The families in the study were drawn from the Simons Simplex Collection, a large repository of genetic, phenotypic and biological data from families with just one affected child and unaffected parents and siblings. The collection was created for the express purpose of facilitating the search for rare, de novo autism mutations.
While the 20 children with autism did not have significantly more de novo point mutations than would be expected in the population at large, their mutations were much more disruptive to the proteins they encoded than is typical. What's more, a significant number of the mutations occurred in regions of the genome in which mutations are rarely found, probably because these regions are so crucial to bodily functioning that individuals with defects in those regions usually die without reproducing.
In four children, the researchers identified de novo mutations that are so deleterious that they likely play a causative role in these children's autism. Probably not coincidentally, these four children are among the most severely affected in the study group.
Three of the four mutated genes FOXP1, GRIN2B and SCN1A have previously been implicated in autism, and are thought to play roles in speech and language disorders, intellectual disability and epilepsy, respectively. The fourth gene, LAMC3, has not previously been linked to autism, but is known to be expressed in many areas of the cortex and limbic system. "Finding a LAMC3 mutation will probably set the stage for some new research agendas," Eichler says.
Two of the four children appear to have experienced a genetic double-whamm
|Contact: Anastasia Greenebaum|