Researchers have found that many people with autism share common genetic variations, a discovery that may improve diagnosis and offers the promise of developing treatments for the frustratingly mysterious disorder.
Their findings, published in the journal Nature, compared the genomes of thousands of autistic people with those of thousands of people without the disorder -- a massive task that new technology has only recently made possible. The genome is the complex system of DNA coding that builds and runs the human body.
The review showed that most autistic people examined have a genetic variation in a portion of their DNA that affects the way brain cells connect with one another. Scientists also reported a link between autism and small "mistakes" in another DNA segment involved with cell communication. Both reports add weight to the idea that autism is related to problems with the way brain cells connect.
"It is very exciting," said study leader Hakon Hakonarson, director of the Center for Applied Genomics at Children's Hospital of Philadelphia. "It opens up the opportunity someday for new interventions to fix the bad consequences this variant has on brain function and development."
A disorder marked by impaired language and ability to interact, autism affects 1 in 150 children in the U.S., according to the Centers for Disease Control and Prevention.
Up to now, the medical community could say very little about what causes autism or how to treat it. The lack of scientific knowledge about autism has led to a proliferation of pseudoscientific explanations for the disorder, as well as unproven treatments.
Though this is not the first time geneticists have found a link between autism and DNA, past discoveries have involved extremely rare instances in which a tiny bit of DNA was missing or there were too many copies of another bit. Those differences were helpful in understanding how trouble in those regions of the genome can lead to autistic symptoms, but they accounted for only a tiny fraction of autism cases.
By contrast, the new research is "a big step," said Thomas Lehner, chief of the Genomics Research Branch at the National Institute of Mental Health.
The first of two Nature studies released Tuesday found that 65% of autistic participants shared a variation between cadherin 10 and cadherin 9, a region of the genome that controls cell-adhesion molecules in the brain. Those molecules help brain cells connect, and autism researchers have long suspected that trouble there may be linked to the disorder. The second study suggested a link between autism and an excess of genetic material associated with ubiquitin, a protein involved with connections between cells.
The reports also do not explain the rising numbers of diagnosed cases of autism. That increase may be occurring because of heightened awareness, because the definition of autism has expanded, because of some environmental factor, some combination of these factors or something else entirely.