Isolation, Culture, and Analysis of Zebrafish Myofibers and Associated Muscle Stem Cells to Explore Adult Skeletal Myogenesis.

Adult skeletal musculature experiences continuous physical stress, and hence requires maintenance and repair to ensure its continued efficient functioning. The population of resident muscle stem cells (MuSCs), termed satellite cells, resides beneath the basal lamina of adult myofibers, contributing to both muscle hypertrophy and regeneration. Upon exposure to activating stimuli, MuSCs proliferate to generate new myoblasts that differentiate and fuse to regenerate or grow myofibers. Moreover, many teleost fish undergo continuous growth throughout life, requiring continual nuclear recruitment from MuSCs to initiate and grow new fibers, a process that contrasts with the determinate growth observed in most amniotes. In this chapter, we describe a method for the isolation, culture, and immunolabeling of adult zebrafish myofibers that permits examination of both myofiber characteristics ex vivo and the MuSC myogenic program in vitro. Morphometric analysis of isolated myofibers is suitable to assess differences among slow and fast muscles or to investigate cellular features such as sarcomeres and neuromuscular junctions. Immunostaining for Pax7, a canonical stemness marker, identifies MuSCs on isolated myofibers for study. Furthermore, the plating of viable myofibers allows MuSC activation and expansion and downstream analysis of their proliferative and differentiative dynamics, thus providing a suitable, parallel alternative to amniote models for the study of vertebrate myogenesis.