MOLECULAR-BASIS OF SP ALPHA-1 65 HEREDITARY ELLIPTOCYTOSIS IN NORTH-AFRICA - INSERTION OF A TTG TRIPLET BETWEEN CODONS 147 AND 149 IN THE ALPHA-SPECTRIN GENE FROM 5 UNRELATED FAMILIES

  • 1 June 1989
    • journal article
    • research article
    • Vol. 73  (8) , 2196-2201
Abstract
Hereditary elliptocytosis in North Africa is frequently associated with the .alpha.I/65 spectrin variant, characterized by an abnormal .alpha. I 65-kD instead of the normal .alpha. I 80-kD peptide following limited trypsin digestion of whole spectrin. A similar variant (although it yielded a 68-KD fragment) has been shown recently, in two black patients, to result from the insertion of a leucyl residue at position 148 (Marchesi et al: J clin Invest 80:191, 1987). In order to determine if the underlying molecular defect was the same in North Africans and blacks (who originate from both sides of the Sahara Desert), we performed analysis directly at the DNA level. Starting from the DNA of an Algerian .alpha.I/65 heterozygote in whom the mutation was associated with identifiable RFLPs, we cloned and sequenced the .alpha.-spectrin gene region which includes the mutation. We thus identified an extra leucine codon (TTG) between codons 147 and 149, the coding sequence becoming CAG TTG TTG CTG instead of CAG TTG CTG. We then used the polymerase chain reaction (PCR) method and dot-blot hybridization of the amplified DNA with mutant and normal allele-specific oligonucleotides to screen the DNA from four other unrelated North African subjects with Sp .alpha.I/65 hereditary elliptocytosis. In all families we studied, these subjects were heterozygous for the TTG insertion. These results demonstrate that Sp.alpha.I/65 hereditary elliptocytosis has the same molecular basis in North Africans and blacks.