Child abuse leaves Chemical marks

By Margaret Munro, Canwest News ServiceFebruary 23, 2009

Child abuse can indelibly mark and alter genes in its young victims leaving them less able to cope with stress later in life, according to new Canadian research.A Montreal team has discovered large numbers of "chemical marks," which inhibit a key mechanism for dealing with stress, in the brains of young men who were physically or sexually abused as children and later committed suicide."It's almost as if there is an imprint left," says Michael Meaney at McGill University, who heads the team that has already toppled many long-held views of how early experience impacts behaviour and genes.Their new study, published Sunday in Nature Neuroscience, is seen as the most convincing evidence yet that childhood abuse permanently modifies genes."Here is a mechanism by which significant adverse experience becomes inscribed in our brains," says neuroscientist Dr. Steven Hyman, provost of Harvard University, who reviewed the paper for Nature.Not only has the Montreal group shown abuse can cause specific changes in the brain, but also a change in expression of an important gene, Hyman said in an interview.Abuse is believed to be prevalent with as many as 10 to 15 per cent of children physically or sexually abused, says Meaney. "It's tragic," he says.The new findings point to how insidious the impact can be. They also provide clues for better understanding the neurological impacts and devising treatments to reverse the damage, says Meaney.Meaney and his colleagues have long been intrigued with resiliency, and how genes and environmental factors interact. They specialize in "epigenetics" which explores how the genes we inherit from our parents are altered and turned on and off by exposures and experiences through life."Obviously genes aren't everything," says Meaney, noting how identical twins often have very different lives. If one twin develops schizophrenia, he says the chance of the other twin developing the disorder is only 45 per cent even though they have identical genes.He says the new study tries to tease out how one of life's most profound experiences -- the quality of parental care and family life -- can "literally affect the genome and its operation."It grew out of the McGill group's research which showed parental care in rats impacts not only behaviour but also the genes of offspring. Baby rats that were licked more -- the rodent equivalent of hugs and good care -- grew up to be more assertive and confident than unlicked pups. The researchers showed neglect altered an important stress regulation gene in the rat brain, a change that lasted into adulthood.They have now found a similar genetic change in men who were abused. The men had suffered "major instances" of physical and sexual abuse as youngsters and committed suicide in their 30s, says Meaney.They looked for differences in chemical marks on a gene involved in stress response. Such marks are laid down early in life and are thought to be a sensitive to one's environment. They punctuate DNA and program it to express genes at the appropriate time and place.The researchers found that the men who had been abused as children had substantially more chemical marks, or flags, along the glucocorticoid receptor gene involved in the brain's stress response. The marks, which are "methyl groups" containing carbon and hydrogen, were three to four times more common on the genes of the abused men. "It's quite significant," says Meaney.They have also shown excess marks impact the functioning of the gene, reducing the amount of protein produced in the brain's stress response pathway. This would have hampered the men's ability to cope with stress, and could have contributed to their suicides, says Meaney. Extra genetic marks were not however found in the 12 men who committed suicide but were not abused. Meaney noted that abuse is just one of many factors linked to suicide. http://www.ptsdforum.org/thread9644.html--