Nuclei from formaldehyde crosslinked (1%; 10min at room temperature) embryos were isolated and chromatin was fragmented using sonicator (Branson). Lysates were cleared and protein-DNA complexes were isolated using target specific antibodies and Dynabeads. DNA fragments were purified and libraries were prepared by NEBnext DNA Library Prep Kit (NEB, E7370L). Adapter ligated DNA was purified using AMPure XP beads (Beckman Coulter, A63881) and sequenced by illumina HiSeq 2500. NEBnext DNA Library Prep Kit