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Researchers have identified changes in two genes that may increase the risk of developing Tourette syndrome.

Tourette syndrome is a neurological disorder that is usually diagnosed in childhood and causes repetitive, involuntary movements or noises called tics. Many with Tourette syndrome experience other problems including inattention, hyperactivity, and impulsivity, as well as obsessive-compulsive symptoms such as intrusive thoughts and worries.

To investigate potential underlying causes, an international collaboration carried out a genetic analysis of people with Tourette syndrome.

The research team was co-led by Doctors Jeremiah Scharf at Massachusetts General Hospital, Giovanni Coppola at the University of California, Los Angeles, Carol Mathews at the University of Florida and Peristera Paschou at Purdue University.

The study was funded in part by the National Institutes of Health (NIH) National Institute of Neurological Disorders and Stroke (NINDS) and National Institute of Mental Health (NIMH).

The team compared more than 2,400 people with Tourette syndrome to more than 4,000 healthy people, focusing on changes in the genetic code resulting in deletions or duplications in sections of genes.

Deletions in the NRXN1 gene or duplications in the CNTN6 gene were each associated with an increased risk of Tourette syndrome. In the study, about one in 100 people with Tourette syndrome carried one of those variants.

The researchers say that more research is needed to learn how NRXN1 and CNTN6 might affect the development of Tourette syndrome and whether they may be potential treatment targets.

Dr Scharf said: ““Our study is the tip of the iceberg in understanding the complex biological mechanisms underlying this disorder. With recent advancements in genetic research, we are at the cusp of identifying many genes involved in Tourette syndrome.

Dr Jill Morris, programme director at NINDS, said: “As we find genes involved in Tourette syndrome and understand more about its biology, we move closer to our ultimate goal of developing treatments to help children affected by the disease.

“Tourette syndrome has a very strong genetic component but identifying the causal genes has been challenging,”

In a separate NIH-backed study, researchers have found that immune cells recognize and react to alpha-synuclein, the protein that builds up in the brains of people with Parkinson’s disease.

A team led by Doctors David Sulzer of the Columbia University Medical Center and Alessandro Sette of the La Jolla Institute for Allergy and Immunology carried out a study comparing T cell responses to alpha-synuclein in people with Parkinson’s disease and healthy volunteers.

The study was supported in part by NIH’s National Institute of Neurological Disorders and Stroke and scientists collected blood samples from 67 people with Parkinson’s disease and 36 healthy adults.

Samples taken from people with Parkinson’s disease were far more likely than samples taken from healthy adults to show strong immune responses to the alpha-synuclein fragments.

Doctor Sulzer said: “ The idea that a malfunctioning immune system contributes to Parkinson’s dates back almost 100 years but until now, no one has been able to connect the dots.”

Dr Sette said: “It remains to be seen whether the immune response to alpha-synuclein is an initial cause of Parkinson’s or if it contributes to neuronal death and worsening symptoms after the onset of the disease. This could, however, provide a much-needed diagnostic test for Parkinson’s disease and could help us to identify individuals at risk or in the early stages of the disease.”

The findings for both studies were reported in NIH News in Health