RNF138 regulates skeletal muscle differentiation via the Wnt/β-catenin signaling pathway.

Rationale: Myogenesis is a strictly regulated process driven by signaling pathways activating muscle-specific gene expression. During myogenesis, muscle stem cells exhibit DNA damage response (DDR) features, which are essential for myoblast differentiation and skeletal muscle regeneration. However, the specific roles of DDR-associated proteins in these processes are not yet fully understood. Methods: Gene knockdown and knockout were used in cell and animal models to study RNF138's function in myoblast differentiation and skeletal muscle regeneration. Multi-omics profiling, including transcriptomics and proteomics, was conducted to identify the key proteins regulated by RNF138 in myogenesis. Protein turnover assays were utilized to investigate RNF138's role in APC protein turnover. Immunofluorescence microscopy was performed to confirm the protein colocalization and subcellular localization. Results: RNF138 expression increases during myoblast differentiation and in regenerating myofibers following muscle injury. Knockdown of RNF138 in C2C12 myoblasts impairs myogenic differentiation and fusion. Additionally, Rnf138-deficient mice exhibit delayed muscle regeneration following cardiotoxin-induced injury. Multi-omics profiling, including transcriptomics and proteomics, reveals that Wnt/β-catenin signaling, a key driver of myogenic differentiation, is enhanced by RNF138. Mechanistically, RNF138 stabilizes β-catenin and enhances its nuclear localization by facilitating lysosomal degradation of APC, a component of the β-catenin degradation complex responsible for mediating the export of β-catenin from the nucleus to the cytoplasm for further ubiquitin-proteasome degradation. Conclusions: We reveal a noncanonical role for RNF138, an E3 ubiquitin ligase, as a positive regulator of myoblast differentiation and skeletal muscle regeneration via the Wnt/β-catenin pathway. This finding highlights the noncanonical function of RNF138 beyond its known roles in DDR and other cellular processes. Therefore, RNF138 provides a potential link between DDR and myoblast differentiation, offering new insights into the molecular regulation of muscle regeneration.