HBE is required to activate ASE during ESC to EpiSC differentiation.

<p>(A) RT-qPCR analysis of <i>YFP</i> expression during 10 d of ESC to EpiSC differentiation of <i>Nodal</i>^condHBE-YFP(HBE+) and <i>Nodal</i>^ΔHBE-YFP(HBE−) ESCs. One representative experiment. (B) Percentage of difference of <i>YFP</i> mRNA levels between <i>Nodal</i>^ΔHBE-YFP and <i>Nodal</i>^condHBE-YFP cells during 10 d of ESC to EpiSC differentiation. Error bars represent the mean + SD of triplicates and two independent experiments. (C–D″) Expression of Oct4 (C, D) and Venus-YFP (C′, D′) in <i>Nodal</i>^condHBE-YFP (C–C″) and <i>Nodal</i>^ΔHBE-YFP (D–D″) ESCs after 10 d of differentiation into EpiSC single confocal sections. <i>n</i> is the number of YFP-positive (C) or YFP-negative (D) samples on the total number of analyzed samples. Scale bar, 25 µm. (E) Part of the <i>Nodal</i> locus in the WT and the recombinant alleles comprising HBE, the first <i>Nodal</i> exon, and ASE and showing the position of regions 1–5 amplified in the ChIP experiments shown in (F) and (G). (F–G) ChIP with anti-H3K27me3 (F), anti-H3K27ac (G), or anti-GFP (F–G) antibodies on material from <i>Nodal</i>^condHBE-YFP ESCs (green bars) and <i>Nodal</i>^ΔHBE-YFP ESCs (red bars). The position in the locus of amplified regions 1–5 is shown in (E). An asterisk denotes significant differences between <i>Nodal</i>^condHBE-YFP and <i>Nodal</i>^ΔHBE-YFP ESCs (<i>p</i><0.01).