ATAC-seq was performed based on the omni-ATAC protocol. Briefly, for each sample 50 000 cells were lysed (10mM Tris pH 7.5, 10 mM NaCl, 3 mM MgCl2, 0.1% NP-40, 0.1% Tween, 0.01% Digitonin), and nuclei were tagmented with 3 ul of Ilumina Tn5 enzyme (Illumina, catalog # 15027865) in TD Buffer with 0.01% Tween and 0.01% Digitonin for 30 minutes at 37°C. DNA was purified using the Zymo DNA Clean and Concentrator and libraries were generated with 7 cycles of PCR with index primers described in the original Buenrostro et al. ATAC-seq protocol. Clean-up was performed with Ampure beads and quantification and quality control of libraries was performed using DNA Qubit and HS DNA Bioanalyser.