Genotype-Specific Pathomechanisms of Dilated and Non-Compaction Cardiomyopathy in Human Tissue Models

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Summary of  Signal Transduction and Targeted Therapy https://doi.org/10.1038/s41392-026-02838-7
Dr. Sabine Rebs  et al.

Points

European researchers investigated rare inherited cardiomyopathies in two families carrying distinct single-amino-acid mutations at position 634 of the RBM20 gene.
Arginine replacement by tryptophan caused dilated cardiomyopathy whereas substitution by leucine resulted in left ventricular non-compaction cardiomyopathy.
Disease modeling using patient-derived induced pluripotent stem cells and CRISPR gene editing revealed that these distinct substitutions disrupt intracellular calcium homeostasis through different mechanisms.
Dilated cardiomyopathy cells demonstrated internal sarcoplasmic reticulum calcium leakage whereas non-compaction cells exhibited hyperactivated calcium cycling and elevated metabolic energy consumption.
Pharmacological intervention using the calcium channel blocker verapamil partially restored contractile function in damaged heart cells offering a potential pathway toward personalized therapy.

Summary

This study evaluated the pathophysiology and divergent clinical manifestations of single-amino-acid missense mutations at position 634 within the arginine/serine-rich (RS) domain of the RNA-binding motif protein 20 (RBM20) gene. While mutations in RBM20 typically cause aggressive dilated cardiomyopathy (DCM) contributing to heart failure with reduced ejection fraction (HFrEF), distinct substitutions at the same locus yield markedly different phenotypes. Investigators analyzed two clinical families presenting with either DCM or left ventricular non-compaction cardiomyopathy (LVNC) to elucidate how specific point mutations disrupt excitation-contraction coupling and intracellular calcium (Ca2+) homeostasis.

To assess pathomechanisms, patient-derived induced pluripotent stem cell cardiomyocytes (iPSC-CMs), three-dimensional cardiospheres, and engineered myocardial tissues were generated alongside CRISPR/Cas9-edited isogenic rescue lines. In cells harboring the RBM20 R634W mutation (associated with DCM), functional analysis revealed increased resting Ca2+ leakage from internal sarcoplasmic reticulum stores and decreased Ca2+ transient amplitudes, accompanied by spatial disorganization of the sarcoplasmic reticulum and mitochondria. Conversely, cells harboring the R634L mutation (associated with LVNC) exhibited hyperactivated Ca2+ signaling characterized by elevated Ca2+ transient amplitudes, faster kinetics, increased cyclic adenosine monophosphate (cAMP) levels, hyperphosphorylated phospholamban (PLN), and elevated metabolic respiration.

Functional characterization across individual cardiomyocytes, organoids, and engineered tissues demonstrated that the single-amino-acid substitution determines distinct intracellular phenotypes. Pharmacological targeting using verapamil, an L-type Ca2+ channel antagonist, attenuated abnormal Ca2+ dynamics and partially restored contractile function in damaged cardiomyocytes. These findings confirm that missense variations at position 634 of RBM20 drive divergent mechanisms of heart failure, establishing a rationale for genotype-guided precision therapies and targeted gene-editing strategies in familial cardiomyopathies.

Link to the article: https://www.nature.com/articles/s41392-026-02838-7

References

Rebs, S., Sedaghat-Hamedani, F., Kayvanpour, E., Eberl, H., Berečić, B., Dudek, J., Wagensohner, N., Seedorf, A., Unsöld, J. K., Hübscher, D., Reich, C., Klein, T., Doose, S., Nikolaev, V. O., Buchwald, T., Wagdi, A., Kohlhaas, M., Dybkova, N., Morais Costa, P., … Streckfuss-Bömeke, K. (2026). RBM20 variants disrupt Ca2+ handling and metabolism in dilated and non-compaction cardiomyopathy stem cell models. Signal Transduction and Targeted Therapy, 11(1), 276. https://doi.org/10.1038/s41392-026-02838-7