library_construction_protocol: Cryopreserved cells were thawed and lysed using the cold lysis buffer following ATAC-seq protocol. Nuclei were collected and resuspended in the transposase reaction mix for transposition reaction, the transposed fragments were immediately purified using a Qiagen MinElute PCR Purification kit (Qiagen). The purified fragments were amplificated 10 cycles on a thermocycler. Libraries were purified using Agencourt AMPure XP beads (Beckman Coulter) following the Manufacturer's instructions. Library quality was examined using Agilent High sensitivity DNA assay (Agilent) and Qubit dsDNA High sensitivity assay kit (ThermoFisher).