Autism, a neurological disorder that impairs a person’s ability to communicate with and relate to others, affects one in every 150 American children. Genetics is thought to be at least partly to blame for this condition, but research aimed at finding the genes involved has been frustratingly slow.
This is due at least in part to the fact that it’s unlikely that there is one or even a small number of “autism genes.” Autism is a “spectrum disorder” that affects individuals differently and to varying degrees. There are probably different genetic and environmental factors at work in different types of autism.
New research, published online this week by the journal Pediatrics, may shed light on the genetic underpinnings of at least one subtype of autism. Research has shown that gastrointestinal (GI) problems are more common in people with autism than the general population. The new work shows that variation in a signaling protein involved in both brain development and gastrointestinal repair may contribute to an increased risk for the types of autism that include gastrointestinal dysfunction.
“Our study is the first to bring together genetic risk for autism and co-occurring GI disorders in a way that provides a biologically plausible explanation for why they are seen together so often,” said Pat Levitt, director of the Zilkha Neurogenetic Institute at the Keck School of Medicine of USC and senior author of the study, in a statement.
Previous research by Levitt’s group showed that a SNP in the Met gene increases the risk of autism. People with one copy of the variation have 1.67 times the risk of autism and people with two copies have 2.27 times the risk.
The current study looked at 918 people from 214 families with at least one child affected by autism and found that the association between the condition and the SNP holds only in those patients with GI disorders such as chronic constipation or diarrhea, irritable bowel syndrome, gastroesophogeal reflux or peptic ulcer disease.
The researchers suggest that types of autism that include GI disorders may be a distinct class of the condition, with the Met gene playing an important part. Their previous work demonstrated that the version of the variation that increases the risk of autism reduces the amount of protein made from the Met gene. People with autism were also shown to have less Met protein in their brains than age and gender matched controls.
The authors warn that their study was small and the association of the variation they focused on does not completely explain the high prevalence of GI disorders in people with autism. They say their results should be considered “exploratory.” Nevertheless, the findings may bring researchers closer to understanding the complex genetics of autism.