Cardiac desmosomes are specialized cell junctions responsible for cardiomyocytes mechanical coupling. Mutation in desmosomal genes cause autosomal dominant and recessive familial arrhythmogenic cardiomyopathy. Motivated by evidence that Mendelian diseases share genetic architecture with common complex traits, we assessed whether common variants in any desmosomal gene were associated with cardiac conduction traits in the general population.

We analysed data of N=4342 Cooperative Health Research in South Tyrol (CHRIS) study participants. We tested associations between genotype imputed variants covering the five desmosomal genes DSP, JUP, PKP2, DSG2, and DSC2, and P-wave, PR, QRS, and QT electrocardiographic intervals, using linear mixed models. Functional annotation and interrogation of publicly available genome-wide association study resources implicated potential connection with antisense lncRNAs, DNA methylation sites, and complex traits. Causality was tested via two-sample Mendelian randomization (MR) analysis and validated with functional in vitro follow-up in human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs).

DSP variant rs2744389 was associated with QRS (P=3.5×10-6), with replication in the Microisolates in South Tyrol (MICROS) study (n=636; P=0.010). Observing that rs2744389 was associated with DSP-AS1 antisense lncRNA but not with DSP expression in multiple GTEx-v8 tissues, we conducted two-sample Mendelian randomization analyses that identified causal effects of DSP-AS1 on DSP expression (P=6.33×10-5; colocalization posterior probability=0.91) and QRS (P=0.015). In hiPSC-CMs, DSP-AS1 expression downregulation through a specific GapmerR matching sequence led to significant DSP upregulation at both mRNA and protein levels.

The evidence that DSP-AS1 has a regulatory role on DSP opens the venue for further investigations on DSP- AS1’s therapeutic potential for conditions caused by reduced desmoplakin production.

Author Summary Arrhythmogenic Cardiomyopathy is a severe condition mainly caused by pathogenic variants in genes encoding components of the cardiac desmosome, a specialised cell junction.

Given complex traits and Mendelian diseases share common genetic background, we hypothesised that common variants in any of the five desmosomal genes (DSP, JUP, PKP2, DSG2, and DSC2) could be associated with electrocardiographic measurements in general population individuals.

Analyzing data from >4000 participants from the Cooperative Research In South Tyrol (CHRIS) study, we identified an association between a variant in the desmoplakin gene (DSP) and QRS, which represents the time needed for ventricular electrical activation.

Downstream gene expression analyses showed that the identified variant was not associated with the expression of DSP but with that of an uncharacterized long non-coding antisense RNA, DSP-AS1.

Mendelian randomization (MR) analyses, performed leveraging publicly available data, supported a causal effect of DSP-AS1 expression on DSP expression.

In vitro functional follow-up showed that silencing DSP-AS1 induces DSP transcript and desmoplakin protein upregulation, suggesting that DSP-AS1 is involved in the regulation of DSP expression and validating MR findings.

Our study represents a first step in the functional characterization of DSP-AS1, a potential target for treatment of diseases caused by low amounts of desmoplakin.

CP has received consultant fees from Quotient Therapeutics. All other authors declared no conflicts of interest.

Not applicable. This study is neither a clinical trial, nor an interventional study.

CHRIS was funded by the Autonomous Province of Bolzano - Department of Innovation, Research, University and Museums, and supported by the European Regional Development Fund (FESR1157). MICROS was supported by the Ministry of Health of the Autonomous Province of Bolzano and the South Tyrolean Sparkasse Foundation. This study was supported by the Department of Innovation, Research and University of the Autonomous Province of Bolzano (Italy) and by the Joint Project Alto Adige-SNSF (Italy-Switzerland), grant number 10.003.119 to MDB. SHIP is part of the Community Medicine Research net of the University of Greifswald, Germany, which is funded by the Federal Ministry of Education and Research (grants no. 01ZZ9603, 01ZZ0103, and 01ZZ0403), the Ministry of Cultural Affairs as well as the Social Ministry of the Federal State of Mecklenburg-West Pomerania, and the network Greifswald Approach to Individualized Medicine (GANI_MED) funded by the Federal Ministry of Education and Research (grant 03IS2061A). Genome-wide data have been supported by the Federal Ministry of Education and Research (grant no. 03ZIK012) and a joint grant from Siemens Healthineers, Erlangen, Germany and the Federal State of Mecklenburg-West Pomerania. DNA methylation data have been supported by the DZHK (grants 81X3400104, 81X2400157). The KORA study was initiated and financed by the Helmholtz Zentrum Muenchen - German Research Center for Environmental Health, which is funded by the German Federal Ministry of Education and Research (BMBF) and by the State of Bavaria. Data collection in the KORA study is done in cooperation with the University Hospital of Augsburg.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

CHRIS was approved by the Ethics Committee of the Healthcare System of the Autonomous Province of Bolzano (approval number 21-2011). MICROS was approved by the Ethics Committee of the Autonomous Province of Bolzano on 26-February-2002 (approval number RD/ac/13/01/18332). The research involving human stem cell lines was approved by the Ethics Committee of the Province of Bolzano (approval number 1/2014). SHIP-START and SHIP-TREND were approved by the Ethics Committee at the University Medicine Greifswald (approval number BB 39/08). The studies conform to the Declaration of Helsinki, and with national and institutional legal and ethical requirements. All participants included in the analysis gave oral and written informed consent.

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