Analysis of serum amyloid A1 exon 4 polymorphism in Japanese population

Nucleotide variation in the triplet codon coding for amino acid position 72 of human serum amyloid A1 (SAA1), which was suggested by amino acid sequence analysis, was analyzed here in order to identify the genomic sequences coding SAA1.2 and to characterize further the SAA1 allele frequency in a Japanese population. The SAA1 exon 4 was amplified by PCR and treated with Nco I. Sequencing of PCR products from genomic DNA of individuals who were heterozygous for the Nco I site revealed GGT(Gly) and GAT (Asp) at the position 72. The allele having (72)Asp showed the exon 3 polymorphism coding (52)Ala and (57)Val. This allele should thus be identified as SAA 1.2. Alleles with (72)Gly were either (52)Val and (57)Ala(SAA1.1) or (52)Ala and (57)Ala (SAA1.3) or (52)Ala and (57)Val (SAA1.5). The frequency of SAA1 alleles in the 321 Japanese subjects was 0.310, 0.012, 0.347 and 0.330 for each SAA allele of 1.1, 1.2, 1.3 and 1.5, respectively. The presence of the SAA.4 allele was not evaluated.