Asymmetric division of clonal muscle stem cells coordinates muscle regeneration in vivo

Skeletal muscle is an example of a tissue that deploys a self-renewing stem cell, the satellite cell, to effect regeneration. Recent in vitro studies have highlighted a role for asymmetric divisions in renewing rare immortal stem cells and generating a clonal population of differentiation competent myoblasts. This model currently lacks in vivo validation. Here we define a zebrafish muscle stem cell population analogous to the mammalian satellite cell and image the entire process of muscle regeneration from injury to fiber replacement in vivo. This analysis reveals complex interactions between satellite cells and both injured and uninjured fibers and provides in vivo evidence for asymmetric satellite cell division driving both self-renewal and regeneration via a clonally restricted progenitor pool.