E14 forestomachs were digested in 0.25% Trypsin EDTA at 37°C for 30 minutes followed by neutralization with FBS and Epcam + cells were sorted by flow cytometry. Cellswere immediately used for chromatin transposition. Whole nuclei were used for chromatin transposition using Nextera Tn5 Transposase (Illumina) The transposed DNA was amplified using NEBNext High-Fidelity 2X PCR Master Mix (New England Biolabs), and 75 bp single-end reads were sequenced on an Illumina NextSeq 500 instrument.