ABSTRACT
Objective To study the molecular mechanism of Bel subtype caused by mutation p.R168W of glycosyltransferase B.Methods Serological test,SSP-PCR and direct sequence the Exon6 and Exon 7 of the ABO gene.Construct a 3D molecular model and predict the structural impact of GTB protein mutations.Results A antigen or B antigen can't be detected on the surface of the propositus' RBC,and only anti-A antibodies were detected in her serum.But serological test indicated her daughter's blood type was a normal B type.SSP-PCR test indicated propositus' ABO gene type is O1 B.By gene sequencing the Exon 6 and Exon 7 of the ABO gene,a ABO Bel allel(c.502C＞T,p.R168W)was discoverd in both the propositus and her daughter.Through the propositus' daughter coexisted Bel gene with normal B gene,her blood type was a normal B type.Conclusions ABO gene c.502C＞T mutations cause Bel phenotypes in patients by reducing the stability of GTB.