June 26, 2017Neurology
NRXN1 and CNTN6 are important during brain development and 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 the cortico-striatal-thalamo-cortical circuit, a loop of brain cells connecting the cortex to specific regions involved in processing emotions and movement. While copy number variants in NRXN1 have been implicated in other neurological disorders including epilepsy and autism, this is the first time that scientists have linked copy number variants in CNTN6 to a specific disease, Tourette syndrome.
According to an article published online in Neuron(21 June 2017), structural changes have been identified in two genes that increase the risk of developing Tourette syndrome, a neurological disorder characterized by involuntary motor and vocal tics. Although involuntary tics are very common in children, they persist and worsen over time in people with Tourette syndrome. Tics associated with Tourette syndrome appear in children, peak during the early teenage years and often disappear in adulthood. Many people with Tourette syndrome experience other brain disorders including attention deficit disorder and obsessive-compulsive disorder.
For the study, genetic analyses were conducted on 2,434 individuals with Tourette syndrome and compared them to 4,093 controls, focusing on copy number variants, changes in the genetic code resulting in deletions or duplications in sections of genes. The results determined that deletions in the NRXN1 gene or duplications in the CNTN6 gene were each associated with an increased risk of Tourette syndrome. In the study, approximately 1 in 100 people with Tourette syndrome carried one of those genetic variants.
The authors are planning to take a closer look at the mutations using animal and cellular models, and more research is needed to learn about ways in which the genes contribute to development of Tourette syndrome and whether they may be potential therapeutic targets.