Mothering, good or bad, sticks with an individual according to a Hot Paper by McGill University researchers Michael Meaney, Ian Weaver, and Moshe Szyf. In 2004, the authors showed that in rat pups, high levels of licking, grooming, and arched-back nursing (LG-ABN) lowered the methylation state of the NGF1-A binding site of the glucocortoid exon 17 promoter, thereby increasing activation of the glucocortoid receptor gene and triggering lasting changes in the expression of genes related to stress response.
Previously, methylation state was perceived as fixed during development, says Szyf. "In this case," says Duke University researcher Randy Jirtle, "Nature is nurture."
The effect was so striking - the site is almost always methylated in pups reared by low-LG-ABN mothers, but almost never so in those reared by high-LG-ABN mothers - that the paper was initially rejected, says Baylor College of Medicine geneticist Robert Waterland....
Whatever the cause, the team recently showed that the effects could be reversed in the adult offspring by treating low-LG-ABN rats with the histone deacetylase inhibitor TSA, or by directly infusing L-methionine into the brains of high-LG-ABN rats,