Figure 7. Model for planarian wound-response and initiation of regeneration.

(A) Planarians regenerate from almost any injury through a single transcriptional response. (B) Transcriptional changes following the wound response are divided into three cellular components. (C) A temporal model of planarian regeneration. Every injury triggers a prototypical generic response (red box; red line). If regeneration is not required following the injury, the response will decline. Otherwise, the expression of an injury-specific response emerges (yellow box; yellow line). These responses involve patterning molecules and neoblast-associated fate specialization genes. About three days following the injury, expression of differentiated tissue markers appears in association with the emergence of the newly regenerated structures (green box; green line).