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Endonuclease G is a novel determinant of cardiac hypertrophy and mitochondrial function.

ABSTRACT: Left ventricular mass (LVM) is a highly heritable trait and an independent risk factor for all-cause mortality. So far, genome-wide association studies have not identified the genetic factors that underlie LVM variation, and the regulatory mechanisms for blood-pressure-independent cardiac hypertrophy remain poorly understood. Unbiased systems genetics approaches in the rat now provide a powerful complementary tool to genome-wide association studies, and we applied integrative genomics to dissect a highly replicated, blood-pressure-independent LVM locus on rat chromosome 3p. Here we identified endonuclease G (Endog), which previously was implicated in apoptosis but not hypertrophy, as the gene at the locus, and we found a loss-of-function mutation in Endog that is associated with increased LVM and impaired cardiac function. Inhibition of Endog in cultured cardiomyocytes resulted in an increase in cell size and hypertrophic biomarkers in the absence of pro-hypertrophic stimulation. Genome-wide network analysis unexpectedly implicated ENDOG in fundamental mitochondrial processes that are unrelated to apoptosis. We showed direct regulation of ENDOG by ERR-? and PGC1? (which are master regulators of mitochondrial and cardiac function), interaction of ENDOG with the mitochondrial genome and ENDOG-mediated regulation of mitochondrial mass. At baseline, the Endog-deleted mouse heart had depleted mitochondria, mitochondrial dysfunction and elevated levels of reactive oxygen species, which were associated with enlarged and steatotic cardiomyocytes. Our study has further established the link between mitochondrial dysfunction, reactive oxygen species and heart disease and has uncovered a role for Endog in maladaptive cardiac hypertrophy.

SUBMITTER: McDermott-Roe C

PROVIDER: S-EPMC3189541 | biostudies-literature | 2011 Oct

REPOSITORIES: biostudies-literature

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Endonuclease G is a novel determinant of cardiac hypertrophy and mitochondrial function.

McDermott-Roe Chris C Ye Junmei J Ahmed Rizwan R Sun Xi-Ming XM Serafín Anna A Ware James J Bottolo Leonardo L Muckett Phil P Cañas Xavier X Zhang Jisheng J Rowe Glenn C GC Buchan Rachel R Lu Han H Braithwaite Adam A Mancini Massimiliano M Hauton David D Martí Ramon R García-Arumí Elena E Hubner Norbert N Jacob Howard H Serikawa Tadao T Zidek Vaclav V Papousek Frantisek F Kolar Frantisek F Cardona Maria M Ruiz-Meana Marisol M García-Dorado David D Comella Joan X JX Felkin Leanne E LE Barton Paul J R PJ Arany Zoltan Z Pravenec Michal M Petretto Enrico E Sanchis Daniel D Cook Stuart A SA

Nature 20111005 7367

Left ventricular mass (LVM) is a highly heritable trait and an independent risk factor for all-cause mortality. So far, genome-wide association studies have not identified the genetic factors that underlie LVM variation, and the regulatory mechanisms for blood-pressure-independent cardiac hypertrophy remain poorly understood. Unbiased systems genetics approaches in the rat now provide a powerful complementary tool to genome-wide association studies, and we applied integrative genomics to dissect ...[more]

PMID: 21979051

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Project description:Cardiac hypertrophy (CH) is characterized by an increase in cardiomyocyte size, and is the most common cause of cardiac-related sudden death. A decrease in gap junction (GJ) coupling and mitochondrial dysfunction are important features of CH, but the mechanisms of decreased coupling and energy impairment are poorly understood. It has been reported that GJA1-20k has a strong tropism for mitochondria and is required for the trafficking of connexin 43 (Cx43) to cell-cell borders. In this study, we investigated the effects of GJA1-20k on Cx43 GJ coupling and mitochondrial function in the pathogenesis of CH. We performed hematoxylin-eosin (HE) and Masson staining, and observed significant CH in 18-week-old male spontaneously hypertensive rats (SHRs) compared to age-matched normotensive Wistar-Kyoto (WKY) rats. In cardiomyocytes from SHRs, the levels of Cx43 at the intercalated disc (ID) and the expression of GJA1-20k were significantly reduced, whereas JAK-STAT signaling was activated. Furthermore, the SHR rats displayed suppressed mitochondrial GJA1-20k and mitochondrial biogenesis. Administration of valsartan (10 mg· [Formula: see text] d-1, i.g., for 8 weeks) prevented all of these changes. In neonatal rat cardiomyocytes (NRCMs), overexpression of GJA1-20k attenuated Ang II-induced cardiomyocyte hypertrophy and caused elevated levels of GJ coupling at the cell-cell borders. Pretreatment of NRCMs with the Jak2 inhibitor AG490 (10 µM) blocked Ang II-induced reduction in GJA1-20k expression and Cx43 gap junction formation; knockdown of Jak2 in NRCMs significantly lessened Ang II-induced cardiomyocyte hypertrophy and normalized GJA1-20k expression and Cx43 gap junction formation. Overexpression of GJA1-20k improved mitochondrial membrane potential and respiration and lowered ROS production in Ang II-induced cardiomyocyte hypertrophy. These results demonstrate the importance of GJA1-20k in regulating gap junction formation and mitochondrial function in Ang II-induced cardiomyocyte hypertrophy, thus providing a novel therapeutic strategy for patients with cardiomyocyte hypertrophy.

Project description:Purpose:RNA-Seq analysis was performed on mouse hearts with or without hispidulin treatment 4 weeks after arotic banding or sham surgery to determining the effect of hispidulin on pressure overload induced cardiac hypertrophy. Methods: the mRNA profiles of mouse hearts underwent sham or arotic banding surgery with treatment of hispidulin or DMSO were generated by RNA-seq analysis in triplicate. The expression level of gene was calculated by RSEM(v.1.2.12). Differential expression analysis was performed using the DESeq2(V 1.4.5). Results: RNA isolation, library construction, and sequencing were performed on a BGISEQ-500 (Beijing Genomic Institution, www.genomics.org.cn, BGI). For the gene expression analysis, the fold changes were also estimated according to the fragments per kilobase of exon per million fragments mapped (FPKM) in each sample. The significance of different gene expression was defined by the following filter criteria: false discovery rate (FDR) ≤0.001 and log2-ratio 1. After comparing of DMSO+AB group and hispidulin+AB group, we found that 113 genes were significantly differentially expressed. Gene ontology and cluster analysis indicated that alternated genes were enriched in fatty acid oxidation, glucose metabolism, TCA cycle, oxidative phosphorylation, hypertrophic cardiomyopathy, ECM organism, oxidative stress and unfolded protein binding. This result indicated that hispidulin improved mitochondrial function. Conclusions: Our study represents the first detailed analysis of heart transcriptomes, with biologic replicates, generated by RNA-seq technology. The optimized data analysis workflows reported here should provide a framework for comparative investigations of expression profiles. Our results show that NGS offers a comprehensive and more accurate quantitative and qualitative evaluation of mRNA content within a cell or tissue. We conclude that RNA-seq based transcriptome characterization would expedite genetic network analyses and permit the dissection of complex biologic functions.

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Endonuclease G is a novel determinant of cardiac hypertrophy and mitochondrial function.

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Endonuclease G is a novel determinant of cardiac hypertrophy and mitochondrial function.

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