Physiological role and effect of (CTG) n of myotonin protein kinase, the product of myotonic dystrophy gene.

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Myotonin protein kinase is the product of the gene that causes Myotonic dystrophy. There were contradictory results on quantities of myotonin protein kinase in MD patients. To clarify whether the protein decrease or increase in the patients, we generated a fusion protein of myotonin protein kinase, and antisera against the fusion protein or peptides deduced from myotonin protein kinase cDNA.By western blot analysis using the antibody identified a specific 53kDa-myotonin protein kinase band, we found decreases in the amount of the protein in skeletal muscle of MD patients about in half. The amount of myotonin protein kinase showed negative correlation with the length of (CTG) n in MD patients. The result demonstrates that the decrease of the enzyme relates to the seriousness of the disease. Further, the antibody recognized a 62kDa protein in cardiac muscle and 53kDa and 62kDa proteins in brain, suggesting that there are tissue specific isoforms in myotonin kinase.To investigate the mechanism of CTG repeats expansion, myoblasts from MD patients were cultured long term. However, there was no change in the length of (CTG) n during the passages. Therefore, the somatic heterogeneity of CTG repeats in MD patients seems to occur before symptom.Since the fusion protein we generated is coverd the most part of myotonin protein kinase, we got some requests from abroad. We served our fusion protein by the requests and could contribute to the research.