Figure 1.

Cell fate changes on Waddington's epigenetic landscape. Pluripotent stem cells (top, yellow) can commit to various somatic lineages (bottom left, green) via a progenitor state (middle left, light blue) during embryonic development and in vitro differentiation. Direct reprogramming, or transdifferentiation, using tissue-specific transcription factors convert the fate of lineage-committed cells (bottom left, green) to another differentiated fate (bottom centre, pink), bypassing the need for a pluripotent state. There are several ways of reprogramming lineage-committed cells (bottom right, purple) toward pluripotency (top, yellow). Adapted, with permission, from Waddington [7]. (Online version in colour.)