Science close to uncovering molecular scars of child abuse
Events from the U.S. Supreme Court confirmation hearings to the rise of the #MeToo movement have brought child abuse, both sexual and non-sexual, out of the shadows. Still, decadesold allegations are often difficult to prove and may hinge on the memories of the people involved. What if there was a physical record of abuse stored in the body that could be analyzed scientifically?
New research may open the door to just such a technique. Scientists at Harvard and the University of British Columbia have discovered significant differences in the sperm of men who were and were not victims of childhood abuse.
Their secrets are written as epigenetic modifications to their genomes. These are biochemical changes, such as the addition of a methyl group, that can turn genes on and off, even though they don’t modify the basic DNA structure.
Researchers led by Andrea Roberts of Harvard’s T.H. Chan School of Public Health compared sperm samples from young adult men who reported childhood physical and/or sexual abuse with those who didn’t. They found eight DNA regions that were more than 10 per cent different, and one region with a 29 per cent difference. The scientists say it’s too early to say if these epigenetic changes will affect the health of the person or his offspring.
In an interview from Cambridge, Mass., Roberts said that, “The big question is how does child abuse get under the skin to affect the physical and mental health, and one of the hypotheses is that it affects these tags that rest on your genes.”
Asked if she thought this technique might have forensic uses in the future, Roberts said, “It’s not implausible, though it would require much bigger studies.” She notes that the “epigenetic clock” is already used by police to determine the approximate age of the person who supplied a blood or other tissue sample. “We also know that people who have had traumatic experiences have an older biological age than their chronological age, so you can sort of see their aging in their tissues.”
There’s even a DNAge™ Epigenetic Aging Clock, based on the work of UCLA professor Steve Horvath, and sold commercially by Zymo Research. It was used in Germany to test a refugee claimant who said he was under the age of 18. Because of a lack of precision with this technique, this application was highly controversial.
UBC medical genetics professor Michael Kobor, senior author on the Harvard/UBC study, is optimistic that sperm epigenetics may someday wind up in courtrooms or even Senate hearing rooms. “It’s conceivable that the correlations we found between methylation and child abuse might provide a percentage probability that abuse had occurred,” he says.
One of the big questions arising from this research is whether or not these epigenetic changes can be passed on to offspring. Roberts notes that “when the sperm meets the egg, there is a massive amount of genetic reshuffling, and most of the methylation is at least temporarily erased.” However, she cites evidence showing that male mice pass on the epigenetic effects of environmental exposure to three generations of their offspring, so “it’s not crazy to think that might happen in humans.”
In addition to legal implications, epigenetics may play a role in designing treatments and new drugs. Researchers at the University of Parma and the U.S. National Institute on Drug Abuse recently published a paper on DNA methylation and cannabis use disorder, which is basically the misuse of pot, which causes serious distress or impairment.
These scientists found “a significantly higher level of DNA methylation in cannabis users compared to controls in two of the genes tested.”
They go on to suggest that “the differentially methylated regions may represent biomarkers and/ or potential targets for designs of pharmacological therapeutic agents.”
Another recent study found that excessive alcohol consumption appears to speed up the epigenetic aging process. Also, Swedish adolescents who had hypermethylation on a particular gene tended to have more psychological stress and reported being bullied and depressed more than those without this epigenetic trait.
The whole field of biomarkers is exploding rapidly, and it’s a good time to think carefully about the implications. The epigenetic enterprise is still in its early days. Scientists have an imperfect understanding of how epigenetic traits affect a person’s health, and there’s always the problem of figuring out what are causes and what are effects.
What we are learning is that the body stores a great deal of information and that machine learning techniques, which were used in the Harvard/UBC study, can assist in unravelling it. It will take a brave expert witness to bring epigenetic evidence of childhood abuse into a court of law. But that day is definitely coming, and these new studies bring it closer in a tantalizing way.