A new study, published in the journal PLoS One, suggests that child abuse can permanently 'mark' genes in the brain, and provides evidence that early life events can affect our genes. Researchers from McGill University in Montreal, Canada, led by Moshe Szyf, examined the postmortem brains of 13 male suicide victims who were victims of child abuse, and 11 brains of men without a previous history of child abuse who died from sudden accidents. They showed that there were epigenetics differences in the brains of the suicide victims that were not present in the brains of other men. The researchers believe that these epigenetic changes occurred during childhood, and as a result of child abuse. Epigenetics refers to changes that affect gene activity in the body, without altering the DNA sequence of genes. For example, nearly every cell in the body contains an identical copy of every gene that makes up an individuals' genome, yet different combinations of genes are active in every cell, and every cell performs a different function in the organs and tissues of the body. These differences in the way the genome is interpreted in different cells are thought to be due to epigenetic markings on genes, switching them on and off. One such method is methylation, which chemically marks genes without changing the DNA sequence. In this way, an epigenetic 'fingerprint' can overlay a cell's DNA, and can confer a 'memory' to individual cells, telling them which specific combination of genes should be turned on or off.
The researchers showed that a gene for rRNA, an important component in the manufacturing of proteins in a cell, was methylated in the brain cells of the suicide victims. In particular, the methylation of rRNA occurred in the hippocampus, a brain region important in learning, memory and mood, and known to be smaller in people who have suffered child abuse. They suggested that the hippocampus was less active because methylation switched off the rRNA, and less protein - the building blocks of cells - was produced in the suicide victims.
In their previous work, the researchers showed that in rats, newborn pups who received maternal care had a different epigenetic profile than those who were neglected after birth. They also showed that these epigenetic changes could be reversed chemically, or by increasing their maternal care. Other studies have also shown that diet and stress can result in epigenetic changes to genes. What remains to be seen is whether the epigenetic changes are detected in victims of child abuse who have not committed suicide.
This study provides evidence that the environment in early life can influence the way genes function in later life, and shows that an individuals' DNA can be shaped by personal history. 'The big remaining questions are whether scientists could detect similar changes in blood DNA - which could lead to diagnostic tests - and whether we could design interventions to erase these differences in epigenetic markings', said Dr Szyf.