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Winnipeg Free Press - PRINT EDITION

Host of genetic factors tied to autism: study

By: Margaret Munro

Posted: 06/10/2010 1:00 AM | Comments: 0 (including replies)

Lisa Bond (middle) with daughter Rebecca and autistic son Joshua. (HANDOUT PHOTO)

Lisa Bond spent years trying to understand why her son, Joshua, wouldn't make eye contact, threw fits when she tried to change his socks, and had so much trouble learning to speak.

It turns out Joshua, now 14, is missing a small chunk of DNA on chromosome 16 -- a deletion so profound it impaired his neurodevelopment, causing autism and serious language and learning disabilities.

For Lisa, the genetic revelation is a huge relief. "Knowing just makes it so much easier to cope," she says.

For Dr. Stephen Scherer, at Toronto's Hospital for Sick Children, it is part of a "paradigm shift" in understanding the causes of the baffling disorder that affects almost one in 100 children.

Scherer and his colleagues have just released the world's largest genetic study of autism. They scanned the DNA of Joshua and 995 other children with the disorder from Canada, the United States and Europe.

The results, published in the journal Nature this week, show that individuals with autism have almost 20 per more gene deletions and duplicates than normal. Dozens of new "autism risk genes" were also uncovered.

Some children, like Joshua, are missing chunks of DNA. Others carry duplicate stretches of DNA. Some of these so-called "copy number variants" were inherited; others are new and not seen in other family members.

"This suggests that tiny genetic errors may occur during formation of the parents' eggs and sperm, and these variations are copied during creation of their child's DNA," says co-author Dr. Daniel Geschwind, at the University of California, Los Angeles.

Autism spectrum disorders can vary quite widely in severity.

They tend to show up as language and social problems in toddlers, and can develop into highly repetitive behaviours, restricted interests and social and communication deficits. individuals have serious lifelong disabilities, and some are brilliant. "I have colleagues at the university who have Asperger's (a mild form of autism)," says Scherer.

It's long been known genes are involved in autism spectrum disorders, but researchers have spent years -- in Scherer's case, 15 years -- trying to home in on the ones responsible.

The study shows there is not a single gene tied to autism but many genes and gene regions that differ from person to person. The researchers, who plan to test 5,000 more Canadian youngsters, expect to find plenty more.

"Most individuals with autism are probably genetically quite unique, each having their own genetic form of autism," says Scherer, who led the study that compared the genes of individuals with autism to genes of 1,287 unaffected people.

It revealed that many of genes involved in autism spectrum disorders play a role in production of proteins that affect the way neurons in the brain "grow, differentiate and communicate with each other."

There was also significant overlap with "intellectual disability genes" previously associated with other mental-health disorders.

Since many of the genes are tied to the same biological pathway, Scherer says, they provide targets for drug therapies and new treatments.

Having a better read on the genetic factors could also mean earlier diagnosis, the researchers say, and could end the long waits parents often endure as they struggle to find out what is wrong with their youngsters.

-- Canwest News Service

Republished from the Winnipeg Free Press print edition June 10, 2010 A6

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