Fig. 1.

Schematic representation of the stages of vertebrate myoblast fusion. Membrane apposition requires cell adhesion and remodeling of the actin cytoskeleton, which is controlled in part by signaling via phosphatidylserine (PS) receptors and BAI3. Myomaker and Minion/Myomerger are proposed to act at later stages, through control of membrane remodeling events that together define fusion competence, drive fusion pore formation, and support pore expansion. Myomaker and Minion/Myomerger also define potential asymmetry in the fusion process and could require an interaction between the two proteins for fusion. The black arrows indicate pathways supported by experimental evidence, whereas red arrows depict proposed functions