title: Characterization of a disease-associated mutation affecting a putative splicing regulatory element in intron 6b of the cystic fibrosis transmembrane conductance regulator (CFTR) gene.
abstract: Cystic fibrosis (CF) is a common recessive disorder caused by >1600 mutations in the CF transmembrane conductance regulator (CFTR) gene. About 13% of CFTR mutations are classified as "splicing mutations," but for almost 40% of these, their role in affecting the pre-mRNA splicing of the gene is not yet defined. In this work, we describe a new splicing mutation detected in three unrelated Italian CF patients. By DNA analyses and mRNA studies, we identified the c.1002-1110_1113delTAAG mutation localized in intron 6b of the CFTR gene. At the mRNA level, this mutation creates an aberrant inclusion of a sequence of 101 nucleotides between exons 6b and 7. This sequence corresponds to a portion of intron 6b and resembles a cryptic exon because it is characterized by an upstream ag and a downstream gt sequence, which are most probably recognized as 5'- and 3'-splice sites by the spliceosome. Through functional analysis of this splicing defect, we show that this mutation abolishes the interaction of the splicing regulatory protein heterogeneous nuclear ribonucleoprotein A2/B1 with an intronic splicing regulatory element and creates a new recognition motif for the SRp75 splicing factor, causing activation of the cryptic exon. Our results show that the c.1002-1110_1113delTAAG mutation creates a new intronic splicing regulatory element in intron 6b of the CFTR gene exclusively recognized by SRp75.
authors.affiliation: From the Istituto di Neurogenetica e Neurofarmacologia, Consiglio Nazionale delle Ricerche, 09042 Cagliari, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Faà
authors.forename: Federica
authors.initials: F
authors.lastname: Incani
authors.forename: Alessandra
authors.initials: A
authors.lastname: Meloni
authors.forename: Denise
authors.initials: D
authors.lastname: Corda
authors.forename: Maddalena
authors.initials: M
authors.lastname: Masala
authors.forename: A Maria
authors.initials: AM
authors.lastname: Baffico
authors.forename: Manuela
authors.initials: M
authors.lastname: Seia
authors.forename: Antonio
authors.initials: A
authors.lastname: Cao
authors.forename: M Cristina
authors.initials: MC
authors.lastname: Rosatelli
mesh_terms: D003550:Cystic Fibrosis / Q000235:genetics; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics*; D020022:Genetic Predisposition to Disease; D006801:Humans; D007438:Introns / Q000235:genetics*; D009154:Mutation; D022821:RNA Splice Sites; D012326:RNA Splicing; D016601:RNA-Binding Proteins / Q000378:metabolism*; D012045:Regulatory Sequences, Nucleic Acid; D017384:Sequence Deletion; D000068103:Serine-Arginine Splicing Factors
chemical_list: D022821:RNA Splice Sites; D016601:RNA-Binding Proteins; C081934:SRSF4 protein, human; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000068103:Serine-Arginine Splicing Factors