Authors
Rebs S, Sedaghat-Hamedani F, Kayvanpour E, Eberl H, Berečić B, Dudek J, Wagensohner N, Seedorf A, Unsöld JK, Hübscher D, Reich C, Klein T, Doose S, Nikolaev VO, Buchwald T, Wagdi A, Kohlhaas M, Dybkova N, Morais Costa P, Guan K, Hasenfuss G, Rog-Zielinska EA, Sossalla S, Sauer M, Maack C, Tiburcy M, Meder B, Streckfuss-Bömeke K
Journal
Signal Transduction and Targeted Therapy
Citation
Signal Transduct Target Ther. 2026 Jul 14;11(1):276.
Abstract
Mutations in the splice-regulator RBM20 cause heart failure with reduced ejection fraction (HFrEF), typically manifesting as dilated cardiomyopathy (DCM). Mutations at position 634 in the RS-domain cause DCM with (R634L) or without (R634W) left ventricular non-compaction (LVNC). However, the mechanisms underlying phenotype variability and personalized therapy beyond HFrEF remain unclear. We generated induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM), 3D-cardiospheres and engineered myocardial tissues from patients with RBM20 mutations R634L (LVNC) or R634W (DCM). Using CRISPR/Cas9, we created isogenic rescue and mutation-insertion lines, identifying RBM20 mis-localization, splicing errors in TTN and RYR2, and sarcomere irregularities in both. DCM-CM showed increased resting Ca2+ leak and reduced Ca2+ transient amplitude, typical of HFrEF, and spatial disorganization of sarcoplasmic reticulum and mitochondria. In contrast, LVNC-CM exhibited elevated Ca2+ transient amplitude with faster kinetics, driven by elevated cAMP and mis-spliced, hyperactive CAMK2D, leading to PLN-hyperphosphorylation and increased metabolic respiration. Further, LVNC showed desmosomal derangement potentially from mis-splicing of Junction plakoglobin and reduced 3D cardiosphere compaction. Despite distinct mechanisms, contractile force was reduced in both. Isogenic controls confirm mutation causality. Drug intervention with verapamil partially improved selected abnormal Ca2+ handling and contractile phenotypes in LVNC- and DCM-CM, whereas the CAMK2D inhibitor AIP improved systolic Ca2+ handling predominantly in LVNC-CM. In conclusion, different amino acid substitutions at the same RBM20-residue induce opposing Ca2+-handling and structural phenotypes. While DCM features impaired Ca2+ handling, LVNC shows defective cell-cell coupling and activated Ca2+ handling and metabolism, yet insufficient to compensate for organ-level dysfunction. This supports personalized pharmacological therapies in early HF, and potential CRISPR/Cas9 repair for RBM20 cardiomyopathy.
