Terminal differentiation program of skeletal myogenesis is negatively regulated by O-GlcNAc glycosylation

Background: O-Linked β-N-acetylglucosaminylation (O-GlcNAcylation) on the Ser/Thr residue of nucleocytoplasmic proteins is a dynamic post-translational modification found in multicellular organisms. More than 500 proteins involved in a wide range of cellular functions, including cell cycle, transcription, epigenesis, and glucose sensing, are modified with O-GlcNAc. Although it has been suggested that O-GlcNAcylation is involved in the differentiation of cells in a lineage-specific manner, its role in skeletal myogenesis is unknown.

Methods and results: A myogenesis-dependent drastic decrease in the levels of O-GlcNAcylation was found in mouse C2C12 myoblasts. The global decrease in O-GlcNAcylation was observed at the earlier stage of myogenesis, prior to myoblast fusion. Genetic or pharmacological inactivation of O-GlcNAcase blocked both the myogenesis-dependent global decrease in O-GlcNAcylation and myoblast fusion. Although inactivation of O-GlcNAcase affected neither cell-cycle exit nor cell survival in response to myogenic stimulus, it perturbed the expression of myogenic regulatory factors. While the expression of myod and myf5 in response to myogenic induction was not affected, that of myogenin and mrf4 was severely inhibited by the inactivation of O-GlcNAcase.

Conclusion: These results indicate that the terminal differentiation program of skeletal myogenesis is negatively regulated by O-GlcNAcylation.

General significance: O-GlcNAcylation is involved in differentiation in a cell lineage-dependent manner, and a decrease in O-GlcNAcylation may have a common role in the differentiation of cells of muscle lineage.