Fig. 1.

Mapping proximal Eomes enhancers active at gastrulation. (A) ChIP-seq of H3K4me1, H3K27me3 and H3K27ac, and DNaseI hypersensitivity (HS) in ESCs, epiblast-like cells (EpiLC) and mesoderm (MES) (Alexander et al., 2015; Buecker et al., 2014; ENCODE Project Consortium, 2012) identify potential proximal Eomes enhancers that are activated during differentiation. The PSE cluster and VPE regions are highlighted in grey. (B,C) X-gal-stained transgenic embryos expressing enhancer-driven LacZ reporters. (B) PSE reporter activity is confined to the primitive streak (PS) at early- (ES), mid- (MS) and late-streak (LS) stages of gastrulation (2/4 transgenic mouse lines). (C) VPE reporter activity detectable in the proximal posterior epiblast (Epi) at the pre-streak (PrS) stage and in the PS at the MS stage, becomes restricted to the anterior PS (APS) and is lost at LS stage. Between the PrS stage and the LS stage, VPE activity is also detectable in the anterior visceral endoderm (AVE) (2/6 transgenic mouse lines).