A novel ABO O allele caused by a large deletion covering two exons of the ABO gene identified in a Caucasian family showing discrepant ABO blood typing results

• Published in: Transfusion (Philadelphia, Pa.) Pa.), 2016-11, Vol.56 (11), p.2739-2743
• Main Authors: Matzhold, Eva M., Drexler, Camilla, Wagner, Thomas
• Format: Article
• Language: English
• Subjects: ABO Blood-Group System - genetics; Alleles; Antigens; Blood Grouping and Crossmatching - methods; Blood groups; European Continental Ancestry Group; Exons; Family; Female; Genes; Humans; Mutation; Phenotype; Sequence Deletion
• ISSN: 0041-1132; 1537-2995
• DOI: 10.1111/trf.13768

BACKGROUND The presence of ABO subgroup alleles and unusual O alleles often is associated with discrepant serologic findings in ABO blood group typing. In the ABO gene of a Caucasian female and her daughters who had aberrant ABO phenotypes, a novel ABO O allele characterized by a large deletion that included two exons was identified. METHODS ABO phenotypes were determined by standard agglutination tests and adsorption‐elution studies. Allele‐specific sequencing analyses of the ABO gene as well as messenger RNA transcripts were carried out. RESULTS All three samples showed the same discrepant ABO blood typing results lacking A and B antigens, indicating Blood Group O, whereas anti‐A1 and anti‐A2 isoagglutinins were not detectable in reverse typing. Analyses of the ABO gene revealed a novel allele characterized by a deletion of 2169 base pairs, including sequences of Intron 1, Exon 2, Intron 2, Exon 3, and Intron 3. Exon 1 was directly joined to Exon 4 in the ABO transcript. CONCLUSION Because the novel allele was associated with a well‐described O allele, the absence of A‐antigens in the inherited ABO subtype phenotype may be due to the identified mutation affecting the transmembrane‐spanning domain of the encoded protein and impairing the transferase activity.