50,000 viable cells were pelleted at 500 RCF at 4°C for 5 min in a fixed angle centrifuge ATAC-seq was performed using the Omni-ATAC protocol as described before (Corces et al., 2017; Song et al., 2018a). Libraries were pooled in equimolar amounts for single-end sequencing on an Illumina HiSeq 4000 instrument