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Titin truncating variantsin hiPSC-cardiomyocytes inducepathogenic proteinopathy, sarcomeredefect and contractile dysfunction independent of the core contractilemachinery [scRNA-seq]

ABSTRACT: Titintruncating variants(TTNtv) have been identified as the single largestgenetic cause of dilated cardiomyopathy(DCM). In this studywe modeled the disease phenotypes of TTNtv-induced DCM in hiPSC-CMsusing CRISPR/Cas9 genome editing and tissue engineering technologies. Transcriptomic, cellular and micro-tissue studies revealed that TTNtv hiPSC-CMs displayed pathogenic proteinopathy, sarcomere defects, aberrant Na+channel activities and, most importantly, contractile dysfunction. These phenotypes establish a dual mechanism of poison peptide effect and haploinsufficiency that collectively contribute to DCM pathogenesis. On the other hand, TTNtv cellular defects did not interfere with normal function of the core contractile machinery, actin-myosin-troponin-Ca2+complex, and preserved the therapeutic mechanism of sarcomere modulators. Treatment of TTNtv cardiac micro-tissues with investigational sarcomere modulators augmented contractility and resulted in sustained transcriptomicchanges that promotereversalof DCM disease signatures, as revealed by single-cell RNA-seqanalysis.Taken together, our findings depict the underlying pathogenic mechanisms of TTNtv-induced DCMand demonstrate the validity of sarcomere modulators as potentialtherapeutic agentsfor this disease.

ORGANISM(S): Homo sapiens

PROVIDER: GSE183217 | GEO | 2023/01/25

REPOSITORIES: GEO

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Project description:Background: Modulation of mRNA splicing acts as an important layer of gene regulation, in addition to transcriptional regulation and epigenetic modifications. RNA binding proteins (RBPs) play essential roles in mediating RNA splicing and are key regulators of heart development and function. Our previous studies demonstrated that RBPMS (RNA-binding protein with multiple splicing) regulates cardiac development through modulating mRNA splicing during embryogenesis. Here we explored the postnatal function of RBPMS in the heart. Methods: We ablated Rbpms in the heart by generating a cardiac-specific knockout mouse line (Myh6-Cre, Rbpmsfl/fl), and evaluated its cardiac functions by histology, echocardiography, and gene expression. Paired-end RNA sequencing and RT-PCR were performed to identify and validate splicing targets of RBPMS in adult mouse hearts. Proximity-dependent Biotin Identification (BioID) assay and mass spectrometry analysis were performed to identify RBPMS binding partners. We also measured contractility and calcium fluxes in isolated mouse cardiomyocytes, and contractile forces of cardiac papillary muscle. Human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) were also used as a model to explore the influence of RBPMS on contractility of human cardiomyocytes. Results: he absence of Rbpms in the heart led to dilated cardiomyopathy (DCM) and heart failure, causing early death in mice. Mice with cardiac-specific knockout of Rbpms showed myocardium noncompaction with reduced cardiomyocyte number at the neonatal stage and developed DCM with pervasive myocardial fibrosis in adulthood. We found that RBPMS mediates a largely distinct RNA splicing profile in adult mouse hearts compared to neonatal hearts, indicating a stage-specific modulation of alternative RNA splicing by RBPMS. In adult hearts, RBPMS mainly influenced alternative splicing of genes associated with sarcomere structures and cardiomyocyte contraction, such as Ttn, Pdlim5 and Nexn, to generate new protein isoforms. In neonatal hearts, RBPMS influenced the splicing of cytoskeletal genes. RBMPS was associated with spliceosome factors and other RNA binding proteins that play important roles in the heart, such as RBM20 and GATA4. Importantly, we found that the absence of Rbpms caused severe cardiomyocyte contractile defects and reduced calcium sensitivity in both mouse and hiPSC-CMs. Our results demonstrated that Rbpms is crucial for postnatal cardiac function and cardiomyocyte contractility by regulating RNA alternative splicing. Conclusions: Loss of Rbpms in the heart causes reduced cardiomyocyte number and impaired cardiomyocyte contraction, leading to DCM and heart failure.

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Titin truncating variantsin hiPSC-cardiomyocytes inducepathogenic proteinopathy, sarcomeredefect and contractile dysfunction independent of the core contractilemachinery [scRNA-seq]

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