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Gene Change Plus Prenatal Exposure to Pollution Ups Autism Risk

Study documents first clear example of long-suspected gene-environment interactions in the development of autism
December 02, 2013

Recent studies have suggested that exposure to high levels of pollution during pregnancy increases children’s risk of autism. A new study shows this risk is higher if a child has a particular gene variation. The research is among the first to show evidence of gene-environment interactions in autism.

The study, published in the journal Epidemiology, was led by Heather Volk and Daniel Campbell of the University of Southern California. Autism Speaks is currently funding an expansion of their research.

“Scientists believe that there are many causes of autism and that the interaction between genetics and the environment plays a strong role,” comments Alycia Halladay, Autism Speaks senior director of environmental and clinical research. “This study provides new documentation of such a link.”

Previous research by Dr. Volk found links between autism and exposure to high air pollution levels during pregnancy and early infancy. Previous research by Dr. Campbell and others has suggested an association between autism and a particular version of the MET gene. This gene variation has also been associated with behavior and GI problems in children with autism.

The investigators decided to study the effects of pollution and the MET gene together, in part, because animal studies suggested that toxic exposures interfere with this gene’s function.

“We remain at the early stages of understanding how air pollution affects brain development and how or why it may contribute to autism,” says Dr. Volk. “Our study represents an important first step in understanding one possible mechanism.”

In their new study, the researchers tracked prenatal exposure to air pollution among 408 children, ages 2 to 5. Of these, 252 had autism spectrum disorder. All were part of California’s Childhood Autism Risks from Genetics and the Environment (CHARGE) study. The investigators identified gene mutations through blood samples. They tracked air pollution exposure using residential histories for the children and their mothers. Pollution estimates came from local traffic levels and regional air quality monitoring. 

When the researchers looked only at the children’s MET gene, they found no significant difference between those who had the variation and those who did not. Similarly, they found no increased autism risk among those who had the changed version of the gene but were not exposed to high pollution during their mother’s pregnancies. By contrast, they found a nearly 3-fold increase in autism prevalence among those who had the MET change and high prenatal exposure to air pollution, compared with those who had neither.

“These results may argue that research on autism’s genetic and environmental risk factors should not be done in isolation,” Dr. Halladay remarks. “We need further research to confirm the findings and determine the mechanisms underlying the gene-environment interaction.”

Drs. Campbell and Volk continue to study autism risk and interactions between genetics and pollution. Their research project, funded by Autism Speaks, used anonymous information provided by families participating in Autism Speaks Autism Genetic Resource Exchange. The researchers are also participating in another Autism Speaks research project looking at a possible role of the immune system in gene-pollution interactions.

Autism Speaks Environmental Factors in Autism Initiative supports research that can advance understanding of the environmental influences that increase – or decrease – autism risk. Read more about this research here.