Subtraction hybridization techniques were used to isolate 91 cDNA clones which are overexpressed in normal control skeletal muscle relative to muscle from patients with myotonic muscular dystrophy. The gene responsible for myotonic dystrophy (DM) has been localized to the 19q13.2-13.3 region of chromosome 19. To test as a candidate gene for DM, clones which represent differences in transcription are analyzed for localization to chromosome 19. One clone, designated MSL 366, was found to be on the long arm of chromosome 19 distal to the CKMM gene at 19q13.2. Sequence analysis confirmed that MSL 366 is the cDNA for human slow skeletal muscle troponin T. A genomic clone has been isolated and linkage studies with DM are in progress.