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WASHINGTON: Spontaneous and rare gene mutations are likely the cause of autism in families with no previous history of the disorder, a trio of new studies have suggested.
Two studies published in the journal Neuron describe a series of genetic variants that boost the risk of autism, a developmental disorder which appears by age three and affects up to 10 out of every 1,000 individuals. A third study sheds light on how these disrupted genes tend to take aim at a particular target - the formation of the brain's synapses, or junctions that allow signals to be passed between neurons.
The researchers honed in on a region of the human genome that, when altered, tends to produce either autism or Williams syndrome in an individual.
Autism can result when genes mutate and form extra copies of the region. But when parts of the region, called 7q11.23, are missing, people may develop Williams syndrome, which is often characterised in part by a highly sociable personality.
"This region of the genome could be a Rosetta Stone for studying the development of the social brain," said lead author on one of the studies, Matthew State at Yale University.
Autism caused randomly
People with Williams syndrome may be extremely trusting of strangers and have a particular affection for music but may also exhibit developmental disabilities, learning disorders and disfigurement of the face and hands.
Autism includes a wide spectrum of developmental differences and may range from mild social awkwardness to a complete inability to communicate, repetitive movements, sensitivity to certain lights and sounds, and behavioural problems.
The two studies led by researchers from Yale and Cold Spring Harbour Laboratory in New York examined the genomes of more than 1,000 families in which one child was autistic and the siblings and parents were not.
Their findings appear to confirm a growing body of evidence that autism can be caused by a randomly occurring mutation at any one of several hundred different sites in the human genome, researchers said.
