Abstract 9140: The Majority of Plakophilin-2 Mutations in Arrhythmogenic Cardiomyopathy are Associated with Haploinsufficiency in the Myocardium and Epidermis

Abstract

Background: Arrhythmogenic cardiomyopathy (AC) is a hereditary cardiac condition associated with ventricular arrhythmias, heart failure and sudden death. The disease is most often caused by mutations in the desmosomal gene for plakophilin-2 (PKP2), which is expressed in both myocardial and epidermal tissue. It was the aim of this study to investigate protein expression in myocardial tissue of ARVC patients carrying PKP2 mutations and elucidate if keratinocytes of the same individuals exhibited a similar pattern of protein expression. Methods and Results: Direct sequencing of 5 ARVC-genes in 71 unrelated ARVC patients identified 10 different PKP2 mutations. One patient, a digenic carrier of heterozygous PKP2- and desmoglein-2 mutations, developed severe heart failure and underwent cardiac transplantation. Western blotting and immunohistochemistry of the explanted heart showed a significant decrease in PKP2 protein expression without detectable amounts of truncated PKP2 protein. Cultured keratinocytes of the patient showed a similar reduction in PKP2 protein expression. Nine additional PKP2 mutations were investigated in both cultured keratinocytes and endomyocardial biopsies from affected individuals. It was evident that PKP2 mutations introducing a premature termination codon in the reading frame were associated with reduced PKP2 transcript and protein levels while a missense variant did not affect PKP2 expression levels. Conclusion: This study indicated that the majority of PKP2 mutations in ARVC are associated with haploinsufficiency. Furthermore, myocardial PKP2 expression in mutation carriers correlate well with PKP2 expression in keratinocytes of the same individuals. This finding makes keratinocyte cultures a promising new tool to characterize desmosomal protein expression in AC patients. Figure legend: A) The explanted heart of a digenic mutation carrier with AC, B) Western blotting of PKP2, C) Western blotting of DSG2