Lived DN2 cells were selected on day10. Cells were cultured as control without OP9-DL1 n aMEM 20% FBS, IL7, FLT3-L, with 10 ug/ml of actinomycin-d . Cells were harvested at 15 min, immediately spun down, and resuspended in PBS. Cells were fixed with 1% formaldehyde. Formaldehyde was quenched with 0.2 M glycine for 10 min. 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).