Genetics of Tourette syndrome and tic disorders.

Tourette syndrome (TS) is a childhood-onset neurodevelopmental disorder characterized by multiple motor tics and at least one vocal tic lasting for more than a year. It is a complex, polygenic, and multifactorial disorder. In this chapter, we briefly discuss the early genetic studies on TS, and then provide a detailed overview of current efforts to uncover common and rare variants contributing to TS susceptibility. We also summarize pathway analyses which combine information from multiple loci to identify converging cellular processes and pathways associated with TS pathogenesis. Since TS is highly comorbid with other psychiatric disorders, we highlight the cross-disorder studies exploring the shared genetic basis of TS and these disorders, as well as the phenome-wide association study which revealed associations of multiple phenotypes with TS genetic risk. We provide an overview of the efforts to investigate the contribution of environmental factors and gene-environment interactions on TS development. Finally, we discuss some future directions that we believe the genetic research on TS will follow.