Exon and intron variants in the human tryptophan 2,3-dioxygenase gene: potential association with Tourette syndrome, substance abuse and other disorders.
There was no evidence to support the hypothesis that genetic variation in the serotonin 5-HT1A receptor and tryptophan oxygenase genes causes susceptibility to Tourette's syndrome and chronic multiple tics.
Many observations have led us to suggest that the genetic defect in TS may be a mutation of tryptophan oxygenase and that TS is inherited as a semidominant semirecessive trait, i.e., homozygosity for a common gene which shows some expression in the heterozygous state.
The low blood serotonin and tryptophan levels in TS are consistent with the wide range of behavioral disorders seen in TS and suggest tryptophan oxygenase as a possible candidate gene.