Harvard Mental Health Letter

In Brief: Chromosome "hot spot" linked to autism

In Brief

Chromosome "hot spot" linked to autism

Autism Consortium researchers reported in 2008 that the deletion or duplication of an area on chromosome 16 may account for about 1% of all cases of autism. Although the impact of the finding might seem small, the report generated considerable excitement in the research community because it represents a new way of identifying genetic factors responsible for autism and other complex brain disorders, which typically develop from the interaction of multiple genes, each exerting relatively small effect.

The researchers analyzed genetic data from the Autism Genetic Resource Exchange, which has collected blood samples and clinical information from more than 3,000 individuals with autism spectrum disorders. The scientists used a new type of gene chip technology that enabled them not only to identify subtle genetic changes but also to detect something known as "copy number variation" to determine whether certain genes were deleted or duplicated.

Of 1,441 individuals diagnosed with autism spectrum disorders, five had deletions and seven had duplications of a particular 25-gene section on chromosome 16. The Consortium researchers then searched for similar deletions or duplications in two separate outside samples. One was a clinical sample of children evaluated at Children's Hospital Boston for autism spectrum disorders, developmental delay, or mental retardation. The other sample was of people in Iceland diagnosed with autism. They found an identical chromosome 16 deletion in five of 512 children referred to Children's Hospital Boston, and in three of 299 people with autism in the Iceland database. In addition, they found a duplication in four of the Boston children.

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