title: Influence of the duplication of CFTR exon 9 and its flanking sequences on diagnosis of cystic fibrosis mutations.
abstract: The DNA sequences of seven regions in the human genome were examined for sequence identity with exon 9 of the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which is mutated in cystic fibrosis, and its intronic boundaries. These sequences were 95% to 96% homologous. Based on this nucleotide sequence similarity, PCR primers for CFTR exon 9 can potentially anneal with other homologous sequences in the human genome. Sequence alignment analysis of the CFTR exon 9 homologous sequences revealed that five registered mutations in the Cystic Fibrosis Mutation Database may be due to the undesired annealing of primers to a homologous sequence, resulting in inappropriate PCR amplification. For this reason, we propose that certain pseudomutations may result from the similarity between CFTR exon 9 (and its flanking introns) and related sequences in the human genome. Here we show that two mutations previously described in the CFTR database (c.1392 + 6insC; c.1392 + 12G>A) were inappropriately attributed to two individuals who sought carrier testing. A more detailed study by either direct sequencing or subcloning and sequencing of PCR products using specially designed primers revealed that these apparent mutations were not, in fact, present in CFTR. In addition, we present new PCR conditions that permit specific amplification of CFTR exon 9 and its flanking regions.
authors.affiliation: Institut de Physiologie et Biologie Cellulaires, Centre National de la Recherche Scientifique Unité Mixte de Recherche 6187, Université de Poitiers, Poitiers, France.
authors.forename: Ayman
authors.initials: A
authors.lastname: El-Seedy
authors.forename: Tony
authors.initials: T
authors.lastname: Dudognon
authors.forename: Frédéric
authors.initials: F
authors.lastname: Bilan
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Pasquet
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Reboul
authors.forename: Albert
authors.initials: A
authors.lastname: Iron
authors.forename: Alain
authors.initials: A
authors.lastname: Kitzis
authors.forename: Véronique
authors.initials: V
authors.lastname: Ladeveze
mesh_terms: D003550:Cystic Fibrosis / Q000175:diagnosis* / Q000235:genetics*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics*; D005091:Exons / Q000235:genetics*; D005260:Female; D006801:Humans; D009154:Mutation / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011247:Pregnancy
chemical_list: D019005:Cystic Fibrosis Transmembrane Conductance Regulator