Disruption of the desmoglein adhesive interface causes Arrhythmogenic Cardiomyopathy

Abstract

Arrhythmogenic Cardiomyopathy (ACM) in the majority of cases is caused by mutations in genes of the desmosomal cell-cell adhesion complex. ACM is characterized by progressive loss of cardiomyocytes with fibrosis, ventricular systolic dysfunction and life-threatening arrhythmias. Even though the pathological phenotype is well known, the underlying mechanisms are controversial and not well understood. Here, we tested the hypothesis that impaired adhesive function of desmosomes is central for disease development and progression. We generated a CRISPR/Cas9-based knock-in mouse model with exchange of tryptophan 2 to alanin in desmoglein-2 (Dsg2-W2A), which is a crucial desmosomal adhesion molecule in cardiomyocytes. This mutation, based on structural data, aims to abrogate the so-called tryptophan swap, a suggested central binding mechanism of Dsg2. In line with the dysfunctional adhesion hypothesis, mutant mice develop a severe cardiac phenotype recalling the characteristics of ACM including cardiac fibrosis, impaired systolic function and arrhythmia after adrenergic stimulation. While protein levels and localization of intercalated disc molecules were unchanged, structurally altered and even disrupted configurations of cardiomyocyte interfaces were evident on the ultrastructural level. Cell-cell dissociation assays and force spectroscopy measurements by atomic force microscopy confirmed the suspected adhesion defect of Dsg2-W2A molecules on cellular and molecular level. In summary, the adhesion-deficient Dsg2-W2A mouse model fulfils the criteria required to establish an ACM diagnosis. This shows that disruption of desmosomal adhesion is sufficient for ACM development with induction of the described phenotype. Further, the Dsg2-W2A mouse line represents a valuable model to study mechanisms of the disease and to identify novel treatments for ACM in vivo.