EXHAUSTIVE MUTATION SCANNING BY FLUORESCENCE-ASSISTED MISMATCH ANALYSIS DISCLOSES NEW GENOTYPE-PHENOTYPE CORRELATIONS IN ANGIOEDEMA

A complete mutational scan of the gene coding for the serpin C1 inhibi tor, comprising all eight exons and adjacent intron sequences and 550 bp preceding the transcription start site, was rapidly accomplished in 36 unrelated angioedema patients by using fluorescence-assisted misma tch analysis (FAMA). Mutations accounting for C1 inhibitor deficiency were identified in every one of 34 patients, with two failures turning out to be spurious cases. Two new substitution dimorphisms were also detected in introns. Changes affecting the C1 inhibitor protein, distr ibuted throughout the seven coding exons, provide new insights into th e molecular pathology of serpins. Six different splice-site and two pr omoter mutations were also found. Among the latter, a C-->T transition within one of two putative CAAT boxes of this TATA-less promoter, the sole idiomorphic nucleotide change in this kindred, was found homozyg ous in the proband, at variance with the dominant mode of transmission observed for structural mutations. FAMA, in the chemical probes confi guration used in this study, is a rapid and robust mutation-scanning p rocedure, applicable to large DNA segments or transcripts and proved c apable of 100% detection. Moreover, it provides accurate positional in formation-and hence recognition of multiple substitutions, precise rel ationship with those already known, and often immediate identification of the nucleotide change.