The conclusion from this section is that there is a strong correlation between the more differentiated state of a cell and its resistance to reprogramming. Resistance is also seen when comparing the activation of quiescent genes in different cell types. We propose that this resistance to reprogramming reflects the stability of the differentiated state, and is the result of the progressive acquisition of epigenetic restrictions during embryonic development. We now review the epigenetic mechanisms that could account for this resistance and stability. Table 1 lists factors known to promote or restrict nuclear reprogramming.
