Amino acid substitutions in human erythroid protein band 3 account for the low‐incidence antigens NFLD and BOW

Abstract

BACKGROUND: The low‐incidence red cell antigens NFLD (700.37) and BOW (700.46) were first described in 1984 and 1988, respectively. Recent investigations showed that antigens of the Diego blood group system (including a number of low‐incidence antigens) are coded by SLC4A1 (solute carrier family 4, anion exchanger member 1 gene). Among these newly characterized Diego system antigens is Wu (designated DI9). Because a serologic relationship among Wu, NFLD, and BOW has been established, a series of genetic and molecular investigations of SLC4A1 in relation to NFLD and BOW were undertaken. STUDY DESIGN AND METHODS: By the use of exon‐specific primers, single‐strand conformational polymorphism (SSCP) analysis of SLC4A1 was performed on DNA isolated from an NFLD+ person from Japan, from the members of a Canadian kindred segregating for NFLD, and from two unrelated BOW+ persons. Exons displaying SSCPs were subjected to genetic linkage analysis (for NFLD only) and DNA sequencing. RESULTS: SSCPs in DNA amplified from exons 12 and 14 of SLC4A1 were observed for all NFLD+ subjects. Linkage between each of these polymorphisms and NFLD was established with peak lods = 4.82 at θ = 0.00 for combined paternal and maternal meiosis. DNA sequencing of exons 12 and 14 of SLC4A1 from NFLD+ persons identified A→T and C→G mutations that underlie Glu429Asp and Pro561Ala substitutions in human erythroid band 3 protein (band 3). DNA from the two unrelated BOW+ persons only exhibited an SSCP in exon 14 of SLC4A1 . Subsequent DNA sequencing revealed a C→T mutation that accounts for a Pro561Ser substitution in band 3. CONCLUSION: SLC4A1 codes for the low‐incidence red cell antigens NFLD and BOW. In light of these findings, both antigens have been assigned to the Diego blood group system.