Profiling Neuronal Methylome and Hydroxymethylome of Opioid Use Disorder in the Human Orbitofrontal Cortex

Abstract

AbstractOpioid use disorder (OUD) is influenced by genetic and environmental factors. While recent research suggests that there are epigenetic disturbances in OUD, these studies were limited to DNA methylation (5mC). DNA hydroxymethylation (5hmC) has been understudied in psychiatric disorders and addiction, despite being highly enriched in the brain where it regulates critical functions, including neural plasticity. Here, we conducted a multi-omic profiling of the orbitofrontal cortex (OFC) of OUD, integrating neuronal-specific 5mC and 5hmC as well as within-subject correlations with gene expression profiles from human postmortem samples (OUD=12; controls=26). Further, co-methylation modules and GWAS enrichment were analyzed for 5mC and 5hmC. Evaluation of single locus methylomic alterations identified 397 and 1740 differentially 5mC and 5hmC CpGs, respectively. Enrichment for neuronal function was observed for 5hmC, while no significant pathways were observed for 5mC. 5mC and 5hmC co-methylation analysis identified modules associated with OUD enriched for Pre-NOTCH Transcription and Translation, and WNT signaling. Transcriptomic analysis identified HBB as significantly associated with OUD. Finally, drug interaction analysis showed seven differential 5hmC genes and one differential 5mC gene interacting with opioid use. Our multi-omic findings suggest an important role of 5hmC and reveal novel loci epigenetically dysregulated in OFC neurons of individuals with OUD.