Frozen primagrafts were mechanically dissociated, formaldehyde cross-linked, and collected. ChIP was performed with 10 antibodies against c-myb (Bethyl, A304-136A), RAR (Santa Cruz, sc-773X), and H3K27ac (Abcam, ab4729). DNA was then de-cross-linked from pulled down proteins and purified by phenol:chloroform:isoamyl alcohol extraction. The NEBNext multiplex oligos for Illumina Kit (NEB) was used to make the samples suitable for multiplexing. The PCR reaction was run for 18 cycles. The indexed libraries were purified for 150 and 350 bp. The concentration of the isolated libraries was estimated with a high-sensitivity DNA chip from Agilent according to manufacturer’s protocol and libraries were mixed in equal quantities and sequenced on Illumina Hi-Seq2500. Index sequences from multiplexed primers were used to identify treatment group and reads were demultiplexed using a perl script.