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Cardiomyocyte-specific Srsf3 deletion reveals a mitochondrial regulatory role

ABSTRACT: Serine-rich splicing factor 3 (SRSF3) was recently reported as being necessary to preserve RNA stability via an mTOR mechanism in a cardiac mouse model in adulthood. Here, we demonstrate the link between Srsf3 and mitochondrial integrity in an embryonic cardiomyocyte-specific Srsf3 conditional knockout (cKO) mouse model. Fifteen-day-old Srsf3 cKO mice showed dramatically reduced (below 50%) survival and reduced the left ventricular systolic performance, and histological analysis of these hearts revealed a significant increase in cardiomyocyte size, confirming the severe remodeling induced by Srsf3 deletion. RNA-seq analysis of the hearts of 5-day-old Srsf3 cKO mice revealed early changes in expression levels and alternative splicing of several transcripts related to mitochondrial integrity and oxidative phosphorylation. Likewise, the levels of several protein complexes of the electron transport chain decreased, and mitochondrial complex I-driven respiration of permeabilized cardiac muscle fibers from the left ventricle was impaired. Furthermore, transmission electron microscopy analysis showed disordered mitochondrial length and cristae structure. Together with its indispensable role in the physiological maintenance of mouse hearts, these results highlight the previously unrecognized function of Srsf3 in regulating the mitochondrial integrity.

ORGANISM(S): Mus musculus

PROVIDER: GSE151168 | GEO | 2021/06/23

REPOSITORIES: GEO

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Project description:Purpose: Next-generation sequencing (NGS) provides the change of cellular pathways at the transcriptomic level. The overall goal for this research are to compare the transcriptome profiling by NGS in cardiomyocyte-specific FAM210A conditional knockout (cKO) hearts and control (Ctrl) hearts at two different time points and to evaluate the signaling pathways affected by FAM210A deficiency in the heart at the molecular level. Methods: Cardiac mRNA profiles of FAM210A cKO and Ctrl hearts were generated by deep sequencing in triplicate at the late stage (~10 weeks post Fam210a cKO by tamoxifen induction) and in quadruplicates at the early stage (~5 weeks post Fam210a cKO by tamoxifen induction). Results: Using an optimized data analysis workflow from the Genomic Research Center at the University of Rochester, we mapped ~30 millian sequence reads per sample to the mouse genome in the hearts of Ctrl and Fam210a cKO mice at both early and late stages. RNA-seq data comfirmed the knockout of FAM210A in the Fam210a cKO hearts. We identified differentially expressed genes at both early and late stages of FAM210A cKO heart compared with Ctrl hearts (adjust P valuse <0.05). Among upregulated genes, we observed enhanced integrated stress response (ISR) gene signature at both early and late stages in Fam210a cKO hearts compared with Ctrl hearts, including aminoacyl-tRNA synthetases, amino acid synthases, and one-carbon metabolic enzymes. The downregulated genes were not common between the two stages. At the early stage, the top enriched pathways include negative regulation of blood coagulation and wound healing and fatty acid metabolic process. In contrast, at the late stage, the major pathways include sulfide oxidation, glucose import, and mitochondrial ETC complex assembly. Conclusions: Our study provides the first detailed transcriptomic anslysis of cardiomyocyte specific knockout of Fam210a in the heart at two different time-points by NGS. The RNA-seq data reported here provide a framework for comparative investigation of expression profiles in the hearts of FAM210A cKO compared with Ctrl hearts. Based on our analysis, we conclude that ISR is persistently activated in Fam210a cKO hearts, which may be a pro-survival compensatory response caused by the dysfunction of mitochondria in Fam210a cKO hearts. ISR activation can reprogram global cap-dependent translation and cellular metabolism simultaneously.

Project description:The cellular and molecular aspects of post-infarct left-ventricle remodeling in presence of type-2 diabetes is poorly understood. In this study we have addressed the cellular and molecular aspects underlying post-infarct left-ventricle remodeling in type 2 diabetic (T2DM) mice using genome-wide mRNA-sequencing. Myocardial infarction was induced by ligating left-anterior descending artery (LAD) in 12-14 month old T2DM and control mice. Cardiac MRI was performed at baseline, day 7 and 14 post-LAD ligation. Blood and tissue samples were collected for biochemical and immunohistochemical, molecular biology analysis after sacrification at day 7 and 14. Genome-wide mRNA sequencing analysis was performed from left-ventricular tissues collected at day 7 post-LAD ligation. Mitochondrial dynamics, Leukocyte recruitment and Collagen I deposition were analyzed using electron microscopy, fluorescent assisted cell sorting (FACS) and fourier-transform infra-red (FTIR) spectroscopy from left ventricular tissues collected at day 7 and 14 post-LAD ligation. Cardiac ejection fraction (EF) and stroke volume (SV) were significantly reduced along with increased mortality in T2DM compared to controls. Ingenuity pathway analyses of differentially expressed genes were enriched for mitochondrial dysfunction, TCA cycle and fatty acid oxidation. Additionally, upstream transcription factor analysis showed inhibition of PGC1a, PGC1b, ESRRA, ESRRB and TFAM in infarcted myocardium of T2DM mice. Electron microscopy analysis showed an altered mitochondrial dynamics and cardiomyocyte death in ischemic myocardium of T2DM mice. Leukocytes exhibited an altered phenotype in ischemic myocardium of T2DM mice. Neovascularization was impaired and collagen deposition was increased in ischemic myocardium of T2DM mice. We conclude that an altered mitochondrial dynamics, cell death modalities, leukocyte phenotype, neovascularization responses and fibrosis may contribute to an increased mortality after myocardial infarction in T2DM. Modulation of mitochondrial dynamics and cardiomyocyte cell death modalities may offer a novel therapeutic target.

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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Cardiomyocyte-specific Srsf3 deletion reveals a mitochondrial regulatory role

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