Typing of the nt343C>T (R95X) allele of the C9 gene by PCR-SSP and the allele frequency of R95X in five ethnic populations.

One of the alleles which leads to ninth component of complement deficiency (C9D) is R95X (nt343C>T), which is present in most cases of C9D in Japan. In this study, we carried out nt343C>T typing by the method of polymerase chain reaction with sequence-specific primers (PCR-SSP), and showed the frequency of the R95X allele in German, Italian, Thai, Korean and Chinese populations. We did not find the R95X allele in the German or Italian populations. The allele frequency of R95X in the three Asian populations is as follows: Thais 0.019, Koreans 0.008, and Chinese 0.002. As the allele frequency in the Japanese population is 0.036, the results provide supporting evidence that the R95X is an allele characteristic of Japanese.