Identification of a novel A2 allele derived from the A transferase gene through a nucleotide substitution G539C.

Background and Objectives: The A2 is a very rare phenotype in the ABO blood group system in the Oriental population. It corresponds to a special ABO allele encoding a glycosyltransferase that is capable of synthesizing A2 antigens, which is weaker than the typical A antigen. In this study, we report a novel A2 allele in two unrelated Taiwanese individuals.
Materials and Methods: Two individuals were identified as the A2 phenotype based on the standard ABO serological test. For analysing the A2 allele, both direct sequencing and gene cloning of the ABO gene were performed.
Results: The ABO gene of the two A2 individuals was composed of O1 and A2 alleles, and the novel A2 allele has a 539G > C that results in the amino acid change Arg180Pro. The mutation was not detected in the general group A population.
Conclusion: We report for the first time that a 539G > C mutation represents a new molecular basis for the A2 blood type. The amino acid substitution from arginine to proline may have effect on the expression of A antigen.