HEALTH

Charting new body-mind links

Upbringing and behaviour may actually shape our brain’s DNA

ALEXANDRA SHIMO July 30 2007
HEALTH

Charting new body-mind links

Upbringing and behaviour may actually shape our brain’s DNA

ALEXANDRA SHIMO July 30 2007

Charting new body-mind links

HEALTH

Upbringing and behaviour may actually shape our brain’s DNA

ALEXANDRA SHIMO

The link between mind and the body tends to be more the subject of New Age books or yoga workshops than respectable research. Not that this link hasn’t been subjected to scientific scrutiny. In the last decade, researchers have measured the size of London cabbies’ hippocampi to find out whether learning all of the city’s streets grows the section of the brain devoted to memory. (It does.) They have studied how our grey matter changes shape and grows after years of meditation. They have examined the brain activity of subjects as they lie or cheat. And despite this flurry of research, they are still a long way from fully fathoming how the 600 billion neurons in the brain create a functioning mind, and how the mind influences the neurological, chemical and biological processes of the body.

One person who is moving us closer to such an understanding is a McGill scientist named Moshe Szyf. Szyf, 52, is a pioneer in the emerging field of epigenetics. Epigenetics is the study of the epigenome—the chemical switching system that turns genes on and off, and it is radically changing how we understand the relationship between our genetics and our environment. “With epigenetics, we are changing how we think of science itself,” says Szyf. “We are analyzing how our thoughts, behaviour and upbringing can shape our DNA.”

It turns out that although we are all born

with a particular genetic makeup, the epigenome determines which genes are active. The epigenome responds to lots of things—how we live, what we eat, our environment, which means our genes are malleable, too.

Szyf’s experiments have shown how environment can stimulate certain thoughts and feelings, and that these thoughts shape which genes are active. In his latest study, with McGill neuroscientist Dr. Gustavo Turecki, Szyf examined the brains of men who had been abused in childhood. His theory is a controversial one—that childhood abuse alters the marking of an individual’s DNA. Prolonged neglect takes its toll, not only on a person’s sense of self, but on his genes too. In particular, it shuts off a gene inside the brain that regulates the body’s response to stress, altering how a person physically copes.

Examining how abuse changes the molecular workings of the brain is completely unchartered territory, says Szyf. Previously, researchers have explored the link between childhood experiences and adult behaviour, but not the changes to the DNA inside the brain that would cause people to react differently.

Szyf first became curious about the brains of abuse victims after completing a widely quoted study involving rats. In that study,

published in December 2004, Szyf and Michael Meaney, a McGill biologist, found that how a mother rat treats her pups determines their behaviour as adults. Rats that were licked grew up more assertive than those that were not. They produced lower levels of the hormone cortisol in response to stress, which meant they were better able to cope— and they were more confident and less anxious. But being licked didn’t just affect the rats’ behaviour. It also altered the stress regulation gene inside the brain, and these changes lasted throughout adulthood.

The rat study was groundbreaking because it showed the markings of the genetic blueprint could change in response to parental care. Moreover, “it provided a possible pathway between our thoughts through the electrical circuitry of the brain to the workings of our DNA,” says Szyf.

The next step was to investigate whether the markings on a human’s DNA would change in a similar manner when exposed to stress, says Turecki, the director of the McGill Group for Suicide Studies. The brains of eight men who had died were analyzed. Their medical records showed that each of them had experienced childhood abuse—physical, sexual or mental, or a combination of the three. All had committed suicide in their mid-thirties. The chemical marking on their brain DNA was compared to that of people who had non-abusive childhoods and died of natural causes.

The results will likely be published later this year, but Maclean’s was given an early synopsis. The gene regulating stress was less active in the eight men. Szyf and Turecki both speculate this left the men hard-wired to have problems coping, which may have contributed to their suicides. “Childhood abuse talks to the genome,” says Turecki. “ft seems to change the molecular structure of the brain. It alters how they respond to stress as adults.” The next stage is to repeat the study with a larger number of subjects. The researchers also want to introduce a control group of suicide victims who were not abused.

“Our environment and our thoughts shape what genes are active, which shapes how our bodies work and how we behave,” says Szyf. “Scientists have not explored this pathway until now. It is very complex—and we have just started to map it out.” M