EMT and MET as paradigms for cell fate switching.

Cell fate determination is a major unsolved problem in cell and developmental biology. The discovery of reprogramming by pluripotent factors offers a rational system to investigate the molecular mechanisms associated with cell fate decisions. The idea that reprogramming of fibroblasts starts with a mesenchymal-epithelial transition (MET) suggests that the process is perhaps a reversal of epithelial to mesenchymal transition (EMT) found frequently during early embryogenesis. As such, we believe that investigations into MET-EMT may yield detailed molecular insights into cell fate decisions, not only for the switching between epithelial and mesenchymal cells, but also other cell types.