Influence of MTHFR gene variations on perceived stress modification: Preliminary results of NURSE study.

Background: High level of perceived stress in nurses is due to a genetic predisposition and environmental stressors. The aim of NURSE (Nursing Unacquainted Related Stress Etiologies) study was to investigate the association of C677T MTHFR gene polymorphism and stress perception among nurses. Methods: In this comprehensive study, 216 female nurses were recruited. Perceived stress was assessed using the Cohen Perceived Stress Scale (PSS). Genomic DNA was extracted from peripheral blood, and MTHFR genotype was detected by the polymerase chain reaction. Results: MTHFR C677T genotype analysis revealed that half of the participants had normal C/C genotype, and the remaining half presented higher frequencies of C/T genotype (39.8%) compared to T/T genotype (10.2%). The mean±SD stress score in morning shift, night shift, and rotation was 15.39±4.75, 15.92±4.94, and 15.83±5.61, respectively (p= 0.7). Perceived stress score was more in highly educated group but it was not significant (p= 0.2). Distribution of different MTHFR genotypes in diverse groups revealed that in groups with more stress score, the frequency of heterozygote (C/T) and homozygote (T/T) genotypes increased. Data revealed that in low stress category, 87% of the participants had a normal genotype. However, in high stress category, 71.3% of the participants had a normal genotype. Conclusion: MTHFR genotype, independent of folate availability and probable confounding parameters, might be a potential risk factor of perceived stress among nurses.

Antipsychotic drugs attenuate aberrant DNA methylation of DTNBP1 (dysbindin) promoter in saliva and post-mortem brain of patients with schizophrenia and Psychotic bipolar disorder.

Due to the lack of genetic association between individual genes and schizophrenia (SCZ) pathogenesis, the current consensus is to consider both genetic and epigenetic alterations. Here, we report the examination of DNA methylation status of DTNBP1 promoter region, one of the most credible candidate genes affected in SCZ, assayed in saliva and post-mortem brain samples. The Illumina DNA methylation profiling and bisulfite sequencing of representative samples were used to identify methylation status of the DTNBP1 promoter region. Quantitative methylation specific PCR (qMSP) was employed to assess methylation of DTNBP1 promoter CpGs flanking a SP1 binding site in the saliva of SCZ patients, their first-degree relatives and control subjects (30, 15, and 30/group, respectively) as well as in post-mortem brains of patients with SCZ and bipolar disorder (BD) versus controls (35/group). qRT-PCR was used to assess DTNBP1 expression. We found DNA hypermethylation of DTNBP1 promoter in the saliva of SCZ patients (∼12.5%, P = 0.036), particularly in drug-naïve patients (∼20%, P = 0.011), and a trend toward hypermethylation in their first-degree relatives (P = 0.085) versus controls. Analysis of post-mortem brain samples revealed an inverse correlation between DTNBP1 methylation and expression, and normalization of this epigenetic change by classic antipsychotic drugs. Additionally, BD patients with psychotic depression exhibited higher degree of methylation versus other BD patients (∼80%, P = 0.025). DTNBP1 promoter DNA methylation may become a key element in a panel of biomarkers for diagnosis, prevention, or therapy in SCZ and at risk individuals pending confirmatory studies with larger sample sizes to attain a higher degree of significance.

DNA hypermethylation of serotonin transporter gene promoter in drug naïve patients with schizophrenia.

INTRODUCTION: Dysfunctional serotonin signaling has been linked to the pathogenesis of autism, obsessive compulsive disorder, mood disorders and schizophrenia. While the hypo-activity of serotonin signaling is involved in the pathogenesis of depression, anxiety and obsessive compulsive disorder; LSD, an agonist of serotonin type 2 receptor (5-HTR2A) induces psychosis. Therefore, anxiety and depressive disorders are treated by SSRIs which inhibit serotonin transporter (5-HTT) while psychotic disorders are controlled by drugs that block serotonin and/or dopamine receptors. Since genetic polymorphisms and epigenetic dysregulation of 5-HTT are involved in the pathogenesis of mental diseases, we analyzed DNA methylation of 5-HTT promoter in post-mortem brains and saliva samples of patients with schizophrenia (SCZ) and bipolar disorder (BD) to evaluate its potential application as a diagnostic and/or therapeutic biomarker in SCZ and BD. METHODS: Whole genome DNA methylation profiling was performed for a total of 24 samples (including two saliva samples) using the Illumina 27K (for 12 samples) and 450K DNA methylation array platform (for another 12 samples), followed by bisulfite sequencing to identify candidate CpGs for further analysis. Quantitative methylation specific PCR (qMSP) was used to assess the degree of CpG methylation of 5-HTT promoter in 105 post-mortem brains (35 controls, 35 SCZ and 35 BD) and 100 saliva samples (30 controls, 30 SCZ, 20 BD and 20 first degree relatives of SCZ or BD). The U133 2.0 Plus Human Transcriptome array for a total of 30 post-mortem brain samples (each group 10) followed by quantitative real-time PCR was used to study 5-HTT expression in 105 post-mortem brain samples. RESULTS: The qMSP analysis for 5-HTT promoter region showed DNA hypermethylation in post-mortem brain samples of SCZ patients (~30%), particularly in drug free patients (~60%, p=0.04). Similarly, there was a trend for DNA hypermethylation in antipsychotic free BD patients (~50%, p=0.066). qMSP analysis of DNA extracted from the saliva samples also exhibited hypermethylation of 5-HTT promoter in patients with SCZ (~30%, p=0.039), which was more significant in drug naïve SCZ patients (>50%, p=0.0025). However, the difference was not significant between the controls and unaffected first degree relatives of patients with SCZ (p=0.37) and versus patients using antipsychotic drugs (p=0.2). The whole genome transcriptome analysis of post-mortem brain samples showed reduced expression of 5-HTT in SCZ compared to the control subjects (~50%, p=0.008), confirmed by quantitative real-time PCR analysis (~40%, p=0.035) which was more significant in drug free SCZ patients (~70%, p=0.022). CONCLUSION: A correlation between reduction in 5-HTT expression and DNA hypermethylation of the 5-HTT promoter in drug naïve SCZ patients suggests that an epigenetically defined hypo-activity of 5-HTT may be linked to SCZ pathogenesis. Furthermore, this epigenetic mark in DNA extracted from saliva can be considered as one of the key determinants in a panel of diagnostic and/or therapeutic biomarkers for SCZ.