library_construction_protocol: Tissues were crosslinked with 1% formaldehyde solution for 2 x 10 min. After quenching, samples were shock-frozen, ground and chromatin was subsequently extracted. Chromatin was sonicated with a Diagenode Bioruptor. Libraries were prepared as follows. End repair (5 μl of End Repair Reaction Buffer + 2.5 μl of End Repair Enzyme Mix from the NEBNext End Repair Module (New England Biolabs)), A-tailing (2.5 µl NEBnext dA-Tailing Reaction Buffer + 1.5 µl Klenow Fragment (3'->5' exo-) (New England Biolabs)), adapter ligation (1 µl TruSeq DNA Unique Dual Indexes (UDIs) v2 (Illumina), 2.5 µl T4 DNA Ligase Reaction Buffer + 1.25 µl T4 DNA Ligase (New England Biolabs)), and PCR enrichment (12.5 µl NEBNext High-Fidelity 2X PCR Master Mix (New England Biolabs).