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

Background and Objectives The A(2) 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 A(2) antigens, which is weaker than the typical A antigen. In this study, we report a novel A(2) allele in two unrelated Taiwanese individuals. Materials and Methods Two individuals were identified as the A(2) phenotype based on the standard ABO serological test. For analysing the A(2) allele, both direct sequencing and gene cloning of the ABO gene were performed. Results The ABO gene of the two A(2) individuals was composed of O-1 and A(2) alleles, and the novel A(2) 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 A(2) blood type. The amino acid substitution from arginine to proline may have effect on the expression of A antigen.