Identification and distribution of some developmental isoforms of myosin heavy chains in avian muscle fibres.

Two monoclonal antibodies that react with all the slow skeletal myosin heavy chains in the mammalian skeletal muscles appeared to react with only SM1 myosin heavy chain in the post-hatch muscles of chicken. Further studies on the developing chicken showed one of these two antibodies to react with an additional myosin heavy chain in the early embryonic skeletal muscle as well as with the cardiac muscle. It is concluded that this antibody identified a slow muscle-like embryonic isoform of myosin heavy chain during earlier stages of development. While this embryonic isoform was more abundant during early development, the synthesis of SM1 myosin heavy chain was restricted to only presumptive slow muscle cells.