title: Myofibrillar M-band proteins in rat skeletal muscles during development.
abstract: The distribution of three myofibrillar M-band proteins, myomesin, M-protein and the muscle isoform of creatine kinase, was investigated with immunocytochemical techniques in skeletal muscles of embryonic, fetal, newborn and four-week-old rats. Furthermore, muscles of newborn rats were denervated and examined at four weeks of age. In embryos, myomesin was present in all myotome muscle fibres of the somites, whereas M-protein was detected only in a small proportion of the myotome muscle fibres and muscle creatine kinase was not detected at all. In fetal and newborn muscles, all fibres contained all three M-band proteins. At four weeks of age, when fibre types (type 1 or slow twitch fibres and type 2 or fast twitch fibres) were clearly discernable, the pattern was changed. Myomesin and muscle creatine kinase were still observed in all fibres, whereas M-protein was present only in type 2 fibres. On the other hand, in muscle fibres denervated at birth all three M-band proteins were still detected. Our results suggest 1) that during the initial stages of myofibrillogenesis expression and incorporation of myomesin into the M-band precede that of M-protein and muscle creatine kinase; 2) that expression and incorporation of all three M-band proteins during fetal development is nerve independent and non coordinated to the expression of different forms of myosin heavy chains, and 3) that the suppression of M-protein synthesis during postnatal development is nerve dependent and reflects the maturation of slow twitch motor units.
authors.affiliation: Department of Anatomy, University of Umeå, Sweden.
authors.forename: E
authors.initials: E
authors.lastname: Carlsson
authors.forename: B K
authors.initials: BK
authors.lastname: Grove
authors.forename: T
authors.initials: T
authors.lastname: Wallimann
authors.forename: H M
authors.initials: HM
authors.lastname: Eppenberger
authors.forename: L E
authors.initials: LE
authors.lastname: Thornell
mesh_terms: D000251:Adenosine Triphosphatases / Q000032:analysis; D000818:Animals; D000831:Animals, Newborn; D000911:Antibodies, Monoclonal; D064211:Connectin; D003402:Creatine Kinase / Q000032:analysis* / Q000276:immunology; D009121:Muscle Denervation; D024510:Muscle Development; D009124:Muscle Proteins / Q000032:analysis* / Q000276:immunology; D009132:Muscles / Q000737:chemistry* / Q000196:embryology / Q000201:enzymology; D009210:Myofibrils / Q000737:chemistry* / Q000201:enzymology; D051381:Rats; D011919:Rats, Inbred Strains; D013194:Staining and Labeling
chemical_list: D000911:Antibodies, Monoclonal; D064211:Connectin; D009124:Muscle Proteins; D003402:Creatine Kinase; D000251:Adenosine Triphosphatases