Abnormal myotonic dystrophy protein kinase levels produce only mild myopathy in mice.
Myotonic dystrophy ( DM ) is commonly associated with CTG repeat expansions within the gene for DM-protein kinase ( DMPK ) . The effect of altered expression levels of DMPK , which is ubiquitously expressed in all muscle cell lineages during development , was examined by disrupting the endogenous Dmpk gene and overexpressing a normal human DMPK transgene in mice . Nullizygous ( - / - ) mice showed only inconsistent and minor size changes in head and neck muscle fibres at older age , animals with the highest DMPK transgene expression showed hypertrophic cardiomyopathy and enhanced neonatal mortality . However , both models lack other frequent DM symptoms including the fibre-type dependent atrophy , myotonia , cataract and male-infertility . These results strengthen the contention that simple loss- or gain-of-expression of DMPK is not the only crucial requirement for development of the disease . .
