title: Real-time imaging of peroxisome proliferator-activated receptor-gamma coactivator-1alpha promoter activity in skeletal muscles of living mice.
abstract: In response to sustained increase in contractile activity, mammalian skeletal muscle undergoes adaptation with enhanced mitochondrial biogenesis and fiber type switching. The peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha) was recently identified as a key regulator for these adaptive processes. To investigate the sequence elements in the PGC-1alpha gene that are responsible for activity-dependent transcriptional activation, we have established a unique system to analyze promoter activity in skeletal muscle of living mice. Expression of PGC-1alpha-firefly luciferase reporter gene in mouse tibialis anterior muscle transfected by electric pulse-mediated gene transfer was assessed repeatedly in the same muscle by using optical bioluminescence imaging analysis before and after low-frequency (10 Hz) motor nerve stimulation. Nerve stimulation (2 h) resulted in a transient 3-fold increase (P < 0.05) in PGC-1alpha promoter activity along with a 1.6-fold increase (P < 0.05) in endogenous PGC-1alpha mRNA. Mutation of two consensus myocyte enhancer factor 2 (MEF2) binding sites (-2901 and -1539) or a cAMP response element (CRE) (-222) completely abolished nerve stimulation-induced increase in PGC-1alpha promoter activity. These findings provide direct evidence that contractile activity-induced PGC-1alpha promoter activity in skeletal muscle is dependent on the MEF2 and the CRE sequence elements. The experimental methods used in the present study have general applicability to studies of gene regulation in muscle.
authors.affiliation: Division of Cardiology, Dept. of Medicine, Duke University Medical Center, 4321 Medical Park Drive, Suite 200, Duke Univ. Independence Park Facility, Durham, NC 27704, USA.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Akimoto
authors.forename: Brian S
authors.initials: BS
authors.lastname: Sorg
authors.forename: Zhen
authors.initials: Z
authors.lastname: Yan
mesh_terms: D000818:Animals; D017362:Cyclic AMP Response Element-Binding Protein / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics; D004558:Electric Stimulation; D005786:Gene Expression Regulation; D018014:Gene Transfer Techniques; D021621:Imaging, Three-Dimensional; D064326:MEF2 Transcription Factors; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008954:Models, Biological; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D018006:Myogenic Regulatory Factors; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics; D014158:Transcription, Genetic; D015533:Transcriptional Activation / Q000502:physiology*; D014162:Transfection
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; D064326:MEF2 Transcription Factors; D018006:Myogenic Regulatory Factors; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; C485290:Ppargc1a protein, mouse; D012333:RNA, Messenger; D015534:Trans-Activators; D014157:Transcription Factors