Characteristics of identified putative distal regulatory elements. (A) Heat maps showing the distribution of H3K4me1/me3 and H3K27ac tags −5kb/+5kb relative to the PDRE center at four developmental stages. (B) The number of PDREs identified at dome (blastula) stage is considerably lower than the number of PDREs identified at 80% epiboly or 24/48 hpf, in line with reduced tissue complexity of blastula embryos. (C) Box plots showing the distribution of PDRE length at four examined developmental stages. The PDREs identified at dome stage are considerably larger than the ones identified at subsequent stages, possibly due to a more relaxed chromatin conformation present during early embryogenesis. (D) Conservation of identified PDREs as judged by genomic overlaps with regions conserved to teleosts (sticklebacks) and humans. Approximately 40% and 20% of PDREs overlap with regions conserved in sticklebacks and humans, respectively. (E) The identified PDREs are significantly enriched (Kolmogorov-Smirnov test, P-value < 0.00001) for developmental genes, indicative of a role these sequences might play in early development.
