Association Study on Multi-Timepoint DNA Methylation Levels of Serotonin Transporter Gene and Adolescent Psychological-Behavioral Development

Abstract

Aims: This study aimed to investigate whether multi-timepoint DNA methylation levels at the SLC6A4 gene during early adolescence are associated with psychopathological and behavioral clusters, SLC6A4 encodes the serotonin transporter, which regulates the concentration of serotonin in the synaptic cleft. The clusters were previously identified by deep learning analysis of self- and parental-report questionnaires from participants in the Tokyo Teen Cohort (TTC) study in Japan. Methods: We extracted genomic DNA from saliva samples of a subset of TTC participants (N = 122) at ages 11, 13, and 15. DNA methylation levels at the functional CpG sites within the SLC6A4 promoter were measured using bisulfite pyrosequencing. Five psychopathological and behavioral clusters were applied from the previous study: minimal problems, persistent or worsening internalizing problems, subjective problems overlooked by caregivers, persistent externalizing problems, and chronic severe problems across symptoms. Linear mixed-effects models were applied to assess the associations between DNA methylation levels and psycho-behavioral clusters. Results: Males exhibited significantly lower mean methylation levels compared to females across all time points. Males classified as persistent externalizing problems showed notably lower methylation levels than those classified as minimal problems. Conclusions: DNA methylation levels in the SLC6A4 could potentially serve as epigenetic signatures for male adolescents exhibiting externalizing behavioral problems. To our knowledge, this is the first study to track SLC6A4 methylation at three developmental time points across early to mid-adolescence. Further epigenetic research is warranted to understand the role of environmental and genetic factors in the manifestation of adolescent behavioral problems.