A novel ABO allele with a 21-bp duplication identified in two unrelated European individuals with weak A expression

Marianne A. Jakobsen*, Annika K. Hult, Åsa Hellberg, Sofia Lejon Crottet, Ulrik Sprogøe, Martin L. Olsson

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Objectives: To carry out genetic and serological analyses of a Swiss blood donor and a Danish patient carrying an aberrant ABO phenotype with weak A expression. Background: ABO is the most clinically important blood group system but also one of the most complex. The system antigens are determined by carbohydrate structures generated by A and B glycosyltransferases encoded by the ABO gene. Genetic variants of ABO may encode a glycosyltransferase with reduced activity, leading to weak expression of A antigen. Methods: Samples from two individuals were examined using genetic testing and extended immunohaematological evaluation, including standard serological methods, flow cytometry and analysis of plasma glycosyltransferase activity. Results: Both individuals were serologically determined to be AweakB. Genetic testing revealed that both were heterozygous for a novel ABO*A1.01-like allele with an in-frame duplication of 21 nucleotides in exon 7 (c.543_563dup), leading to the insertion of seven amino acids (QDVSMRR). Flow cytometric testing of native red blood cells (RBCs) showed very weak A antigen expression. This was in accordance with the enzyme activity test. Conclusion: In summary, we describe a novel A allele with a duplication of 21 nucleotides in exon 7 that significantly decreases the enzyme activity and leads to very weak expression of A antigen. (200 words).

Original languageEnglish
JournalTransfusion Medicine
Volume30
Issue number6
Pages (from-to)508-512
ISSN0958-7578
DOIs
Publication statusPublished - Dec 2020

Keywords

  • ABO
  • blood group variant
  • weak A allele

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