Esrrb down-regulation is a later event in the ES-Epiblast transition. Real-time PCR analysis of mouse embryonic stem (ES) cells treated for 12 and 48 hr with a pharmacological inhibitor against JAK to inhibit LIF/JAK/STAT3 signaling, which induces a partial transition to the epiblast state. Note that the known LIF/STAT3 target genes Socs3 and Klf4 are rapidly down-regulated at 12 hr. At this timepoint, Esrrb expression is almost unaffected. As suggested by the model, however, Esrrb inlines down-regulation at 48 hr, whilst Oct4 expression is stable (the FGF/MEK/ERK-inhibitor PD (PD0325901) was applied in all experiments).