Approximately 1 in 1,000 people have autism or autistic disorder. It appears to be the most highly genetic of all psychiatric disorders. If a family with one autistic child has another child the chance that this child would be autistic is 50 to 100 times more likely to than would be expected by chance. However, it's clear that no single gene produces the disorder. Rather, the commonly accepted model states that it is a result of the accumulation of between five to ten genetic mutations.
"Identifying all or most of the genes involved will lead to new diagnostic tools and new approaches to treatment," said Joseph Buxbaum, PhD, Associate Professor of Psychiatry, Mount Sinai School of Medicine and lead author of the study.
Several studies have implicated a region on chromosome 2 as likely to be involved in autism. An earlier study by Dr. Buxbaum and his colleagues narrowed the target to a specific region on this chromosome. He and his colleagues conducted a systematic screening of this region in 411 families that have members with autism or autistic disorder. The families were recruited through The Seaver Autism Research Center at Mount Sinai School of Medicine and the Autism Genetic Resource Exchange.
They found genetic variations in one gene that occur with greater frequency in individuals with autism disease and their family members. This gene codes for a protein that is involved in production of ATP, the molecule that acts as fuel providing the energy cells need to function. The mutations identified lead to production of excessive amounts of this protein. Dysfunction of this gene could lead to irregularities in the production of molecules that fuel the cells. Since brain cells consume large amounts of energy even minor disruptions in production of such fuel can significantly affect the cells ability to function normally.
The variants of this gene found in this study appear to be very common. In and of themselves they do not cause autism, nor do individuals with these variants necessarily have any symptoms. "Having one of these variants appears to approximately double an individuals risk for the disorder, but it is an accumulation of genetic factors that cause the disease," said Dr. Buxbaum. "So, our current challenge is to identify more of these genes."