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16-04-2012 | Psychology | Article

Social stress has genetic consequences


Free abstract

MedWire News: Changes in social status are associated with altered gene expression in the immune cells of female rhesus macaques, report researchers.

Jenny Tung (University of Chicago, Illinois, USA) and team found widespread differences in gene expression in the macaques' peripheral blood mononuclear cells (PBMCs).

They report that the expression of 987 of 6097 genes was associated with the macaques' rank within their social groups. Of these, 535 genes were most highly expressed in high-ranking individuals (ranks 1 and 2 of five), and 452 genes were most highly expressed in low-ranking individuals (ranks 4 and 5).

The affected genes were not predominantly related to one specific function, but a large minority (112) were involved in the immune response, affecting functions, such as interleukin signaling, T-cell activation, and chemokine and cytokine inflammation.

In the wild, the social standing of female rhesus macaques is dictated by that of their mothers. But Tung et al dictated rank in the current study by moving the macaques to new social groups; social standing was associated with the order in which the animals were introduced to their new groups.

Expression levels of these rank-associated genes predicted the ranks of the macaques with 80.0% accuracy, the team reports in the Proceedings of the National Academy of Sciences.

Seven macaques changed rank within their group after the initial introduction. Their gene expression pattern changed in line with their social standing, and expression levels were highly predictive for their new rank, being 85.7% accurate.

Tung et al then looked at the mechanisms underlying this effect. They found that changes in glucocorticoid signaling and in the proportion of immune cell subsets in low- versus high-ranking macaques had a modest effect on the expression of about 70% of the genes.

In addition, they found that DNA methylation patterns that related to the rank-associated genes were significantly different between low- and high-ranking macaques. DNA methylation data distinguished between the rank-associated genes and 1000 other genes with 58.1% accuracy.

The researchers say their findings "support the idea that changes in gene regulation help to explain links between the social environment and physiology, potentially supplying an important piece to the puzzle of how social effects 'get under the skin.' "

In a press statement, Tung said: "There's a concerning side to this kind of research, in that an individual's social environment probably partially determines health status. But there's also a hopeful side. For the seven females that changed ranks, their gene status changed with them."

By Eleanor McDermid

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