Gene sheds light on Tourette's syndrome

US scientists have identified gene mutations linked to Tourette's syndrome, a disorder characterised by involuntary tics and outbursts. The team, based at Yale University in Connecticut, found that some people with the condition have a mutated version of a gene called SLITRK1. The discovery should pave the way for a deeper understanding of the disorder, say the researchers, who published their findings in the journal Science.    

Tourette's syndrome can vary in severity, but affected people are usually prone to repetitive, sudden movements and verbal outbursts. The condition is known to run in families, suggesting that genetic factors are involved. In the latest study, the scientists looked at DNA from an affected boy who had an unusual chromosome 13 - one of the bundles of genetic material that makes up the human genome. The chromosome contained an 'inversion', a section of DNA that had flipped and reinserted itself the opposite way around.

The scientists discovered that the SLITRK1 gene, which makes a protein involved in brain development, was located close to the breakpoint of this inversion. They then looked at the gene in 174 people with Tourette's syndrome, and found that one had a mutation in the SLITRK1 gene. The mutation was not present in 3,600 samples from unaffected people. The researchers then grew mouse nerve cells with the mutated SLITRK1 gene in the laboratory, and found that they didn't grow properly - the dendrites, which make connections with other nerve cells, weren't as long as those from normal cells.

The team identified two other unrelated Tourette's individuals who had mutations that affected the SLITRK1 gene. The team now hope to create a 'knockout' mouse that is missing the gene, to further investigate its role in development. 'The more we know about what's occurring at the molecular and cellular level, the better chance we have for improving diagnosis and developing new treatments', said team leader Matthew State. However, he stresses that there are likely to be 'multiple genes, interacting, and probably different sets of genes in different people that contribute to Tourette's'.