More detailed immunophenotyping showed that the majority of CRISPRMLL-AF4+ cells were CD34−CD19+CD10+IgM/IgD− preB cells, of which ~10% aberrantly expressed the leukemia-associated marker CD133 (Fig. 2c, d), a direct gene target of the MLL-AF4 fusion protein33. Here, AFF1 is linked to leukemia.