MiR-34c Regulates The Proliferation And Differentiation Of Skeletal Muscle Cells By Targeting YY1

The development of skeletal muscle is a long and complicated process,including the proliferation and differentiation of myoblasts which plays a key role in this process.The proliferation and differentiation of myoblasts are precisely regulated by some signaling pathways,transcription factors and microRNAs(miRNAs).miRNAis a class of single small non-coding RNA,and combines with the 3'UTR of target gene to suppress the expression of target genes to regulate a variety of biological processes.Recently,many studies have shown that miRNAs play important roles in skeletal muscle development and regeneration,in the activation of satellite cells,as well as in the proliferation and differentiation of myoblasts.miR-34c,as a tumor suppressor,is becoming a hot area of research in recent years.miR-34c can suppress the growth,migration and invasion of many tumors by inhibiting the proliferation of cells.However,few studies focus on the function of miR-34c in skeletal muscle.Therefore,in this study,we mainly explore the function of miR-34c in the proliferation and differentiation of myoblasts by using the C2C12 myoblast cell line,and investigate the target genes involved in miR-34c function to further clarify the function and regulation mechanisms of miR-34c in the development process of skeletal muscle.In this study,we found that miR-34c was maintained at a low level in proliferating C2C12 myoblasts and was upregulated during differentiation.Overexpression of miR-34c in C2C12 myoblasts and primary myoblasts,could inhibit cell proliferation,lead to cell cycle arrest in G0/G1 phase and reduce the expression of cell cycle genes.Conversely,functional inhibition of miR-34c in myoblasts could promote cell proliferation,reduce the proportion of cells in the G0/G1 phase and upregulate the expression of cell cycle genes.Subsequently,we found that overexpression of miR-34c in C2C12 myoblasts could promote cell differentiation,up-regulate the expression of MyoG and MyHC,and increase the number of myotubes.Moreover,functional miR-34c interference in C2C12 myoblasts could represse cell differentiation,down-regulate the expression of MyoG and MyHC,and decrease the number of myotubes.Finally,we found that YY1 was a target gene of miR-34c,and miR-34c could inhibite the expression of YY1.Similar to the effect of miR-34c overexpression,inhibited the expression of YY1 in C2C12 myoblasts,could inhibit cell proliferation,lead to cell cycle arrest in G0/G1 phase,reduce the expression of cell cycle genes,up-regulate the expression of MyoG and MyHC and increase the number of myotubes.In addition,we found that miR-34c also play an important role in the activation of satellite cells.Compared with the quiescent satellite cells,the expression of miR-34c was up-regulated after satellite cells activation.miR-34c knockdown in satellite cells,could down-regulate the expression of Pax7 and MyoD,decrease the number of myotubes and down-regulate the expression of MyoG and MyHC after differentiation.These results suggested that the activation and differentiation of satellite cells were also positively regulated by miR-34c.Beyond that,this study also found miR-34c could inhibite the growth of rhabdomyosarcoma.Overexpression of miR-34c in RD cells which derived from a human rhabdomyosarcoma reduced the number of EdU+ cells,induced G0/G1 cell cycle arrest and decreased the expression of cell cycle genes.In conclusion,we find that miR-34c can regulate myoblast proliferation and differentiation through its target gene YY1.In addition,miR-34c plays an important role in the regulation of the activation and differentiation in satellite cells.Moreover,miR-34c can inhibite the proliferation of rhabdomyosarcoma.Thus,this study provides a new view for exploring the function of miR-34c in skeletal muscle development and regeneration and offers a potential therapeutic target for the treatment of rhabdomyosarcoma.