ATAC-seq library was prepared using Nextera DNA Library Prep Kit (Illumina). Briefly, 100,000 cells were resuspended in 50µl of cold lysis buffer (10mM Tris·Cl pH 7.4, 10mM NaCl, 3mM MgCl2, 0.1% (v/v) Igepal CA-630) and incubated on ice for 15 min. Immediately after lysis, nuclei were collected and re-suspended in the transposase reaction mix (25 μL 2× TD buffer, 2.5 μL transposase (TDE1) and 22.5 μL nuclease-free water). The transposition reaction was carried out for 30 minutes at 37 °C and immediately put on ice. Then the sample was purified using MinElute PCR Purification Kit (Qiagen). Following purification, the library was amplified using indexed Nextera PCR primers and NEBNext High-Fidelity 2× PCR Master Mix. Finally the library was purified using MinElute PCR Purification Kit. Libraries were prepared via the Nextera® DNA Sample Preparation library preparation protocol according to manufacturer's instructions