library_construction_protocol: Cell storage reagent, CELLBANKER plus 1. Fragmentation and amplification of ATAC-seq libraries were conducted according to Buenrostro et al.(2015). Briefly, approximately 50,000 cells were lysed and transposition reaction was performed with the Tn5 Transposase (Illumina Catalog #FC121-1030) at 37°C for 30 minutes. The reaction liquid was purified with Qiagen MinElute PCR Purification Kit. Then 5 cycles of PCR with custom Nextera PCR primers (from Wu and Buenrostro 2013) were conducted using NEBNext Q5 Hot Start HiFi PCR Master Mix (New England Biolabs). Additional number of PCR cycles was determined by qPCR of the partly amplified products, following Wu and Buenrostro 2013. The PCR products were purified with Agencourt AMPure XP beads (Beckman Coulter:A63881), using double size selection (left ratio: 1.4x, right ratio: 0.5x) according to the manufacturer's protocol.