Effect of artificial (CTG) repeat expansion on the expression of myotonin protein kinase (MtPK) in COS-1 cells.

A major challenge in the study of a new genetic entity called triplet-repeat disease is to identify the role of triplet repeats in the pathogenesis of the disease. We have developed a strategy to demonstrate the effect in the 3'-untranslated end of the (CTG) repeats in myotonic dystrophy gene (MtPK) and found that repeat expansion (CTG46) causes a slight decrease in the translation rate of MtPK cDNA which correlates with the finding in patients with myotonic dystrophy of a low amount of MtPK protein in muscle. These results provide an important clue for characterizing the genetic abnormality in other triplet-repeat diseases.