Moleskin is essential for the formation of the myotendinous junction in Drosophila

► Moleskin protein localizes to muscle-tendon attachment sites in Drosophila. ► Msk mutants are defective in somatic muscle-tendon attachment. ► Stripe, activated MAPK, and pFAK are abnormal in msk mutants. ► Msk signals non-autonomously to the tendon cells.