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Study finds way to track exposures that may contribute to autism

Epigenetic changes linked to smoking in pregnancy still present at age 5; method offers new way to track hidden environmental risk factors for autism
November 24, 2015

Autism researchers have found a promising new method to detect prenatal exposures that may increase risk for autism – and to do so years after the exposures occurred.

In their study, the researchers showed that a chemical signature of prenatal exposure to cigarette smoke persists in the blood of preschoolers. It’s not known whether smoking during pregnancy contributes to autism. Rather, since a mother can say whether or not she smoked, the researchers could see if a clear chemical signature of prenatal exposure persisted into childhood.

They will now look for markers for less-obvious toxic exposures suspected to increase autism risk. These include exposure to pesticides, air pollution, plasticizers and maternal inflammation during pregnancy. 

The study, led by Daniele Fallin and Christine Ladd-Acosta, appears this week in the journal Environmental Research. It was funded, in part, by Autism Speaks’ inaugural Geier Grant in Environmental Research.

Fallin directs the Bloomberg School's Wendy Klag Center for Autism & Developmental Disabilities, at Johns Hopkins University. Her Geier grant supports her team’s study of gene-environmental interactions across the entire genome of children who have autism.

More specifically, Fallin’s team is looking at so-called epigenetic markers. These chemical tags sit atop a gene’s DNA and help control when and where the gene is active.

Epigenetic control of gene activity is particularly crucial for guiding early brain development. And it’s known that chemical exposures, infection and other stresses can alter epigenetics – and so alter gene activity in important and lasting ways.

“We have long known that the body is an accumulator of past exposures – evidence of lead exposure lives on in our bones, for example,” Fallin says. “But we did not know that something as easy-to-collect as blood could contain evidence of exposures not only during your life but prenatally. That's what makes this so compelling.”

“Smoking is one thing,” she adds. “But if this turns out to be possible for other kinds of exposures, this could be a paradigm shift.”

In the study, the researchers performed whole genome epigenetic analysis on the blood of 531 children, ages 3 to 5, from six sites across the United States. They also asked the children’s mothers about smoking during pregnancy.

They then analyzed epigenetic patterns (methylation) at 26 locations across the children’s genomes. Based on this analysis, they were able to identify which mothers smoked during pregnancy with 81 percent accuracy.

Other researchers had previously identified these epigenetic signatures of prenatal smoking in infant cord blood. The new study is the first to show that the tell-tale chemical evidence persists to at least age 5.

Fallin says she hopes this area of research has broader reach. With smoking, she says, it is relatively easy to determine whether someone was exposed prenatally: You simply ask the mother or ask someone whether their mother smoked while she was pregnant. But exposures to other toxins are more difficult to tease out. For many, the mother may not know whether she was exposed.

To learn more, also see:

What is epigenetics, and what does it have to do with autism?

Your Dollars@Work: Investigating early influences on autism risk

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