# Genome‐Wide 5‐Methylcytosine and 5‐Hydroxymethylcytosine Signatures Analysis of Plasma Cell‐Free DNA in Schizophrenia

## TL;DR

This study identifies epigenetic patterns in blood DNA that differ between people with schizophrenia and healthy individuals, offering potential biomarkers for diagnosis and understanding disease mechanisms.

## Contribution

The study is the first to analyze genome-wide 5mC and 5hmC signatures in cfDNA for schizophrenia, revealing novel epigenetic biomarker candidates.

## Key findings

- 954 DMRs and 1474 DhMRs were identified in schizophrenia patients compared to controls.
- DMRs and DhMRs were enriched in brain-expressed genes and psychiatric GWAS loci.
- DhMRs overlapped with schizophrenia GWAS loci and correlated with brain MRI measurements.

## Abstract

Schizophrenia (SCZ) is a highly heritable neuropsychiatric disorder that affects ∼1% of people globally. Despite extensive research, there remains a lack of biomarkers for SCZ diagnosis and disease pathogenesis delineation. Cell‐free DNA (cfDNA), which carries the genetic and epigenetic signatures of origin tissue cells, may provide a noninvasive method for biomarker discovery. We performed cfDNA 5‐methylcytosine (5mC) and 5‐hydroxymethylcytosine (5hmC) sequencing of plasma samples from 66 individuals with SCZ and 77 healthy controls. We identified 954 differentially 5mC methylated regions (DMRs) and 1474 differentially 5hmC hydroxymethylated regions (DhMRs) that showed distinct patterns between SCZ and control samples. Many DMRs and DhMRs were associated with genes specifically expressed in brain tissues and were enriched in neuronal functions, as well as were enriched for genome‐wide association study (GWAS) of psychiatric and brain volume traits. Additionally, colocalization analysis revealed that DhMRs but not DMRs locations significantly overlapped with GWAS‐identified genomic loci of SCZ. Moreover, we observed associations between DMRs and DhMRs with brain regional measurements depicted by magnetic resonance imaging. Together, our findings indicated that cfDNA 5mC and 5hmC patterns are accessible epigenomic signatures that can serve as potential biomarkers and to help delineate SCZ pathogenesis.

We performed cfDNA 5‐methylcytosine (5mC) and 5‐hydroxymethylcytosine (5hmC) sequencing of plasma samples from 66 individuals with SCZ and 77 healthy controls (HC). We identified differentially 5mC methylated regions (DMRs) and differentially 5hmC hydroxymethylated regions (DhMRs) that showed distinct patterns between SCZ and control samples. The analysis of DMRs and DhMRs as well as brain structure provided multiple insights into SCZ pathogenesis.