Previous studies with nonhuman species have found that animals exposed to early adversity show differential DNA methylation relative to comparison animals. DNA methylation in the promoter or control region of a gene tends to “silence” or reduce the transcription of the gene into mRNA and subsequent translation into protein product. This methylation, an “epigenetic” alteration, occurs at cytosine bases linked to a guanosine, referred to as CpG sites.
The study examined differential methylation among 14 children raised since birth in institutional care and 14 comparison children raised by their biological parents. Blood samples were taken from children in middle childhood. Analysis of whole-genome methylation patterns was performed using the Infinium HumanMethylation27 BeadChip assay (Illumina), which assesses the methylation status of over 27,000 CpG sites, covering the promoters of approximately 14,000 genes. The differences seen across groups were characterized primarily by greater methylation in the institutionalized group relative to the comparison group. Most of the observed differences in promoter methylation were in genes involved in the control of immune response and cellular signaling systems, including a number of crucial players important for neural communication and brain development and functioning.
The findings suggest that patterns of differential methylation seen in nonhuman species with altered maternal care are also observed in children who experience early maternal separation. Although preliminary, the research is a first step to understanding the extent and specific nature of the epigenetic changes caused by the early loss of parental care and their impact on subsequent human development.