ATAC-seq: Eight ATAC libraries were prepared: iPSCs, TSCs, MEFs, and MEFS at three days of reprogramming by OSKM, GETM, GTMS or GETMS. ATAC-seq: Library preparation was performed as previously described (Buenrostro et al., 2016). Libraries were subjected to paired-end sequencing using Illumina Next-Seq 500 platform.