Sifting through the DNA of hundreds of families, researchers have picked out a gene that may contribute to some cases of autism. Mutations in the gene, active during fetal development of the nervous system in frogs and probably humans, are linked to the severe language problems seen in some people with autism.
Evidence from studies of twins suggests that genes play a central role in autism. No single gene causes the syndrome, but as many as 15 genes may interact to produce the symptoms, which include an inability to form emotional bonds with others, poor language skills, and repetitive behavior, such as rocking or head banging.
Some studies have traced autism to a portion of chromosome 7, so when psychiatric geneticist Thomas Wassink of the University of Iowa in Iowa City began hunting for autism genes, he started there. One gene within the linked region caught his attention: WNT2, a member of a family of genes crucial to the early development of the central nervous system. Mice whose WNT pathway is disabled exhibit behavioral problems similar to those seen in autism, such as decreased social interaction.
Wassink and his team screened 135 autistic people and their families for WNT2 mutations and found two in the region of the gene that encodes protein. The mutations showed up only in autistic children; nonautistic siblings never had the mutations. But these mutations showed up in just two families. So Wassink broadened his search to nearby stretches of DNA that flank WNT2 and tell it when to turn on and off. There he found a mutation that was inherited by autistic children 50% more often than would be expected by chance. Most of the children had severe language impairments, the team reports in the 17 May online edition of the American Journal of Medical Genetics.
Finding WNT2 mutations in autistic people "makes perfect biological sense," says autism researcher Patricia Rodier of the University of Rochester Medical Center in New York, because the gene likely directs brain development. "Looking at genes that are involved in patterning in the developing brain is the way to go."
Abstract of paper in the American Journal of Medical Genetics