title: Denervation in murine fast-twitch muscle: short-term physiological changes and temporal expression profiling.
abstract: Denervation deeply affects muscle structure and function, the alterations being different in slow and fast muscles. Because the effects of denervation on fast muscles are still controversial, and high-throughput studies on gene expression in denervated muscles are lacking, we studied gene expression during atrophy progression following denervation in mouse tibialis anterior (TA). The sciatic nerve was cut close to trochanter in adult CD1 mice. One, three, seven, and fourteen days after denervation, animals were killed and TA muscles were dissected out and utilized for physiological experiments and gene expression studies. Target cDNAs from TA muscles were hybridized on a dedicated cDNA microarray of muscle genes. Seventy-one genes were found differentially expressed. Microarray results were validated, and the expression of relevant genes not probed on our array was monitored by real-time quantitative PCR (RQ-PCR). Nuclear- and mitochondrial-encoded genes implicated in energy metabolism were consistently downregulated. Among genes implicated in muscle contraction (myofibrillar and sarcoplasmic reticulum), genes typical of fast fibers were downregulated, whereas those typical of slow fibers were upregulated. Electrophoresis and Western blot showed less pronounced changes in myofibrillar protein expression, partially confirming changes in gene expression. Isometric tension of skinned fibers was little affected by denervation, whereas calcium sensitivity decreased. Functional studies in mouse extensor digitorum longus muscle showed prolongation in twitch time parameters and shift to the left in force-frequency curves after denervation. We conclude that, if studied at the mRNA level, fast muscles appear not less responsive than slow muscles to the interruption of neural stimulation.
authors.affiliation: Centro di Ricerca Interdipartimentale per le Biotecnologie Innovative Biotechnology Center, University of Padova, Padua, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Raffaello
authors.forename: Paolo
authors.initials: P
authors.lastname: Laveder
authors.forename: Chiara
authors.initials: C
authors.lastname: Romualdi
authors.forename: Camilla
authors.initials: C
authors.lastname: Bean
authors.forename: Luana
authors.initials: L
authors.lastname: Toniolo
authors.forename: Elena
authors.initials: E
authors.lastname: Germinario
authors.forename: Aram
authors.initials: A
authors.lastname: Megighian
authors.forename: Daniela
authors.initials: D
authors.lastname: Danieli-Betto
authors.forename: Carlo
authors.initials: C
authors.lastname: Reggiani
authors.forename: Gerolamo
authors.initials: G
authors.lastname: Lanfranchi
mesh_terms: D000818:Animals; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D051379:Mice; D008931:Mitochondria, Muscle / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D009121:Muscle Denervation; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism*; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D018482:Muscle, Skeletal / Q000294:innervation / Q000378:metabolism*; D009133:Muscular Atrophy / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D012333:RNA, Messenger / Q000378:metabolism; D015203:Reproducibility of Results; D013997:Time Factors
chemical_list: D024101:Mitochondrial Proteins; D009124:Muscle Proteins; D012333:RNA, Messenger