Autophagy in Zebrafish Extraocular Muscle Regeneration

Zebrafish extraocular muscles regenerate after severe injury. Injured myocytes dedifferentiate to a mesenchymal progenitor state and reenter the cell cycle to proliferate, migrate, and redifferentiate into functional muscles. A dedifferentiation process that begins with a multinucleated syncytial myofiber filled with sarcomeres and ends with proliferating mononucleated myoblasts must include significant remodeling of the protein machinery and organelle content of the cell. It turns out that autophagy plays a key role early in this process, to degrade the sarcomeres as well as the excess nuclei of the syncytial multinucleated myofibers. Because of the robustness of the zebrafish reprogramming process, and its relative synchrony, it can serve as a useful in vivo model for studying the biology of autophagy. In this chapter, we describe the surgical muscle injury model as well as the experimental protocols for assessing and manipulating autophagy activation.