Genome-wide epigenetic analysis of Japanese immigrant plantation workers with Parkinson’s Disease

Parkinson’s Disease (PD) is a disease of the central nervous system that progressively affects the motor system. Epidemiological studies have provided evidence that exposure to agriculture-related occupations or agrichemicals elevate a person’s risk for PD. Here, we sought to examine the possible epigenetic changes associated with working on a plantation on Oahu, HI and/or exposure to organochlorines (OGC) in PD cases. We measured genome-wide DNA methylation using the Illumina Infinium HumanMethylation450K BeadChip array in matched peripheral blood and postmortem brain biospecimens in PD cases (n=20) assessed for years of plantation work and presence of organochlorines in brain tissue. The comparison of 10+ to 0 years of plantation work exposure detected 7 and 123 differentially methylated loci (DML) in brain and blood DNA, respectively (P<0.0001). The comparison of cases with 4+ to 0-2 detectable levels of OGC, identified 8 and 18 DML in brain and blood DNA, respectively (P <0.0001). Pathway analyses revealed links to key neurotoxic and neuropathologic pathways related to impaired immune and proinflammatory responses as well as impaired clearance of damaged proteins, as found in the predominantly glial cell population in these environmental exposure-related PD cases. Genome-wide DNA methylation was analyzed using the Illumina HumanMethylation450K BeadChip array in matched peripheral blood and postmortem brain biospecimens in PD cases (n=20) assessed for years of plantation work and presence of organochlorines (OGC count) in brain tissue.