Myoblasts fail to fuse if they lack the mannose receptor (bottom).

If myoblasts are to fuse with nascent myotubes and thus form muscles, they must apparently migrate and chew up extracellular matrix (ECM), according to Jansen and Pavlath (page 403). These activities require expression of the mannose receptor (MR) in differentiating myoblasts.

The pathway is induced when nascent myotubes secrete IL-4, which induced expression of the MR in myoblasts. Although MR-null myoblasts fused normally with other myoblasts, they were retarded in their ability to fuse with nascent myotubes, which is the second stage of myotube formation.

MR expression appears to be required in vivo as well as in vitro for normal myotube formation, as the myofibers in MR-null mice were smaller than those in wild-type animals.

The researchers found that MR-null myoblasts migrated more slowly than wild-type cells in response to chemotactic stimuli. Moreover,...

The Rockefeller University Press
2006
The Rockefeller University Press
2006
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