THE WORLD'S LARGEST DNA SCAN for familial autism has uncovered new genetic changes in autistic children that are often not present in their parents. Identified in less than 1 percent of the population, these rare variants occur nearly 20 percent more in autistic children.
Published in the June 2010 online edition of the journal Nature, the findings by an international consortium of scientists from more than 60 countries emphasize the need for larger study samples to illuminate the diverse genetic causes of the brain disorder.
Using blood samples from 996 elementary school–age children diagnosed on the autism spectrum, the scientific teams combed the children’s DNA for rare deletions and duplications. In particular, they hunted for changes in the genetic information that a child inherits from each parent.
“We discovered two striking things. First, the rare variants interfered nearly 20 percent more in the genes of autistic children than in healthy children,” says Daniel Geschwind, M.D., Ph.D., director of the UCLA Center for Autism Research and Treatment and one of the study’s lead investigators. “Second, we found a number of disruptions that are new – the autistic child is the first in his or her family to carry that variant. This finding suggests that tiny genetic errors may occur during formation of the parents’ eggs and sperm, and these variations are copied in the creation of the child’s DNA. The finding parallels what takes place in chromosomal disorders like Down syndrome.”
The researchers’ next step will be to uncover patterns by identifying groups of disrupted genes that work together in the body to establish key functions or biological processes. The results may reveal clues to where genes go awry and increase autism risk, offering hope for common treatments.