Scientists Link 'Sets' of Genetic Abnormalities to Autism Risk
Posted Mar 01 2011 12:00pm
DNA analysis of more than 1,000 kids may one day lead to better treatments, researchers say.
TUESDAY, March 1 (HealthDay News) -- While the genetic underpinnings of autism are enormously complex, new DNA research is honing in on sets of abnormal genes that may play a role in the disorder.
Researchers from the Center for Biomedical Informatics at The Children's Hospital of Philadelphia (CHOP) said that, while other scientists have theorized about a connection between gene mutations, impaired brain development, and the onset of autism, their work is the first to establish the link.
The medical problem, the CHOP researchers said, has to do with genetically driven disturbances in the way nerve cells communicate (via synapses) as well as the manner in which these communications are handled by key neural "messengers," or neurotransmitters.
"This large study is the first to demonstrate a statistically significant connection between genomic variants in autism and both [nerve cell] synaptic function and neurotransmission," senior author Peter S. White, a molecular geneticist and director of the Center for Biomedical Informatics, said in a hospital news release.
White and his colleagues report their findings in the March 1 online issue of Molecular Psychiatry.
The study authors pointed out that while prior research has implicated individual gene abnormalities with an increased risk of autism, each particular abnormality that has been identified to date has been linked to very small percentage of autism cases.
What's new about the current effort, the team said, is the uncovering of entire collections of genes with similar neural roles which, taken as a group, seem to be associated with a greater proportion of autism risk.
The finding stems from a DNA analysis involving about 1,000 autistic children and their families, as well as parallel research with mice.
Searching for links between genetic irregularities and abnormal motor control and/or learning disabilities, the study authors focused on so-called CNVs -- "copy number variations" -- that occur when the number of copies of a particular gene varies from one individual to the next. These CNVs accounted for relatively big chunks of the genetic mutations, the researchers said.
The gene sets of CNVs, they noted, are comprised of more DNA structure than simple individual "snips" of DNA. These CNV gene sets have previously been associated with a range of neuropsychiatric disorders, such as schizophrenia, bipolar disorder, and attention-deficit hyperactivity disorder (ADHD).
In all, about 800 CNVs were identified as exclusive to autistic children. In addition, the CNVs in question tended to be found in genes central to the impaired biological functions that show up in autistic behavior, such as those involving synapse function, nerve cell communication, and brain development, the CHOP researchers said.
"This suggested to us that there may be many different -- possibly even hundreds -- of genetic paths to autism, with only a few gene alterations relevant to each individual patient," White said. "But if those hundreds of genes have similar roles in the nervous system, the end result may lead to the same diagnosis: an autism spectrum disorder."
"Because the gene alterations that we found influence brain development, our hope is that they may eventually provide clues to developing diagnostic tests as well as treatments for children with autism," study co-author and CHOP child psychiatrist Dr. Josephine Elia also noted in the news release.
Ashley Scott-Van Zeeland, a postdoctoral research fellow at the Scripps Translational Science Institute in San Diego, suggested that the new findings may ultimately enable researchers to approach the question of autism treatment with a broader brush.
"What this study found is that there are perhaps many autisms," she said. "There may be a number of unique or very rare genetic mutations associated with the disorder. But this suggests that they follow a common pathway that leads to autism.
"So that could mean that instead of the old paradigm of finding one mutated gene or protein and then developing a drug targeting just for that, now we could look for entire pathways involved in autism. And then potentially we could intervene with those processes with new therapeutics," she added.