MicroRNA-184 Is Decreased In Arrhythmogenic Cardiomyopathy And Contributes To The Pathogenesis Of The Disease Phenotype

Rationale:Pathogenesis of fibro-adipogenesis in arrhythmogenic cardiomyopathy (AC) is largely unknown.Objective:To elucidate the pathogenic role of microRNAs (miRNAs) in AC.Methods and Results:Control and plakophilin-2 (PKP2)-knocked down HL-1 (HL-1Pkp2-shRNA) myocytes were screened for 750 miRNAs using low-density microfluidic panels.59 miRNAs were differentially expressed. MiR-184 was the most down-regulated miRNA. It was also down-regulated in the heart and isolated cardiomyocytes from mouse models of AC as compared to wild type. MiR-184 was predominantly expressed in immature myocytes and cardiac CD44+mesenchymal cells and its expression was progressively suppressed during cardiac development. The E2F pathway, which was suppressed in AC models, regulated expression of miR-184 by binding of E2F1 to the 5’genomic region of miR-184. Activation of E2F1, upon overexpression of its activator CCND1 or knock down of its inhibitor RBI, partially rescued miR-184 levels. In addition, DNMT1 was recruited to the promoter region of miR-184 leading to hyper-methylation of the CpG sites at the upstream region of miR-184. Treatment with 5-Aza-2’-Deoxycytidine, a de-methylation agent and knock down of Dnmtl partially rescued miR-184 level. Pathway analysis of paired miR-184:mRNA targets identified cell proliferation, differentiation, and death as the main affected pathways. Knock down of miR-184 in HL-1 myocytes and CD44+cells induced and conversely, its over-expression attenuated adipogenesis.Conclusions:miR-184 levels are suppressed in cell and mouse models of AC because of suppressed E2F1 pathway and hyper-methylation of the CpG sites at miR-184 promoter. Suppressed miR-184 enhances adipogenesis and contributes to the pathogenesis of AC.