CHARACTERIZATION OF MYOTONIC-DYSTROPHY KINASE (DMK) PROTEIN IN HUMAN AND RODENT MUSCLE AND CENTRAL NERVOUS-TISSUE

Myotonic dystrophy (DM) is the most common form of inherited neuromusc ular disease in adults and is characterized by progressive muscle wast ing and myotonia, The mutation responsible for DM has been identified as the amplification of a polymorphic (CTG)(n) repeat in the 3' untran slated region of a gene encoding a serine/threonine kinase (DMK), We h ave produced a polyclonal rabbit antibody preparation against a fusion protein encoding the C-terminal amino acids 471-629 of the human DMK gene, This antibody specifically detects products of both full length and truncated human DMK genes expressed in bacteria and in insect cell s, On immunoblots, we observed protein species of similar to 74 and 82 kDa in cardiac muscle, skeletal muscle, ependyma and choroid plexus. By immunofluorescence, DMK was found to localize post-synaptically at the neuromuscular junction of skeletal muscle, at intercalated discs o f cardiac tissue and at the apical membrane of the ependyma and choroi d plexus. We have also detected two to three species (similar to 45-60 kDa) in other regions of the brain, Synaptic localization of DMK in t he cerebellum, hippocampus, midbrain and medulla was noted, These resu lts suggest that DMK plays a specialized role in intercellular communi cation.