PTEN is a key regulator of cell proliferation, differentiation, and motility, and its dysregulation is associated with the occurrence of cancer. Here, Néstor Oviedo and colleagues show that PTEN is also necessary for the regenerative capacity of stem cells in the planarian flatworm Schmidtea mediterranea. Planarians are a tractable system for understanding tissue regeneration and stem cell function due to their unique ability to regenerate parts or even whole organisms from just a fraction of viable tissue. Two orthologs of the human PTEN gene are identified, Smed-PTEN-1 and Smed-PTEN-2, which are highly expressed in stem cells. Suppression of PTEN protein levels using RNAi, induced hyperproliferation of stem cells causing abnormal growths, significant morphological changes and eventually death. The authors propose that planarian PTEN recapitulates many functions of the human protein, and demonstrate a potential role for PTEN in tissue regeneration.
