A unique 502C>T mutation in exon 7 of ABO gene associated with the Bel phenotype in Taiwan.

Background: The ABO system includes many variant subgroups. Some of them are difficult to identify serologically, leading to mistyping of blood groups. For example, Bel is often typed as O blood group.

Study Design And Methods: DNA sequencing and a molecular approach were explored to accurately determine the genotypes of Bel subgroups. Seven Bel blood donors and 106 individuals with other blood groups were analyzed serologically and molecularly.

Results: The serologic results of these seven Bel blood donors showed that their RBCs do not react with anti-B or anti-A,B, and their B antigen was detected by adsorption and elution methods. Sequencing results for exons 6 and 7 of ABO genes showed a new Bel allele with a C>T substitution at nucleotide position 502 in exon 7 of the ABO gene in all seven cases but not in other blood groups. Consequently, an amplification-created restriction site protocol was designed to detect the 502C>T genotype in Bel subgroup cases.

Conclusion: A novel 502C>T mutation was found in the Bel subgroup in Taiwan and successfully developed a rapid and accurate molecular protocol to detect this mutation. To our knowledge, the new Bel allele that was found is unique in Taiwanese residents.