According to international research involving 19 countries, 120 scientists and 50 institutions, tiny variations in genes may increase the risk for autism spectrum disorders (ASD). The Autism Genome Project (AGP) Consortium's report can be seen in the journal Nature Genetics, February 18th issue.
The AGP's aim is to identify specific genes and variants that might raise vulnerability to autism. This includes looking into the how genes interact with other genes, as well as other factors, such as the environment. The scientists are also looking into how potential susceptibility genes may work in the brain to bring about ASD.
NIH Director Elias A. Zerhouni, M.D., said "This is the most ambitious effort yet to find the locations of genes that may confer vulnerability to autism. The AGP is revealing clues that will likely influence the direction of autism research for years to come."
Dr. Bernie Devlin, University of Pittsburgh Medical School , one of the corresponding authors on the project, said "Although we know autism is highly heritable, complex gene interactions and submicroscopic anomalies create a din of statistical noise that drowns out detection of signals from linked sites in the genome. To amplify these signals, we brought to bear gene chip technology with a huge sample, and also screened for these fine-level anomalies, factoring them into the analysis."
The scientists say there are now clues that implicate components of the brain's glutamate neurotransmitter system in ASD. Glutamate is crucial in wiring up the brain early on in its development - glutamate enhances neuronal activity. Some genes that are associated with the glutamate system are located in chromosome regions that are linked to ASD, say the scientists.
New evidence has also emerged linking autism and gene sites for neurexins. Neurexins are molecules that construct glutamate synapses - through which brain cells communicate.
A site on chromosome 11 most strongly linked to autism in this study harbors genes for proteins that shuttle glutamate across the synapse. Although detected previously, the linkage signal at this site was regarded as less important until now.
Submicroscopic anomalies - tiny deletions, or the doubling, tripling or even multiplying of stretches of genetic material - are relatively common in the human genome and aren't necessarily harmful. However, recent evidence suggests that these anomalies may contribute to risk for - or rarely even cause - autism if they affect certain sites associated with the disorder. The AGP researchers found a number of these variations in such suspect chromosomal locations in affected individuals, including deletion of a neurexin gene.
-- Nature Genetics
-- Autism Speaks and the World's Leading Autism Experts Announce the Publication of the Autism Genome Project Phase 1 Results
Written by: Christian Nordqvist
Editor: Medical News Today
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