Update on the genetics of Tourette syndrome

There has been significant progress in the understanding of the genetics of TS since the last international symposium. At the present time, we stand at the threshold of identifying the regions harboring the genes important in the manifestation of this syndrome. The localization and characterization of genes important for the expression of the TS phenotype will be a major advance in our understanding of the pathogenesis of this disorder and will also provide a model for the study of other developmental disorders. Unquestionably, the replication of these initial linkage findings and the localization and characterization of genes responsible for the expression of TS and related disorders will be a major step forward in our understanding of the genetic/biologic risk factors important for the expression of these disorders. Furthermore, once genes conferring susceptibility to TS and associated behaviors have been characterized, further work will allow the identification of additional nongenetic factors that are important for the manifestation or the amelioration of the symptoms of the disorders (84). As discussed by Kidd (85) and Pauls (84), the identification of a linked marker will permit the design of much more incisive studies to illuminate the physiological/biochemical etiology of TS by examination of the gene product and its impact on the development of the disorders. On the other hand, by controlling for genetic factors, through the genetic case-control research paradigm (85), it will be possible to document more carefully the environmental/nongenetic factors important for the expression of TS and other disorders.