title: Failure to Target RANKL Signaling Through p38-MAPK Results in Defective Osteoclastogenesis in the Microphthalmia Cloudy-Eyed Mutant.
abstract: The Microphthalmia-associated transcription factor (MITF) is a basic helix-loop-helix leucine zipper family factor that is essential for terminal osteoclast differentiation. Previous work demonstrates that phosphorylation of MITF by p38 MAPK downstream of Receptor Activator of NFkB Ligand (RANKL) signaling is necessary for MITF activation in osteoclasts. The spontaneous Mitf cloudy eyed (ce) allele results in production of a truncated MITF protein that lacks the leucine zipper and C-terminal end. Here we show that the Mitf(ce) allele leads to a dense bone phenotype in neonatal mice due to defective osteoclast differentiation. In response to RANKL stimulation, in vitro osteoclast differentiation was impaired in myeloid precursors derived from neonatal or adult Mitf(ce/ce) mice. The loss of the leucine zipper domain in Mitf(ce/ce) mice does not interfere with the recruitment of MITF/PU.1 complexes to target promoters. Further, we have mapped the p38 MAPK docking site within the region deleted in Mitf(ce). This interaction is necessary for the phosphorylation of MITF by p38 MAPK. Site-directed mutations in the docking site interfered with the interaction between MITF and its co-factors FUS and BRG1. MITF-ce fails to recruit FUS and BRG1 to target genes, resulting in decreased expression of target genes and impaired osteoclast function. These results highlight the crucial role of signaling dependent MITF/p38 MAPK interactions in osteoclast differentiation.
authors.affiliation: Department of Molecular Virology, Immunology and Medical Genetics, Comprehensive Cancer Center, The Ohio State University Wexner Medical Center, Columbus, Ohio.
authors.forename: Heather A
authors.initials: HA
authors.lastname: Carey
authors.affiliation: Harvey Cushing Neuro-Oncology Laboratories, Department of Neurosurgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Bronisz
authors.affiliation: Department of Molecular Virology, Immunology and Medical Genetics, Comprehensive Cancer Center, The Ohio State University Wexner Medical Center, Columbus, Ohio.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Cabrera
authors.affiliation: Department of Molecular Virology, Immunology and Medical Genetics, Comprehensive Cancer Center, The Ohio State University Wexner Medical Center, Columbus, Ohio.|College of Veterinary Medicine, The Ohio State University, Columbus, Ohio.
authors.forename: Blake E
authors.initials: BE
authors.lastname: Hildreth
authors.affiliation: Department of Molecular Virology, Immunology and Medical Genetics, Comprehensive Cancer Center, The Ohio State University Wexner Medical Center, Columbus, Ohio.
authors.forename: Maria
authors.initials: M
authors.lastname: Cuitiño
authors.affiliation: Department of Molecular Virology, Immunology and Medical Genetics, Comprehensive Cancer Center, The Ohio State University Wexner Medical Center, Columbus, Ohio.
authors.forename: Qi
authors.initials: Q
authors.lastname: Fu
authors.affiliation: Department of Molecular Virology, Immunology and Medical Genetics, Comprehensive Cancer Center, The Ohio State University Wexner Medical Center, Columbus, Ohio.
authors.forename: Asrar
authors.initials: A
authors.lastname: Ahmad
authors.affiliation: College of Veterinary Medicine, The Ohio State University, Columbus, Ohio.
authors.forename: Ramiro E
authors.initials: RE
authors.lastname: Toribio
authors.affiliation: Department of Molecular Virology, Immunology and Medical Genetics, Comprehensive Cancer Center, The Ohio State University Wexner Medical Center, Columbus, Ohio.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Ostrowski
authors.affiliation: Department of Molecular Virology, Immunology and Medical Genetics, Comprehensive Cancer Center, The Ohio State University Wexner Medical Center, Columbus, Ohio.
authors.forename: Sudarshana M
authors.initials: SM
authors.lastname: Sharma
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000235:genetics*; D020935:MAP Kinase Signaling System / Q000235:genetics; D051379:Mice; D051739:Microphthalmia-Associated Transcription Factor / Q000378:metabolism*; D008850:Microphthalmos / Q000235:genetics*; D009154:Mutation / Q000235:genetics; D010010:Osteoclasts / Q000166:cytology / Q000378:metabolism*; D010766:Phosphorylation; D053245:RANK Ligand / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D051739:Microphthalmia-Associated Transcription Factor; C497235:Mitf protein, mouse; D053245:RANK Ligand; D048051:p38 Mitogen-Activated Protein Kinases