title: SH3BP2 gain-of-function mutation exacerbates inflammation and bone loss in a murine collagen-induced arthritis model.
abstract: OBJECTIVE
  SH3BP2 is a signaling adapter protein which regulates immune and skeletal systems. Gain-of-function mutations in SH3BP2 cause cherubism, characterized by jawbone destruction. This study was aimed to examine the role of SH3BP2 in inflammatory bone loss using a collagen-induced arthritis (CIA) model.
  
  
  METHODS
  CIA was induced in wild-type (Sh3bp2(+/+)) and heterozygous P416R SH3BP2 cherubism mutant knock-in (Sh3bp2(KI/+)) mice, an SH3BP2 gain-of-function model. Severity of the arthritis was determined by assessing the paw swelling and histological analyses of the joints. Micro-CT analysis was used to determine the levels of bone loss. Inflammation and osteoclastogenesis in the joints were evaluated by quantitating the gene expression of inflammatory cytokines and osteoclast markers. Furthermore, involvement of the T- and B-cell responses was determined by draining lymph node cell culture and measurement of the serum anti-mouse type II collagen antibody levels, respectively. Finally, roles of the SH3BP2 mutation in macrophage activation and osteoclastogenesis were determined by evaluating the TNF-α production levels and osteoclast formation in bone marrow-derived M-CSF-dependent macrophage (BMM) cultures.
  
  
  RESULTS
  Sh3bp2(KI/+) mice exhibited more severe inflammation and bone loss, accompanying an increased number of osteoclasts. The mRNA levels for TNF-α and osteoclast marker genes were higher in the joints of Sh3bp2(KI/+) mice. Lymph node cell culture showed that lymphocyte proliferation and IFN-γ and IL-17 production were comparable between Sh3bp2(+/+) and Sh3bp2(KI/+) cells. Serum anti-type II collagen antibody levels were comparable between Sh3bp2(+/+) and Sh3bp2(KI/+) mice. In vitro experiments showed that TNF-α production in Sh3bp2(KI/+) BMMs is elevated compared with Sh3bp2(+/+) BMMs and that RANKL-induced osteoclastogenesis is enhanced in Sh3bp2(KI/+) BMMs associated with increased NFATc1 nuclear localization.
  
  
  CONCLUSIONS
  Gain-of-function of SH3BP2 augments inflammation and bone loss in the CIA model through increased macrophage activation and osteoclast formation. Therefore, modulation of the SH3BP2 expression may have therapeutic potential for the treatment of rheumatoid arthritis.
authors.affiliation: Department of Oral and Craniofacial Sciences, School of Dentistry, University of Missouri-Kansas City, Kansas City, Missouri, United States of America.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Mukai
authors.affiliation: Department of Oral and Craniofacial Sciences, School of Dentistry, University of Missouri-Kansas City, Kansas City, Missouri, United States of America.
authors.forename: Richard
authors.initials: R
authors.lastname: Gallant
authors.affiliation: Department of Oral and Craniofacial Sciences, School of Dentistry, University of Missouri-Kansas City, Kansas City, Missouri, United States of America; Department of Periodontal Medicine, Applied life Sciences, Institute of Biomedical and Health Sciences, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Shu
authors.initials: S
authors.lastname: Ishida
authors.affiliation: Department of Oral and Craniofacial Sciences, School of Dentistry, University of Missouri-Kansas City, Kansas City, Missouri, United States of America.
authors.forename: Teruhito
authors.initials: T
authors.lastname: Yoshitaka
authors.affiliation: Department of Oral and Craniofacial Sciences, School of Dentistry, University of Missouri-Kansas City, Kansas City, Missouri, United States of America.
authors.forename: Mizuho
authors.initials: M
authors.lastname: Kittaka
authors.affiliation: Department of Orthopaedic Surgery, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan; Department of Human Morphology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
authors.forename: Keiichiro
authors.initials: K
authors.lastname: Nishida
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, United States of America.
authors.forename: David A
authors.initials: DA
authors.lastname: Fox
authors.affiliation: Department of Rheumatology, Kawasaki Medical School, Kurashiki, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Morita
authors.affiliation: Department of Oral and Craniofacial Sciences, School of Dentistry, University of Missouri-Kansas City, Kansas City, Missouri, United States of America.
authors.forename: Yasuyoshi
authors.initials: Y
authors.lastname: Ueki
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics* / Q000378:metabolism; D019943:Amino Acid Substitution; D000818:Animals; D001169:Arthritis, Experimental / Q000175:diagnosis / Q000235:genetics* / Q000276:immunology / Q000473:pathology*; D001862:Bone Resorption / Q000235:genetics*; D002356:Cartilage / Q000473:pathology; D049109:Cell Proliferation; D016207:Cytokines / Q000378:metabolism; D015870:Gene Expression; D008221:Lymphoid Tissue / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation; D050778:NFATC Transcription Factors / Q000378:metabolism; D010010:Osteoclasts / Q000378:metabolism; D053245:RANK Ligand / Q000378:metabolism / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism; D055114:X-Ray Microtomography
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D016207:Cytokines; D050778:NFATC Transcription Factors; D053245:RANK Ligand; C484644:Sh3bp2 protein, mouse; D014409:Tumor Necrosis Factor-alpha