Approximately 50,000 nuclei were resuspended in 20µL ice-cold Tagmentation Buffer, and incubated with 1µL Tagmentation enzyme (Illumina, #FC-121-1030) at 37 °C for 30 min with shaking 500 rpm. The tagmentated DNA was purified using MinElute PCR purification kit (Qiagen, #28004). libraries were amplified using NEBNext High-Fidelity 2X PCR Master Mix (NEB, #M0541) with primer extension at 72°C for 5 min, denaturation at 98°C for 30s, followed by 8 cycles of denaturation at 98°C for 10s, annealing at 63°C for 30s and extension at 72°C for 60s. Amplified libraries were then purified using MinElute PCR purification kit (Qiagen, #28004), and two size selection steps were performed using SPRIselect bead (Beckman Coulter, #B23317) at 0.55X and 1.5X bead-to-sample volume rations, respectively. Each library was then sequenced on an Illumina NextSeq500 or HiSeq4000 to a depth of >= 20 million usable reads pairs