Distinct Impacts of Alpha-Synuclein Overexpression on the Hippocampal Epigenome of Mice in Standard and Enriched Environments

Elevated alpha-synuclein (SNCA) gene expression is associated with transcriptional deregulation and increased risk of Parkinson's disease, which may be partially ameliorated by environmental enrichment. At the molecular level, emerging evidence indicates that excess alpha-synuclein protein (aSyn) impacts the epigenome through direct and/or indirect mechanisms. However, the extents to which both aSyn and the environment converge at the epigenome and whether epigenetic alterations underpin the preventive effects of environmental factors on transcription remain to be elucidated. Here, we profiled five DNA and histone modifications in the hippocampus of wild-type and transgenic mice overexpressing human SNCA. Mice of each genotype were housed under either standard conditions or in an enriched environment (EE) for 12 months. SNCA overexpression induced similar hippocampal DNA hydroxymethylation and H3K27 acetylation changes in both environments, and was associated with environment-dependent changes to H3K4 methylation. These H3K4 methylation changes included loci where the EE ameliorated the impacts of the transgene as well as loci resistant to the effects of environmental enrichment in transgenic mice. In addition, select H3K4 monomethylation alterations were associated with changes in mRNA expression. Our results suggested an environment-dependent impact of excess aSyn on some functionally relevant parts of the epigenome, and will ultimately enhance our understanding of the molecular etiology of Parkinson's disease and other synucleinopathies. Overall design: Reduced representation bisulfite sequencing of paried oxidative bisulfite and bisulfite-converted libraries, for wild type and SNCA transgenic mice housed for 12 months in standard conditions or enriched environment