ESC populations were harvested and crosslinked in formaldehyde. Cell pellets (frozen, or fresh) were subjected to chromatin preparation and immunopreciptiation with an antibody against H3K27me3, followed by extraction of genomic DNA. DNA samples were quantified, and libraries were generated and amplified by PCR, followed by library size determination using a Agilent BioAnalyzer. Libraries were then pooled, quantified, and sequenced on an Illumina MiSeq to determine the amount required for deep sequencing. Pooled libraries were then diluted accordingly and loaded on an Illumina NovSeq6000 for sequencing.