UC San Diego

Regulation of the geroprotective histone-deacetylase SIRT1 is an important physiological strategy to protect against cardiovascular disease. SIRT1 activity regulates the oxidative stress response, DNA damage pathways, cell death, and cardioprotective SIRT1 levels decreases with age. Based on this and GWAS studies implicating misregulation linked to myocardial infarction risk, we hypothesized that disrupting proximal promoter regulation of SIRT1 causes cardiac stress. Focusing on Single Nucleotide Polymorphisms (SNPs) in the SIRT1 promoter, we used reporter gene assays to test if the transcriptional regulation of SIRT1 after oxidative stress is altered by the SNPs. Identifying a candidate A/G polymorphism at the -92 position in the promoter of SIRT1 , we show that the presence of the minority allele causes a disrupted epigenetic activation of SIRT1 . In model cell systems, binding of CCCTC-binding factor (CTCF) in the promoter of SIRT1 is reduced after oxidative stress in cells carrying the minority allele, correlating with a lack of activation of stress-protective SIRT1 expression in iPSC-derived cardiomyocytes. To investigate the physiological consequences of this mutation, we used Crispr/Cas9 to generate global Sirt1 promoter CTCF site mutant (Sirt1-mut) mice. Echocardiography in 7-month-old male mice shows reduced FS% (control 31.1±1.5%, Sirt1-mut 20.9±0.8%, mean±sem, p<0.0001, n=10-12 each), as well as increased LVIDs and decreased LVPWd wall dimensions in Sirt1-mut mice. RNA-seq on left ventricular cardiac tissue of 8-month-old control and Sirt1-mut mice identified 130 genes that are differentially regulated. Gene Ontology term enrichment analysis finds the differentially expressed genes are in pathways linked to regulation in response to reactive oxygen species and oxidative stress. In conclusion, we show that a mutation in the Sirt1 promoter critical for oxidative stress responses leads to systolic cardiac dysfunction. The transcriptional regulation of cardioprotective SIRT1 is an important and hitherto overlooked factor in the pathophysiology of heart failure.