lncMGPFis a novel positive regulator of muscle growth and regeneration

Background Long non-coding RNAs (lncRNAs) play critical regulatory roles in diverse biological processes and diseases. While a large number of lncRNAs have been identified in skeletal muscles until now, their function and underlying mechanisms in skeletal myogenesis remain largely unclear. Methods We characterized a novel functional lncRNA designatedlncMGPF(lncRNA muscle growth promoting factor) using RACE, Northern blot, fluorescencein situhybridization and quantitative real-time PCR. Its function was determined by gene overexpression, interference, and knockout experiments in C2C12 myoblasts, myogenic progenitor cells, and an animal model. The molecular mechanism by whichlncMGPFregulates muscle differentiation was mainly examined by cotransfection experiments, luciferase reporter assay, RNA immunoprecipitation, RNA pull-down, and RNA stability analyses. Results We report thatlncMGPF, which is highly expressed in muscles and positively regulated by myoblast determination factor (MyoD), promotes myogenic differentiation of muscle cellsin vivoandin vitro.lncMGPFknockout in mice substantially decreases growth rate, reduces muscle mass, and impairs muscle regeneration. Overexpression oflncMGPFin muscles can rescue the muscle phenotype of knockout mice and promote muscle growth of wild-type mice. Mechanistically,lncMGPFpromotes muscle differentiation by acting as a molecular sponge of miR-135a-5p and thus increasing the expression of myocyte enhancer factor 2C (MEF2C), as well as by enhancing human antigen R-mediated messenger RNA stabilization of myogenic regulatory genes such asMyoDandmyogenin(MyoG). We confirm that pig lncRNAAK394747and human lncRNAMT510647are homologous to mouselncMGPF, with conserved function and mechanism during myogenesis. Conclusions Our data reveal thatlncMGPFis a novel positive regulator of myogenic differentiation, muscle growth and regeneration in mice, pigs, and humans.