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A mitochondrial long-chain fatty acid oxidation defect leads to uncharged tRNA accumulation and activation of the integrated stress response in the mouse heart

ABSTRACT: The heart relies mainly on mitochondrial fatty acid beta-oxidation (FAO) for its high energy requirements. Cardiomyopathy and arrhythmias can be severe complications in patients with inherited defects in mitochondrial long-chain FAO, reinforcing the importance of FAO for cardiac health. However, the pathophysiological mechanisms that underlie the cardiac abnormalities in long-chain FAO disorders remain largely unknown. Here, we investigated the cardiac transcriptional adaptations to the FAO defect in the long-chain acyl-CoA dehydrogenase (LCAD) knockout (KO) mouse. We found a prominent activation of the integrated stress response (ISR) mediated by the eIF2a/ATF4 axis in both fed and fasted states, accompanied by a reduction in cardiac protein synthesis during a short period of food withdrawal. Notably, we found an accumulation of uncharged tRNAs in LCAD KO hearts, consistent with a reduced availability of cardiac amino acids, in particular, glutamine. We replicated the activation of the cardiac ISR in hearts of mice with a muscle-specific deletion of carnitine palmitoyltransferase 2 deletion (Cpt2M-/-). Our results show that perturbations in amino acid metabolism caused by long-chain FAO deficiency impact cardiac metabolic signaling, in particular the ISR, and may play a role in the associated cardiac pathology.

ORGANISM(S): Mus musculus

PROVIDER: GSE176553 | GEO | 2021/06/11

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.

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A mitochondrial long-chain fatty acid oxidation defect leads to uncharged tRNA accumulation and activation of the integrated stress response in the mouse heart

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