Stem Cell Pluripotency: A Cellular Trait That Depends on Transcription Factors, Chromatin State and a Checkpoint Deficient Cell Cycle

Embryonic stem (ES) and induced pluripotent stem (iPS) cells self-renew and are pluripotent. Differentiation of these cells can yield over 200 somatic cell types, making pluripotent cells an obvious source for regenerative medicine. Before the potential of these cells can be maximally harnessed for clinical applications, it will be necessary to understand the processes that maintain pluripotentiality and signal differentiation. Currently, three unique molecular properties distinguish pluripotent stem cells from somatic cells. These include a unique transcriptional hierarchy that sustains the pluripotent state during the process of self-renewal; a poised epigenetic state that maintains chromatin in a form ready for rapid cell fate decisions; and a cell cycle characterized by an extremely short gap I (G 1) phase and the near absence of normal somatic cell checkpoint controls. Recently, B-MYB (MYBL2) was implicated in the gene regulation of two pluripotency factors and normal cell cycle progression. In this article, the three pluripotency properties and the potential role of B-Myb to regulate these processes will be discussed. J. Cell. Physiol. 221: 10-17, 2009. (C) 2009 Wiley-Liss, Inc.