Eating for Two, or an Entire Lineage
By Mignon Fogarty, The Scientist
7 September 2003: Duke University researchers give a new twist to the old adage, "You are what you eat." By feeding female agouti (Avy ) mice methyl-rich supplements such as folic acid and vitamin B12, Randy Jirtle and Robert Waterland reduced agouti gene expression in their offspring. This change, caused by direct methylation of a transposon at the 5' end of the agouti locus, resulted in dramatic, visible changes in pups, including darkened coat color and decreased weight gain.1 "Transposons are genomic parasites," says Jirtle, explaining that epigenetic mechanisms such as methylation have evolved to counteract transposon-initiated gene expression.
The research has broad implications. Such epigenetic effects could muddle sequence-driven disease gene hunts; the fact that environmental factors can cause potentially heritable genetic changes blurs the boundaries between nature and nurture. "It's definitely Lamarckian," says Jirtle, referring to the largely discredited 19 th century evolutionist who proposed the inheritance of acquired traits.
Ted Steele, Australian researcher and author of Lamarck's Signature, lauds the work's contribution. "It is clear, phenotypic diversity influenced by a direct environmental trigger, in this case food," he says. Arthur Beaudet, Baylor College of Medicine in Houston, says the work will change the way people think about dietary supplements. Jirtle adds,
"Trivial doses can dramatically affect gene expression."