Dedifferentiation and the role of sall4 in reprogramming and patterning during amphibian limb regeneration.

A central feature of epimorphic regeneration during amphibian limb regeneration is cellular dedifferentiation. Two questions are discussed. First, what is the origin and nature of the soluble factors involved in triggering local cellular and tissue dedifferentiation? Secondly, what role does the key stem cell transcription factor Sall4 play in reprogramming gene expression during dedifferentiation? The pattern of Sall4 expression during Xenopus hindlimb regeneration is consistent with the hypothesis that Sall4 plays a role in dedifferentiation (reprogramming) and in maintaining limb blastema cells in an undifferentiated state. Sall4 is involved in maintenance of ESC pluripotency, is a major repressor of differentiation, plays a major role in reprogramming differentiated cells into iPSCs, and is a component of the stemness regulatory circuit of pluripotent ESCs and iPSCs. These functions suggest Sall4 as an excellent candidate to regulate reprogramming events that produce and maintain dedifferentiated blastema cells required for epimorphic regeneration.