Sequence variants in the proximal promoter and +5.8‐kb site of ABO in Koreans with weak B phenotypes

BACKGROUND AND OBJECTIVES: Several studies on Chinese and Japanese populations have revealed that a substantial proportion of weak B subgroups are caused by variants in the major regulatory regions of ABO, the proximal promoter, CCAAT-binding factor/NF-Y binding site and +5. 8-kb site. We performed molecular analyses of these regions in Koreans with weak B phenotypes. MATERIALS AND METHODS: ) harbouring no subgroup-causing variants in ABO exons 6 and 7. These samples were subjected to sequencing analysis of exons 1-5 and the major regulatory regions of ABO. RESULTS: Of the 16 samples, 14 were found to carry a sequence variant either in the proximal promoter (g. 4991₅008del n = 3) or the +5. 8-kb site (g. 10893G>A n = 4 and g. 10925C>T n = 7). The remaining two samples were found to contain no subgroup-causing variants. CONCLUSION: Our study demonstrates that sequence variants in the proximal promoter and +5. 8-kb site account for a substantial proportion of weak B subgroups in Koreans, suggesting that molecular analysis of these regions is essential for the accurate determination of ABO genotypes in Koreans with weak B phenotypes.