It's associated with both brain development and GI system functions, study finds.
"This association was not present in another group who have autism and don't have gastrointestinal problems," said study author Dr. Daniel B. Campbell, a research assistant professor of pharmacology at Vanderbilt University in Nashville. "We think we're subdividing types of autism in a way that's finally useful."
The report was published in the March issue of Pediatrics.
Autism is widely recognized to be not one condition, but a collection of very heterogeneous disorders. Many prefer to use the term "autism spectrum disorders" (ASD) to describe the variety.
Several studies have now shown an association between ASD and this specific genetic variant.
The study authors put this together with the fact that 30 percent to 70 percent of children with autism have GI problems and the fact that the MET C gene is involved with both brain development and how the GI system functions.
"It's involved in how well it repairs itself, how well it responds to insults, taking in foods that upset the stomach," Campbell explained. "We wondered if this MET gene variant that we'd identified two years ago might be involved specifically in a subset of these patients who have both autism and a GI problem."
The authors looked at medical histories and genetic profiles of 918 individuals with autism from 214 families.
The MET C allele was linked with autism spectrum disorder and GI problems in 118 families who had at least one child with both conditions.
No such link was found in the remaining 96 families who did not have a child with both autism and GI conditions.
"It looks like this particular genetic variation affects cellular processes in the brain during development and in the gut for your whole life," said Keith Young, vice chair for research for the department of psychiatry and behavioral science at Texas A&M Health Science Center College of Medicine and neuroimaging and genetics core leader at VA Center of Excellence for Research on Returning War Veterans, part of the Central Texas Veterans Health Care System.
"What we predict is going to happen is that other genes that provide proteins for this pathway might be affected in those families, so they're not going to show up with a gut problem, but they can still get autism," continued Young, who was recently named chair of the Tissue Advisory Board for Autism Speaks, a group that aims to increase awareness about autism and to fund research into the disorder. "The long-term importance of this is it's providing information about this cellular pathway where we can start looking to find out what it has to do with development. . . This gene is found more in social parts of the brain."
This line of research may turn up targets for new drugs.
Although the finding is not likely to change the lives of individuals with autism in the near future, Campbell said, "It's important for the public to know that GI problems are present in autism. And in this particular set of individuals who have problems with communication, it's not always that obvious that they have GI problems. Often they can't say, 'My tummy hurts.' They have to find other ways to express that, and it's not always productive."
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