Figure 5.
Model summarizing the presented data. iPSCs derived from different somatic cell types retain a transient epigenetic and transcriptional memory of their cell type of origin at early passage, despite acquiring pluripotent gene expression, transgene-independent growth and the ability to contribute to tissues in chimeras. Continuous passaging resolves these differences, giving rise to iPSCs that are molecularly and functionally indistinguishable. Note the difference between early passage iPSCs and partially reprogrammed cells, which require continuous viral transgene expression and fail to activate endogenous pluripotency genes or support the development of viable mice.