AN A(EL) ALLELE-SPECIFIC NUCLEOTIDE INSERTION AT THE BLOOD-GROUP ABO LOCUS AND ITS DETECTION USING A SEQUENCE-SPECIFIC POLYMERASE CHAIN-REACTION

Genomic DNA from each of four A(el), individuals (genotypes AO(1), AO( 1var), AO(2)) and one A(cl)B individual was used as a template for amp lifying exons 6 and 7 of the ABO genes, which were subsequently sequen ced. In all the A(el) alleles a single nucleotide insertion, compared to the A consensus sequence, was observed that would alter the amino a cid sequence of the glycosyltransferase immediately after its postulat ed nucleotide sugar binding site and furthermore extend the translated protein by 37 amino acids (16 more than the A(2) enzyme). A sequence- specific primer PCR assay was developed to detect the nucleotide inser tion. It was possible to differentiate all 20 serologically defined A( cl)/A(cl)B individuals available from 145 blood donors with normal ABO phenotypes and genotypes and 26 individuals with various A subgroups other than A(1), A(2) and A(cl). This mutation explains the A(cl) phen otype and forms the basis of a method for detecting the A(el) allele. (C) 1995 Academic Press, Inc.