POINT MUTATION IN THE BAND-4.2 GENE ASSOCIATED WITH AUTOSOMAL RECESSIVELY INHERITED ERYTHROCYTE BAND-4.2 DEFICIENCY

A patient who represented acute hemolytic crisis was studied. Analysis of the erythrocyte membrane proteins by SDS-PAGE revealed a deficienc y of band 4.2. In the family, the sister of the patient who had been c hemically normal was also shown to be deficient in band 4.2. Binding s tudies showed that the propositus' membranes were able to bind normal band 4.2 protein as much as control. It was suggested that the binding sites for the protein were prepared on the membrane. We analyzed the band 4.2 cDNA of the propositus and detected a mutation that changes a codon for alanine to one for threonine at residue 142. Band 4.2 exon III of genomic DNA which included the mutation site was amplified and sequenced directly in the family members, and it was revealed that onl y the homozygotes of the mutation allele manifested band 4.2 deficienc y and the parents, who were heterozygotes, showed normal amounts of ba nd 4.2. Recently, the same mutation was reported as Protein 4.2NIPPON in another 4 cases (Bouhassira et al. Blood 1992: 79: 1846-1854). This study supports the hypothesis that this mutation is the pathogenetic cause of band 4.2 deficiency and not a polymorphism.