title: Expression of the myodystrophic R453W mutation of lamin A in C2C12 myoblasts causes promoter-specific and global epigenetic defects.
abstract: Autosomal dominant Emery-Dreifuss muscular dystrophy (EDMD) is characterized by muscle wasting and is caused by mutations in the LMNA gene encoding A-type lamins. Overexpression of the EDMD lamin A R453W mutation in C2C12 myoblasts impairs myogenic differentiation. We show here the influence of stable expression of the R453W and of the Dunnigan-type partial lipodystrophy R482W mutation of lamin A in C2C12 cells on transcription and epigenetic regulation of the myogenin (Myog) gene and on global chromatin organization. Expression of R453W-, but not R482W-lamin A, impairs activation of Myog and maintains a repressive chromatin state on the Myog promoter upon induction of differentiation, marked by H3 lysine (K) 9 dimethylation and failure to hypertrimethylate H3K4. Cells expressing WT-LaA also fail to hypertrimethylate H3K4. No defect occurs at the level of Myog promoter DNA methylation in any of the clones. Expression of R453W-lamin A and to a lesser extent R482W-lamin A in undifferentiated C2C12 cells redistributes H3K9me3 from pericentric heterochromatin. R453W-lamin A also elicits a redistribution of H3K27me3 from inactive X (Xi) and partial decondensation of Xi, but maintains Xist expression and coating of Xi, indicating that Xi remains inactivated. Our results argue that gene-specific and genome-wide chromatin rearrangements may constitute a molecular basis for laminopathies.
authors.affiliation: Institute of Basic Medical Sciences, Department of Biochemistry, Faculty of Medicine, University of Oslo, PO Box 1112 Blindern, 0317 Oslo, Norway.
authors.forename: Anne-Mari
authors.initials: AM
authors.lastname: Håkelien
authors.forename: Erwan
authors.initials: E
authors.lastname: Delbarre
authors.forename: Kristine G
authors.initials: KG
authors.lastname: Gaustad
authors.forename: Brigitte
authors.initials: B
authors.lastname: Buendia
authors.forename: Philippe
authors.initials: P
authors.lastname: Collas
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D001120:Arginine / Q000235:genetics; D002454:Cell Differentiation; D002460:Cell Line; D002467:Cell Nucleus / Q000201:enzymology; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D006657:Histones / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D034904:Lamin Type A / Q000235:genetics* / Q000378:metabolism; D008745:Methylation; D051379:Mice; D020389:Muscular Dystrophy, Emery-Dreifuss / Q000235:genetics*; D020125:Mutation, Missense; D032446:Myoblasts / Q000166:cytology / Q000378:metabolism*; D018008:Myogenin / Q000096:biosynthesis / Q000235:genetics*; D011401:Promoter Regions, Genetic; D014364:Tryptophan / Q000235:genetics; D015854:Up-Regulation; D014960:X Chromosome / Q000201:enzymology
chemical_list: D006657:Histones; C494847:LMNA protein, human; D034904:Lamin Type A; D018008:Myogenin; D014364:Tryptophan; D001120:Arginine