Environmental factors can lead to epigenetic changes, such as DNA methylation, and these affect the expression of crucial genes. Tissue-specific, epigenetic changes that can predispose an individual to psychiatric problems have not been studied as brain tissues are required for this purpose. Using recent advances in genome-wide analyses, the EU-funded project SEEM (Assessing the effect of early social environment on epigenetic modification) assessed the impact of prenatal maternal depression on epigenetic modification. The work included confirming methylation patterns in selected genes in the brain and T cells, as well as the identification of epigenetic markers in T cells. Researchers first compared different methylation levels in offspring from mothers with mood disorders with a control group. They found that DNA methylation changes in T cells can be involved in the effects of maternal depression and foetal anxiety in the womb. An animal study involving rhesus monkeys revealed that buccal cell samples did not yield good results, probably due to the presence of bacterial DNA in the mouth. However, as in the T cell human study, whole blood samples gave reliable results. By applying a more reliable methylation assay, researchers were able to compare blood samples and non-invasively collected biological samples from saliva. Results supported the hypothesis that DNA methylation patterns found in peripheral tissues can mirror the physiological effects of social experiences. Researchers also carried out and improved candidate gene methylation analyses by assessing cell heterogeneity of the samples. These were corrected for in association studies due to the very different epigenetic landscapes of different cell types. SEEM has given a new dimension to ongoing collaborative projects in the field of developmental psychology and psychiatric genetics. The employment of non-invasively obtained samples will have a significant impact on epigenetic research involving infants as well as large-scale epidemiological studies involving adults. The project's technical achievements will benefit both sample collection and the accuracy of retrieved data at the end stage of epigenetic association studies.
Epigenetic changes, DNA methylation, SEEM, maternal depression, T cells