New Genetic Clues to Autism Found
May 3, 2010 -- Researchers have discovered two new genes that may beinvolved with autism, the brain disorder marked by difficulty incommunicating and relating to others.
The evidence for one of the two new "susceptibility genes" is stronger thanthat for the other, says Daniel Notterman, MD, the senior author of the studyand a professor of pediatrics, biochemistry, and molecular biology at PennState College of Medicine in Hershey.
One of the newly discovered gene mutations is in NCAM2 and the other is inPTPRD.
"We are more confident about NCAM2 and less about PTPRD," Notterman tellsWebMD.
The researchers announced the discovery Sunday at the Pediatric AcademicSocieties annual meeting in Vancouver, British Columbia.
Autism or autismspectrum disorder, involving less severe forms of the condition, affect onein 110 U.S. children, according to estimates from the CDC.
The new finding, Notterman says, adds to the growing evidence for geneticlinks for autism but doesn't rule out a role for environmental factors. "Overthe last couple of years, beginning in 2007, it's become clear that some casesof autism, maybe up to 15%, will be caused by rare mutations, either occurringspontaneously or that can be inherited by a parent," he says.
Tracking the Autism Genes
Notterman and his colleagues analyzed data from the Autism Genetic ResourceExchange (AGRE), a collaborative gene bank for autism, on 943 families,most of whom had more than one child diagnosed with autism. In all, theyevaluated 3,742 family members.
They compared these with genetic data from 6,317 people withoutdevelopmental or neuropsychiatric conditions.
Comparing genetic information on those affected with autism and those not,Notterman says, ''gave us a starting list of about 25 genetic mutations" foundmore commonly in those with autism.
Next, the researchers looked at whether the 25 were substantially differentin the two groups, and in the process narrowed the list of suspect genes tofour.
Two of the four had already been identified by researchers as linked withautism. The other two were new. "No one had shown this [link] statistically,"Notterman says.
Next, Notterman's team validated the finding to see if the genes wereexpressed in the brain. They found that NCAM2 was ''expressed in some regionsof the brain that may be associated with autism -- the hippocampus and thecerebellum."
''Many of the genes described [recently as having a link to autism] aregenes involved in the synapse," Notterman says. A synapse is a specializedjunction at which a nerve cell communicates with another cell.
The genetic mutation of NCAM2 is probably rare, Notterman says. "We wouldestimate that 0.5% or fewer of kids with autism have the NCAM2 [mutation]."
"About six to 10 rare genetic mutations to date have been associated withautism," Notterman says. "Most people working in the field predict there willbe 50 to 100."
Some parents and siblings of the children with autism were found to have theNCAM2 mutation but not the disorder, which the researchers expected to find.This suggests other genetic factors or environmental triggers play a role.
Notterman conducted the research while at Princeton University. The researchwas supported by the Simons and Nancy Laurie Marks Foundations and the AGREConsortium.
http://www.webmd.com/brain/autism/news/20100503/new-genetic-clues-autism-found?src=RSS_PUBLIC
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