title: CDKN1C mutation in Wiedemann-Beckwith syndrome patients reduces RNA splicing efficiency and identifies a splicing enhancer.
abstract: Wiedemann-Beckwith syndrome (WBS) is a human overgrowth disorder that is accompanied by an increased risk of embryonal tumors and is associated with dsyregulation of the imprinting of genes in chromosome 11p15.5. Maternally inherited mutations in the imprinted CDKN1C gene are known to be associated with WBS. We have identified a novel mutation in several members of a large family affected by WBS. The mutation is a G --> T change in a run of seven G's near the 5' splice site of intron 3. All obligate carriers and affected individuals carry the mutation, and in each affected case, the allele was inherited maternally, strongly suggesting a role in causing WBS. The mutation is located in a poly-G tract in the intron; intronic G-rich sequences in other genes have been shown to have a role in promoting splicing. In transfected 293HEK cells, we found that the G --> T mutation reduced splicing efficiency. Mutation of all seven G's in the poly-G tract further reduced splicing efficiency, supporting a role for the G-tract as a splicing enhancer. The fibroblasts of one affected patient showed a similar reduction in splicing efficiency. Maternal monoallelic expression of CDKN1C was verified in this patient cell line. However, the total amount of spliced message was not reduced by the mutation in spite of the reduced efficiency of splicing. We discuss the possible role of the splicing defect in the pathogenesis of WBS in this pedigree.
authors.affiliation: Department of Molecular and Medical Genetics, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Jocelyne M
authors.initials: JM
authors.lastname: Lew
authors.forename: Yan Ling
authors.initials: YL
authors.lastname: Fei
authors.forename: Kirk
authors.initials: K
authors.lastname: Aleck
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Blencowe
authors.forename: Rosanna
authors.initials: R
authors.lastname: Weksberg
authors.forename: Paul D
authors.initials: PD
authors.lastname: Sadowski
mesh_terms: D001483:Base Sequence; D001506:Beckwith-Wiedemann Syndrome / Q000235:genetics*; D002461:Cell Line, Transformed; D003001:Cloning, Molecular; D050761:Cyclin-Dependent Kinase Inhibitor p57; D004247:DNA; D017931:DNA Primers; D006801:Humans; D007438:Introns; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009687:Nuclear Proteins / Q000235:genetics*; D012326:RNA Splicing; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C493964:CDKN1C protein, human; D050761:Cyclin-Dependent Kinase Inhibitor p57; D017931:DNA Primers; D009687:Nuclear Proteins; D004247:DNA