title: Genetic analysis of p38 MAP kinases in myogenesis: fundamental role of p38alpha in abrogating myoblast proliferation.
abstract: The p38 mitogen-activated protein kinase (MAPK) pathway plays a critical role in skeletal muscle differentiation. However, the relative contribution of the four p38 MAPKs (p38alpha, p38beta, p38gamma and p38delta) to this process is unknown. Here we show that myoblasts lacking p38alpha, but not those lacking p38beta or p38delta, are unable to differentiate and form multinucleated myotubes, whereas p38gamma-deficient myoblasts exhibit an attenuated fusion capacity. The defective myogenesis in the absence of p38alpha is caused by delayed cell-cycle exit and continuous proliferation in differentiation-promoting conditions. Indeed, activation of JNK/cJun was enhanced in p38alpha-deficient myoblasts leading to increased cyclin D1 transcription, whereas inhibition of JNK activity rescued the proliferation phenotype. Thus, p38alpha controls myogenesis by antagonizing the activation of the JNK proliferation-promoting pathway, before its direct effect on muscle differentiation-specific gene transcription. More importantly, in agreement with the defective myogenesis of cultured p38alpha(Delta/Delta) myoblasts, neonatal muscle deficient in p38alpha shows cellular hyperproliferation and delayed maturation. This study provides novel evidence of a fundamental role of p38alpha in muscle formation in vitro and in vivo.
authors.affiliation: Differentiation and Cancer Program, Center for Genomic Regulation CRG-PRBB, Barcelona, Spain.
authors.forename: Eusebio
authors.initials: E
authors.lastname: Perdiguero
authors.forename: Vanessa
authors.initials: V
authors.lastname: Ruiz-Bonilla
authors.forename: Lionel
authors.initials: L
authors.lastname: Gresh
authors.forename: Lijian
authors.initials: L
authors.lastname: Hui
authors.forename: Esteban
authors.initials: E
authors.lastname: Ballestar
authors.forename: Pedro
authors.initials: P
authors.lastname: Sousa-Victor
authors.forename: Bernat
authors.initials: B
authors.lastname: Baeza-Raja
authors.forename: Mercè
authors.initials: M
authors.lastname: Jardí
authors.forename: Anna
authors.initials: A
authors.lastname: Bosch-Comas
authors.forename: Manel
authors.initials: M
authors.lastname: Esteller
authors.forename: Carme
authors.initials: C
authors.lastname: Caelles
authors.forename: Antonio L
authors.initials: AL
authors.lastname: Serrano
authors.forename: Erwin F
authors.initials: EF
authors.lastname: Wagner
authors.forename: Pura
authors.initials: P
authors.lastname: Muñoz-Cánoves
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D002453:Cell Cycle / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics; D002460:Cell Line; D049109:Cell Proliferation; D047369:Chromatin Immunoprecipitation; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D051379:Mice; D024510:Muscle Development / Q000235:genetics; D009154:Mutation; D032446:Myoblasts / Q000166:cytology / Q000378:metabolism*; D010766:Phosphorylation; D020133:Reverse Transcriptase Polymerase Chain Reaction; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics* / Q000378:metabolism
chemical_list: D007527:Isoenzymes; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases