"Long before it's in the papers"
May 08, 2008

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Brain’s molecules may tell of child abuse

Finding could lead to treatments

May 6, 2008
Courtesy McGill University
and World Science staff

Sci­en­tists have found what they say are key dif­fer­ences be­tween the brains of or­di­nary peo­ple, and of those who took their own lives af­ter suf­fer­ing child­hood abuse.

Al­though their genes didn’t show sig­nif­i­cant dif­fer­ences, re­search­ers said there were dif­fer­ences in ep­i­ge­net­ic mark­ing—a chem­i­cal coat­ing on the DNA, in­flu­enced by life ex­pe­ri­ences.

“It’s pos­si­ble” the abuse caused these changes, though it’s hard to prove such cause-and-ef­fect in hu­mans, said Mo­she Szyf of McGill Uni­ver­s­ity in Mont­real, one of the re­search­ers. But in rats, he added, sci­en­tists have es­tab­lished si­m­i­lar cause-and-ef­fect links be­tween ep­i­ge­net­ic mark­ers and the qual­ity of par­ent­ing re­ceived.

“The big re­main­ing ques­tions are wheth­er sci­en­tists could de­tect si­m­i­lar changes in blood DNA, which could lead to di­ag­nos­tic tests” in peo­ple, he said. These in turn could lead to treat­ments that might “erase these dif­fer­ences” and the re­sult­ing stress re­s­ponses, he added—which also has been done in rats.

Szyf and col­leagues at McGill ex­am­ined the brains of 13 male vic­tims of su­i­cide and child abuse from Que­bec. The re­search is to ap­pear in the May 6 is­sue of the on­line re­search jour­nal P­LoS One.

Epi­ge­net­ics is the study of changes in gene func­tion that don’t in­volve changes in the ac­tu­al DNA se­quence. 

That se­quence is in­her­it­ed and re­mains fixed through­out life and through­out the body. But dur­ing gesta­t­ion, the DNA ac­quires a chem­i­cal coat­ing called me­thyl­a­t­ion. This is some­what sen­si­tive to one’s en­vi­ron­ment, es­pe­cially in child­hood. These “ep­i­ge­net­ic marks” punc­tu­ate the DNA in or­der to pro­gram it to ac­ti­vate the ap­pro­pri­ate genes at the right times and parts of the body.

The re­search­ers fo­cused on a set of genes that code for rRNA, a key piece of the cel­lu­lar ma­chin­ery for mak­ing pro­teins, which in turn are crit­i­cal for learn­ing, mem­o­ry and build­ing new con­nec­tions in the brain. Thus pro­tein pro­duc­tion can af­fect decision-mak­ing and oth­er be­hav­iour. The sci­en­tists found that rRNA, in turn, can be gov­erned by ep­i­ge­net­ic mark­ings.

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Scientists have found what they say are key differences between the brains of ordinary people, and of those who took their own lives after suffering childhood abuse. Although the genes weren’t significantly different, researchers said there were differences in epigenetic marking—a chemical coating on the DNA, influenced by life experiences. “It’s possible” the abuse caused these changes, though it’s hard to prove such cause-and-effect in humans, said Moshe Szyf of McGill University in Montreal, one of the researchers. But in rats, he added, scientists have established similar cause-and-effect links between epigenetic markers and the quality of parenting received. “The big remaining questions are whether scientists could detect similar changes in blood DNA—which could lead to diagnostic tests” in people, he said. That in turn could lead to treatments that might “erase these differences,” he added, which has also been done in rats. Szyf and colleagues at McGill examined the brains of 13 male victims of suicide and child abuse from Quebec. The research is to appear in the May 6 issue of the online research journal PLoS One. Epigenetics is the study of changes in the function of genes that don’t involve changes in the actual DNA sequence. That sequence is inherited and remains fixed throughout life and throughout the body. But during gestation, the DNA acquires a chemical coating called methylation. This is somewhat sensitive to one’s environment, especially in childhood. These “epigenetic marks” punctuate the DNA in order to program it to activate the appropriate genes at the right times and parts of the body. The researchers focused on a set of genes that code for rRNA, a key piece of the cellular machinery for making proteins, which in turn are critical for learning, memory and the building of new connections in the brain. Thus protein production can affect decision-making and other behaviour. The scientists found that rRNA, in turn, can be governed by epigenetic markings.