Cowan et al., in an elegant study published in Science, showed that human embryonic stem cells (ESCs) could be used to reprogram adult somatic cell nuclei. This result had added one more possibility to the methods of alternate derivation of ESC-like cells (Fig. 1) previously described.
Figure 1. Deriving ESCs from Fusion
The method described by Cowan et al. to generate ESC-like cells—fusion of a fibroblast and an ESC—represents one of several alternate methods for generating embryonic stem cells. Other methods include the use of somatic cell nuclear transfer, nonviable blastocysts, persistent pluripotent cells and transdifferentiation. [Image courtesy of Mahendra Rao]
The cells themselves are tetraploid and contain genomic information from both donor and recipient, and currently it is unclear how one could separate such genomic information. The present result also does not describe in detail how complete the activation of the ES cell program was and whether the somatic program...