The
pluripotent state, which is first established in the primitive
ectoderm cells of
blastocysts, is lost progressively and irreversibly during subsequent development. For example, development of post-implantation
epiblast cells from primitive
ectoderm involves significant
transcriptional and
epigenetic changes, including
DNA methylation and
X chromosome inactivation, which create a robust
epigenetic barrier and prevent their reversion to a primitive-ectoderm-like state.
Epiblast cells are refractory to
leukaemia inhibitory factor (LIF)-
STAT3 signalling, but they respond to
activin/
basic fibroblast growth factor to form self-renewing
epiblast stem cells (EpiSCs), which exhibit essential properties of
epiblast cells and that differ from
embryonic stem (ES) cells derived from primitive
ectoderm. Here we show
reprogramming of advanced
epiblast cells from
embryonic day 5.5-7.5
mouse embryos with uniform expression of
N-cadherin and inactive
X chromosome to ES-cell-like cells (rESCs) in response to LIF-STAT3 signalling. Cultured
epiblast cells overcome the
epigenetic barrier progressively as they proceed with the erasure of key properties of
epiblast cells, resulting in
DNA demethylation, X reactivation and expression of
E-cadherin. The accompanying changes in the
transcriptome result in a loss of
phenotypic and
epigenetic memory of
epiblast cells. Using this approach, we report reversion of established EpiSCs to rESCs. Moreover, unlike
epiblast and EpiSCs, rESCs contribute to
somatic tissues and
germ cells in chimaeras. Further studies may reveal how signalling-induced
epigenetic reprogramming may promote reacquisition of
pluripotency.
