Genotyping the-521C/T functional polymorphism in the promoter region of dopamine D4 receptor (DRD4) gene

The -521C/Tsingle nucleotide polymorphism (SNP) in the promoter region of t he dopamine D4 receptor gene (DRD4) has recently been detected in oriental (Japanese) individuals and related to novelty seeking and schizophrenia. He re, we report the analysis of the -521C/T polymorphism in a Caucasian (Hung arian) population using two independent genotyping methods. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) procedur e utilized the Fspl restriction site around the -521 position. An additiona l, nonpolymorphic cleavage site was also included into the amplified region to serve as an internal standard for verifying the completion of the diges tion. As another independent method, a tetraprimer system for single-tube a llele-specific PCR (SAS-PCR) was developed to generate -521C and -521T spec ific PCR products with different fragment sizes. Consequently, genotyping w ith SAS-PCR is based on the gel-electrophoretic separation of the allele-sp ecific double-stranded DNA (dsDNA) fragments. 119 healthy Hungarian individ uals were genotyped for -521C/T polymorphism of the dopamine D4 promoter re gion, using both methods. Similar allele frequencies were found (-521C alle le: 0.43; -521T allele: 0.57) as reported earlier for the Japanese populati on.