In situ hybridization of myoglobin mRNA: results on the skeletal muscles of normal subjects and patients with neuromuscular diseases

The intracellular localization of myoglobin(Mb) mRNA in the skeletal muscles of normal subjects and patients with Duchenne muscular dystrophy(DMD) or amyotrophic lateral sclerosis(ALS) was examined by in situ hybridization using a biotin-labeled cDNA probe. In cross sections of normal muscles, Mb mRNA signals were demonstrated to be diffusely distributed as granular reaction products throughout the sarcoplasm, and in longitudinal sections the products were observed preferentially on the A-band. In DMD or ALS muscles, the distribution of granular mRNA signals showed some similarities with that in normal muscles, although degenerated fibers revealed a heterogenous distribution of the signals. In DMD muscles, the optical density(OD) of stained signal was higher in non-atrophic fibers and lower in atrophic fibers than in normal muscles. In ALS muscles, the OD was lower than in normal muscles. These results suggest that Mb mRNA is distributed preferentially on the A-band of the muscle fibers, and that in diseased muscle fibers Mb synthesis is affected by pathological changes.