Selective amputation of the pharynx identifies a FoxA-dependent regeneration program in planaria

Planarian flatworms can regenerate every organ after amputation. Adult pluripotent stem cells drive the ability to regenerate, but how injury activates these cells and directs them into the appropriate lineages is not understood. To study the regeneration response in a simplified context, we selectively induced the ejection of the planarian pharynx by briefly exposing animals to sodium azide followed by microarray analysis. Tissue surrounding the wound site was examined at 6, 12, 18, 24, 48, and 72 hours post amputation by comparison to tissue isolated immediately after amputation (time zero). Stem cells are required for the regeneration process, and can be eradicated by exposure to radiation. A parallel time course was also performed on worms that had been irradiated with 10k rads of gamma irradiation. Two time courses consisting of irradiated or unirradiated worms following chemical amputation of the pharynx. Tissue samples taken at 6, 12, 18, 24, 48 and 72 hours are each compared to a reference sample at time zero. The experiment was performed in triplicate for a total of 42 samples on 36 arrays.