Epigenetic MRI: Noninvasive Imaging of DNA Methylation in the Brain

Both neuronal and genetic mechanisms regulate brain function. While there are excellent methods to study neuronal activity in vivo, there are no nondestructive methods to measure global gene expression in living brains. Here we present a method, epigenetic magnetic resonance imaging (eMRI), that overcomes this limitation via direct imaging of DNA methylation, a major gene expression regulator. eMRI exploits the methionine metabolic pathways for DNA methylation to label genomic DNA through 13 C-enriched diets. A novel 13 C magnetic resonance spectroscopic imaging method then maps the spatial distribution of labeled DNA. We validated eMRI using pigs, whose brains have stronger similarity to humans in volume and anatomy than rodents, and confirmed efficient 13 C labeling of brain DNA. We also discovered strong regional differences in global DNA methylation. Just as MRI measurements of regional neuronal activity have had a transformational effect on neuroscience, we expect that the eMRI signal as a surrogate for regional gene expression will enable many new investigations into the roles of gene expression in human brain function, behavior, and disease.