Objective: To explore the correlations of dopamine transporter gene (DAT) and dopamine D(2) receptor gene (DRD2) to stuttering.
Methods: To examine the correlations of the 5 single nucleotide polymorphisms (SNPs) in dopaminergic gene (C252T, C1804T, and C1820T in DAT gene, and T1054C and C1072T in DRD(2) gene) to stuttering in Han Chinese individuals, a case-control study involving 112 patients with stuttering and 112 gender-matched controls was carried out. Genotyping was performed by a combined approach using polymerase chain reaction (PCR) and pyrosequencing.
Results: C1804T showed no polymorphism in either the patients or the control subjects and was therefore excluded from the following analysis. The C allele frequency at C1072T site was significantly higher, but T allele frequency significantly lower in the stuttering group than in the control group. The patients had significantly higher CC and lower CT genotype frequencies than the control group. There were no significant differences in the allelic frequencies of C252T, C1820T and T1054C between the patients and the controls, suggesting a Hardy-Weinberg equilibrium at these 3 loci.
Conclusion: The presence of the C allele at C1072T in DRD(2) gene is associated with increased susceptibility to stuttering in Han Chinese, whereas the T allele provides protection against the onset of stuttering.