A Deletion Mutation of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Locus: DeltaI507

Summary

During the development of an amplification refractory mutation system (ARMS)¹ assay for the detection of the DeltaF508 mutation^2,3,4 and corresponding normal locus in cystic fibrosis we discovered a family in which a further variant of the sequence exists. PCR amplification and direct sequencing of a region of exon 10 of the CFTR locus indicated the deletion of the three base pairs encoding isoleucine₅₀₆ or isoleucine₅₀₇, or possibly the presence of a single base substitution in conjunction with the DeltaF508 mutation. The resulting protein has a deletion of an isoleucine residue at position 507 as opposed to the previously described deletion of phenylalanine at position 508. We conclude that the loss of an isoleucine residue at position 507 (DeltaI507) is another defective variant of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene product.