Molecular genetic analysis of the B_el phenotype

Background and Objectives: In addition to the common ABO phenotypes, numerous phenotypes with a weak expression of the A or B antigens on the red blood cells have been found. This study describes the molecular genetic analysis of the B_e phenotype in Taiwanese individuals. Materials and Methods: The exon 6-7 region of the ABO gene of an individual with the B _el phenotype was amplified by the polymerase chain reaction (PCR), cloned, and the sequences of the exons and their adjacent splice sites were analysed. A PCR-based restriction fragment length polymorphism (RFLP) analysis was designed to detect the 502C>T nucleotide change identified in the B ^el allele. Six unrelated individuals with the B_el phenotype were analysed, and samples from 40 randomly selected individuals with the common B phenotype were also assessed. Results: All six unrelated Taiwanese individuals with the B_el phenotype were shown to possess a B gene with the 502C>T mutation. The mutation was not detected in the general group B population. The 502C>T nueleotide change predicts an amino acid alteration of Arg168→Trp in the encoded B transferase. Conclusions: The results suggest a new molecular basis, a 502C>T missense mutation in the B allele, for the B_el phenotype and an association of the B ^el502C>T allele with the B_el phenotype in the Taiwanese population.