LAUSR

Abstract Background Among the adversities found in schizophrenia, the dysfunctions in the glutamatergic system, specifically the N-methyl-D-aspartate receptor (NMDAR) are apparent. GRIN2B (coding a NMDAR subunit) has a critical role in synaptic plasticity and important participation in CNS neurodevelopment, this gene is closely associated with behavioural and cognitive impairments. One of the mechanisms that may underlie the deficiencies seen in the glutamatergic system in psychosis is DNA methylation as it is known to regulate gene expression. As part of a major study investigating the relationship of DNA methylation with schizophrenia and its symptom response to antipsychotic drug treatment, we determined whether methylation of the GRIN2B promoter region was associated with specific symptoms of schizophrenia determined by the Positive and Negative Syndrome Scale (PANSS). Methods Blood samples were collected from schizophrenia patients (n = 79) on admission to the study. Bisulphite conversion and pyrosequencing were used to determine methylation levels in 5 CpG sites in the GRIN2B promoter. PANSS score and the five factor subscores (Wallwork et al, 2012) at baseline and at 6 weeks was collected, and the change in PANSS following treatment was determined. Results Mean methylation at the five CpG sites was not associated with overall PANSS score or with the change in PANSS. However, a highly significant positive correlation of mean methylation with the baseline excited factor score (r=0.342, p=0.002), but with no other PANSS subscore, was found. No significant correlation with changes in PANSS, or in changes in subscores, over the treatment period was found. Discussion This is the first evidence showing GRIN2B methylation correlation with the excited component (EC) of schizophrenia symptoms. PANSS-EC is used to assess agitated patients (Lindenmayer et al., 2008, Montoya et al., 2011), and is valuable in identifying risks associated with agitation and aggression related to primary psychiatric disturbances. This result suggests that this GRIN2B epigenetic signature may relate to agitation and aggressive behaviour in schizophrenia.