DNA modifications that occur in children but hadn’t been inherited from their parents contribute to certain cases of autism, a new study finds.
Such spontaneous mutations show up in many children who are the only members of their families with autism, say geneticist Jonathan Sebat of Cold Spring Harbor (N.Y.) Laboratory and his colleagues.
The scientists tested DNA from parents and children in 264 families for evidence of deletions or repeats of DNA segments. Spontaneous mutations, primarily deletions, occurred in 12 of 118 youngsters with autism or related developmental disorders who had no siblings with those ailments, Sebat’s team reports in a paper published March 15 online in Science. In contrast, such genetic changes turned up in 2 of 77 children with an autistic disorder who had at least one sibling with the disease and in 2 of 196 healthy kids who had no such siblings.
Individuals with autism rarely had the same spontaneous genetic alterations. Several of these DNA modifications affect genes that influence brain function and development.
Because the tests had only a limited capacity to detect tiny mutations, the new results underestimate the frequency of spontaneous DNA changes in autism, the researchers contend. They predict that advances in genetic testing will identify smaller deletions than can now be assessed.
The team theorizes that inheritance of autism-promoting genes from parents may typify families that have two or more affected children, as suggested in a prior study (SN: 2/24/07, p. 117: Available to subscribers at Decoding Autism: Study finds DNA clues to developmental disorders).