title: Influence of life stress, 5-HTTLPR genotype, and SLC6A4 methylation on gene expression and stress response in healthy Caucasian males.
abstract: BACKGROUND
  Previous research reported that individual differences in the stress response were moderated by an interaction between individuals' life stress experience and the serotonin transporter-linked polymorphic region (5-HTTLPR), a common polymorphism located in the promoter region of the serotonin transporter gene (SLC6A4). Furthermore, this work suggested that individual differences in SLC6A4 DNA methylation could be one underlying mechanism by which stressful life events might regulate gene expression. The aim of this study was to understand the relation between early and recent life stress experiences, 5-HTTLPR genotype, and SLC6A4 methylation. In addition, we aimed to address how these factors influence gene expression and cortisol response to an acute psychosocial stressor, operationalized as the Trier Social Stress Test (TSST). In a sample of 105 Caucasian males, we collected early and recent life stress measures and blood samples to determine 5-HTTLPR genotype and SLC6A4 methylation. Furthermore, 71 of these participants provided blood and saliva samples before and after the TSST to measure changes in SLC6A4 and NR3C1 gene expression and cortisol response.
  
  
  RESULTS
  Compared to S-group individuals, LL individuals responded with increased SLC6A4 mRNA levels to the TSST (t(66) = 3.71, P < .001) and also showed increased global methylation as a function of ELS (r (32) = .45, P = .008) and chronic stress (r (32) = .44, P = .010). Compared to LL individuals, S-group individuals showed reduced SLC6A4 mRNA levels (r (41) = -.31, P = .042) and increased F3 methylation (r (67) = .30, P = .015) as a function of ELS; as well as increased F1 methylation as a function of chronic stress and recent depressive symptoms (r = .41, P < .01), which correlated positively with NR3C1 expression (r (42) = .31, P = .040).
  
  
  CONCLUSIONS
  Both early and recent life stress alter DNA methylation as a function of 5-HTTLPR genotype. Some of these changes are also reflected in gene expression and cortisol response, differentially affecting individuals' stress response in a manner that may confer susceptibility or resilience for psychopathology upon experiencing stressful life events.
authors.affiliation: Integrative Neuroscience, Department of Psychology, Stony Brook University, Stony Brook, NY 11794-2500 USA ; Department of Psychology, Bogazici University, Bebek, 34342 Istanbul, Turkey ; Center for Life Sciences and Technologies, Bogazici University, Bebek, 34342 Istanbul, Turkey.
authors.forename: Elif A
authors.initials: EA
authors.lastname: Duman
authors.affiliation: Integrative Neuroscience, Department of Psychology, Stony Brook University, Stony Brook, NY 11794-2500 USA ; Department of Radiology, Stony Brook University, Stony Brook, NY 11794 USA ; Program in Neuroscience, Stony Brook University, Stony Brook, NY 11794 USA ; Program in Genetics, Stony Brook University, Stony Brook, NY 11794 USA.
authors.forename: Turhan
authors.initials: T
authors.lastname: Canli
keywords: DNA methylation; Depression; Early life stress; Gene expression; Glucocorticoid receptor; Hypothalamic-pituitary-adrenal axis; Serotonin transporter