DNA ‘glitches’ – tiny gene mutations pose more risk for autism than had been previously thought.
These spontaneous deletions and duplications of genetic material were found to be ten times more prevalent in sporadic cases of autism spectrum disorders than in healthy control subjects ? but only twice as prevalent in autism cases from families with more than one affected member.
The results implicate the anomalies as primary, rather than just contributory, causes of the disorder in most cases when they are present, according to the researchers. Although they might share similar symptoms, different cases of autism could thus be traceable to any of 100 or more genes, alone or in combination.
Drs. Jonathan Sebat, Michael Wigler, Cold Spring Harbor Laboratory (CSHL), and 30 colleagues from several institutions, report on their discovery online in Science Express.
“These structural variations are emerging as a different kind of genetic risk for autism than the more common sequence changes in letters of the genetic code that we?ve been looking for,” explained NIMH director Thomas Insel, M.D. “The best evidence yet that such deletions and duplications are linked to the disorder, these findings certainly complicate the search for genes contributing to autism. These are rare changes, dispersed across the genome, and they tell us that autism may be the final common path for many different genetic abnormalities.”
“Our results show conclusively that these tiny glitches are frequent in autism, occurring in at least ten percent of cases, and primarily in the sporadic form of the disease, which accounts for 90 percent of affected individuals,” added Sebat. “Understanding such sporadic autism will require different genetic approaches and stepped-up recruitment of families in which only one individual has the disease.”