The NUP98-NSD1 cells were generated according to the method described before10 (link). The cDNA encoding NUP98-NSD1 cDNA in MSCV-Neo vector was a kind gift from Dr. Ani Deshpande, Sanford Burnham, Medical Discovery Institute9 (link). Briefly, the 5 ×105 enriched Lin− bone marrow progenitors from Balb/c mice were infected with retroviral supernatant from platE cells transfected with NUP98-NSD1(MSCV-neo) plasmids by two rounds spinoculation, followed by 7 days of G418 selection (1 mg/mL). The NUP98-NSD1 cells are cultured in IMDM media supplemented with 15% FBS, P/S and recombinant murine SCF (50ng/mL, R&D System) and IL3 (10 ng/mL, R&D System). Cells from a single colony were expanded and used in the experiments. MOZ-TIF2 and HM-2 (transformed with Hoxa9/Meis1) cells were generated as described previously27 (link),40 (link). All animal experiments in this study were approved by the University of Michigan Committee on Use and Care of Animals and Unit for Laboratory Animal Medicine (ULAM).