Harvested cells were stained with lineage marker, CD25, CD117, ghost dye red 780. Cells were fixed with PBS containing 1% formaldehyde. Formaldehyde was quenched with 0.2 M glycine for 10 min. Lineage negative DN2 cells were sorted by FACS AriaII and washed with PBS. Fixed cells were stored at -80 degrees until use. Libraries were prepared with NEBNext primer set. Fragment size was selected with AMPure beads (Beckman Coulter).