A novel DI*A allele without the Band 3-Memphis mutation in Amazonian Indians.

Abstract

The blood-group antigens Dia and Dib are carried on erythrocyte band 3 and are defined by a single amino acid substitution at position 854 (Leu for Dia and Pro for Dib). The Band 3-Memphis variant has a point mutation (166A>G) in the SLC4A1 gene, which encodes the amino acid substitution Lys56Glu. Two types of Band 3-Memphis, variants I and II, are distinguished by their susceptibility to covalent labelling with 4,4'-diisothiocyanato-1,2-diphenylethane-2,2'-disulphonic acid (H2DIDS). Memphis II is more readily labelled than Memphis I or normal band 3. It is reported that Memphis II is associated with Dia. In a study designed to determine the frequency of the DI*A/DI*B and 166A>G polymorphisms in different populations in Brazil, we found a new DI*A allele. We studied DNA samples from 70 Amazonian Indians, 71 individuals of Japanese descent, 93 random Brazilian blood donors and 84 blacks with sickle cell disease. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analyses were performed on all samples, using MspI for DI*A/DI*B (exon 19) and MnlI for 166A>G (exon 4). Exon 4 and exon 19 from four outliers were sequenced. Among Amazonian Indians, DI*A and 166G mutations both had a high frequency (0.57 and 0.54, respectively). In individuals of Japanese descent, these alleles were moderately frequent (0.07 and 0.19, respectively). We identified a new allele with DI*A and 166A (56Lys) in four Amazonian Indians. Our results revealed that DI*A does not have a strict association with 166G. They also show the relevance of testing a cohort of different populations.