Last week Nature published the results of three studies (1,2,3) looking at the sequences of protein-coding genes from hundreds of individuals with autism and their parents. The main results are that there is a higher rate of de novo mutations in affected individuals, that these primarily come from fathers, and that the affected genes are enriched for those involved in brain development and activity.
I think a bit too much is being made of these studies – they’re generally technically sound, but there remains no definitive link between any single mutation or groups of mutations and the disease. However, the authors of one of the papers have made a big deal about having found a mutation in the same gene in two unrelated individuals. This is described in a piece last week by Benedict Carey in the New York Times:
In one of the new studies, Dr. Matthew W. State, a professor of genetics and child psychiatry at Yale, led a team that looked for de novo mutations in 200 people who had been given an autism diagnosis, as well as in parents and siblings who showed no signs of the disorder. The team found that two unrelated children with autism in the study had de novo mutations in the same gene — and nothing similar in those without a diagnosis.
“That is like throwing a dart at a dart board with 21,000 spots and hitting the same one twice,” Dr. State said. “The chances that this gene is related to autism risk is something like 99.9999 percent.”
Wow. 99.9999 percent. That’s impressive. But I have no idea where it came from.
If the study had looked at exactly two families, and they had found a single de novo mutation in the affected individual in each family, and these had been in the same gene, then yes, it would have been like throwing a dart at a dart board with 21,000 spots (roughly the number of genes examined) and hitting the same one twice – or roughly 1 in 21,000. But this is not what they did.
Read full article and numerous comments at http://www.michaeleisen.org/blog/?p=1009