ATAC-seq library was prepared as described in a previous report (Buenrostro et al., 2013). NKX2-1GFP/w ESCs and 72 day old organoids (8 hMGEOs and 8 hCOs from individual culture wells) were dissociated into single cells. 50,000 cells from each group were lysed by cold lysis buffer (10mM Tris-HCl, pH7.4, 10mM NaCl, 3mM MgCl2, 0.1% IGEPAL CA-630). After spinning at 500g for 5min, the pellet was used for transposition reaction by Nextera® DNA Library Prep Kit. Following purification by Qiagen EinElute kit, ATAC-seq library was constructed and amplified by NEB High Fidelity 2xPCR master mix. Finally, the library was purified by AxyPrepTM Mag PCR Clean-up kit.
