Desmin p.R406W mutation is associated with arrhythmias through structural and electrophysiological remodeling

<jats:title>Abstract</jats:title> <jats:sec> <jats:title>Background and Aims</jats:title> <jats:p> Mutations in the desmin ( <jats:italic>DES</jats:italic> ) gene cause a variety of cardiomyopathies associated with arrhythmias, yet the electrophysiological consequences of these variants remain largely uncharacterized. The aim of this study was to investigate the pathogenic mechanisms of the <jats:italic>de novo DES</jats:italic> p.R406W variant, which was identified in a 9-year-old patient who suffered from severe ventricular arrhythmias and sudden cardiac death without overt structural heart disease. </jats:p> </jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p> Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) carrying the <jats:italic>DES</jats:italic> p.R406W variant (including the patient’s line) were compared to isogenic controls. Action potentials (AP) of hiPSC-CMs were recorded using patch-clamp. Furthermore, 3D engineered heart tissues (EHTs) were generated from hiPSC-CMs and their APs were recorded with sharp microelectrodes. Analytical techniques also included transmission electron microscopy (TEM) and integrated transcriptomic and proteomic profiling. Finally, a heterozygous knock-in (KI) mouse model carrying the <jats:italic>Des</jats:italic> p.R405W ortholog was evaluated through surface ECG, echocardiography and <jats:italic>ex vivo</jats:italic> cardiac optical mapping. </jats:p> </jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p> The <jats:italic>DES</jats:italic> p.R406W mutation prolonged AP duration in IM-R406W hiPSC-CMs and EHTs vs Control ones. Multi-omics analysis of EHTs revealed a dysregulation of genes and proteins involved in contractile function, cell adhesion, and electrical activity. TEM imaging revealed changes in Z-disc architecture in mutant tissues. Twenty-week-old <jats:italic>Des</jats:italic> p.R405W KI mice exhibited ventricular conduction slowing (prolonged QRS) and a high susceptibility to ventricular tachyarrhythmias, likely due to reentrant mechanisms. Mild hypertrophy was also observed, but only in females. </jats:p> </jats:sec> <jats:sec> <jats:title>Conclusion</jats:title> <jats:p> The <jats:italic>DES</jats:italic> p.R406W variant is highly pathogenic, causing electrical and structural remodeling of the myocardium. This study highlights the effectiveness of hiPSC-CMs and EHTs in recapitulating the clinical phenotype of desminopathy, providing a platform for investigating the mechanisms of early-onset cardiac arrhythmias and SCD. </jats:p> </jats:sec>