Association between the polymorphism in the promoter region of dopamine D4 receptor gene and chronic tic disorder

Abstract:

OBJECTIVE: To study a possible association between the three functional polymorphisms in the promoter region of dopamine D4 receptor (DRD4) gene and chronic tic disorder. METHODS: Genomic DNA was isolated from the venous blood leukocytes of 84 unrelated patients with chronic tic disorder (Study group) and 100 healthy unrelated individuals (Control group). Polymorphisms of DRD4, -1240L/S, -616C/G and -521C/T, were genotyped by the allele-specific primer (ASP) PCR. Genotype, allele and haplotype frequencies were analysed by SHEsis online. RESULTS: There were significant differences in both allele and genotype frequencies (χ~2 =8.419, P<0.01;χ~2=7.860, P<0.05 respectively) of DRD4-616C/G between the Study and the Control groups. Haplotypic frequencies of LCT (-1240L/S, -616C/G, -521C/T) in the Study group were noticeably higher than in the Control group (χ~2 =6.371, P<0.05). CONCLUSIONS: There is an association between the DRD4-616C/G polymorphism and chronic tic disorder. The individuals with haplotype LCT (-1240L/S, -616C/G, -521C/T) are susceptible to this disorder.