Fusion with the Fused: A New Role for Interleukin-4 in the Building of Muscle

In this issue of Cell, G. Pavlath and coworkers demonstrate a novel role for Interleukin-4 (IL-4) in regulating the fusion of myoblasts with differentiated myotubes. The authors demonstrate that NFATc2 signaling in newly formed myotubes induces IL-4 expression and secretion which promotes myoblast fusion with pre-existing myotubes.