[Analysis of B antigen weaken expression caused by nucleotide mutations in the promoter of ABO gene].

Objective: To investigate the molecular mechanism of B antigen weaken expression in 4 cases of ABO blood group samples.

Methods: ABO blood group phenotypes were detected by micro-column gel method and saline test tube method. Exon 1-7 and promoter region of the ABO gene were amplified by polymerase chain reaction (PCR) and PCR products were directly sequenced.

Results: Mixed agglutination occurs between RBC and B antibody in all the 4 samples. Three patients were identified as ABweak phenotype, and the mother of the patient ID 2 was identified as Bweak. Direct sequencing and pedigree analysis showed that there were -35 to -18 del GGCGGAAGGCGGAGGCCG mutation in the B allele of 3 samples and C>T mutation in -119 base site of one sample in promoter regions.

Conclusion: The promoter of ABO gene plays an important role in the normal expression of ABO blood group, and the mutation of the promoter can lead to the decreased expression of ABO blood group antigen. In this study, a new abnormal mutation (C>T of -119 base site) in the promoter was found, which should be concerned.