Myosin light chain components in single muscle fibers of Duchenne muscular dystrophy.

Single muscle fibers were prepared from biopsy specimens of Duchenne muscular dystrophy (DMD), normal, and neuromuscular disease controls. Single muscle cells were classified as type 1, type 2, or intermediate by the skinned fiber method. The intermediate fiber was most abundant in DMD, comprising 29% of fibers examined. The fiber type of single muscle fibers was contrasted to the composition of myosin light chain (MLC) components, which was analyzed by micro two-dimensional gel electrophoresis. In DMD, each of the components exhibited the same electrophoretic mobility as those in the controls. Type 1 fibers of DMD were more diverse in the composition of MLC than those of controls; 55% of type 1 fibers of DMD contained distinct fast-type MLC 3. Some intermediate fibers contained all five MLC components, but in others the composition was not different from usual type 1 or type 2 fibers. The diversity of MLC composition in DMD muscle cells might reflect the abundance of young muscle fibers in the tissue due to active muscle regeneration and/or retardation of maturation.