A researcher at Seattle Children's Hospital and Research Institute has found a genetic identifier for autism that includes physical features that may eventually allow clinicians to identify babies who are at risk for autism before they are born. This is the first time a genetic mutation has been linked to autism.
Dr. Raphael Bernier, clinical director of Seattle Children's Autism Center and Associate Professor at the University of Washington, who led the research in collaboration with 13 institutions worldwide, has discovered a mutation of the CHD8 gene that, in addition to significantly increasing a child's risk of developing a specific subtype of autism, also causes several physical traits and symptoms that are unique to children with the same subtype of autism.
The physical traits - subtle facial features, such as larger heads and prominent foreheads - are features that, combined with confirmation of a CHD8 gene mutation, could allow clinicians to screen babies still in utero for a higher risk of developing autism, much like clinicians now screen for physical and genetic indicators of disorders like Down's Syndrome.
"This is a big leap forward in our insight into the causes of autism," said Bernier, who led the study published today in the scientific journal Cell. "It's possible we may be able to look at features in utero and determine a higher risk of autism, possibly even early detection."
Early detection is critical in the treatment of autism symptoms, Bernier said. Research studies of behavioral therapies used with younger siblings of kids with autism, who are at higher risk for developing autism themselves, suggest that intervention between three to six months of age can lessen or even prevent symptoms from developing. The goal, Bernier said, is to be able to use these same exercises on babies with a higher risk of autism who have been identified before birth.
"We know that if we can intervene by three or six months of age instead of later in life, we can help the child learn important social communication skills, like eye contact," he said.
The study, titled "Disruptive CHD8 Mutations Define a Subtype of Autism Early in Development," followed 6,176 children with autism spectrum disorder for nine months. Researchers found that 15 had a CHD8 mutation and that all of those cases had similar characteristics in appearance as well as issues with sleep disturbance and gastrointestinal problems including constipation.
Bernier and his team interviewed all 15 cases with CHD8 mutations, and confirmed the findings by working with scientists who study zebrafish, a tropical freshwater fish commonly used in research because of its regenerative abilities. Researchers disrupted the CHD8 gene in the fish, which then developed large heads and wide set eyes. They then fed the fish fluorescent pellets and found that the fish also were constipated and had problems discarding food waste.
"For years, parents of children with autism have been telling us the gastrointestinal symptoms are real, but science has been slow to respond. Now, we have clear evidence that in a subgroup of individuals with autism, both the autism symptoms and constipation are a result of the CHD8 disruptions," Bernier said.
Bernier said this is the first time researchers have shown a definitive cause of autism to a specific gene mutation. Previously identified gene mutations like Fragile X, which account for a greater number of autism cases, are more often associated with other impairments, such as intellectual disability, than autism. Although less than half a percent of kids with autism will have the CHD8 mutation, Bernier said it is likely one of the most common genetic causes.
"This will be a game changer in the way scientists are researching autism," he said. "Children with autism are incredibly diverse so we must determine the genetic causes of different subtypes to find effective treatments."
Seattle Children's Research Institute