Epigenome and phenome study reveals circulating markers pertinent to brain health

Characterising associations between the epigenome, proteome and phenome may provide insight into molecular regulation of biological pathways governing health. However, epigenetic signatures for many neurologically-associated plasma protein markers remain uncharacterised. Here, we report an epigenome and phenome-wide association study of the circulating proteome in relation to brain health. We perform epigenome-wide studies of 4,235 plasma proteins (n=778), identifying 2,895 CpG-protein associations (protein quantitative trait methylation loci; pQTMs) after stringent correction for multiple testing. These were independent of known genetic protein quantitative trait loci (pQTL) and common lifestyle effects, extending current knowledge by analysing a further 3,286 protein measurements with 2,854 novel pQTMs. We then perform a phenome-wide study of each protein in relation to neurological traits in 1,065 individuals, identifying 644 proteins related to cognitive, brain imaging phenotypes or APOE status. By integrating our pQTM dataset with our phenome association study, we uncovered 88 epigenetic associations for protein markers of neurological traits, 83 of which were previously unreported. These data are pertinent to understanding heterogeneity in brain health.