Washington, Jan 18 : A new study has found evidence that previously unknown chromosomal abnormalities have a substantial role in autism spectrum disorder (ASD).
According to the researchers, structural variants in the chromosomes were found to influence ASD with sufficiently high frequency to suggest that genomic analyses must be considered in routine clinical workup.
"Historical studies in identical twins and their families have provided strong evidence for a genetic basis of autism. Last year, with the Autism Genome Project Consortium, we did an initial study to look at the rate of chromosomal changes in autism. Now, we've really pinned down those numbers," said Stephen Scherer of The Hospital for Sick Children and the University of Toronto.
Structural changes, including gains and losses of genes as well as chromosomal translocations (in which a chromosomal segment ends up in the wrong place) or inversions (in which a portion of the genome is oriented backwards) have been previously identified in some individuals with ASD, but their role hasn't been understood.
For the new study, the researchers examined structural abnormalities in 427 unrelated ASD cases.
They found while most chromosomal abnormalities were inherited, seven percent of kids with autism carry structural changes in the genome that are not found in their parents.
Scherer said that the rate of such de novo changes in the general population is typically less than one percent.
The researchers identified 13 regions of the genome with overlapping or recurrent chromosomal changes in unrelated people with autism, suggesting that genes located at these sites may cause or contribute to the complexity of the condition.
They reported that the most prevalent change, occurring in one percent of ASD cases, was found on chromosome 16.
Scherer noted that the altered portion of chromosome 16 has structural characteristics that make it more prone to errors.
In a subset of ASD cases, the researchers found abnormalities in several genes known to be involved in neuron function. They also identified at least two sites that have previously been linked to mental retardation.
"Our understanding of the full etiologic role of structural variation in ASD will require genomic and phenotypic analyses of more cases (and their families) and population controls," the researchers said.
The researchers also call for new testing in the clinic.
"From our current data it is already apparent that for a proportion of individuals, it will be possible to describe their ASD based on the underlying structural characteristics of their genome," they said.
"If we found certain changes, we could then watch those children closer," they added.
The study was published online Jan. 17th in the American Journal
of Human Genetics.