8 ±27.9 bpm; p < 0.01), and prolongations of PQ (46.3 ±4.1 ms vs. 38.6 ±6.5 ms; p < 0.01), QRS (16.2 ±2.6 ms vs. 12.6 ±1.4 ms; p < 0.01), and QTc interval (55.8 ±6.0 ms vs. 45.2 ±3.3 ms; p = 0.02) in comparison to wild type mice. The PQ prolongation was due to an infra-Hisian conduction delay (HV: 9.7 ±2.1 ms vs. 6.5 ±3.1 ms; p = 0.02). The inducibility of ventricular tachycardias during the electrophysiological studies was significantly elevated in the mutant mice (inducible animals: 88% vs. 33%; p = 0.04). Cap2 (gt/gt) showed more abnormal distribution of connexin43 compared to WT (23.0 ±4.7% vs. 2.9 ±0.8%; p < 0.01). Myocardial fibrosis was elevated in Cap2 (gt/gt) hearts (9.1 ±6.7% vs. 5.5 ±3.3%; p < 0.01).
  
  
  CONCLUSIONS
  Loss of CAP2 results in marked electrophysiological disturbances including impaired sinus node function, conduction delays, and susceptibility to malignant arrhythmias. Structural changes in Cap2 (gt/gt) are associated with alterations in myocardial connexins and fibrosis.
authors.affiliation: Department of Medicine - Cardiology, University Hospital Bonn, Bonn, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Stöckigt
authors.affiliation: Institute of Biochemistry I, University of Cologne, Cologne, Germany; Center for Molecular Medicine Cologne (CMMC), Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany.
authors.forename: Vivek Shahaji
authors.initials: VS
authors.lastname: Peche
authors.affiliation: Department of Medicine - Cardiology, University Hospital Bonn, Bonn, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Linhart
authors.affiliation: Department of Medicine - Cardiology, University Hospital Bonn, Bonn, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Nickenig
authors.affiliation: Institute of Biochemistry I, University of Cologne, Cologne, Germany; Center for Molecular Medicine Cologne (CMMC), Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany.
authors.forename: Angelika Anna
authors.initials: AA
authors.lastname: Noegel
authors.affiliation: Department of Medicine - Cardiology, University Hospital Bonn, Bonn, Germany.
authors.forename: Jan Wilko
authors.initials: JW
authors.lastname: Schrickel
keywords: arrhythmia; cardiomyopathy; electrophysiology; mouse model