| The POU family transcription factor, Oct-4, has demonstrated an association with the undifferentiated cell phenotype in the developing embryo and in cultured embryonic stem cells (ESCs). In these cells, Oct-4 functions as a transcriptional regulator, activating expression of target genes that correlate with the pluripotent state and repressing transcription of those associated with differentiation along a specific lineage pathway. A number of groups have shown that pluripotent embryonic cells are able to induce Oct-4 expression in somatic cell nuclei, either through somatic cell nuclear transfer or fusion. Activation of Oct-4 results in a reversion of the somatic cells to a more developmentally potent state. Additionally, several recent studies suggest that ESCs produce factors that act in an autocrine or paracrine manner to help them sustain expression of Oct-4. I hypothesized that Oct-4 could be used to reprogram somatic mouse skin keratinocytes to become more developmentally potent in vitro. The work presented here demonstrates that Oct-4 can be used to increase the development potential of mouse skin keratinocytes in vitro. Specifically, expression of Oct-4 in keratinocytes is sufficient to induce expression of pluripotency-associated target genes, as well as to confer the ability to respond to neuronal differentiation factors. Furthermore, I demonstrate that ESCs in coculture with mouse skin keratinocytes are able to reprogram the keratinocytes to a de-differentiated state by secreting bone morphogenetic factor-4 (BMP4), (presumably along with other factors), which then activates keratinocyte Oct-4 expression. The resultant reprogramming of the keratinocytes to a less-differentiated state results in an increase in the keratinocyte potential and enables their re-differentiation in response to neuronal culture conditions. Together these data demonstrate the ability of Oct-4 to revert a differentiated cell to a less-differentiated, more ESC-like, state. Because the skin is the largest organ in the body and is easily accessible, it is a particularly viable candidate for derivation of reprogrammable cells. Therefore, the work presented here could have vast implications for the use of somatic cells, specifically skin keratinocytes, in cell-based disease therapies. |
