Isolation and characterization of cDNA clones for human erythrocyte beta-spectrin.

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Abstract
Spectrin is an important structural component of the membrane skeleton that underlies and supports the erythrocyte plasma membrane. It is composed of nonidentical .alpha. (Mr 240,000) and .beta. (Mr 220,000) subunits each of which contains multiple homologous 106-amino acid segments. We report here the isolation and characterization of a human erythroid-specific .beta.-spectrin cDNA clone that encodes parts of the .beta.-9 through .beta.-12 repeat segments. This cDNA was used as a hybridization probe to assign the .beta.-spectrin gene to human chromosome 14 and to begin molecular analysis of the gene and its mRNA transcripts. RNA transfer blot analysis showed that the reticulocyte .beta.-spectrin mRNA is 7.8 kilobases in length. Southern blot analysis of genomic DNA revealed the presence of restriction fragment length polymorphisms (RFLPs) within the .beta.-spectrin gene locus. The isolation of human spectrin cDNA probes and the identification of closely linked RFLPs will facilitate analysis of mutant spectrin genes causing congenital hemolytic anemias associated with quantitative and qualitative spectrin abnormalities.