Myoblast Fusion

Cell-to-cell fusion is essential for development in most eukaryotes. In sexually reproducing organisms, development begins with sperm-egg fusion and, in humans, pregnancy depends on fusion of epithelial cells in the placenta that form the syncytiotrophoblast, separating fetal and maternal blood. In addition, fiber cells of the eye fuse to form the lens syncytium, and macrophage fusion produces either multinucleated osteoclasts, which function in bone resorption, or giant cells, which form at sites of chronic inflammation. Cell-to-cell fusion has also been implicated in neuronal function, stem-cell trans-differentiation and cancer metastasis.

Moreover, partial cell fusion is essential for the formation of intercellular nanotubes, demonstrating a widespread role for fusion in cell-to-cell communication. In muscle tissue, in particular, cell fusion plays a pivotal role. During embryonic development, myoblasts fuse to form multinucleated myofibers. In adults, myoblasts differentiate from quiescent muscle stem-cells, called satellite cells, and fuse with existing myofibers to regenerate the muscle.

Consequently, loss of myoblast fusion diminishes the ability of muscles to regenerate, leading to muscle wasting with age and muscle disease. Nevertheless, cell-to-cell fusion remains poorly understood at the molecular level.





Fusion between myoblasts. Movie by Giulia Zarfati

Fusion between myoblasts. Video by Giulia Zarfati.