Polymorphisms at the ABO locus in subgroup a individuals

Background: The common ABO allele sequences are known, but little or no genetic information is available on the rare but important A subgroups. Study Design and Methods: Blood group ABO polymorphism was analyzed in genomic DNA from 45 rare subgroup A individuals by sequence-specific primer polymerase chain reaction and amplified fragment length polymorphism investigating exons VI and VII in the ABO genes, These methods are used to detect specific mutations only, and not all changes that might be present can be detected. ABO genotypes discriminating six alleles (A', A(2), B, O-1, O-1var, and O-2) were determined. Results: The C-->T substitution at nucleotide position 467 (C467T) is not restricted to A(2) and cis-AB individuals, but was found also in some A subgroups. Detection of the functionally more relevant C1060- single-point deletion in A(2) was accomplished by a novel sequence-specific primer polymerase chain reaction approach. A 100-percent correlation between the C467T and the C1060- mutations was found, Fifteen of 17 samples showing the T646A mutation (described earlier in one case of A(x)) showed a positive correlation with the C771T mutation in a frequently occurring O-1var allele. The two exceptions were defined serologically as A(x). Conclusion: Indications have been found of an evolutionary relationship between A(1) alleles and A(el) and A(3) subgroups as well as between A(2) alleles and A(end) and A(weak) subgroups. Genetic heterogeneity within the A(x) and A(int) subgroups was also seen.