Pathomechanism and treatment of distal myopathy with rimmed vacuoles and GNE gene aberration

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Mutation in GNE gene, encoding UDP-N-acetyIglucosamine-2-epiraerase/N-acetylmannosamine kinase, are believed to play a causative role in the onset of distal myopatiiy with rimmed vacuoles (DMRV). Tb understand the pathomechanism and development of the therapy for DMRV, we studied on lysosomal function in the muscle fiber animal rimmed vacuolar myopathies, localization and function of GNE in mammalian tissues and cells, and preparation of mutant GNE cells and GNE knock-down cells.Our immunohistochemical, Western blot, and real time RT-PCK studies showed that GNE is ubiquitously expressed in both murine and human tissues. GNE was induced in regenerating fibers, especially in nuclei, as well as degenerating fibers of murine muscles after injection with cardiotoxin, suggesting that GNE may play a specific functional role in nuclei of regeneration of muscles fibers.The denervated muscle of chloroquine-treated rats is known as animal model of human DMRV Accumulation of vacuoles was observed … More only in chloroquine-treated denervated muscles. We found that microtubule associated protein-1 light chain-3 (LC3)protein and gene increased in association with rimmed vacuolar formation in denervated muscles from chloroquine-treated rata, suggesting an increase in autophagy at the molecular level. Abnormal accumulation of rimmed vacuoles in this myopathy does not appear to be mediated by inhibition of autophagosome-related genes or GNE gene. Furthermore, we demonstrated that increased proteasomes, ubiquitin ligases, and ubiquitin in denervated muscles of chloroquine-treated rats and suggest that the ubiquitin-proteasome proteolytic pathway as well as the lysosomal proteolytic pathway mediate muscle fiber destruction in experimental myopathy. IGF-1 treatment inhibited the overdevelopment of rimmed vacuolar in these muscles.We prepared the HEK293 cells with mutant GNE gene (C303stop) and GNE knocked-down C2C4 myotube cells. Both atrophy and death were more frequent in mutant GNE cells than in wild-type cells, despite of neither rimmed vacuoles nor lysosome-derived vacuoles such as autolysosomes and autophagosomes Less