Peripheral SLC6A4 DNA Methylation Is Associated with In Vivo Measures of Human Brain Serotonin Synthesis and Childhood Physical Aggression

Dongsha Wang,Chawki Benkelfat,Moshe Szyf,Richard E Tremblay,Sylvana M Côté,Gustavo Turecki,Linda Booij,Nadine Provençal,Frank Vitaro,Doretta Caramaschi,Juri G Gelovani

doi:10.1371/journal.pone.0039501

Abstract

The main challenge in addressing the role of DNA methylation in human behaviour is the fact that the brain is inaccessible to epigenetic analysis in living humans. Using positron emission tomography (PET) measures of brain serotonin (5-HT) synthesis, we found in a longitudinal sample that adult males with high childhood-limited aggression (C-LHPA) had lower in vivo 5-HT synthesis in the orbitofrontal cortex (OBFC). Here we hypothesized that 5-HT alterations associated with childhood aggression were linked to differential DNA methylation of critical genes in the 5-HT pathway and these changes were also detectable in peripheral white blood cells. Using pyrosequencing, we determined the state of DNA methylation of SLC6A4 promoter in T cells and monocytes isolated from blood of cohort members (N = 25) who underwent a PET scan, and we examined whether methylation status in the blood is associated with in vivo brain 5-HT synthesis. Higher levels of methylation were observed in both T cells and monocytes at specific CpG sites in the C-LHPA group. DNA methylation of SLC6A4 in monocytes appears to be associated more reliably with group membership than T cells. In both cell types the methylation state of these CpGs was associated with lower in vivo measures of brain 5-HT synthesis in the left and right lateral OBFC (N = 20) where lower 5-HT synthesis in C-LHPA group was observed. Furthermore, in vitro methylation of the SLC6A4 promoter in a luciferase reporter construct suppresses its transcriptional activity supporting a functional role of DNA methylation in SLC6A4 promoter regulation. These findings indicate that state of SLC6A4 promoter methylation is altered in peripheral white blood cells of individuals with physical aggression during childhood. This supports the relevance of peripheral DNA methylation for brain function and suggests that peripheral SLC6A4 DNA methylation could be a marker of central 5-HT function.

Highlights

It is important to study the interactions between epigenetic processes such as DNA methylation and human behaviours
Synthesis We examined whether the rate of 5-HT synthesis as determined by positron emission tomography (PET) correlates with the state of SLC6A4 methylation in T cells and monocytes
The main challenge in addressing the role of DNA methylation in human behaviour is the fact that the brain is inaccessible to epigenetic analysis in living humans

Summary

Introduction

It is important to study the interactions between epigenetic processes such as DNA methylation and human behaviours. This is a challenging task if we wish to establish a link between the behaviours in living human subjects and their epigenetic profile, as brain samples cannot be readily obtained for analysis. Observations in humans and animals have shown that aggressive behaviour is associated with low 5-HT neurotransmission [3,4]. Using positron emission tomography (PET), we previously compared, in a longitudinal sample followed since childhood, in vivo brain 5-HT synthesis in healthy adult males with high and low levels of childhood physical aggression [5]. We found that adult males with high childhood-limited aggression (C-LHPA)

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