ABSTRACT
【Objective】 To identify two ABO discrepancy samples and explore the molecular mechanism. 【Methods】 The serological phenotype of the proband was determined with standard serological methods. ABO genotype was determined by polymerase chain reaction-sequence specific primer (PCR-SSP). Exon 6 and 7 of the ABO gene were amplified with PCR and sequence-based typing (SBT). The amplicon of exon 6 and 7 was also cloned and sequenced. Pymol software was used to simulate the 3D structural model and predict the effect of GTB protein mutation on the structure. The sample were collected from proband’s father and analyzed. 【Results】 The proband’s erythrocytes were detected with B antigens, along with the presence of anti-B in serum. The genotype O1/B of the proband was identified by PCR-SSP. Direct sequencing of the proband revealed 261delG/G, 297A/G in exon 6 and 526C/G, 646A/T, 657C/T, 681A/G, 703A/G, 771C/T, 796A/C, 803C/G, 829A/G, 905A/G, 930A/G, 1096A/G heterozygote in exon 7, which was assigned as Bx02/O02 genotype. Clone sequencing showed that a 905 A>G mutation in the ABO*B.01 allele. The 3D structure simulation suggested that Asp302Gly may cause the change of GTB enzyme activity or function. 【Conclusion】 Two cases of Bx02 allele were identified. Combined detection of serological and genotyping methods is important for identification of ABO blood group.