Abstract Body (Do not enter title and authors here): Background: Arrhythmogenic cardiomyopathy (ACM) arises from mutations in desmosomal genes, such as desmoglein (DSG) and desmoplakin (DSP), which converge into a common pathophysiological phenotype at the cellular level, whose hallmarks include disruption of Connexin43 (Cx43) trafficking and membrane localization and suppression of the Wnt/β-catenin signaling pathway. These cellular changes in turn contribute to cardiomyocyte loss, fibrofatty infiltration, and decreased cellular coupling, leading to heart failure, arrhythmias, and sudden cardiac death. GJA1-20k, an internally translated isoform of Cx43, has previously shown therapeutic potential in a DSG model of ACM by preserving Cx43 trafficking and cell-cell coupling.
Objective: To investigate the role of GJA1-20k in protecting against a DSP model of ACM by evaluating its effect on Cx43 trafficking and Wnt/β-catenin signaling.
Methods: A DSP mutant mouse model of ACM (Dsp^-/-) received retroorbital injections of AAV9 vectors expressing either GJA1-20k-GFP or GST-GFP at 1×10¹² vg/kg. Echocardiographic measurements were recorded at 4-week intervals until the endpoint was reached, wherein hearts were excised and underwent further processing for histological and biochemical assays. Mechanistic pathways identified were validated in vitro using cell lines.
Results: Dsp^-/- mice that received GST developed heart failure associated with pathological fibrosis and cardiac remodeling. However, GJA1-20k treated Dsp^-/- mice had preserved heart function and absent fibrotic infiltration. At the cardiomyocyte level, GST-treated Dsp^-/- mice had significantly reduced Cx43 localization to the intercalated discs and reduced intercalated disc and nuclear localization of β-catenin compared to control mice. This was accompanied by an increase in β-catenin phosphorylation and degradation. However, upon GJA1-20k administration, Dsp^-/- mice had restored Cx43 trafficking, increased β-catenin nuclear translocation and activity, and reduced β-catenin degradation.
Conclusion: GJA1-20k offers therapeutic potential against ACM by preventing pathological changes in Cx43 localization and Wnt/β-catenin signaling. Moreover, this work introduces the novel concept of next generation gene therapy, whereby targeting common pathological cellular phenotypes downstream of the causative mutation serves as a viable low dose therapeutic approach to diseases of different genetic origin such as ACM.