Fig. 5. PBX complexes remodel the chromatin environment for LEF1 recruitment.

a Representative immunofluorescence staining for LEF1 (green) and SOX2 (magenta) on sagittal sections of E8.5 mouse embryos, revealing specific localisation of LEF1 in PSM and posterior somites of control and Pbx-DKO embryos. LEF1 expression is bloated in the tailbud of Pbx-DKO (white arrowhead). DAPI was counterstained in grey. Scale bars: 100 µm. b Heatmap of LEF1 ChIP-seq signals of WT (black) and Pbx-DKO cells (yellow) reveals PBX crucial role in LEF1 recruitment, as demonstrated by the extensive drop of LEF1 occupancy in Pbx-DKO cells along differentiation. c Left: overlap of genes bound by PBX1 (light blue), PBX2 (grey) and LEF1 (brown). A representative subset of target genes co-bound by PBX and LEF1 is reported in the lower box. Right: heatmap of tag densities of LEF1, PBX1 and PBX2 ChIP-seq peaks at the co-bound regions identified at 24 h of differentiation. In b and c, the scale represents normalised counts (RPKM) for ChIP-seq peak signals ±1 kb around the centre of the peak. d GO-term enrichment analysis of genes bound by PBX and LEF1 displays significant overrepresentation of terms associated with WNT signalling and somite development (Binomial test with Bonferroni correction). e RNA-seq, ChIP-seq and ATAC-seq coverage tracks for PBX-LEF1-activated (Msgn1, Aldh1a2) and repressed (Sox2, Cdx2) target genes. Threshold of vertical viewing range of data based on RPKM values is noted. Conservation across vertebrates is indicated in green.