Fig. 6

a–c 3847 accessible regions bound by both Pou5f3 and SoxB1 (sp peaks) were used for analysis. For the heatmaps, the regions were sorted by descending SoxB1 Chip-seq signal. a Heatmaps show TF occupancy and motif density on sp peaks. b Chromatin accessibility on sp peaks is reduced in the single and double mutants at 4.3 hpf. c Chromatin accessibility change. Three top heatmaps: mutant to wild-type change. Two bottom heatmaps: double to single mutant change. Note the strongest chromatin accessibility reduction in the double mutant and the weakest in MZsox19b. d Chromatin accessibility changes at 4.3 hpf were compared between sp peaks without (−) or with (+) motifs indicated above (e, f). Scale-motif density. e Mutants to wild-type change. Sox19b binding to sox motifs and Pou5f3 binding to pou motifs promotes chromatin accessibility. On sox:pou motifs, binding of any factor has a significant effect, but Sox19b effects are weaker. f Double to single mutant change. Blue frame: on sox:pou and pou motifs, chromatin accessibility is similarly reduced in the double MZsox19bspg mutant compared to MZspg. Hence, the gain of chromatin accessibility on sox:pou and pou motifs results from Pou5f3 binding. On some of sox:pou motifs Sox19b may act by facilitating or stabilizing Pou5f3 binding. Red frame: on sox motifs, chromatin accessibility is stronger reduced in MZsox19bspg compared to MZsox19b, suggesting additive or redundant effects of Pou5f3. As shown at Fig. ^S7g, this effect is due to the sp peaks where both types of motifs (sox and sox:pou or sox and pou) are present. Hence, Pou5f3 and Sox19b may promote chromatin accessibility additively or redundantly when they bind to different motifs within the same AR. MZsox = MZsox19b. At e, f: The lower border, middle line and upper border of the white box plots correspond to 0.25, 0.5 (median), and 0.75 quantile, respectively. n(wt) = 3, n(MZspg) = 3, n(MZsox19b) = 3, n(double) = 4, where n is a number biologically independent ATAC-seq experiments. P-values in two-tailed Student’s t-test. Source data for b, c, e, and f are provided as a Dataset ^S3. Source data for a, d are provided as Dataset ^S4.