Mapping the epigenomic landscape of post-traumatic stress disorder in human cortical neurons

Most epigenetic research on post-traumatic stress disorder (PTSD) has primarily focused on DNA methylation (5mC) in peripheral tissues, particularly at CpG sites. DNA hydroxymethylation (5hmC) has been found to be highly enriched in the mammalian brain, while 5mC at non-CpG sites shows high enrichment in neurons. However, little is known about their role in PTSD. Here, we characterize genome-wide differential 5mC and 5hmC at both CpG and non-CpG sites in postmortem orbitofrontal neurons from PTSD cases and controls. Utilizing reduced-representation oxidative bisulfite sequencing, we found that genome-wide significant (GWS) differential CpGs were primarily hyper-5mC/5hmC, whereas GWS differential non-CpGs were hypo-5mC/5hmC. Compared with 5mC, we show that 5hmC is a more sensitive epigenetic mark in PTSD, with a higher number of differential 5hmC sites and a stronger significance in enriched pathways. Integrating other -omics data highlighted developmental processes as significant convergent pathways and revealed overlap of our GWS 5hmC findings with 50 previously reported PTSD-associated genes, including potential therapeutic targets such as CRHR1 and DRD4. This study underscores the importance of evaluating 5hmC in the human brain and our multi-omics integration provides insights into potential target genes for future therapeutic interventions in PTSD. Graphical abstractThe study conducted a comprehensive genome-wide analysis of differential 5mC and 5hmC modifications at both CpG and non-CpG sites in postmortem orbitofrontal neurons from 25 PTSD cases and 13 healthy controls. It was observed that PTSD patients exhibit a greater number of differential 5hmC sites compared to 5mC sites. Specifically, individuals with PTSD tend to show hyper-5mC/5hmC at CpG sites, particularly within CpG islands and promoter regions, and hypo-5mC/5hmC at non-CpG sites, especially within intragenic regions. Functional enrichment analysis indicated distinct yet interconnected roles for 5mC and 5hmC in PTSD. The 5mC marks primarily regulate cell-cell adhesion processes, whereas 5hmC marks are involved in embryonic morphogenesis and cell fate commitment. By integrating published PTSD findings from central and peripheral tissues through multi-omics approaches, several biological mechanisms were prioritized, including developmental processes, HPA axis regulation, and immune responses. Based on the consistent enrichment in developmental processes, we hypothesize that if epigenetic changes occur during early developmental stages, they may increase the risk of developing PTSD following trauma exposure. Conversely, if these epigenetic changes occur in adulthood, they may influence neuronal apoptosis and survival mechanisms. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=106 SRC="FIGDIR/small/24315258v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@4bbfborg.highwire.dtl.DTLVardef@d19b59org.highwire.dtl.DTLVardef@12dfdd0org.highwire.dtl.DTLVardef@727efd_HPS_FORMAT_FIGEXP M_FIG C_FIG