Identification of a novel DI*02(2558T) allele associated with weakened expression of DI2 antigen.

Background The distribution of DI1/DI2 antigens of the Diego blood group system is polymorphic in Mongoloid populations and the corresponding alloantibodies are clinically significant. Here a novelDIvariant was found by donor screening, and the effect of the novel and previously reported mutations on expression of DI1/DI2 antigens and Band 3 protein was explored. Study Design and Methods DNA samples of 1150 Chinese donors were collected.DI*01/DI*02genotyping was determined by Sanger sequencing. For the carrier of novel allele, the expression of Band 3 and DI1/DI2 antigens on red blood cells (RBCs) was detected by Western blot and flow cytometry, respectively. in vitro expression studies were conducted by transfecting the mutant (including the novel and three reportedDI*02(2534T),DI*02(2358_2359insCAC),andDI*02(2572T)alleles) or wild-typeDI*02constructs into HEK 293T cells, the expression of Band 3 and DI1/DI2 antigens was analyzed. Results A novel heterozygous mutation (c.2558C>T, p.Thr853Met), which is located near the DI1/DI2 polymorphism site (c.2561T>C), was identified in a donor with DI:-1,2 phenotype. Reduced expression of DI2 antigen was observed on the RBCs, while weakened expression of Band 3 and absence of DI2 antigen were detected in cells transfected with the mutantDI*02(2558T)construct. In addition, absent or decreased expression of Band 3 and DI2 antigen was also detected in cells transfected with three reported mutant constructs. Conclusion The novelDI*02(2558T)allele and three previously describedDImutations can affect the expression of Band 3 protein and/or DI2 antigen and/or interfere withDI*01/DI*02genotyping result.