A splice site mutation of the beta-spectrin gene causing exon skipping in hereditary elliptocytosis associated with a truncated beta-spectrin chain

We studied a French kindred with hereditary elliptocytosis associated with a spectrin variant (spectrin LePuy) containing a beta-spectrin chain that is truncated at its C terminus (Dhermy, D., Lecomte, M., Garbarz, M., Bournier, O., Galand, C., Gautero, H., Feo, C., Alloisio, N., Delaunay, J., and Boivin, P. (1982) J. Clin. Invest. 70, 707-715). The structure of the 3' end of the beta-spectrin gene, the region encoding the C terminus of beta-spectrin, was determined. Nucleotide sequencing of amplified genomic DNA revealed a mutation at position +4 (A---G) of the 5' donor consensus splice site of the intron following the third-to-last exon (exon X) in one beta-spectrin allele of a heterozygous patient. Agarose gel electrophoresis of polymerase chain reaction-amplified cDNA revealed an extra band of lower molecular weight, suggesting that the shortened beta-spectrin chain of spectrin LePuy arises from aberrant mRNA splicing. Nucleotide sequencing of the shorter cDNA amplification product revealed that the sequences encoding exon X were absent. Southern blotting of cDNA amplification products confirmed this result. The skipping of exon X causes a shift in the normal reading frame resulting in the encoding of a new amino acid sequence at the C terminus of the mutant beta-spectrin chain. A new in-frame stop codon is encountered following a single residue of this novel sequence.