A certain
gene mutation and exposure to air pollution can interact to heighten the risk
for autism, finds a groundbreaking study that will be published in Epidemiology.
The lead
author of the study, Heather Volk, at the Keck School of Medicine of USC, had
already drawn a link between autism and certain
levels air pollution exposure during pregnancy and early infancy.
Additionally,
work done by study co-author, Daniel Campbell (also at USC), furthered evidence that autism is more likely to
occur when people carry a certain form of the so-called MET gene.
The
current study aimed to explore whether these seperate factors could combine and
augment the chances for autism, especially since animal studies showed that
pollution could interfere with the MET gene.
The
researchers assessed children participating in California’s Childhood Autism
Risk from Genetics and the Environment study. The 408 children in the study
were between the ages of 2 and 5, and more than half of them had a form of
autism spectrum disorder.
The presence of MET gene mutations were
detected via blood samples while the residential history of the children and
their mothers and the respective traffic patterns and air quality readings of
these areas provided an estimate of pollution exposure.
Nothing
stood out when the authors compared children based on variation of the MET gene
nor when there was a MET mutation but low level of pollution exposure.
But when the authors looked at children who carried the altered MET gene
and who were also prenatally exposed to high levels of pollution, they
discovered that the likelihood for autism tripled compared to those who
experienced neither of these risk factors.
“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,” Campell explained in Autism
Daily Newscast.
The MET
gene variant, Campbell explained, controls expression of the 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,” he said.
The
study’s multifaceted takeaway corroborates with an extensive amount of research
showing that the causes of autism are numerous and complex, with various
factors usually interacting and ultimately altering the course of a child’s
development.
“The results may argue that research on autism’s genetic and
environmental risk factors should not be done in isolation,” Alycia Halladay,
senior director of environmental and clinical research at Autism Speaks, noted
on the organization’s website.
“We need further research to
confirm the findings and determine the mechanisms underlying the
gene-environment interaction.”
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