Genome-wide DNA Methylation Profiling

Genome-wide methylation in peripheral blood cells from a subset of the EIRA, EIMS and InCHIANTI cohorts were evaluated by Illumina Infinium Human Methylation 450 BeadChip according to the manufacturer’s recommendations. Illumina Infinium Human Methylation 450 BeadChip array quantifies methylation levels at specific loci within the genome. The percentage methylation value for a particular CpG site, which represents the fraction of DNA with this CpG site methylated, was calculated on a scale of 0–1, per Illumina’s recommendations, using the formula: $\mathrm{M}/\left(\mathrm{M}+\mathrm{U}+100\right)\text{,}$ where M and U represent the methylated and unmethylated signal intensities, respectively. Methylation data from EIRA was published previously [12 (link)] and can be downloaded from Gene Expression Omnibus [GEO:GSE42861].