Abstract
Since mouse embryonic stem (ES) cells was first derived in 1981, the ability of this unprecedented cell type to selfβrenew and differentiate without limit has revolutionized the discovery tools that are used to study gene functions and development. Furthermore, they have inspired others to hunt for similar cells from other species. The derivation of human ES cells in 1998 has accelerated these discoveries and has also widely provoked public interest, due to both the scientific significance of these cells for human tissue regeneration and the ethical disputes over the use of donated early human embryos. However, this is no longer a barrier, with the recent discovery of methods that can convert differentiated somatic cells into ESβlike cells or induced pluripotent stem (iPS) cells, by using defined reprogramming factors. This review attempts to summarize the progresses in the derivation of ES cells (as well as other embryoβderived pluripotent cells) and iPS cells from various species. We will focus on the molecular and biological features of the cells, as well as the different determinants identified thus far to sustain their pluripotency. J. Cell. Biochem. 109: 16β25, 2010. Β© 2009 WileyβLiss, Inc.