Fig. 5

Elk1/3/4 is a putative feedback regulator of MAPK signaling. A Log2 fold-change of the expression level of the top 50 most variably expressed transcription factors in U0126 sensitive cell type clusters compared to their U0126 insensitive sibling cell type clusters. B, C Expression of Elk1/3/4 (purple colorscale) in DMSO (B) and U0126 (C) treated embryos. UMAP space is identical to Fig. 1G. D Scatter plot of sequence length and number of predicted Ets sites for all ATACseq predicted open chromatin regions. The ATACseq peak for Elk1/3/4 is highlighted in red. E Putative Elk1/3/4 sites in the 1500 bp upstream of the Elk1/3/4 transcription start site. The orange tracks show ATACseq open chromatin profiling at multiple stages from [63]. F Ets TFBS and Elk1/3/4 expression enrichment in sibling cell types distinguishes between bifurcations controlled directly versus indirectly by MAPK/ETS signaling. Ets TFBS by sibs—Ets TFBS enrichment score comparing the genes upregulated in the first sibling cluster compared to the genes upregulated in the second sibling cluster. Ets TFBS by enriched—Ets TFBS enrichment score comparing the genes upregulated versus downregulated in that particular cluster. Elk1/3/4 enrichment—Log2 fold-change in Elk1/3/4 expression in sibling cluster 1 compared to sibling cluster 2. FGF-dependent score—negative-log10(p value) of the chi-square test for association between sibling cluster numbers and treatment status, hatched boxes could not be measured due to loss of a precursor cell type. The negative log transformation makes the FGF dependency score viewable using the same color map as the other columns, but it was not included in the clustering. Expectation notes—expectation for signal dependency in each bifurcation based on the literature cited