title: A missense mutation in the APC tumor suppressor gene disrupts an ASF/SF2 splicing enhancer motif and causes pathogenic skipping of exon 14.
abstract: A missense mutation at codon 640 in the APC gene was identified in a familial adenomatous polyposis (FAP) patient, however, its pathological consequence remained unclear. Here we found that this missense mutation interferes at the nucleotide level with an exonic splicing regulatory element and leads to aberrant splicing of the mutant APC transcript rather than exerting its effect through the observed amino acid change. Analysis of the patient RNA revealed complete skipping of exon 14 in transcripts from the mutant APC allele, leading to a frameshift and a premature stop codon. When cloned into a splicing reporter minigene and transfected into colorectal cell lines, the exon 14 point mutation c.1918C>G (pR640G) was found sufficient to cause the observed exon skipping. Bioinformatic analysis predicted the mutation to change SRp55, hnRNP A1 or ASF/SF2 splicing factor binding sites. Using RNA interference methodology these predictions were experimentally validated and revealed that only ASF/SF2 was required for exon 14 inclusion. These research data identify APC mutation c.1918C>G (pR640G) as pathogenic and indicate a mechanism involving disruption of an ASF/SF2 exonic splicing enhancer element. The results allow genetic diagnosis of a hereditary tumour predisposition but also illustrate the need to complement in silico prediction by splicing reporter assays.
authors.affiliation: Centro de Genética Humana, Instituto Nacional de Saúde Dr. Ricardo Jorge, Lisboa, Portugal.
authors.forename: Vânia
authors.initials: V
authors.lastname: Gonçalves
authors.forename: Patrícia
authors.initials: P
authors.lastname: Theisen
authors.forename: Ofélia
authors.initials: O
authors.lastname: Antunes
authors.forename: Ana
authors.initials: A
authors.lastname: Medeira
authors.forename: José Silva
authors.initials: JS
authors.lastname: Ramos
authors.forename: Peter
authors.initials: P
authors.lastname: Jordan
authors.forename: Glória
authors.initials: G
authors.lastname: Isidro
mesh_terms: D011125:Adenomatous Polyposis Coli / Q000235:genetics; D025601:Adenomatous Polyposis Coli Protein / Q000235:genetics*; D017398:Alternative Splicing / Q000235:genetics*; D004742:Enhancer Elements, Genetic / Q000235:genetics*; D005091:Exons / Q000235:genetics*; D017930:Genes, Reporter; D006801:Humans; D008297:Male; D008875:Middle Aged; D020125:Mutation, Missense / Q000235:genetics*; D009687:Nuclear Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins; D000068103:Serine-Arginine Splicing Factors
chemical_list: D025601:Adenomatous Polyposis Coli Protein; D009687:Nuclear Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D000068103:Serine-Arginine Splicing Factors