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

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.

This study included 16 samples with weak B phenotypes (4 B₃ , 1 B_w , 5 A₁ B₃ and 6 A₁ B_w ) 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.

Of the 16 samples, 14 were found to carry a sequence variant either in the proximal promoter (g.4991_5008del [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.

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.