Genomic analysis of induced pluripotent stem (iPS) cells: routes to reprogramming

The phenomenal proliferation of scientific studies into the nature of induced pluripotent stem (iPS) cells following publication of the findings of Takahashi and Yamanaka little more than 2 years ago, have significantly expanded our understanding of cellular mechanisms relating to cell lineage, differentiation, and proliferation. While the full potential of iPS cell lineages for both scientific tool and therapeutic applications is as yet unclear, findings from several lines of investigation suggests that multipotential and terminally differentiated cells from an array of cell types are competent to undergo epigenetic reprogramming to a pluripotential state. The nature of this pluripotential state appears to be similar to, but not identical with that previously described for embryonic stem (ES) cells. Understanding the nature of this induced reprogrammed state will be critical to determining the full potential of iPS cells. Recently, this issue has been examined through an integrated analysis of the genome in fully and partially reprogrammed iPS cell lineages. These results provide a window onto the temporal components of reprogramming and suggest mechanisms by which the efficacy of reprogramming can be enhanced.