Planarian stem cells sense the identity of the missing pharynx to launch its targeted regeneration

In order to regenerate tissues successfully, stem cells must detect injuries and restore missing cell types through largely unknown mechanisms. Planarian flatworms have an extensive population responsible for regenerating any organ after amputation. Here, we compare planarian responses different by either amputation of a single organ, the pharynx, or removal from other organs decapitation. We find that adopt distinct behaviors depending on what tissue is target progenitor production towards tissues. Loss non-pharyngeal only increases progenitors, while pharynx selectively triggers division expansion progenitors. By pharmacologically inhibiting mitosis activation MAP kinase ERK, identify narrow window time during which ERK signaling produces progenitors necessary regeneration. These results indicate can tailor their output match regenerative needs animal.