Entorhinal cortex EWAS meta-analysis highlights four novel loci showing differential methylation in Alzheimer's disease

Studies on DNA methylation (DNAm) in Alzheimer9s disease (AD) have recently highlighted several genomic loci showing association with disease onset and progression. Here, we conducted an epigenome-wide association study (EWAS) using DNAm profiles in entorhinal cortex (EC) from 149 AD patients and control brains and combined these with two previously published EC datasets by meta-analysis (total n=337). We identified 12 cytosine-phosphate-guanine (CpG) sites showing epigenome-wide significant association with either case-control status or Braak9s tau-staging. Four of these CpGs, located in proximity to TENT5A, PALD1, PRF1, and DIRAS1, were not reported previously. Integrating DNAm levels with RNA sequencing-based mRNA expression data generated in the same individuals showed significant DNAm-mRNA correlations for 6 of the 12 significant CpGs. By calculating rates of epigenetic age acceleration using two recently proposed "epigenetic clock" estimators we found a significant association with accelerated epigenetic aging in AD patients vs. controls. In summary, our study represents the hitherto most comprehensive EWAS in AD using EC and highlights several novel differentially methylated loci with potential effects on gene expression.