A THR(552)-]ILE SUBSTITUTION IN ERYTHROID BAND-3 GIVES RISE TO THE WARRIOR BLOOD-GROUP ANTIGEN

BACKGROUND: Recent family studies established that the low-incidence r ed cell antigen WARR is not part of the MNS, Lutheran, Lewis, Duffy, K idd, Xg, Chido/Rodgers, Kx, or Gerbich blood group systems. Continued serologic and genetic studies of WARR suggest that it is carried on er ythroid 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 c onformational polymorphism (SSCP) in DNA from WARR-positive and WARR-n egative individuals. RESULTS: An SSCP was detected in exon 14. Subsequ ent 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 fam ily members. To study the possible effect of the Thr(552)-->Ile substi tution on the expression and function of band 3, polymerase chain reac tion-amplified reverse-transcribed reticulocyte mRNA was digested with Bbs I. Both alleles of band 3 mRNA were detected in similar quantitie s, which suggests that the substitution underlying WARR did not interf ere with mRNA stability. Comparison of sodium dodecyl sulfate-polyacry lamide gel electrophoretic mobility and size patterns revealed no diff erence between proteins isolated from WARR-positive and WARR-negative red cells. Further, the presence of WARR did not alter the di-isothioc yano-dihydrostilbene disulfonate (DIDS)-inhibitable influx of radiolab eled sulfate. CONCLUSION: Although it appears inconsequential to the f unction of band 3, the red cell polymorphism known as WARR is controll ed by AE1. WARR should be therefore included in the Diego blood group system.