TWEAK-induced alternative NF-κB signaling regulates Cxcl10 and Mymx to promote myoblast-to-myotube fusion and muscle regeneration.

Myoblast fusion is essential for skeletal muscle growth and repair, yet the upstream signals regulating this process remain incompletely understood. Here, we show that the cytokine TWEAK promotes myotube formation through activation of alternative NF-κB signaling. Transcriptomic profiling of TWEAK-treated myotubes reveals upregulation of Myomixer (Mymx) and the chemokine CXCL10, both critical for fusion. Mechanistically, the NF-κB member RelB directly binds the Mymx and Cxcl10 gene promoters, enhancing their transcription. Genetic or pharmacological disruption of this pathway impairs myoblast fusion in both C2C12 and primary mouse myoblasts, while Mymx overexpression rescues fusion in TWEAK-deficient myoblasts. In mouse models, TWEAK treatment enhances myotube formation during muscle regeneration, whereas loss of TWEAK reduces fusion efficiency. These findings identify TWEAK-alternative NF-κB signaling as a key regulator of muscle cell fusion through direct transcriptional control of Mymx and Cxcl10 and defines targetable pathways to enhance repair in muscle disease.