Identification of an ABO*A2-like allele based on a novel combination of three previously known ABO gene polymorphisms. Novel ABO*A2-like allele

Discrepant serological findings in ABO blood group typing often are the results of ABO gene variants, influencing the ABO transferase activity. In a sample with aberrant ABO phenotype, a novel ABO allele was identified. Material and methods ABO blood groups were determined with standard serologic and gel matrix techniques (Bio-Rad). The samples were genotyped using the ABO Type Variant molecular blood group diagnostic kit (BAGene Helthcare) which is based on sequence specific PCR. Haplotype specific sequence analyses of exons 2 to 7 including intermediate intronic regions were performed by allele-specific long-range PCR (KAPA longrange) and direct sequencing (AB 3500, Applied Biosystems). The regulatory regions of ABO (enhancer, promoter, Intron 1 +5.8kb GATA site ) were analyzed. Results Antigen typing indicated week blood group A (++). The serum contained reactive anti-B. Weak agglutination of anti-A1 (+/-) and a lack of anti-A2 isoagglutinin were found in reverse blood group typing. While genotyping remained inconclusive, allelspecific analysis revealed a novel ABO*A2-like allele based on the presence of c.467C>T (p.Pro156Leu), c.778G>A (p.Glu260Lys) and c.1061delC (p.Pro354Argfs*23). Additionally, the O1 allele was detected in trans. Analysis of the ABO regulatory regions did not reveal any deleterious variation. Conclusion Since the new allele is associated with the inactive O1 allele the week A phenotype is considered to be caused by the novel allele.