The rat homolog of the exon 1F NR3C1 promoter, the exon 17 region, is differentially methylated as a function of variations in maternal care4,17,22. Cytosine methylation is a highly stable epigenetic mark that regulates gene expression via its effects on transcription factor binding23,24. We used sodium bisulfite mapping25 to examine the methylation status of individual CpG dinucleotides in the NR3C1 promoter sequence extracted from the hippocampal tissue of the same subjects used for glucocorticoid receptor expression analysis. Sodium bisulfite mapping revealed a significant effect on the percentage of methylated clones (that is, the number of clones with at least one methylated CpG site divided by the total number of clones) between groups (F = 3.47, P < 0.05). Post hoc tests revealed a significant difference between suicide victims with a history of childhood abuse compared with nonabused suicide victims (P = 0.05) or controls (P < 0.05). There was no difference in the percentage of methylated clones between suicide victims without childhood abuse and controls (P > 0.05; Fig. 2a). Methylation was limited to specific sites, with no clone showing
