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 novel DI variant 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. DI01/DI02 genotyping 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 reported DI02(2534T), DI02(2358_2359insCAC), and DI02(2572T) alleles) or wild-type DI02 constructs 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 mutant DI*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 novel DI02(2558T) allele and three previously described DI mutations can affect the expression of Band 3 protein and/or DI2 antigen and/or interfere with DI01/DI*02 genotyping result.