p53 as a barrier to pluripotency

Induced pluripotent stem (iPS) cells are generated from mouse and human somatic cells by introduction of four genes. Efficiency of this process, however, is low. Here it is reported that up to 10% of transduced mouse embryonic fibroblasts (MEF) lacking p53 became iPS cells, even without the Myc retrovirus. In the p53-null background, iPS cells can be generated from terminally differentiated T lymphocytes. The authors propose that the p53–p21 pathway serves as a barrier not only in tumorigenicity, but also in iPS cell generation.