| PART1: Myotubularins constitute a large family of phosphatases which preferably dephosphorylate phosphatidylinositol 3-phosphate (PI3P) and phosphatidylinositol3,5-bisphosphate. Mutations of MTM1 are responsible for X-linked myotubular myopathy in human, and mutations in MTMR2 and MTMR13 can also lead Charcot-Marie-Tooth disease (type 4B). However, the mechanisms underlying how MTM dysfunction leads to these diseases are still not clear. Here, we characterized functions of myotubularin homologs ceMTM3, ceMTM6 and ceMTM9 in nematode Caenorhabditis elegans.In our study,we demonstrate that ceMTM3, a FYVE-domain containing myotubalarin family phosphatase, is required for the maintenance of muscle fibers by preventing autophagy in Caenorhabditis elegans. Knockdown of ceMTM3 by using feeding-based RNA interference caused loss of muscle fibers accompanied by shortening of muscle cell and body size in aged C. elegans worms. This was preceded by the occurrence of excessive autophagy in the muscle and other tissues, which subsequently resulted in increased lysosomal activity and necrotic cell death. However, knockdown of ceMTM3 did not aggravate the abnormalities of muscle wasting in autophagy-deficient atg18 mutant worms. Our data suggest an important role of ceMTM3 in regulating autophagy and maintaining muscle fibers. This study has clinical implications for prevention and treatment of sarcopenia.We also characterized functions of myotubularin homolog ceMTM6 and ceMTM9 in nematode Caenorhabditis elegans. Worms without ceMTM6 displayed smaller body size and impaired locomotion associated with abnormal muscle cell assembling. Loss of mtm-6 also caused gonad abnormalities during development due to misguided migratory path of DTC cells. In consistence with the reported role of ceMTM6 in regulating endocytosis, we found that loss of MTM-6 affected distributions of integrin INA-1 which has an essential role in cell-cell attachment, cytoskeleton remodeling, and cell migration. The data suggest that ceMTM6 affects muscle assembling and DTCs migration by regulating endocytosis of integrin. ceMTM9 does not have catalytic activity, and it has been shown to form a complex with ceMTM6 thereby regulating its activity. Worms without ceMTM9 displayed a smaller body size, delayed development, a smaller brood size, a higher rate of bagged worms, and a shorter lifespan. Interestingly, knockdown ceMTM3 under the mtm-9 mutation background produced much more severe phenotypes, suggesting certain functional redundancies between these two proteins.PART2:Alcoholic beverages are consumed widely throughout the world. While the harmful effects of alcoholism are well recognized, the beneficial effects of moderate alcohol consumption to human health remain debatable. In this study, we investigated the effects of long-term ethanol exposure on the mobility and mortality of nematode C. elegans. High concentrations (≥4%) of ethanol significantly impaired their mobility, reduced their fertility, and shortened their lifespan. Interestingly, lower concentration of ethanol (1-2%) prolonged their lifespan, accompanied with a slower decline of mobility during aging, although it slightly reduced their fertility. The beneficial effects of the low concentration ethanol in prolonging lifespan were seen in worms exposed to ethanol from egg, young larva, and young adult stages but were not observed with age-1 and sir-2.1 mutant worms which suggests the involvement of these genes. Our study demonstrated the beneficial effects of lower concentrations of ethanol and further established C. elegans as a suitable animal model to study ethanol related problems. |
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