title: p38γ activity is required for maintenance of slow skeletal muscle size.
abstract: BACKGROUND
  p38γ kinase is highly enriched in skeletal muscle and is implicated in myotube formation. However, the activation status of p38γ in muscle is unclear.
  
  
  METHODS
  p38γ activity in slow and fast adult mouse skeletal muscle tissue was examined, as was the impact of p38γ deficiency on muscle development and gene expression.
  
  
  RESULTS
  p38γ is preferentially activated in slow muscle, but it is inactive in fast muscle types. Furthermore, the loss of p38γ in mice led to decreased muscle mass associated with a smaller myofiber diameter in slow muscle, but there was no impact on fast muscle in either mass or myofiber diameter. Finally, p38γ-deficient muscle showed selective changes in genes related to muscle growth in slow muscle fibers.
  
  
  CONCLUSIONS
  This study provides evidence that p38γ is selectively activated in slow skeletal muscle and is involved in the normal growth and development of a subset of skeletal muscle.
authors.affiliation: Molecular, Cellular, and Integrated Physiology Program, University of California at Los Angeles, Los Angeles, California, USA.
authors.forename: William H
authors.initials: WH
authors.lastname: Foster
authors.forename: James G
authors.initials: JG
authors.lastname: Tidball
authors.forename: Yibin
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000818:Animals; D019703:Calcineurin / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000235:genetics*; D051275:Glucose Transporter Type 4 / Q000235:genetics / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018657:Muscle Fibers, Slow-Twitch / Q000201:enzymology*; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism; D009929:Organ Size / Q000235:genetics; D047495:PPAR gamma / Q000235:genetics / Q000378:metabolism; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D012333:RNA, Messenger; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000172:deficiency / Q000378:metabolism*
chemical_list: D051275:Glucose Transporter Type 4; D036341:Intercellular Signaling Peptides and Proteins; D047908:Intracellular Signaling Peptides and Proteins; D047495:PPAR gamma; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; C485290:Ppargc1a protein, mouse; C548050:RCAN1 protein, rat; D012333:RNA, Messenger; C495693:Slc2a4 protein, mouse; D015534:Trans-Activators; D014157:Transcription Factors; D048051:p38 Mitogen-Activated Protein Kinases; D019703:Calcineurin; D018995:Myosin Heavy Chains