autism
In the largest genetics study of its kind to date, scientists have identified 102 genes associated with the risk for autism spectrum disorder (ASD).

Researchers also gained further insight into which of these genes are associated with both ASD and other disorders that cause intellectual disability and developmental delay.

For the study, an international team of researchers analyzed more than 35,000 participant samples, including almost 12,000 from people with ASD.

Researchers used a genetic technique called "exome sequencing," which looks at all the regions of a person's genetic information — or genome — that are translated into proteins. This testing can pick up rare genetic mutations that might not show up with other methods.

Dr. Lonnie Zwaigenbaum, a professor in the Department of Pediatrics and the Stollery Children's Hospital Foundation Chair in Autism at the University of Alberta, called this an "exciting" study, both for the sophisticated methods used and the large sample size.

These enabled researchers to "identify a larger number of genes than ever before, which gives insight into how those genes operate and how they might increase the risk of ASD," said Zwaigenbaum, who wasn't involved in the research.

The study results were published January 23 in the journal Cell.

Greater understanding of genetics of ASD

ASD is a group of neurological and developmental conditions that affect communication and behavior. There's wide variation in the type and severity of symptoms in people with ASD.

Scientists believe that both genes and environment are involved in the development of ASD, with genetics playing a big part.

"We know that inherited and unique mutations in the genome are a major source of risk for developing ASD, but specific causes of ASD are not yet well understood," said Lori J. Warner, PhD, director of the Center for Human Development and Ted Lindsay Foundation HOPE Center at Beaumont Children's Hospital in Royal Oak, Michigan, who wasn't involved in the study.

Although environmental factors play some role in ASD, scientific studies have found that there's no link between receiving vaccines and developing ASD.


The new study marks an important step forward in scientists' understanding of the genetic basis of ASD.

Researchers identified both inherited genetic mutations and de novo mutations — ones that occur spontaneously when an egg or sperm form.

They also found that the ASD genes identified in the study can affect brain development or brain function. And they showed that two major types of nerve cells can be affected in ASD.

Of the 102 genes identified in the study, 49 were associated with other developmental delays.

"Some genes appear connected to the development of ASD, whereas others may increase risk for ASD plus severe neurodevelopmental disorder," said Warner. "We don't yet understand fully this process, but differentiating ASD from other disorders is important for effective treatment."

Zwaigenbaum said the overlap between ASD and other neurodevelopmental disorders fits with previous research.

"This study reinforces that there are many genes that may have some role in autism vulnerability, but that also have a broader role in early brain development," said Zwaigenbaum.

These genes have a "broader expression in terms of developmental abilities and challenges of the affected individual."

Study points toward treatment and diagnosis

While scientists now understand ASD better as a result of this study, this kind of research also points toward better ways to help children with ASD.

"The greatest benefit of studies of this type is helping researchers, families, and interventionists better understand how genetic factors actually function in the developing brain and body of the individual," said Warner, "so that treatments can be developed to ameliorate or completely block the disruptive changes that lead to disorders such as ASD."

But Zwaigenbaum cautions that the results of the study will not lead to clinical benefits right away.

"There's a lot of translational work that would still need to happen in order to assess whether the findings from this study will directly inform assessment, diagnosis, or treatment," he said.

Still, he said the results provide direction for future research into potential biological treatments, as well as genetic tests that could allow earlier diagnosis of ASD.

Warner said there are medications currently approved for use in children with ASD, but they address symptoms like agitation or anxiety, rather than the core social or behavioral deficits of ASD.

Early diagnosis is another goal of ASD research, because "the sooner children are identified and appropriately assessed, the sooner families can receive needed supports," said Warner.

But ASD is a complex condition, so genetic diagnosis isn't always straightforward.

"Although studies like this continue to expand our appreciation for the increasing number of genes associated with ASD, the reality is that a genetic cause is seldom identified in most children with ASD — even with the most sophisticated genetic testing," said Andrew Adesman, MD, chief of Developmental & Behavioral Pediatrics at Cohen Children's Medical Center in Queens, New York, who wasn't involved in the study.

But he said there's still value in parents of a child with ASD seeking out genetic testing, especially as genetic technologies advance.

"There have been steady gains in terms of the diagnostic 'yield' of genetic testing," said Adesman. "For this reason, parents of children with ASD may wish to discuss with their pediatrician whether their child should have the newer genetic tests done."

In the absence of a simple test for ASD, there are still things parents can do for their children.

"The single most important things families and healthcare providers can do is to be aware of the risk factors and early signs and symptoms of autism, and get connected with needed services as soon as possible," said Warner.