Abnormal myosin heavy chain variant associated with avian muscular dystrophy.

Avian muscular dystrophy is characterized by the degeneration of fast white skeletal muscle fibers, with onset during development. Using a one-dimensional peptide mapping technique, we have detected two forms of the myosin heavy chain in the fast white fibers of adult domestic chickens, one form characteristic of birds homozygous for muscular dystrophy, the other of their normal controls. Four dystrophic strains carrying the same gene for muscular dystrophy were examined. No differences were detected in the embryonic heavy chain peptide maps of normal and dystrophic chickens, consistent with the developmental onset of the condition. Differences were also absent from the peptide maps of heavy chains from slow red fibers, which are unaffected in dystrophy. No dystrophy-specific peptide map differences were detected in the three light chains. Analysis of peptide maps of rod and the heavy chain component of subfragment-1 from normal and dystrophic heavy chains indicates the presence of amino acid sequence differences in the two proteins.