The Function And Mechanism Of MiR-34b In The Process Of Myogenic Differentiation

Background: Myogenesis involves myoblast proliferation and differentiation to myocytes,followed by fusion and hypertrophy to form myotubes during muscle development.The C2C12 cell is a common cell model for myogenesis research.MicroRNAs(miRNAs)are small non-coding RNAs which post-transcriptionally regulate gene expression by binding to the 3?UTR of target mRNA to inhibit translation or induce mRNA degradation.miRNAs play important roles in the regulation of myogenesis.Recently,we have identified 39 novel miRNAs associated with myogenesis,including miR-34 b,a member of the miR-34 family(as are miR-34 a,miR-34 b and miR-34c).This miRNA regulates differentiation in various cell types,though its function in myogenesis remains to be elucidated.Objective: To explore the function of miR-34 b in myogenesis and its regulatory mechanism.Methods and Results: We detected the expression of miR-34 b during myogenesis and muscle regeneration after damage,miR-34 b is steadily increased during these two process.In C2C12 cells transfection of miR-34 b mimic or inhibitor,we show that miR-34 b inhibit myoblast proliferation and promote differentiation.We identified that miR-34 b targets 14-3-3 protein gamma,adenosylhomocysteinase and nucleolin by binding to their 3?UTR.One of them,nucleolin(Ncl),was of potential interest because its protein expression pattern corresponded perfectly with the cell differentiation state.Further analysis of these proteins expression patterns show that nucleolin is a cognate target of miR-34 b during myogenic differentiation.Analysis of protein expression between nucleolin and myogenin,shown that NUCL promote or inhibit myogenesis depends on the quantity of protein expression.Here,we proved that a moderate reduction of nucleolin in cells enhanced the myotube formation.In addition,our study indicates that the expression of miR-34 b is regulated by methylation in C2C12 cell.Conclusions: The above results show that miR-34 b promote muscle differentiation and regulate a series of protein.Our data demonstrated that nucleolin regulates myogenesis in a protein-abundance-dependent manner.And miR-34 b regulate Ncl in the form of fine-tuning exactly during muscle differentiation.