Detection and analysis of the human D4 dopamine receptor gene (DRD4) sequence variant in the Japanese and Mongolian...

A PCR-based Sma I restriction fragment length polymorphism (RFLP) in the human D4 dopamine receptor (DRD4) gene was investigated in 200 subjects each of Japanese and Mongolian populations. When compared to allele frequencies for Caucasians previously reported by Petronis et al., Japanese and Mongolian populations showed a decreased frequency of the allele which could not be digested with Sma I. The difference in allele distributions between these two ethnically defined populations (Japanese and Mongolians, and Caucasians) was statistically significant (p<0.05). This RFLP was suggested to be a racial difference between Asian and European populations. However, since the frequency of the non-digested allele was extremely low (1%) in the Asian populations, we cannot exclude the possibility that this allele represents a mutation. Sma I PCR-RFLP typing would not only be one of genetic markers, but might also be a specific marker for searching some neuropsychiatric abnormalities.