Children with a genetic predisposition for autism who are exposed to air pollution appear to be at a greater risk for developing the disorder, according to new research from the Keck School of Medicine at the University of Southern California (USC).
The researchers analyzed previous studies that showed a link between air pollution and autism, and between autism and the MET gene (a leading candidate gene for autism risk that influences the strength of connections between brain regions involved in social behaviors). They found it was a combination of these factors that increases the risk.
“The MET gene variant has been associated with autism in multiple studies, controls expression of MET protein in both the brain and the immune system and predicts altered brain structure and function.
“It will be important to replicate this finding and to determine the mechanisms by which these genetic and environmental factors interact to increase the risk for autism,” said senior author Daniel B. Campbell, Ph.D., assistant professor of psychiatry and behavioral sciences at the Keck School of Medicine of USC.
The research included 408 children, between the ages of 2 and 5 years, from the Childhood Autism Risks From Genetics and the Environment Study — a population-based, case-control study of preschool children from California. Of these, 252 kids met the criteria for autism or ASD.
Air pollution exposure was based on the past residences of the children and their mothers, local traffic-related sources and regional air quality measures. MET genotype was determined through blood sampling.
“Our research shows that children with both the risk genotype and exposure to high air pollutant levels were at increased risk of autism spectrum disorder compared to those without the risk genotype and lower air pollution exposure,” said first author Heather E. Volk, Ph.D., M.P.H., assistant professor of research in preventive medicine and pediatrics at USC and principal investigator at the Saban Research Institute of Children’s Hospital Los Angeles.
The researchers continue to study the interaction of air pollution exposure and the MET genotype in women during pregnancy.
“Although gene-environment interactions are widely believed to contribute to autism risk, this is the first demonstration of a specific interaction between a well-established genetic risk factor and an environmental factor that independently contribute to autism risk,” said Campbell.
The study will be published in the January 2014 edition of Epidemiology.