Canadian researchers have led an international team in the discovery of a chromosomal region containing the genes that cause autism, a finding considered a breakthrough in the effort to better understand the condition.
Researchers at Hospital for Sick Children in Toronto and the Offord Centre for Child Studies say the finding is a major breakthrough in the effort to better understand the condition and to eventually improve treatment for patients.
The discovery was part of the largest genome scan ever attempted in autism research. Called the Autism Genome Project, the initiative involved 137 researchers from 50 institiutions in nine countries, including Canada.
Working together, the scientists were able to share samples, data, and expertise to analyze DNA from about 1,600 families worldwide.
They zeroed in on a special group of neurons and the genes affecting their development and function. They then used cutting-edge Copy Number Variation (CNV) analysis to look for genetic commonality as well as unique differences in autistic individual.
The scientists were able to implicate a previously unidentified region of chromosome 11, and neurexin 1, a member of a family of genes believed to be important in neuronal contact and communication.
The neurexin finding in particular highlights a special group of neurons, called glutamate neurons, that could play a critical role in autism spectrum disorders.
"The clinical implications of this discovery are unprecedented," said Dr. Peter Szatmari, director of the Offord Centre for Child Studies.
"Not only have we found which haystack the needle is in, we now know where in the haystack that needle is located.
Dr. Stephen Scherer, a senior scientist in Genetics and Genomic Biology at SickKids, was the first to discover the existence of common genetic variants and is delighted with the discoveries the consortium was able to make.
"We first used genome scanning technology to test genetic markers in autistic children and find regions in the genome linking to autism susceptibility genes," said Dr. Scherer, a senior scientist in Genetics and Genomic Biology at SickKids.
"By combining this with cutting edge CNV analysis we were able to reveal, for the first time, the genetic architecture underlying autism susceptibility."
The findings have been published online in the prestigious journal Nature Genetics.
Autism affects roughly one in 165 children, making it the most common form of any neurological disorder or severe developmental disability of childhood.
Those affected exhibit severe impairments in reciprocal social interaction and communication, and a preference for repetitive, stereotyped behaviours.
