IVAN SEMENIUK - SCIENCE REPORTER
The Globe and Mail
With symptoms that can range from missed social cues to severe linguistic and cognitive impairments, autism spectrum disorder (ASD) has proved a complex condition for geneticists to get their heads around.
Now the largest study to date based on the whole genome sequences of siblings with ASD, together with their non-autistic parents, is throwing a genetic spotlight on those complexities and yielding some surprises.
Among them: In only one third of the cases where the autism of one sibling with ASD was linked to a genetic variant did the other sibling with autism share the same variant.
At face value, such a result might seem to defy common sense. Autism is thought to affect about 1 in 68 children, which means the odds of two siblings having the disorder for entirely unrelated reasons should be very low.
One possible explanation is some of the variants the study looked at will prove in time not to be implicated in autism. Or there could be other still-hidden inherited factors that the siblings share that may increase the likelihood of ASD in some way. “Then, if they have another mutation, they’re pushed across the autism threshold,” says Stephen Scherer, director of the Centre for Applied Genomics at the Hospital for Sick Children in Toronto who led the study. MORE >