Low-cell-number ChIP-seq followed the method described by Brind'Amour et al. We used approximately 1.5 × 10e4 cells per ChIP with 1 ng antibodies of H3K4me3 (Abcam, ab8580), H3K27me3 (Millipore, 07-449), H3K4me1 (Millipore, 07-436), H3K27ac (Active motif, 39133), respectively. Library preparation was conducted with “Ultra DNA Library Prep Kit for Illumina” (NEB. E7370).