SYSTEMS BIOLOGY OF PTSD REVEALS MECHANISMS OF RISK AND DISEASE PROCESSES AT BRAIN MULTI-OMIC, BRAIN CELL TYPE, AND BLOOD LEVELS

Stress-related disorders stem from the interplay of genetic susceptibility and stress exposure, shaping gene and protein expression through epigenetic modifications across the lifespan. Studies on postmortem brains of PTSD and MDD patients, compared to neurotypical controls, reveal genetic overlaps, sex disparities, and immune and interneuron signaling involvement, yet lack integrative analyses. To address this gap, we established a brain multi-omic, multi-region database comprising individuals with PTSD, MDD, and NCs (77/group, n = 231). We analyzed molecular changes across the central nucleus of the amygdala (CeA), medial prefrontal cortex (mPFC), and hippocampal dentate gyrus (DG) at transcriptomic, methylomic, and proteomic levels. Our approach is supplemented by single-nucleus RNA sequencing (snRNA-seq), genetics, and blood proteomics, aiming for a comprehensive systems perspective. Our findings highlight predominant molecular

changes in the mPFC, with differentially expressed genes (DEGs) and exons carrying disease signals. Notably, methylation alterations were concentrated in the DG for PTSD and CeA for MDD. Findings supported by replication analyses across two cohorts (n = 114). We observed a moderate overlap between disorders, with childhood trauma and suicide driving molecular variations, and sex-specificity was more notable in MDD. Pathway analyses link disease-associated molecular signatures to immune mechanisms, metabolism, mitochondria function, and stress hormone signaling, albeit with low concordance across omics. Top upstream regulators include IL1B, GR, STAT3, and TNF. Multi-omic factor and gene network analyses suggest latent factors and modules related to aging, inflammation, vascular processes, and stress.

Complementing multi-omics, our snRNA-seq in the dorsolateral PFC reveals dysregulated pathways and upstream regulators in neuronal and non-neuronal cell types, including stress-related genes. Examining brain multi-omics with blood proteins in the large UK Biobank cohort shows significant correlation, overlap, and directional similarity, implying potential blood-based biomarkers. Fine-mapping of PTSD and MDD genome-wide association study results reveals limited overlap between risk and disease processes at the gene and pathway level.

Ultimately, prioritized genes with multi-omic, multi-region, or multi-trait associations are implicated in pathways/networks, exhibit cell-type specificity, demonstrate blood biomarker potential, or are linked to genetic risk for PTSD and MDD.

In conclusion, our study unveils shared and unique brain multi-omic molecular dysregulations in PTSD and MDD, elucidating distinct cell-type involvement and paving the way for blood-based biomarker development. These insights not only implicate established stress-related pathways but also offer potential therapeutic avenues.