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Gene link to intellectual disability

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Researchers have pinpointed a gene that may cause a commonly inherited intellectual disability if affected by a genetic mutation.

University of Adelaide researchers examined the Aristales related homeobox (ARX) mutation in more than 100 families, and found that some of the mutations led to a significant reduction in ARX proteins in the brain.

Almost three per cent of Australians are affected by some kind of intellectual disability, costing the economy more than $14 billion each year. ARX is one of the top four types of intellectual disability linked to the X-chromosome in males.

Researchers found considerable variation in the disability across the families examined, with symptoms always including intellectual disability, as well as a range of movement disorders of the hand and, in some cases, severe seizures.

After testing six genes that the ARX protein interacts with, the researchers found one – a gene likely to be important to early brain development – that was adversely affected by a reduction in the number of ARX proteins.

Lead author Associate Professor Shoubridge from the University of Adelaide said the gene plays an important role in setting up architecture and networks in the brain, which can be disrupted by mutation of the ARX gene.

“The discovery of this genetic link is an important step forwards, but there is still much work to be done,” Associate Professor Shoubridge said. “We’re now looking further at the mechanism of the reduction in ARX protein, and what that means for the brain at a functional level.

“The personal cost to families is enormous, especially in the most severe cases. Being able to unravel why and how these disabilities occur is very important to us, and to the many people whose lives are affected by these conditions.”

The research was published in the Human Molecular Genetics journal.

Kirsty Waterford

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