TRANSCRIPT ANALYSIS OF CFTR NONSENSE MUTATIONS IN LYMPHOCYTES AND NASAL EPITHELIAL-CELLS FROM CYSTIC-FIBROSIS PATIENTS

The mutational effects at the mRNA level were investigated by RT-PCR a nalysis of nine different nonsense mutations (Q39X, E60X, R75X, G542X, L719X, Y1092X, R1162X, S1196X, W1282X) and one frameshift mutation (1 078delT) within the CFTR gene. With the exception of mutation R1162X, reduced mRNA levels ranging from 30% to less than 5% of the wild type have been observed. In case of the R75X and E60X mutations, the mRNA r eduction was accompanied by the appearance of atypical CFTR isoforms. Single exon 3 skipping, as well as joint exon 2 and 3 skipping, was ob served in lymphocyte and nasal epithelial mRNA derived from R75X allel es, The analysis of mRNA transcribed from E60X alleles revealed skippi ng of exon 3 (lymphocytes and nasal epithelial cells) or skipping of e xons 3 and 4 (nasal epithelial cells), With the exception of the E60X mutation, no obvious tissue-specific differences in the splicing patte rn and ratios of mutation to wild-type transcripts were detected betwe en lymphocytes and nasal epithelial cells. In addition to aberrant spl icing, the reduction of transcripts is the most common effect of nonse nse and frameshift mutations within the CFTR gene. (C) 1995 Wiley-Liss , Inc.