Analysis of human complement genes

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Single nucleotide polymorphisms (SNPs) in C6, C7 and C9 genes of the human complement system have been analyzed by PCR-based methods and PCR direct-sequencing in the present study. I. SNPs in the C6 gene are as follows, (i) Nt413A→C (aa98:Glu→Cys) in exon 3. Allotypes C6A and C6B/C6B2 are associated with nt413A and nt413C, respectively. (ii) Nt1674T→C (aa518:Cys→Cys) in exon 10. (iii) Nt2145T→A (aa675:Asp→Glu) in exon 13. Both T and A at nt2145 were found in the sample with allotype B (homozygote), suggesting the existence of two subtypes of C6B allotype. (iv) Nt[357+32]G→A in intron 2. The SNP of nt[357+32] was analyzed by PCR-RFLP with restriction enzyme HinfI. Allele frequencies in a Japanese population were *G=0.920 and *A=0.080. (v) Nt[503-78]G→A in intron 3. The analysis data of nt[357+32] and nt[503-78] showed the linkage (or association) between the two loci. II. SNPs in the C7 gene are as follows. (i) Nt1166G→C in exon 9. This SNP was analyzed by PCR-RFLP with restriction enzyme DdeI. The allele frequencies in Japanese were *G=*C=0.5. (ii) Nt382T→C (aa106:Cys→Arg) in exon 4. Nt382C is responsible for C7-5 allotype. The allele frequency of nt382C in Asian and European populations were; Koreans 0.023, Chinese 0.046, and Japanese 0,045. Nt382C was not found in Thai and Italian populations, (iii) Nt1OG→A in intron 13. This SNP was analyzed by PCR-RFLP with restriction enzyme Hin1I. The allele frequencies in Japanese were *G=0.822 and *A=0.178. III. Distribution of R95X (nt343C→T in exon 4 of C9 gene) allele in 4 Asian and 2 European populations was studied, and the results showed R95X was an Asian population-specific allele.