Cells were collected in Gentle Cell Disociation Reagent (StemCell Technologies) and resuspended in cold PBS to 1e6 cells /ml Cells were subjected to the ATACseq protocol as described by Buenrostro, et al. 2015, with the following parameters (Buenrostro et al., 2015). Buffer: CSK buffer (10 mM PIPES pH 6.8, 100 mM NaCl, 300 mM sucrose, 3 mM MgCl2, 0.1% Triton X-100). Transposase volume/25 µl cell suspension: 5 µl.