Rbm20-deficient cardiogenesis reveals early disruption of RNA processing and sarcomere remodeling establishing a developmental etiology for dilated cardiomyopathy

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Dilated cardiomyopathy (DCM) due to mutations inRBM20, a gene encoding an RNA-binding protein, is associated with high familial penetrance, risk of progressive heart failure and sudden death. Although genetic investigations and physiological models have established the linkage ofRBM20with early-onset DCM, the underlying basis of cellular and molecular dysfunction is undetermined. Modeling human genetics using a high-throughput pluripotent stem cell platform was herein designed to pinpoint the initial transcriptome dysfunction and mechanistic corruption in disease pathogenesis. Tnnt2-pGreenZeo pluripotent stem cells were engineered to knockdownRbm20(shRbm20) to determine the cardiac-pathogenic phenotype during cardiac differentiation. Intracellular Ca2+ transients revealedRbm20-dependent alteration in Ca2+ handling, coinciding with known pathological splice variants ofTitinandCamk2dgenes by Day 24 of cardiogenesis. Ultrastructural analysis demonstrated elongated and thinner sarcomeres in the absence ofRbm20that is consistent with human cardiac biopsy samples.Furthermore,Rbm20-depleted transcriptional profiling at Day 12 identifiedRbm20-dependent dysregulation with 76% of differentially expressed genes linked to known cardiac pathology ranging from primordialNkx2.5to mature cardiacTnnt2as the initial molecular aberrations. Notably, downstream consequences ofRbm20-depletion at Day 24 of differentiation demonstrated significant dysregulation of extracellular matrix components such as the anomalous overexpression of theVtngene. By using the pluripotent stem cell platform to model human cardiac disease according to a stage-specific cardiogenic roadmap, we established a new paradigm of familial DCM pathogenesis as a developmental disorder that is patterned during early cardiogenesis and propagated with cellular mechanisms of pathological cardiac remodeling.

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