75000 cells were resuspended in 50 μl of cold lysis buffer (10 mM Tris-HCl, pH 7.4, 10 mM NaCl, 3 mM MgCl2, 0.1% (v/v) Igepal CA-630) for nuclei preparation and treated with Nextera Tn5 Transposase (Nextera DNA Library Preparation Kit, Illumina) at 37°C for 30 min. DNA was purified using MinElute PCR Purification Kit (Qiagen). ATAC libraries were prepared using NEBNext High-Fidelity 2x PCR Master Mix (NEB) following manufacturer's instructions for 11 cycles. Amplified libraries were purified using PureLink PCR Purification Kit (Thermo Fisher Scientific).