In the largest genetic studies yet of autism, a team from across the United States has pinpointed previously overlooked DNA that predisposes children to the disorder. The suspect DNA includes the first variant that might underlie a large percentage of autism cases.
- Most of the DNA linked to autism involves copy-number variation, in which segments of DNA are repeated or deleted in the genomes of affected children. But these copy-number variants (CNVs) tend to be extremely rare, showing up in less than 1% of children with autism. In addition, it's been difficult to repeat the findings from individual genetic studies--partly, researchers think, because autism is so variable and may really be many different diseases.
- They lie in a region of chromosome 5 that sits squarely between two genes that produce cell-adhesion molecules, which govern how neurons connect to each other. The variants don't raise risk all that much--about 20% for the strongest.
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The first of two Nature studies released Tuesday found that 65% of autistic participants shared a variation between cadherin 10 and cadherin 9, a region of the genome that controls cell-adhesion molecules in the brain. Those molecules help brain cells connect, and autism researchers have long suspected that trouble there may be linked to the disorder. The second study suggested a link between autism and an excess of genetic material associated with ubiquitin, a protein involved with connections between cells.
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