Why can a transplanted salamander limb blastema still develop into a limb?

A transplanted salamander limb blastema can develop into a limb because its cells bear an "indelible stamp" of the specific appendage from which they were produced.1

During the process of regeneration, tissues at the site of an injury undergo dedifferentiation, losing their specialized characteristics to form a blastema—a mass of undifferentiated cells. Even when this blastema is transplanted to a different location on the animal's body, such as the back, the cells retain the developmental instructions required to form the original structure.21

These cells are programmed to develop into the tissues they were destined to become, following a specific sequence that produces parts normally located distal to the level of amputation. Because the blastema cells contain the necessary information to develop everything "downstream" of their origin, they maintain their identity and developmental trajectory regardless of their new position on the body.13