title: miR-31 controls osteoclast formation and bone resorption by targeting RhoA.
abstract: BACKGROUND
  Increased activity of osteoclasts is responsible for bone loss and joint destruction in rheumatoid arthritis. For osteoclast development and bone resorption activity, cytoskeletal organization must be properly regulated. MicroRNAs (miRNAs) are endogenous small noncoding RNAs that suppress expression of their target genes. This study was conducted to identify crucial miRNAs to control osteoclasts.
  
  
  METHODS
  miRNA expression in the bone marrow-derived macrophages (BMM) with or without receptor activator of nuclear factor κB ligand (RANKL) stimulation was analyzed by miRNA array. To examine the role of specific miRNAs in osteoclast formation, bone resorption activity and actin ring formation, the BMM were retrovirally transduced with miRNA antagomirs. To confirm whether the suppressive effects on osteoclastogenesis by miR-31 inhibition were mediated by targeting RhoA, osteoclast formation was analyzed in the presence of the RhoA inhibitor, exoenzyme C3.
  
  
  RESULTS
  miR-31 was identified as one of the highly upregulated miRNAs during osteoclast development under RANKL stimulation. Inhibition of miR-31 by specific antagomirs suppressed the RANKL-induced formation of osteoclasts and bone resorption. Phalloidin staining of osteoclasts revealed that actin ring formation at the cell periphery was severely impaired by miR-31 inhibition, and clusters of small ringed podosomes were observed instead. In these osteoclasts, expression of RhoA, one of the miR-31 target genes, was upregulated by miR-31 inhibition in spite of the impaired osteoclastogenesis. Treatment with the RhoA inhibitor, exoenzyme C3, rescued the osteoclastogenesis impaired by miR-31 inhibition.
  
  
  CONCLUSIONS
  miR-31 controls cytoskeleton organization in osteoclasts for optimal bone resorption activity by regulating the expression of RhoA.
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Mizoguchi
authors.forename: Yousuke
authors.initials: Y
authors.lastname: Murakami
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Saito
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Miyasaka
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Kohsaka
mesh_terms: D036002:ADP Ribose Transferases / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D001862:Bone Resorption / Q000235:genetics* / Q000378:metabolism; D001905:Botulinum Toxins / Q000378:metabolism / Q000494:pharmacology; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051379:Mice; D008811:Mice, Inbred DBA; D035683:MicroRNAs / Q000037:antagonists & inhibitors / Q000235:genetics*; D050778:NFATC Transcription Factors / Q000235:genetics / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D009841:Oligonucleotides / Q000235:genetics; D010010:Osteoclasts / Q000187:drug effects / Q000378:metabolism*; D053245:RANK Ligand / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D059467:Transcriptome; D015854:Up-Regulation / Q000187:drug effects; D020742:rhoA GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism
chemical_list: D035683:MicroRNAs; C539917:Mirn31 microRNA, mouse; D050778:NFATC Transcription Factors; C494005:Nfatc1 protein, mouse; D009841:Oligonucleotides; D053245:RANK Ligand; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D001905:Botulinum Toxins; D020742:rhoA GTP-Binding Protein