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How Nurture Changes Nature

Posted By Prucia Buscell, Thursday, July 4, 2013
Updated: Monday, July 8, 2013
The traumatic experiences of our own past and even the adversities and deprivations of ancestors can leave inheritable molecular scars that negatively influence behavior, personality and physical health later in life, many scientists believe.

A story by Dan Hurley in Discover Magazine, describes research by Moshe Szyf, molecular biologist, pharmacologist and geneticist at McGill University and Michael Meaney, a McGill neurobiologist. Their new findings in behavioral epigenetics not only hold promise for unraveling the impact of the past, but suggest profound new possibilities for treatments to heal the damage done by both recent and ancient suffering.

They have found what seems to be evidence of a chain of connection from experience to changes in gene expression in the brain to behavior. Behavioral epigenetics is a new but fast-growing field that has generated some skepticism. See a story by Lizzie Buchen in Nature.com for a range of views. Szyf says a different mindset in neuroscience is needed-a focus on molecular modification in the cell molecules rather than on inter-neural circuitry and anatomy. While genes are inherited and stay the same throughout life, Szyf explains, outside factors such as diet, toxins, and social factors such as abuse, stress and extreme poverty can set off chemical changes in the nucleus of cells that changes the way genes are expressed. When stimulated, an arrangement of molecules called a methyl group attaches itself to the control center of the gene and turns it off. The gene function changes, but the DNA doesn't.

Szyf has spent years studying DNA methylation. He and Meaney studied the brains of rats raised by attentive mother rats who groomed them frequently, and neglectful rat mothers who didn't. In the brains of badly-mothered rats, the genes regulating reaction to stress were highly methylated, and the rats were nervous wrecks. And when those pups grew up, they too were inattentive to their babies.

In the offspring of good mother rats, those genes were rarely methylated, and the rats were calm. In a second experiment, to show the changes were behaviorally induced, the rat pups born to bad mothers were given to the good mother rats to raise, and those born to good mother given to bad moms. The well raised rats with the biochemical capacity to manage stress were calm and brave. The poorly raised rats were behaviorally difficult. With no changes to their genetic code, the neglected rats had gained inheritable changes-the addition of methyl groups that alter brain function-solely because of their childhood experiences.

In another extraordinary experiment, Szyf and Meaney infused the brains of badly raised rats with a drug that removes methyl groups, and the animals then showed none of the behavioral deficits typical of their group.

Brains of living people can't be sampled, but blood samples are common. Szyf looked for epigenetic markers of methylated genes in the blood of 40 male study participants who were either very rich or very poor. Szyf studied the methylation state of some 20,000 human genes, and found 6,176 varied significantly based on poverty or wealth. He found methylation changes were most likely when poverty had occurred in early childhood.

In an interview with the McGill Reporter, Szyf says: "My work bridges the humanities and sciences by showing how the nonphysical environment effects our genes. It also emphasizes we cannot understand biology and medicine without taking into account the social, economic and perhaps even the political environment. Is cancer just a cellular disease? A problem with bad genes? Humans cannot be reduced to a single cell, and we can't separate people from their environment."

Tags:  buscell  complexity matters  neuroscience  research 

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