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A Surprising Clue to Tourette Syndrome - ScienceNOW
http://news.sciencemag.org/sciencenow/2010/05/a-surprising-clue-to-tourette.html?rss=1

• Now researchers have found a mutated gene that appears to cause the disorder in one extremely unusual family with nine afflicted individuals.
• Although this mutation is not the cause of the vast majority of Tourette syndrome cases, it may push researchers to investigate a mechanism—and potential treatments—they otherwise would not have considered.
• Much recent attention has focused on a brain region called the basal ganglia that is involved in repetitive behaviors and on the neurotransmitter dopamine
• In 2005, a team led by child psychiatrist and geneticist Matthew State of Yale University School of Medicine, reported one of the first genetic clues to the disorder, a mutation in a gene called SLITRK1 that seems to be responsible for a rare handful of cases. But the function of SLITRK1 and its contribution to Tourette syndrome are still largely a mystery.
• Extensive genetic detective work led them to a mutation in a gene called HDC, which encodes L-histidine decarboxylase, an enzyme involved in the production of histamine, a signaling molecule with a wide variety of roles throughout the body.
• The mutated version of the HDC gene likely results in a truncated version of the enzyme, which would result in reduced histamine levels, State says.
• Histamine may be best known for its role in provoking sneezing and itchy eyes during allergy season, but it also functions as a neurotransmitter in the brain
• Moreover, he says, there's evidence that certain histamine receptors cluster in the basal ganglia and that histamine signaling can act as a brake on dopamine signaling.
• If histamine is actually an active player in Tourette's syndrome, it really would open up a whole new avenue of treatment"