ATAC-seq Profiling of Sorted Cells

ATAC-seq was performed on 3000–5000 sorted cells similarly to that previously described^{48 (link),66 (link)}. Briefly, cells were pelleted at 500 × g for 10 min at 4 °C and resuspended in 50 μl nuclei lysis buffer (10 mM Tris pH 7.4, 10 mM NaCl, 3 mM MgCl₂, 0.1% IGEPAL) and centrifuged at 500 × g for 30 min at 4 °C. Nuclei were resuspended in 22.5 μl of tagmentation DNA buffer (Illumina) with 2.5 μl tagmentation enzyme (Illumina) at 37 °C for 60 min. DNA was isolated by proteinase K digestion (2 μg) at 40 °C for 30 min followed by negative (0.6×) and positive (1.2×) size selection with SPRI beads (Agencourt AMPure XP, Beckman Coulter). ATAC-seq libraries were amplified 12–13 times with Hifi Polymerase (Kapa Biosystems) and quantitated by qPCR (Kapa Biosystems) and high sensitivity bioanalyzer (Agilent) and sequenced using 50 bp paired-end sequencing on an Illumina HiSeq 2500 (Illumina) by NYU Genome Technology Center.