Abstract
Introduction: Arrhythmogenic cardiomyopathy (ACM) is a genetic disease characterized by fibro-fatty myocardial replacement, associated with malignant ventricular arrhythmias and sudden cardiac death. Rare pathogenetic variants affecting genes encoding desmosomal proteins are well-established causes of ACM. Common genetic variants located in desmosomal genes are expected to impact cardiac conduction traits also in the general population.
Aim: To investigate the association between common genetic variants in ACM desmosomal genes (DSC2, DSG2, PKP2, JUP, DSP) with P-wave, PR, QRS and QT intervals, and their possible role in ACM.
Materials and Methods: The research was conducted using data from N=4295 participants in the Cooperative Health Research in South Tyrol (CHRIS) study, data release 2. Cardiac conduction traits were measured using 10 second 12-lead electrocardiogram (ECG). Samples were genotyped using the Illumina HumanOmniExpressExome array and imputed against the 1000 Genome Phase 1 panel. We conducted genetic association studies on 3458 variants in Linkage Disequilibrium blocks originating in the desmosomal genes and extending outside the gene boundaries. We assumed an additive model, at 1.9x10-4 significance threshold, and complemented the analyses by Mendelian Randomization (MR) integrating ECG traits and Genotype-Tissue Expression (GTEx) database transcription levels. Downregulation of the antisense RP3-512B11.3 lncRNA was obtained through a sequence specific locked nucleic acid (LNA) GapmeR and digital droplet PCR was used to check lncRNA and desmoplakin (DSP) gene expression in human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs).
Results: The rs2744389 in the DSP promoter was associated with shorter QRS interval (beta= -1.10 ms, standard error=0.24, p=3.5*10-6 ). In the GTEx database rs2744389 results being an expression quantitative locus (eQTL) of the antisense RP3-512B11.3 lncRNA, rather than DSP, for which no eQTLs are currently listed. MR analyses supported a causal effect of RP3-512B11.3 on QRS. To assess the hypothesis that RP3-512B11.3 controlled DSP expression, we identified a LNA Gapmer capable of downregulating RP3- 512B11.3 expression of about 50% in hiPSC-CMs. The RP3-512B11.3 downregulation led to a significant increase of DSP mRNA expression compared to cells treated with a non-human sequence LNA GapmeR, used as a negative control (beta=2.76 DSP/RPP30, standard error=0.34, p=5.1*10-16).
Conclusions: This functional follow-up of the results from a population-based genetic study suggested that the RP3-512B11.3 lncRNA plays a role in regulating the expression of the downstream DSP. While needing further experimental evidence to confirm it, these findings highlight a new mechanism of DSP regulation, suggesting a possible therapeutic approach in ACM patients carrying DSP mutations causing a desmoplakin reduction