Seattle A gene that may affect a child's chances of having autism has been identified by University of Washington scientists and other members of an international research team.
In the largest genetic study ever of the disease, the team also found the area of a chromosome where another possible autism gene is located.
The discoveries further establish basic concepts about the cause of the devastating disease and offer new hope for developing treatments.
"This isn't the end, but it's a major first step. ... And it's one of the few times almost everyone in the field is trying to work together," said Gerard Schellenberg, a UW geneticist working at the Veterans Affairs medical center in Seattle and a lead scientist in the project.
More than 120 scientists from 19 countries in North America and Europe in the "Autism Genome Project" worked on the new research reported in Sunday's online edition of the journal Nature Genetics.
The investigators worked with nearly 1,200 families that had two or more children with autism, including 200 families mostly from the Northwest. The number of participants was unprecedented and required years of recruitment. Many came from the Northwest because the UW is highly active in autism research.
The new findings "show the power of this kind of collaboration for making progress," said Geraldine Dawson, director of the UW Autism Center and a lead investigator.
Dawson said further research could identify specific genetic markers that will enable diagnosis of autism at birth. Babies could then begin treatment immediately to promote normal development of the brain.
The Autism Genome Project is a collaboration by scientists at 50 institutions. It was financed by the National Institutes of Health and Autism Speaks, a private organization that raises money for research.
People with autism have difficulty relating to others, have language deficiencies and may have significant mental impairment. Others with any of several "autism spectrum disorders" have similar difficulties in varying degrees.
In early February, the Centers for Disease Control and Prevention said a new 14-state study suggested autism spectrum disorder could be present in as many as one in 150 children.
Dawson said it's believed that genetics plays a significant role in the majority of autism cases. If one child in a family has the disease, a sibling has a 5 percent risk of having it. An identical twin of someone with autism has a 60 percent chance of having all aspects of the disease and a 90 percent risk of having some of them, such as a language deficiency or problems with social interaction.
Scientists suspect 40 to 50 genes may be linked to autism, including four or five that are more likely than others to play a part in the disease.
The Autism Genome Project identified one gene, "neurexin 1," and an area of chromosome 11 with another gene, both of which were found in many of the participating families.
"These two genetic sites are the best we've seen as (possible) autism genes," said Schellenberg.
Neurexin 1 is associated with the release of glutamate, a chemical that allows brain cells to send impulses to one another. The substance plays an important role in early development of the brain and has previously been implicated in autism.
Glutamate is "critical in the development of learning and in forming memories, and if you have a disruption in the (glutamate system), you have a problem," explained Dawson.
The scientists don't know yet how the chromosome 11 region is involved in autism. Pinpointing a specific gene in the region that is linked to the disease is the object of the next phase of the research, beginning soon.