Environmental Influences on DNA Expression
Changes in DNA methylation shown on chromosomes
from 3-year-old twins (left) compared to those from 50-year-old twins.
Image from PNAS.
Twins are beloved in genetics research. Unlike the rest of us singletons, twins share a uterus before they are born and are exposed to the same in utero environment. Identical twins are even more special because they have the same exact genes as each other.
Once twins are out in the real world, however, they’re subjected to the same changing environmental conditions as the rest of us. Recent research has shown that over a lifetime, even identical twins with their identical genes have different risks of disease, like diabetes, which may be partially explained by the influence of environment on DNA expression. (Nature, July 4, 2005)
Without changing the actual sequence of DNA, the expression of genes can be influenced by a variety of chemical factors and proteins. One such external influence is DNA methylation. Researchers found that the pattern of DNA methylation between 40 pairs of twins, ranging from 3 to 74 years old, was most different among twins over 28 years old. And those who spent the most time apart, had the great differences in gene activation.
“Most people had the hypothesis that changes in DNA methylation are effected by the environment,” says lead author Mario Fraga of the Spanish National Cancer Centre in Madrid. “This is the first time that somebody has demonstrated that this is the case.”
Understanding how the environment can affect the way our DNA works is critical to developing better preventions and cures. Despite the many limitations of twin studies, studying twins is still yielding new findings.
Thank you to all the twins who have participated in scientific research. We owe you one.
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POSTED IN: General Genetics and Health
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