DNA methylation levels of the proximal promoter of the serotonin transporter gene in the Discovery cohort were determined using quantitative bisulfite Pyrosequencing by EpigenDx Inc (Worcester, MA). Briefly, the human serotonin transport gene (SLC6A4) proximal promoter methylation assays analyze 20 CpG dinucleotides in the promoter region from −213 to −69 base pairs of the transcriptional start site (TSS), based on Ensembl Gene ID ENSG00000108576 and the Transcript ID ENST00000394821. The SLC6A4 promoter assays (ADS580-FS1 and ADS580-FS2) are targeted to the antisense sequence of SLC6A4 gene. The targeted CpG loci are listed in Supplementary Table 1, along with their genomic location and position relative to the translational start site. The target sequences (genomic DNA and bisulfite converted DNA) are available upon request.
