| dc.description.abstract | Abstract
FKHR（FOXO1）,FKHRL1（FOXO3）, AFX（FOXO4）, and FOXO6 constitute an evolutionarily conserved subgroup within the larger family known as winged helix/fork-head (fox) transcription regulators. Previous studies have indicated that PI3K pathway and FKHR regulate terminal muscle differentiation; however, the molecular mechanisms remain to be determined. Besides, the functions of other members were not examined to date. So far, we have cloned the promoter of FOXOs for analyzing their activity during myogenesis. In our experiment, it appeared that MyoD and FKHR, the regulators of muscle terminal differentiation may activate the promoter of FOXO4. We also found out that when myoblasts differentiate into myotube, the expression of FOXOs are up-regulated, especially FOXO4 and FOXO6. Hence, FOXOs are suggested to be involved in the process of muscle terminal differentiation. Based on this, individual FOXO-overexpression mediated by retrovirus infection and FOXO knocked-down by siRNA in myoblast have been established. We induced the stable clones of FOXOs-overexpressed and FOXO4 siRNA-treated myoblasts differentiate into myotubes by 5％HS in DMEM. We found that FOXO1-AAA over-expressed cells, lose the ability to differentiate, but the patterns of others after differentiation are not markedly different relative to control cells. We then collected the RNA from stable clones with stage of proliferating myoblast, confluent myoblast and myotube, and the expression level of relative genes in myogenesis were detected. We found that Atrogin-1 and Msx1 are upregulated, Mef2C is down-regulated in FOXO1-AAA-overexpressed cells in three stages, and the expression levels of MyoD are down-regulated significantly in the stage of myotube. Since MyoD, Mef2C and Msx1 are suggested to be the principal factors regulating myogenesis, our results indicate that FOXO can inhibit muscle terminal differentiation by regulating these genes relative to myogenesis. | en_US |