An example is asthmatic children. Wan-Yee Tang, a researcher at the University of Cincinnati, found that children in New York City exposed in the womb to high levels of polycyclic aromatic hydrocarbons (PAHs), common air pollutants from traffic, were much more likely to have asthma than those who were not exposed. By studying cord blood, she found that a particular gene (ACSL3) was methylated in the asthmatic children and unmethylated in the unexposed children, and concluded that the abnormal methylation patterns probably caused the asthma.
The finding could in part explain why worldwide asthma rates have skyrocketed in much of the world, reaching epidemic proportions among children. In the boroughs of New York City with the worst air pollution, about 25 percent of children are asthmatic.
Epigenetic changes also have been observed in children conceived with assisted reproductive technologies, said Richard Meehan of the Medical Research Council in Scotland.
One of the disorders that occurs at a higher rate in these children is Beckwith-Wiedemann syndrome, which is characterized by abdominal wall defects and a higher risk of certain childhood cancers. The culture medium where fertilized eggs are grown for several days before implantation probably causes the syndrome, he said. It appears that all the different media used for the eggs might be problematic because they contain chemicals that stimulate the addition of methyl groups to the cells.
The scientists at the workshop said it’s important to understand epigenetics not only to figure out which chemicals might endanger public health, but to find new ways to prevent or treat diseases.
Scientists are just now beginning to figure out normal methylation patterns in the genome so they can learn what is abnormal, said Karl T. Kelsey, professor of community heath and pathology at Brown University in Rhode Island. As a result of this new understanding, epigenetic therapies have been developed for some types of cancers, and some have been successful in clinical trials, he said. Unlike traditional cancer drugs, which kill cells, the new drugs simply change how the cells act.
Research with rats shows that gene-altering chemicals can change animals’ brains—in some cases, in a beneficial way.
Moshe Szyf, a pharmacology and therapeutics professor at McGill University Medical School in Montreal, found that rats that received healthy doses of maternal licking as pups grew up to be calmer than pups who had inattentive mothers. The maternal grooming brought about a chemical change in the part of the pup’s brain that produces stress hormones, he said.