title: A novel exon in the cystic fibrosis transmembrane conductance regulator gene activated by the nonsense mutation E92X in airway epithelial cells of patients with cystic fibrosis.
abstract: Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. We report on a novel nonsense mutation that leads to exon skipping and the activation of a cryptic exon. Screening of genomic DNA from 700 German patients with CF uncovered four cases with the nonsense mutation E92X, a G-->T transversion that creates a termination codon and affects the first base of exon 4 of the CFTR gene. Lymphocyte RNA of two CF patients heterozygous for E92X was found to contain the wild type sequence and a differentially spliced isoform lacking exon 4. In RNA derived from nasal epithelial cells of E92X patients, a third fragment of longer size was observed. Sequencing revealed the presence of E92X and an additional 183-bp fragment, inserted between exons 3 and 4. The 183-bp sequence was mapped to intron 3 of the CFTR gene. It is flanked by acceptor and donor splice sites. We conclude that the 183-bp fragment in intron 3 is a cryptic CFTR exon that can be activated in epithelial cells by the presence of the E92X mutation. E92X abolishes correctly spliced CFTR mRNA and leads to severe cystic fibrosis.
authors.affiliation: Abteilung für Humangenetik, Medizinische Hochschule, Hannover, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Will
authors.forename: T
authors.initials: T
authors.lastname: Dörk
authors.forename: M
authors.initials: M
authors.lastname: Stuhrmann
authors.forename: T
authors.initials: T
authors.lastname: Meitinger
authors.forename: R
authors.initials: R
authors.lastname: Bertele-Harms
authors.forename: B
authors.initials: B
authors.lastname: Tümmler
authors.forename: J
authors.initials: J
authors.lastname: Schmidtke
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence; D001483:Base Sequence; D002648:Child; D002675:Child, Preschool; D003550:Cystic Fibrosis / Q000209:etiology / Q000235:genetics*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005091:Exons; D005260:Female; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D009297:Nasal Mucosa / Q000378:metabolism*; D012326:RNA Splicing
chemical_list: C505032:CFTR protein, human; D008565:Membrane Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator