Functional analysis of four splice site variants, including a novel variant, on antigen expression and ABO subgroup formation

Splice site variants within the ABO gene have the potential to impair ABO glycosyltransferase biosynthesis, leading to decreased expression of A or B antigens on the surface of red blood cells. This study characterized how four intron 6 splice site variants—three in the A1 allele (c.374+4A>T, c.374+4A>G, c.374+5G>A) and one in the ABO*B.01 allele (c.374+2_374+3insT)—affect ABO pre-mRNA splicing. A combination of serological, molecular genetic, bioinformatic, and minigene assays established a genotype-splicing-phenotype association model.