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Cardiovasc Res. 2016 Aug 1;111(3):274-86. doi: 10.1093/cvr/cvw083. Epub 2016 Apr 20.

Desmosomal junctions are necessary for adult sinus node function.

Author information

1
Department of Medicine, University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0613C, USA.
2
Department of Bioengineering, University of California-San Diego, La Jolla, CA 92093, USA.
3
Scripps Translational Science Institute, Department of Medicine, Scripps Green Hospital, La Jolla, CA 92037, USA.
4
Department of Cardiac Electrophysiology, University of California-San Francisco, San Francisco, CA 94143, USA.
5
Skaggs School of Pharmacy, University of California-San Diego, La Jolla, CA 92093, USA.
6
Cardiovascular Genetics Program, New York University School of Medicine, New York, NY 10016, USA.
7
Department of Medicine, University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0613C, USA Department of Bioengineering, University of California-San Diego, La Jolla, CA 92093, USA.
8
Department of Medicine, University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0613C, USA fasheikh@ucsd.edu.

Abstract

AIMS:

Current mechanisms driving cardiac pacemaker function have focused on ion channel and gap junction channel function, which are essential for action potential generation and propagation between pacemaker cells. However, pacemaker cells also harbour desmosomes that structurally anchor pacemaker cells to each other in tissue, but their role in pacemaker function remains unknown.

METHODS AND RESULTS:

To determine the role of desmosomes in pacemaker function, we generated a novel mouse model harbouring cardiac conduction-specific ablation (csKO) of the central desmosomal protein, desmoplakin (DSP) using the Hcn4-Cre-ERT2 mouse line. Hcn4-Cre targets cells of the adult mouse sinoatrial node (SAN) and can ablate DSP expression in the adult DSP csKO SAN resulting in specific loss of desmosomal proteins and structures. Dysregulation of DSP via loss-of-function (adult DSP csKO mice) and mutation (clinical case of a patient harbouring a pathogenic DSP variant) in mice and man, respectively, revealed that desmosomal dysregulation is associated with a primary phenotype of increased sinus pauses/dysfunction in the absence of cardiomyopathy. Underlying defects in beat-to-beat regulation were also observed in DSP csKO mice in vivo and intact atria ex vivo. DSP csKO SAN exhibited migrating lead pacemaker sites associated with connexin 45 loss. In vitro studies exploiting ventricular cardiomyocytes that harbour DSP loss and concurrent early connexin loss phenocopied the loss of beat-to-beat regulation observed in DSP csKO mice and atria, extending the importance of DSP-associated mechanisms in driving beat-to-beat regulation of working cardiomyocytes.

CONCLUSION:

We provide evidence of a mechanism that implicates an essential role for desmosomes in cardiac pacemaker function, which has broad implications in better understanding mechanisms underlying beat-to-beat regulation as well as sinus node disease and dysfunction.

KEYWORDS:

Arrhythmia (mechanisms); Desmosome; Heart rate variability; Physiology/function; Sinus node dysfunction

PMID:
27097650
PMCID:
PMC4957488
DOI:
10.1093/cvr/cvw083
[Indexed for MEDLINE]
Free PMC Article

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