title: Five percent of normal cystic fibrosis transmembrane conductance regulator mRNA ameliorates the severity of pulmonary disease in cystic fibrosis.
abstract: Estimates of the level of transcripts from the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) gene required to develop a CF phenotype range from 4-20% of normal. Due to the importance of obtaining reliable data on this issue for therapeutic strategies, we developed a novel polymerase chain reaction-based method to quantify CFTR transcripts and applied it to the analysis of nasal epithelium RNA of five patients with CF and the 3272-26A>G/F508del genotype. We calculated that 8.2 +/- 0.84% of the total CFTR RNA present in these five patients is normal full-length CFTR mRNA. We then demonstrated (in nasal samples from F508del carriers, n = 30) that the abundance of full-length F508del CFTR transcripts is reduced compared with wild-type transcripts, and estimated that the average ratio of F508del/wild-type transcripts is 0.87 +/- 0.06. To determine the amount of full-length transcripts relative to levels found in normal individuals, we corrected for the lower abundance of the F508del transcripts and calculated that the five patients with CF have, on average, 4.7 +/- 0.45% of the normal level of wild-type CFTR mRNA. Because these patients have mild CF compared with F508del homozygotes, this CFTR mRNA level appears to be sufficient to avoid the severe complications of the disease.
authors.affiliation: Centro de Genética Humana, Instituto Nacional de Saúde, Lisboa, Portugal.
authors.forename: Anabela S
authors.initials: AS
authors.lastname: Ramalho
authors.forename: Sebastian
authors.initials: S
authors.lastname: Beck
authors.forename: Michelle
authors.initials: M
authors.lastname: Meyer
authors.forename: Deborah
authors.initials: D
authors.lastname: Penque
authors.forename: Garry R
authors.initials: GR
authors.lastname: Cutting
authors.forename: Margarida D
authors.initials: MD
authors.lastname: Amaral
mesh_terms: D017398:Alternative Splicing; D003550:Cystic Fibrosis / Q000235:genetics*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics*; D005091:Exons; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D008168:Lung / Q000503:physiopathology; D009154:Mutation; D012333:RNA, Messenger / Q000378:metabolism; D012016:Reference Values; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C505032:CFTR protein, human; D012333:RNA, Messenger; D019005:Cystic Fibrosis Transmembrane Conductance Regulator