[Molecular analysis of a B(A)04 phenotype individual and his family members]

To investigate the serological and genetic characteristics of an individual with B(A) phenotype of the ABO subtype and his family members.

Serological assaying was carried out to characterize the erythrocyte phenotype of the discrepant samples. Exons 6 and 7 of the ABO gene were amplified with PCR and subjected to direct sequencing. Exon 7 of the ABO gene was also subjected to single strand sequencing.

The serological results of two samples from the family were prelimilarily typed as AwB and genotyped as B(A)04/O1 by sequence-specific primer PCR (PCR-SSP). Direct and single strand sequencing confirmed that the three samples all carried a B(A)04 allele and had a nt640A>G mutation in exon 7 of the ABO gene.

The nt640A>G mutation of the B allele has resulted in an amino acid substitution (Met214Val), which probably underlies the B(A)04 subtype. Blood samples with serological typing difficulty may be resolved by pedigree analysis using molecular methods such as PCR-SSP and DNA sequencing.