Figure 9. Steady State Values of TG Expression as a Function of the Input Concentration A ₊, for the Differentiation and Sel-Renewal Genes for the Case when NANOG Binds Weakly/Strongly to the OCT4 and SOX2 Genes.

(A) The effects of weak feedback of NANOG to the OCT4 and SOX2 genes. The inefficient binding of NANOG to these genes leads to a loss of the switch-like behavior.

(B) The consequence of weak NANOG binding on the TG expression. With weak feedback, the expression level does not fall off sharply as compared with the case with strong feedback, thereby demonstrating that strong feedback is essential to prevent the differentiation TGs from being expressed.