Fig. 7.

Model of TCF7L1 role in hESC and epiblast pluripotency and differentiation. Epiblast cells (blue) in vivo – which can be thought of as synonymous with hESCs in vitro – remain in an undifferentiated state until necessary inductive signals are received. In the undifferentiated state, TCF7L1 represses genes involved in PS differentiation (blue-orange gradient). At the onset of gastrulation, BMP4 signaling triggers downregulation of TCF7L1, thereby relieving repression of PS gene targets. Whether the effect of BMP4 on TCF7L1 is direct or indirect remains to be determined.