GENETIC POLYMORPHISMS OF MICA GENE IN JAPANESE POPULATION
M Otal) Y Katsuyama2), H Ando3), S Saito1), H Inoko 4), Dept. of Legal Med.1) and Dept. of Pharmacy2), Shinshu Univ. School of Med., Nagano , Japanese Red Cross, Kanagawa Shonan Blood Center3), Dept. of Genetic Information, Division of Molecular Life Science4), Tokai Univ. School of Med., Kanagawa.
We examined genetic polymorphisms of the MICA gene in a Japanese population using the sequencing based typing (SBT) method. For detection of genetic polymorphism in the exon 2 to 4 domains of MICA, a 2.2 kb segment including exons 2, 3 and 4 of the MICA gene was amplified by a pair of generic primers followed by cycle sequencing using exon-specific nested primers. In total, eight alleles were observed in a Japanese population and the most frequent allele was MICA008 with the gene frequency of 30.8%. MICA009 was the second most frequent (16.5%), whereas the rarest one was MICA007 (1.2%). MICA alleles displayed strong linkage equilibria with HLA-B antigens (i.e., MICA008 with B7, B48, B60 and B61; MICA009 with B51 and B52; MICA002 with B35, B39, B58 and B67; MICA004 with B44, MICA007 with B13 and B27; MICA010 with B46, B62 and B48, MICA012 with B54, B55, B56 and B59; MICA019 and B70, B71 and B62). Recently, the B48 haplotype has been reported to lack the entire MICA gene by a large-scale deletion in a Japanese population. Among eight serologically B48 homozygous individuals four were found to represent this MICA null allele as assessed by no PCR amplification using MICA-specific primers, whereas the remaining four possessed the intact MICA gene with MICA008 or MICA010.