Many cases of autism could be linked to spontaneous genetic changes that result in large chunks of missing DNA, according to a new US study. The research, published early online in Science, shows that so-called 'copy number variants' could be an important factor in the appearance of autism, especially in families with just one affected child. Lead author Jonathon Sebat, of Cold Spring Harbour Laboratory, said the data showed there could be many 'autism genes' in the genome.
Autism - along with several related conditions together known as autistic spectrum disorders - is a lifelong developmental disability that typically appears during the first three years of life. The disorder affects social and language skills, and the way in which a child relates to people, objects and events. Although autism often runs in families, many children are born to parents with no history of the condition.
The team studied 118 families with just one affected child, 47 with multiple children with an autism spectrum disorder, and 99 unaffected families. They looked at DNA samples from the participants, to try and detect regions that were either deleted or duplicated in affected individuals. The researchers identified such a genetic change in over 10 per cent of the children, most of which were not present in either parent. Their locations varied between individuals, involving many different genes.
Most of the changes were deletions, leading to missing copies of genes - in one case, 27 genes were encompassed by a single deletion. Since the spontaneous changes were typically present in families with only one affected child, testing for these variations may allow doctors to inform parents about their risk for having a second child with autism, according to Sebat. The genetics of autism may be different in families with several affected children, he says.
'The majority of genetic studies to date have focussed on the minority of families with multiple affected kids', Sebat told the Scientist magazine, adding 'the sporadic cases might be a rich source of genetic information'. The team now plans to screen at least another 2000 further families, using higher-resolution technology, to try and detect more genetic changes associated with autism.