Epigenome-wide association study, meta-analysis, and multiscore profiling of whole blood in Parkinson's disease

An increasing body of evidence indicates altered DNA methylation in Parkinson's disease, yet the reproducibility and utility of such methylation changes are largely unexplored. We aimed to further elucidate the role of dysregulated DNA methylation in Parkinson's disease and to evaluate the biomarker potential of methylation-based profiling.

We conducted an epigenome-wide association study (EWAS) in whole blood, including 280 Parkinson's disease and 279 control participants from Oslo, Norway. Next, we took advantage of data from the Parkinson's Progression Markers Initiative (PPMI) and a previously published EWAS to conduct a whole blood EWAS meta-analysis in Parkinson's disease, incorporating results from a total of 3068 participants. Finally, we generated multiple methylation-based scores for each Oslo and PPMI participant and tested their association with disease status, individually and in a joint multiscore model.

In EWAS meta-analysis, we confirm SLC7A11 hypermethylation and nominate a novel differentially methylated CpG near LPIN1. A joint multiscore model incorporating polygenic risk and methylation-based estimates of epigenetic Parkinson's disease risk, smoking, and leukocyte proportions differentiated patients from control participants with an area under the receiver-operator curve of 0.82 in the Oslo cohort and 0.65 in PPMI.

Our results highlight the power of DNA methylation profiling to capture multiple aspects of disease risk, indicating a biomarker potential for precision medicine in neurodegenerative disorders. The reproducibility of specific differentially methylated CpGs across data sets was limited but may improve if future studies are designed to account for disease stage and incorporate environmental exposure data.