Abstract 13147: The Internally Translated Isoform of Connexin 43, GJA1-20k Rescues Cx43 Trafficking and Reduces Arrhythmias in the DSG2 Mutant Model of Arrhythmogenic Cardiomyopathy

Abstract

Introduction: Arrhythmogenic cardiomyopathy (ACM) is an inherited condition caused by mutations of junctional proteins resulting in heart rhythm abnormalities, heart failure and sudden cardiac death. ACM subjects exhibit a loss of normal trafficking of the gap junction protein Connexin 43 (Cx43) to the intercalated disk. Our group has previously demonstrated that the Cx43 gene, GJA1, undergoes internal translation to form multiple truncations of the full-length protein. The 20 kilodalton isoform, (GJA1-20k) is required for trafficking of Cx43 gap junction channels, and exogenous expression of GJA1-20k increases trafficking of full length Cx43 to the membranes and the intercalated disk. Here, we hypothesize that GJA1-20K will reduce dysrhythmias by improving trafficking of Cx43 to the intercalated disc in a mouse model of ACM. Methods: Desmoglein 2 (DSG2) homozygous knock-out mice, producing a typical ACM phenotype, were injected with a viral vector containing either GJA1-20K-GFP or GFP alone at four weeks of age along with wild-type littermate controls. Echocardiography was performed every four weeks and Telemetry was recorded at ~18-19 weeks of age to record cardiac electrical activity over a continuous 12 hour period. At 20 weeks, the mice were sacrificed, and hearts were harvested for further analysis. Results: Compared to WT littermates DSG2-KO mice that received a GFP viral vector demonstrated over a 100 fold increase in mean number of PVCs observed over a 12 hour period (2 vs 371 respectively p=0.0005). Mice that received the GJA1-20k viral vector in contrast demonstrated significantly fewer PVCs than their GFP treated littermates 43 vs 371. (analysis of variance of Log(#PVC) p =0.015 N = 6-7 mice/group). Quantitative immunofluorescence analysis of hearts confirmed an increase in Cx43 localization at the intercalated disk (as measured as a percent of N-Cadherin-Cx43 colabeling) in mice treated with GJA1-20k relative to GFP (25% vs 6% respectively N= 7 images/mouse and 3 mice/ group) t-test p=0.0009). Conclusions: Our data indicate that GJA1-20K significantly reduces the number of PVCs and recovers Cx43 trafficking to the intercalated disk in a mouse model of ACM. Our results point to a therapeutic option for the treatment of ACM related arrhythmias.