title: Myomesin and M protein: differential expression in embryonic fibers during pectoral muscle development.
abstract: By applying immunocytochemistry using monoclonal antibodies, we found that the myofibrillar M band of both presumptive type-I and -II fibers in the pectoralis major muscle of chickens contains two high-molecular-weight proteins, i.e., myomesin (Mr, 185,000) and M protein (Mr, 165,000), early in embryonic development (7 days in ovo), even though adult type-I fibers lack M protein. The developmental expression of M protein is unusual in that, from 10 to 14 days in ovo, it is gradually suppressed not only in presumptive type-I fibers but also in presumptive type-II fibers formed from primary-generation myotubes. This latter suppression is transient, as M protein is expressed in all adult type-II fibers derived from both the primary- and second-generation myotubes. Myomesin, on the other hand, is continuously expressed in all myotubes throughout development. This finding shows that myomesin and M protein expression is regulated independently in different myotube populations, and that the suppression of M protein in primary-generation myotubes accounts for the delayed accumulation of M protein during development, as previously revealed by biochemical analysis. Presumptive type-I fibers, which form in the deep portion of the muscle, become concentrated in a narrow band known as the red strip.
authors.forename: B K
authors.initials: BK
authors.lastname: Grove
authors.forename: B
authors.initials: B
authors.lastname: Holmbom
authors.forename: L E
authors.initials: LE
authors.lastname: Thornell
mesh_terms: D000375:Aging; D000818:Animals; D002454:Cell Differentiation; D002642:Chick Embryo; D002645:Chickens; D064211:Connectin; D006651:Histocytochemistry; D007124:Immunoenzyme Techniques; D008970:Molecular Weight; D024510:Muscle Development; D009124:Muscle Proteins / Q000032:analysis / Q000096:biosynthesis*; D009132:Muscles / Q000166:cytology / Q000196:embryology*
chemical_list: D064211:Connectin; D009124:Muscle Proteins