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Gene changes may increase risk of Tourette syndrome

Tourette syndrome can last a lifetime, but most people experience their worst symptoms in their early teens.IPGGutenbergUKLtd/iStock/Thinkstock

Tourette syndrome is a neurological disorder that is usually diagnosed in childhood. It 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. Symptoms are usually worst during the early teen years, with improvements for most people in the late teens and early adulthood.

The risk factors that contribute to Tourette syndrome aren't well understood. A variety of genetic and environmental factors likely play a role in this complex disorder. Researchers are studying factors that occur before and after birth.

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 Drs. 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 NIH’s National Institute of Neurological Disorders and Stroke (NINDS) and National Institute of Mental Health (NIMH). Results were published on June 21, 2017, in Neuron.

The team compared more than 2,400 people with Tourette syndrome to more than 4,000 healthy controls. They focused 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 1 in 100 people with Tourette syndrome carried one of those variants.

NRXN1 and CNTN6 are important during brain development. These genes produce molecules that help brain cells form connections with one another. In addition, the two genes are turned on in areas that are part of a brain circuit that connect regions of the brain involved in processing emotions and movement. Studies suggest that errors in this brain circuit may play a role in Tourette syndrome.

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.

“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,” Scharf explains.

“Tourette syndrome has a very strong genetic component but identifying the causal genes has been challenging,” says Dr. Jill Morris, program director at NINDS. “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.”