G6PD Orchestrates Genome-Wide DNA Methylation and Gene Expression in the Vascular Wall

Recent advances have revealed the importance of epigenetic modifications to gene regulation and transcriptional activity. DNA methylation, a determinant of genetic imprinting and the de novo silencing of genes genome-wide, is known to be controlled by DNA methyltransferases (DNMT) and demethylases (TET) under disease conditions. However, the mechanism(s)/factor(s) influencing the expression and activity of epigenetic writers and erasers, and thus DNA methylation, in healthy vascular tissue is incompletely understood. Based on our recent studies, we hypothesized that glucose-6-phosphate dehydrogenase (G6PD) is a modifier of DNMT and TET expression and activity and an enabler of gene expression. In the aorta of CRISPR-edited rats with the Mediterranean G6PD variant, we determined DNA methylation by whole-genome bisulfite sequencing, gene expression by RNA sequencing, and large artery stiffness by echocardiography. Here, we documented higher expression of Dnmt1, Dnmt3a, Tet2, and Tet3 in aortas from Mediterranean G6PD^S188F variant (a loss-of-function single nucleotide polymorphism) rats than their wild-type littermates. Concomitantly, we identified 17,618 differentially methylated loci genome-wide (5787 hypermethylated loci, including down-regulated genes encoding inflammation- and vasoconstriction-causing proteins, and 11,827 hypomethylated loci, including up-regulated genes encoding smooth muscle cell differentiation- and fatty acid metabolism-promoting proteins) in aortas from G6PD^S188F as compared to wild-type rats. Our results demonstrated that nitric oxide, which is generated in a G6PD-derived NADPH-dependent manner, increases TET and decreases DNMT activity. Further, we observed less large artery (aorta) stiffness in G6PD^S188F as compared to wild-type rats. These results establish a noncanonical function of the wild-type G6PD and G6PD^S188F variant in the regulation of DNA methylation and gene expression in healthy vascular tissue and reveal that the G6PD^S188F variant contributes to reducing large artery stiffness.