Libraries (single end reads) were prepared according to the manufacturers description Cells were isolated in PBS supplemented with 10% Fetal Calf Serum. Samples were further made single cell by collagenase treatment and applying a cell-strainer cap (BD Biosciences). Chromatin was crosslinked in the presence of 2% formaldehyde. Nuclei were sonicated to generate fragments with average length around 300 bp. Immuno-precipitated DNA was prepared using the TruSeq ChIP Sample Preparation Kit (Illumina)