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Genomewide screen for autism points to chromosomes 2, 7, and 16
By Birgit Hofmann-Reinert

In one of the largest genomewide screens for autism, researchers have identified regions of chromosomes 2, 7, and 16 that may contain risk factors for the disease. The findings are based on genome scans of 152 pairs of affected siblings, including three trios.

The publication is available from The National Institute of Mental Health.

The International Molecular Genetic Study of Autism Consortium initially identified 13 candidate regions using a subset of the 152 families, but when they added more families the statistical measures of linkage dropped below the standard of significance for all but three regions. The strongest evidence for linkage was for chromosome 2, followed by regions on chromosomes 7 and 16. The stretches of chromosomes 7 and 16 have previously been linked to autism.

"These findings demonstrate the utility of enlarging collections of affected relative-pair families," the researchers write in The American Journal of Human Genetics. Larger sample sizes can strengthen true cases of linkage and eliminate cases of linkage that may be false positives. No autism screen to date has reached a sample size of 200 affected pairs of relatives, which is "the generally accepted minimum sample size for a whole genome scan of complex diseases," according to the researchers.

Autism is a complex neurodevelopmental disorder characterized by difficulties in communication and social interaction as well as repetitive behavior. Symptoms usually occur during the first three years of life. The Autism Society of America estimates that as many as one in 500 individuals has the disorder. It is four times more prevalent in males than females.

The International Molecular Genetic Study of Autism Consortium was founded with the aim of establishing the genetic basis of autism, as twin and family studies have indicated a strong genetic component to this developmental disorder. The consortium includes clinicians, laboratory researchers and statistical geneticists from several European countries and the United States.

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International Molecular Genetic Study of Autism Consortium (IMGSAC). Genomewide screen for autism: strong evidence for linkage to chromosomes 2q, 7q, and 16p. Am J Hum Genet 69, 570-581 (September 2001).

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