Immunofluorescence analysis of the primordial myosin detectable in embryonic striated muscle.

Abstract

Immunofluorescence analysis showed that the earliest myosin detectable in both the embryonic chicken heart and somitic myotome, the precursor to skeletal muscle, was strongly reactive with two different monoclonal antibodies specific for the heavy chain of cardiac ventricular myosin, but it showed no reactivity with affinity-purified polyclonal antibodies specific for the heavy chains of either fast-twitch or slow-tonic skeletal myosins. The heart remained reactive exclusively with the antibodies to cardiac myosin throughout development, while late embryonic (day 20) skeletal muscles were strongly reactive only with their homologous skeletal myosin antibodies. Our findings suggest that the primordial myosin heavy chain detectable in both forms of embryonic chicken striated muscle, the myotome and the heart, is immunologically distinct from myosins expressed in later embryonic as well as adult skeletal muscles, but it contains antigenic determinants similar to those present in cardiac ventricular myosin.There is abundant evidence that myosin expression undergoes transitions during the development of both skeletal (1-11) and cardiac muscle (1,(12)(13)(14)(15)(16)) in a number of species. However, there has been considerable controversy as to the nature of both the heavy-chain and light-chain subunit composition of the myosin isozymes expressed in embryonic muscle. With respect to heavy-chain composition, there are several lines of evidence to suggest that skeletal muscle development is characterized by the expression of a distinct embryonic isomyosin (1-8). Other evidence has suggested that the developmental program for embryonic skeletal muscle involves either the expression of fast skeletal myosin initially (10), the coexpression offast and slow skeletal isomyosins (7, 9), or the expression of cardiac as well as skeletal isomyosins (11,17,18). In the case of cardiac muscle, it is unclear whether the developmental program involves the coexpression of skeletal as well as cardiac isomyosins (17, 18).We examined myosin isozyme expression in the chicken embryo from the earliest demonstrated stages of myogenic differentiation and contractile protein expression in both the developing heart (19, 20) and somitic myotome (21-23), the precursor to skeletal muscle. The antigenic properties of the primordial striated-muscle myosins were analyzed by indirect immunofluorescence with specific monoclonal antibodies produced against the heavy chains of chicken cardiac ventricular (V3) myosin, and with affinity-purified polyclonal antibodies produced against the heavy chains of adult fast and slow skeletal myosins. We found that the earliest myosin heavy chain detectable in both forms of striated muscle was indistinguishable with these antibodies from cardiac ventricular myosin expressed in the adult heart but immunologically distinct from myosins expressed in later embryonic as well as adult skeletal muscles. Myotomal cross-reactivity with the cardiac antibodies was in striking contrast to the absence of reactivity of adu...

Isomyosin expression pattern during formation of the tubular chicken heart: A three‐dimensional immunohistochemical analysis

“…Our data on isomyosin distribution during chicken heart development agree with those of Sweeney et al (1983Sweeney et al ( , 1984Sweeney et al ( , 1985Sweeney et al ( , 1987 as far as the adult ventriclespecific isomyosin distribution is concerned. However, in contrast to our data, they emphasize that adult atrium-specific isomyosin expression is confined to the atrial part of the heart throughout development.…”

Nascent muscle fiber appearance in overloaded chicken slow‐tonic muscle

“…4e,f). Although the anti-PLD antibody has been shown to react with myosin in adult fast muscle (Umeda et al, 1980), antibody CCM-31A reacts with neither adult fast nor adult slow myosin (Sweeney et al, 1984). Therefore, the dual reactivity with the anti-PLD antibody and antibody CCM-31A indicates that these cells express a myosin complement which is similar to that of the 10-day embryonic ALD muscle.…”

“…Antibody HPM-7 does react with ALD myofibers of the 10-day embryo which have been shown to contain SM-1 and SM-2 (Matsuda et al, 1983). A sequential expression of isomyosins may be anticipated based on transitions in myosin antigenicity which occur at 5 and 6 days of development (Sweeney et al, 1984). In view of recent data (Miller et al, 1985;Schafer et al, 19871, it is also conceivable that the myogenic cells which give rise to the overload-induced cells described here are of a different lineage than the cells responsible for ALD muscle development.…”

“…The area of muscle fiber sampled was 7,340 + 690 pm2 (mean SD, n = 14), and the length of sarcolemma sampled was 560 f 150 pm. Prints at 8,000 times magnification were Sweeney et al (1984) ' A summary of previously published literature shows the known antimyosin reactivities of antibodies used in this study.…”

“…During embryonic, neonatal, and adult life, there are different forms of the fast skeletal muscle MHC which are sequentially expressed in chickens (Bandman et al, 1982;Bader et al, 1982;Lowey et al, 1983) and in mammals (Whalen et al, 1981;Lyons et al, 1983). The situation for chicken slow-tonic muscle myosin is less clear, although there is a different form of the protein expressed during embryonic development Matsuda et al, 1983;Sweeney et al, 1984). Compensatory hypertrophy of the rat plantaris muscle induced by synergist removal increases the level of slow myosin expression and also intermediate myosin (Gregory et al, 1986).…”