Chromatin immunoprecipitation was performed with 100 µl of fragmented chromatin, protein G magnetic beads, and 5 µg of anti-TCF21 antibody ChIP Grade (ab32981, Abcam, Cambridge, UK) using the ChIP-IT Express kit (Active Motif, Carlsbad, CA, USA) following the manufacturer's instructions. Chromatin was fragmented by sonication with 6 pulses of 10 sec each at 25% amplitude using a VCX130PB ultrasonic processor (Sonics & Materials, Newtown, Connecticut, USA). Libraries were prepared using the TruSeq® ChIP Sample Preparation kit (Illumina, San Diego, CA, USA), starting with 7 ng of enriched ChIP DNA and selecting 250 bp fragments on average.