Researchers have discovered the importance of a well-known protein, myeloid differentiation primary response gene 88 (MyD88), in the development and regeneration of muscles.

MyD88 is an adaptor protein that mediates Toll-like receptors and interleukin-1 receptor signaling. 

In the formation of muscle, specialized progenitor or stem cells multiply. They then differentiate into preliminary muscle cells called myoblasts. The myoblasts fuse together and subsequently form muscle fiber. Using animal models, the researchers worked with both neonatal cells and adult cells to determine that MyD88, a key signaling protein in the human body, is required in sufficient quantity for myoblasts to fuse.

Authors show that deletion of MyD88 impairs fusion of myoblasts without affecting their survival, proliferation, or differentiation. MyD88 regulates non-canonical NF-κB and canonical Wnt signaling during myogenesis and promotes skeletal muscle growth and overload-induced myofiber hypertrophy in mice.

Ablation of MyD88 reduces myofiber size during muscle regeneration, whereas its overexpression promotes fusion of exogenous myoblasts to injured myofibers.

"Since MyD88 promotes only the fusion of myoblasts without affecting their proliferation or differentiation, enhancing the levels of MyD88 levels could be a means to enhance engraftment of exogenous myoblasts in cellular therapies," author said.

http://uoflnews.com/releases/uofl-researchers-discover-key-signaling-protein-for-muscle-growth/

https://www.nature.com/articles/s41467-017-01866-w