[Identification of a novel T421C mutation of α-1,3-N-acetylgalactosaminyltransferase allele responsible for an A variant].

OBJECTIVE

To investigate the molecular basis of an individual featuring weak A phenotype of ABO blood group system.

METHODS

Serologic investigations, serum transferases activity assay and absorption-elution test were carried out to identify the ABO blood group. The 7 exons and flanking introns of ABO glycosyltransferase gene were amplified with polymerase chain reaction (PCR). The products were sequenced bidirectinally following enzyme digestion. Haplotypes of exons 6 and 7 of the ABO gene were analyzed.

RESULTS

A weak A antigen was identified on red blood cells of the proband. Eight heterozygous sites in exons 6 and 7 (261delG 297A/G, 421C/T, 467C/T, 646T/A, 681G/A, 771C/T, 829G/A) of the ABO gene were identified. Based on haplotype analysis, one allele was determined as O02, while a novel mutation 421T>C was identified in another allele, which resulted in the amino acid change Ser141Pro of the A glycosyltransferase.

CONCLUSION

Above results suggested that amino acid substitutions resulted from a novel mutation 421T>C of the ABO gene may decrease the enzymatic activity and result in the weak A phenotype.