Decreased myotonin-protein kinase in the skeletal and cardiac muscles in myotonic dystrophy.

To investigate the role of myotonin-protein kinase (MT-PK) in the pathophysiology of myotonic dystrophy (DM), we developed specific antibodies against synthetic MT-PK peptides. The antibody identified a 53kDa protein in skeletal muscle and recognized decreases in the amount of the protein in both adult and congenital DM patients, compared with amounts in controls and in patients with other muscle diseases. In cardiac muscle, this antibody identified a 62kDa protein, and in brain, both the 53 and 62kDa proteins were detected. These results suggest the presence of tissue-specific isoforms of MT-PK.