Identification of an AB phenotype caused by significant ABO gene deletion in a Chinese woman.

Background And Objectives: The AB is a rare phenotype in the ABO blood group system. Here, we first report a novel ABO mutation discovered in a Chinese woman with an AB. Third-generation sequencing was employed to investigate the molecular mechanisms underlying AB. By correctly identifying the phenotype, it was useful for increasing the safety of blood transfusion.

Materials And Methods: ABO blood group was identified by the standard ABO serological test and polymerase chain reaction with sequence-specific primers (PCR-SSP). To analyse the ABO gene sequence, single-molecule real-time (SMRT) sequencing was performed to obtain full-length sequencing of the ABO gene.

Results: The Chinese individual was serologically identified as AB subtype, and SMRT sequencing analysis revealed that there were large fragment deletion mutations in the promoter (c.1-1326_1-1321del, c.1-1010_1-975del, c.1-952_1-1del) and Exon 1 region (c.1_28del).

Conclusion: We report for the first time that large fragment deletions represent a novel molecular basis for the AB. These deletions may potentially influence the expression of the A antigen.