title: A splice mutation and mRNA decay of EXT2 provoke hereditary multiple exostoses.
abstract: BACKGROUND
  Hereditary multiple exostoses (HME) is an autosomal dominant disease. The classical paradigm of mutation screening seeks to relate alterations in the exostosin glycosyltransferase genes, EXT1 and EXT2, which are responsible for over 70% of HME cases. However, the pathological significance of the majority of these mutations is often unclear.
  
  
  METHODS
  In a Chinese family with HME, EXT1 and EXT2 genes were screened by direct sequencing. The consequence of a detected mutant was predicted by in silico analysis and confirmed by mRNA analysis. The EXT1 and EXT2 mRNA and protein levels and the HS patterns in the HME patients were compared with those in healthy controls.
  
  
  RESULTS
  A heterozygous transition (c.743+1G>A) in the EXT2 gene, which co-segregated with the HME phenotype in this family, was identified. The G residue at position +1 in intron 4 of EXT2 was predicted to be a 5' donor splice site. The mRNA analysis revealed an alternative transcript with a cryptic splice site 5 bp downstream of the wild-type site, which harbored a premature stop codon. However, the predicted truncated protein was not detected by western blot analysis. Decay of the mutant mRNA was shown by clone sequencing and quantification analysis. The corresponding downregulation of the EXT2 mRNA will contribute to the abnormal EXT1/EXT2 ratio and HS pattern that were detected in the patients with HME.
  
  
  CONCLUSIONS
  The heterozygous mutation c.743+1G>A in the EXT2 gene causes HME as a result of abnormal splicing, mRNA decay, and the resulting haploinsufficiency of EXT2.
authors.affiliation: Department of Medical Genetics, Nanjing University School of Medicine, Nanjing, China; Jiangsu Key Laboratory of Molecular Medicine, Nanjing, China.
authors.forename: Chen
authors.initials: C
authors.lastname: Tian
authors.affiliation: Jinling Hospital, Nanjing University School of Medicine, Nanjing, China.
authors.forename: Rengna
authors.initials: R
authors.lastname: Yan
authors.affiliation: Department of Medical Genetics, Nanjing University School of Medicine, Nanjing, China; Jiangsu Key Laboratory of Molecular Medicine, Nanjing, China.
authors.forename: Shuzhen
authors.initials: S
authors.lastname: Wen
authors.affiliation: Department of Medical Genetics, Nanjing University School of Medicine, Nanjing, China; Jiangsu Key Laboratory of Molecular Medicine, Nanjing, China.
authors.forename: Xueling
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Medical Genetics, Nanjing University School of Medicine, Nanjing, China; Jiangsu Key Laboratory of Molecular Medicine, Nanjing, China.
authors.forename: Tianfeng
authors.initials: T
authors.lastname: Li
authors.affiliation: Department of Medical Genetics, Nanjing University School of Medicine, Nanjing, China; Jiangsu Key Laboratory of Molecular Medicine, Nanjing, China.
authors.forename: Zhenming
authors.initials: Z
authors.lastname: Cai
authors.affiliation: Department of Medical Genetics, Nanjing University School of Medicine, Nanjing, China; Jiangsu Key Laboratory of Molecular Medicine, Nanjing, China.
authors.forename: Xinxiu
authors.initials: X
authors.lastname: Li
authors.affiliation: Jinling Hospital, Nanjing University School of Medicine, Nanjing, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Du
authors.affiliation: Department of Medical Genetics, Nanjing University School of Medicine, Nanjing, China; Jiangsu Key Laboratory of Molecular Medicine, Nanjing, China.
authors.forename: Huimei
authors.initials: H
authors.lastname: Chen
mesh_terms: D017398:Alternative Splicing; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000473:pathology; D004252:DNA Mutational Analysis; D005097:Exostoses, Multiple Hereditary / Q000175:diagnosis / Q000235:genetics*; D005260:Female; D056726:Genetic Association Studies; D005838:Genotype; D006801:Humans; D008297:Male; D009154:Mutation; D017351:N-Acetylglucosaminyltransferases / Q000235:genetics*; D010375:Pedigree; D022821:RNA Splice Sites; D020871:RNA Stability; D011859:Radiography; D000099065:Exostosin 2
chemical_list: D022821:RNA Splice Sites; D017351:N-Acetylglucosaminyltransferases; D000099065:Exostosin 2
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