[Genetic analysis of weakened expression of ABO blood group antigen in 20 cases].

Objective: To explore the molecular mechanism for weakened expression of ABO blood group antigens in 20 cases.

Methods: Blood samples were collected from 20 cases with weakened expression of ABO blood group antigens, including 12 children undergoing elective surgery and 8 of their parents or grandparents. Serological identification of the ABO blood group was performed using microcolumn agglutination method and saline test tube method. The PCR products of exons 1-7 and their upstream promoter region of the gene were directly sequenced for genotyping.

Results: In 11 of the cases, the genotype could be determined by pedigree analysis (including 1 case of /, 1 case of / , 1 case of , 2 cases of B, 2 cases of , and 4 cases of ). Pedigree analysis revealed deletion mutation at -35_-18 nt in the ABO promoter region in 3 cases, indicating that the mutation occurred in the B allele; a C > T mutation occurred at -119 nt in the ABO promoter region in 1 case; a C deletion at 1054 nt in exon 7 was identified in 1 case; no mutation was found in exons 1-7 and their regulatory region of gene in 4 cases.

Conclusion: The C > T mutation at-119 nt in the promoter region and the deletion mutation at 1054 nt in exon 7 of gene are probably new mutations leading to abnormal expression of ABO blood group antigens. Some ABO subtypes may be associated with abnormal introns or mRNA synthesis.