The field of epigenetics sits precariously on the precipice of the classic nature versus nurture debate. Instead of a simple environment versus genetics dichotomy, epigenetic examines how specific genes are either switched on or off through external forces encountered in a person's lifetime. Striking new research from scientists at the University of British Columbia and Harvard University is suggesting that adults who were victims of abuse as children may carry an imprint of that trauma in regions of their DNA.
At the crux of this research is a process called DNA methylation. This process involves methyl groups interacting with a DNA molecule to alter the expression of a gene. Over the course of a person's life a broad array of factors can influence DNA methylation, from diet to stress.
This new research initially set out to look at methylation markers in several samples of sperm. The primary goal was to find out if these methylation markers could be passed down to a subject's offspring. It is generally thought that most methylation markers are erased in primordial gene cells, the precursors to eggs and sperm. This is an important evolutionary process, acting like a reset button between generations to stop any temporary environmentally triggered aberrations from passing to one's children.
In 2013 a study from researchers at Cambridge upended this idea, suggesting that a small volume of methylation markers can in fact survive this reset process and be found in subsequent generations. This hypothesis has only been shown so far in a small amount of animal studies but it does back up some controversial observational research finding children of Holocaust survivors were more likely to develop depression, anxiety and other psychological disorders.
The long-term data from this new research is yet to be published but an early paper has just been revealed, finding that adult victims of child abuse do display distinctive methylation markers in several DNA regions that non-victims do not display.
This is a small study, comprising just 34 men, and much more follow-up work is needed to validate the findings. However, the researchers do believe this traumatic DNA marking to be distinct, with eight separate regions displaying over 10 percent difference in methylation markers, and one specific region showing a striking 29 percent difference between victims and non-victims.
"Methylation is starting to be viewed as a potentially useful tool in criminal investigations – for example, by providing investigators with an approximate age of a person who left behind a sample of their DNA," explains senior author Michael Kobor. "So it's conceivable that the correlations we found between methylation and child abuse might provide a percentage probability that abuse had occurred."
It's not that surprising that a major childhood trauma could leave such a notable epigenetic mark on a person's DNA. But it is revealing that researchers may be able to clearly identify these molecular scars.
This research undoubtedly raises some thorny ethical issues. One implication, if the work can be further verified and detailed, is that these biological markers could validate decades old accusations of assault or abuse when these cases are eventually raised in court. A he-said/she-said debate could be suddenly upended with a genetic biomarker that purportedly confirms whether a traumatic event did, or did not, take place.
A huge amount in this new research is still incredibly unclear, including whether these methylation markers have any health consequences. Up for even more debate is whether these epigenetic methylation markers can be passed on to other generations. That is one of the next steps for this research team, now that they believe they have found a clear molecular signature for childhood abuse and trauma.
"When the sperm meets the egg, there is a massive amount of genetic reshuffling, and most of the methylation is at least temporarily erased," says Andrea Roberts, lead author on the new study. "But finding a molecular signature in sperm brings us at least a step closer to determining whether child abuse might affect the health of the victim's offspring."
The new study was published in the journal Translational Psychiatry.
Source: University of British Columbia
