Muscle Cells Provide Instructions for Planarian Regeneration

Regeneration requires both potential and instructions for tissue replacement. In planarians, pluripotent stem cells have the potential to produce all new tissue. The identities of the cells that provide regeneration instructions are unknown. Here, we report that position control genes (PCGs) that control regeneration and tissue turnover are expressed in a subepidermal layer of nonneoblast cells. These subepidermal cells coexpress many PCGs. We propose that these subepidermal cells provide a system of body coordinates and positional information for regeneration, and identify them to be muscle cells of the planarian body wall. Almost all planarian muscle cells express PCGs, suggesting a dual function: contraction and control of patterning. PCG expression is dynamic in muscle cells after injury, even in the absence of neoblasts, suggesting that muscle is instructive for regeneration. We conclude that planarian regeneration involves two highly flexible systems: pluripotent neoblasts that can generate any new cell type and muscle cells that provide positional instructions for the regeneration of any body region. [Display omitted] •Planarian position control genes (PCGs) are expressed together•PCG expression occurs in planarian muscle•PCG expression is dynamic in muscle following injury•PCG expression in regeneration influences neoblast specialization Regeneration requires potential and instructions for cell production. Planarians regenerate all body parts, with neoblasts producing new cells. Position control genes (PCGs) provide regeneration and tissue-turnover instructions. Reddien and colleagues demonstrate that PCGs are expressed together in subepidermal, nonneoblast cells. These cells are body-wall muscle cells that express different PCGs across body axes. Muscle PCG expression is dynamic following injury and impacts regeneration. These findings suggest that planarian regeneration involves two flexible systems: neoblasts for cell production and muscle cells for instructions regarding position.