Phosphatidylserine directly and positively regulates fusion of myoblasts into myotubes

► PS broadly and persistently trans-locates to the outer leaflet of plasma membrane during myoblast fusion into myotubes. ► Robust myotubes are formed when PS liposomes are added exogenously. ► PS increases the width of de novo myotubes and the numbers of myonuclei, but not the myotube length. ► Annexin V or PS antibody inhibits myotube formation by masking exposed PS.