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Mitochondrial Polymerase Gamma Dysfunction and Aging Cause Cardiac Nuclear DNA Methylation Changes [100929_MM9_Deluxe_Prom_Meth_HX1]

ABSTRACT: Cardiomyopathy (CM) is an intrinsic weakening of the myocardium with contractile dysfunction and congestive heart failure (CHF). CHF has been postulated to result from decreased mitochondrial energy production and oxidative stress. The effects of decreased mitochondrial oxygen consumption can also accelerate with aging, with the mitochondrial theory of aging forming the basis of this knowledge. We previously showed DNA methylation changes in human hearts with CM. This was associated with mitochondrial DNA depletion, being another molecular marker of CM. We examined the relationship between mitochondrial dysfunction and cardiac epigenetic DNA methylation changes in both young and old mice. We used genetically engineered C57Bl/6 mice transgenic for a cardiac-specific mutant of the mitochondrial polymerase (termed Y955C). Y955C mice undergo left ventricular hypertrophy (LVH) at a young age (~94 days old), and LVH decompensated to CHF at old age (~255 days old). In Y955C hearts, 95 differentially expressed genes were found, while 4,452 genes were differentially expressed in aged hearts. Moreover, cardiac DNA methylation patterns differed between Y955C (4,506 peaks with 68.5% hypomethylation) and aged hearts (73,286 peaks with 80.2% hypomethylated). Correlatively, of the 95 Y955C-dependent differentially expressed genes, 30 genes (31.6%) also displayed differential DNA methylation; in the 4,452 age dependent differentially expressed genes, 342 gene (7.7%) displayed associated DNA methylation changes. Both Y955C and aging demonstrated significant enrichment of CACGTG-associated E-box motifs in differentially methylated regions. Cardiac mitochondrial polymerase dysfunction alters nuclear DNA methylation. Furthermore, aging causes a robust change in cardiac DNA methylation that is partially associated with mitochondrial polymerase dysfunction. This study addresses how Y955C-mutated mitochondrial DNA polymerase g and aging affect cardiac (left ventricle) gene expression and epigenetic nuclear DNA methylation.

ORGANISM(S): Mus musculus

PROVIDER: GSE72889 | GEO | 2016/05/06

SECONDARY ACCESSION(S): PRJNA295274

REPOSITORIES: GEO

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Project description:Cardiomyopathy (CM) is an intrinsic weakening of the myocardium with contractile dysfunction and congestive heart failure (CHF). CHF has been postulated to result from decreased mitochondrial energy production and oxidative stress. The effects of decreased mitochondrial oxygen consumption can also accelerate with aging, with the mitochondrial theory of aging forming the basis of this knowledge. We previously showed DNA methylation changes in human hearts with CM. This was associated with mitochondrial DNA depletion, being another molecular marker of CM. We examined the relationship between mitochondrial dysfunction and cardiac epigenetic DNA methylation changes in both young and old mice. We used genetically engineered C57Bl/6 mice transgenic for a cardiac-specific mutant of the mitochondrial polymerase (termed Y955C). Y955C mice undergo left ventricular hypertrophy (LVH) at a young age (~94 days old), and LVH decompensated to CHF at old age (~255 days old). In Y955C hearts, 95 differentially expressed genes were found, while 4,452 genes were differentially expressed in aged hearts. Moreover, cardiac DNA methylation patterns differed between Y955C (4,506 peaks with 68.5% hypomethylation) and aged hearts (73,286 peaks with 80.2% hypomethylated). Correlatively, of the 95 Y955C-dependent differentially expressed genes, 30 genes (31.6%) also displayed differential DNA methylation; in the 4,452 age dependent differentially expressed genes, 342 gene (7.7%) displayed associated DNA methylation changes. Both Y955C and aging demonstrated significant enrichment of CACGTG-associated E-box motifs in differentially methylated regions. Cardiac mitochondrial polymerase dysfunction alters nuclear DNA methylation. Furthermore, aging causes a robust change in cardiac DNA methylation that is partially associated with mitochondrial polymerase dysfunction. This study addresses how Y955C-mutated mitochondrial DNA polymerase g and aging affect cardiac (left ventricle) gene expression and epigenetic nuclear DNA methylation.

Project description:VEGF family members are important regulators of vascular functions. Promoting VEGFA signalling in aged mice has been shown to delay various aging phenotypes and extend the survival of aged mice. Although there is profound knowledge on functions of VEGFA, VEGFB has not been investigated in the context of cardiac aging. Our RNA data of aged mouse hearts revealed significant downregulation of Vegfb in the heart, specifically in endothelial cells and cardiomyocytes, while VEGFB expression was reduced in endothelial cells, fibroblasts and cardiomyocytes in aged human hearts. By contrast, VEGFB expression was exclusively reduced in cardiomyocytes of patients with cardiac hypertrophy. Hence, we investigated whether Vegfb gene therapy can revert age-dependent cardiac pathologies. We overexpressed Vegfb186, the soluble VEGFB isoform, via AAV9 vector transduction into 18-month-old C57Bl/6J male mice. AAV9-Vegfb treatment prevented progression age-related diastolic dysfunction and decreased cardiac fibrosis. We further found a rescue of aging-related left ventricular denervation in the hearts of AVV9-Vegfb treated old mice which was associated with an increase in heart rate variability. However, heart to body weight ratio and cardiomyocyte hypertrophy were increased in the AAV9-Vegfb treated mouse hearts, without alteration of cardiac systolic or diastolic function. Histological and transcriptomic analyses revealed that VEGFB186 induces compensatory cardiac hypertrophy which was accompanied by a rescued length-width-ratio, reduced fibrosis and the absence of cardiac inflammation. Cardiac single-nuclei RNA sequencing further suggested that AAV9-Vegfb treatment affects cardiac hypertrophy putatively via STAT3 which was validated in vitro. In conclusion, our data reveals that Vegfb overexpression partially reverses pathological alterations in the aging heart. Despite the overall improvement of the age-related cardiac phenotype, the AAV9-Vegfb-mediated induced cardiac hypertrophy which might reflect protective hypertrophy.

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Mitochondrial Polymerase Gamma Dysfunction and Aging Cause Cardiac Nuclear DNA Methylation Changes [100929_MM9_Deluxe_Prom_Meth_HX1]

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