Fig 1.

Intestinal remodeling during Xenopus laevis metamorphosis as a model to study adult organ-specific stem cell development in vertebrates. In premetamorphic tadpoles at stage 51, the intestine has only a single fold, the typhlosole, and is structurally similar to the mammalian embryonic intestine. At the metamorphic climax around stage 61, the larval epithelial cells begin to undergo apoptosis, as indicated by the open circles. Concurrently, the proliferating adult progenitor/stem cells are developed de novo from larval epithelial cells through dedifferentiation, as indicated by black dots. By the end of metamorphosis at stage 66, the newly differentiated adult epithelial cells form a multiply folded epithelium, similar to mammalian adult intestines.