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Famine leaves its mark on fetal DNA
29 October 2008 by Ewen Callaway
http://www.newscientist.com/article/mg20026804.100-famine-leaves-its-mark-on-fetal-dna.html
SIX decades after their pregnant mothers were starved during the second world
war, the genes of Dutch men and women retain chemical changes that may put them
at risk of diabetes and cancer.
Our genes are subject to "epigenetic" changes that affect the way we produce proteins. For example, environmental influences can cause changes in the number of chemical "caps" called methyl groups that are added to DNA bases. These help determine how much protein the gene makes.
The caps can last a lifetime, and may even be passed to offspring. In 2006, researchers at University College London and Umeå University in Sweden found a link between the nutrition and smoking habits of a group of men and the health of their sons and grandsons, which they attributed to epigenetics (New Scientist, 6 January 2006, p 10). Other studies have found that if pregnant mice skimp on foods important for DNA methylation, their pups' genes carry fewer methyl caps.
To look for chemical evidence of epigenetics in people, Lambert Lumey, an epidemiologist
at Columbia University in New York, and colleagues studied 60 people who were
conceived while German forces occupying the Netherlands were preventing food
reaching local people. "You can't do a lab experiment in people but you
can maybe learn from a war situation that in many ways resembles a lab experiment,"
Lumey says.
You can't do a lab experiment in people but you can maybe learn from a war situation
that resembles a lab experiment.
The food shortage meant pregnant women ate as little as 500 calories a day between December 1944 and May 1945. The team looked at children born to these women, focusing on the IGF2 gene, which is involved in growth. To minimise differences in genetics and upbringing, they compared it with the same gene in a brother or sister conceived during more plentiful times.
The IGF2 genes of the famine babies carried about 5 per cent fewer methyl caps than their siblings, on average (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0806560105). A lack of caps could crank up IGF2 expression enough to make a biological difference, says Lumey's colleague Bastiaan Heijmans of Leiden University in the Netherlands.
A preliminary analysis found no link between IGF2 methylation and body weight, but a reduction in the number of methyl caps has been linked to colorectal cancer in humans. Heijmans speculates that fewer caps may encourage a fetus to extract more energy from food; this might help during starvation but lead to diabetes when calories are no longer scarce.
Though interested to see how diet affects IGF2, geneticist Robert Waterland at Baylor College of Medicine in Houston, Texas, doubts that the change is large enough to have a significant effect on the production of IGF2 protein. Other genes may be more affected, he suggests.
