Myotonin protein kinase (MtPK) affects the chloride permeability of C2C12 myogenic cells

An expansion mutation of CTG-repeat motifs within the myotonin protein kina se (MtPK) gene is responsible for the pathological role of the mutated gene in skeletal muscle. A full-length human MtPK cDNA was stably transfected i nto a mouse C2Cl2 myogenic cell line. The recombinantly expressed human MtP K protein in C2Cl2 cells has a predicted molecular mass of 70 kDa, and is l ocalized in the perinuclear region that resembles SR. Overexpression of MtP K in C2Cl2 cells causes the activation of chloride efflux. These results su ggest that MtPK affects chloride channel activity. A possible change in chl oride permeability in myotonia in myotonic dystrophy is discussed.