Background: The ABO blood type B 3 is the most common B subtype in the Chinese population with a frequency of 1/900. Although IVS3+5G > A (rs55852701) mutation of B gene has been shown to associate with the development of B 3 blood type, genetic and mechanistic evaluation for the unique mixed-field agglutination phenotype has not yet been completely addressed. Methodology/Principal Findings: In this study, we analyzed 16 cases of confirmed B 3 individuals and found that IVS3+5G > A attributes to all cases of B 3 . RT-PCR analyses revealed the presence of at least 7 types of aberrant B 3 splicing transcripts with most of the transcripts causing early termination and producing non-functional protein during translation. The splicing transcript without exon 3 that was predicted to generate functional B 3 glycosyltransferase lacking 19 amino acids at the N-terminal segment constituted only 0.9% of the splicing transcripts. Expression of the B 3 cDNA with exon 3 deletion in the K562 erythroleukemia cells revealed that the B 3 glycosyltransferase had only 40% of B 1 activity in converting H antigen to B antigen. Notably, the typical mixed-field agglutination of B 3 -RBCs can be mimicked by adding anti-B antibody to the K562-B 3 cells. Conclusions/Significance: This study thereby demonstrates that both aberrant splicing of B transcripts and the reduced B 3 glycosyltransferase activity contribute to weak B expression and the mixed-field agglutination of B 3 , adding to the complexity for the regulatory mechanisms of ABO gene expression. © 2012 Chen et al.
Chen, D. P., Tseng, C. P., Wang, W. T., & Sun, C. F. (2012). Genetic and mechanistic evaluation for the mixed-field agglutination in B3 blood type with IVS3+5g>A abo gene mutation. PLoS ONE, 7(5). https://doi.org/10.1371/journal.pone.0037272