Objective: The authors' goal was to establish if a mutation in D1 dopamine receptor locus (DRD1), or one genetically close to it, could cause Gilles de la Tourette's syndrome.
Method: DRD1 and linked markers (D5S36, D5S61, and D5S62) were studied in a large Mennonite Tourette's syndrome kindred. Only individuals with the full Tourette's syndrome were considered to be affected in one series of analyses; in another series the diagnostic spectrum was broadened to include chronic multiple tics. Liability classes were defined to take into account age at onset and sex differences; dominant inheritance was assumed. The authors' version of the LINKMAP program of the LINKAGE package modified to run under distributed parallel processing (Linda LINKMAP) was used for the multipoint linkage analysis.
Results: Complete (theta = 0.0) linkage of Tourette's syndrome with DRD1 was ruled out (lod score of -10.1) when the disease was defined narrowly. The area of exclusion of linkage (lod score between -2 and -10.5) extended from map position -0.10 to map position 0.50. The authors conducted an additional (centromeric) multipoint analysis with D5S36 as well as glucocorticoid receptor (GRL) and D5S22, resulting in an overlapping area of exclusion to map position -0.30 when the disease was defined narrowly.
Conclusions: This result provides strong evidence against linkage of the DRD1 D1 dopamine receptor locus with Tourette's syndrome. This exclusion extends the authors' earlier work with the dopamine system in Tourette's syndrome to exclude the two best characterized dopamine receptors from linkage with Tourette's syndrome.