title: Allele-specific expression of APC in adenomatous polyposis families.
abstract: OBJECTIVE
  Germline mutations in the APC gene cause of most cases of familial adenomatous polyposis (FAP) and a lesser proportion of attenuated FAP (AFAP). Systematic analysis of APC at the RNA level could provide insight into the pathogenicity of identified mutations and the molecular basis of FAP/AFAP in families without identifiable mutations. Here, we analyzed the prevalence of imbalances in the allelic expression of APC in polyposis families with germline mutations in the gene and without detectable mutations in APC and/or MUTYH.
  
  
  METHODS
  Allele-specific expression (ASE) was determined by single nucleotide primer extension using an exon 11 polymorphism as an allele-specific marker. In total, 52 APC-mutation-positive (36 families) and 24 APC/MUTYH-mutation-negative (23 families) informative patients were analyzed. Seventy-six controls also were included.
  
  
  RESULTS
  Of the APC-mutation-positive families, most of those in whom the mutation was located before the last exon of the gene (12 of 14) had ASE imbalance, which is consistent with a mechanism of nonsense-mediated decay. Of the APC/MUTYH-mutation-negative families, 2 (9%) had ASE imbalance, which might cause the disease. Normal allele expression was restored shortly after lymphocytes were cultured with puromycin, supporting a 'nonsense-mediated' hypothesis.
  
  
  CONCLUSIONS
  ASE analysis might be used to determine the pathogenesis of some cases of FAP and AFAP in which APC mutations are not found. ASE also might be used to prioritize the order in which different areas of APC are tested. RNA-level studies are important for the molecular diagnosis of FAP.
authors.affiliation: Translational Research Laboratory, Institut d'Investigacions Biomédiques de Bellvitge-Institut Català d'Oncologia, Barcelona, Spain.
authors.forename: Ester
authors.initials: E
authors.lastname: Castellsagué
authors.forename: Sara
authors.initials: S
authors.lastname: González
authors.forename: Elisabet
authors.initials: E
authors.lastname: Guinó
authors.forename: Kristen N
authors.initials: KN
authors.lastname: Stevens
authors.forename: Ester
authors.initials: E
authors.lastname: Borràs
authors.forename: Victoria M
authors.initials: VM
authors.lastname: Raymond
authors.forename: Conxi
authors.initials: C
authors.lastname: Lázaro
authors.forename: Ignacio
authors.initials: I
authors.lastname: Blanco
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Gruber
authors.forename: Gabriel
authors.initials: G
authors.lastname: Capellá
mesh_terms: D011125:Adenomatous Polyposis Coli / Q000235:genetics*; D022981:Allelic Imbalance; D045647:DNA Glycosylases / Q000235:genetics*; D004252:DNA Mutational Analysis; D005091:Exons; D017491:Genes, APC; D020022:Genetic Predisposition to Disease; D018095:Germ-Line Mutation; D006801:Humans; D010375:Pedigree; D010641:Phenotype; D011401:Promoter Regions, Genetic; D020871:RNA Stability; D012333:RNA, Messenger / Q000032:analysis*; D012307:Risk Factors
chemical_list: D012333:RNA, Messenger; D045647:DNA Glycosylases; C061738:mutY adenine glycosylase