A Thr552 -->Ile substitution in erythroid band 3 gives rise to the Warrior blood group antigen

Abstract

Background: Recent family studies established that the low-incidence red cell antigen WARR is not part of the MNS, Lutheran, Lewis, Duffy, Kidd, Xg, Chido/ Rodgers, Kx, or Gerbich blood group systems. Continued serologic and genetic studies of WARR suggest that it is carried on erythroid band 3.

Study design and methods: To test the hypothesis that expression of WARR is controlled by the anion exchanger 1 gene (AE1), AE1 intronic primers that flank the exons encoding the membrane domain of band 3 were prepared. Polymerase chain reaction-amplified products corresponding to exons 11-20 of AE1 were analyzed for single-strand conformational polymorphism (SSCP) in DNA from WARR-positive and WARR-negative individuals.

Results: An SSCP was detected in exon 14. Subsequent sequencing revealed a C-->T mutation in codon 552 that leads to a Thr-->Ile substitution. Because the C-->T mutation eliminates a Bbs I restriction site, it was possible to confirm the phenotypes of all family members. To study the possible effect of the Thr552-->Ile substitution on the expression and function of band 3, polymerase chain reaction-amplified reverse-transcribed reticulocyte mRNA was digested with Bbs I. Both alleles of band 3 mRNA were detected in similar quantities, which suggests that the substitution underlying WARR did not interfere with mRNA stability. Comparison of sodium dodecyl sulfate-polyacrylamide gel electrophoretic mobility and size patterns revealed no difference between proteins isolated from WARR-positive and WARR-negative red cells. Further, the presence of WARR did not alter the di-isothiocyano-dihydrostilbene disulfonate (DIDS)-inhibitable influx of radiolabeled sulfate.

Conclusion: Although it appears inconsequential to the function of band 3, the red cell polymorphism known as WARR is controlled by AE1. WARR should be therefore included in the Diego blood group system.