AC220 effectively ameliorated FLT3-ITD, but not FLT3-TKD–induced, myeloid expansion. The human D835Y TKD mutation (FLT3-TKD) was generated based on the vector containing the human FLT3-WT sequence by a site-directed mutagenesis. The vectors containing the FLT3-ITD-T2a-egfp and FLT3-TKD-T2a-egfp were microinjected into 1-cell–stage embryos. Embryos were treated with DMSO control or AC220 (2.5 μmol/L) from 6 hpf to 36 hpf. (A-F) WISH showing the expression of pu.1 (A-B), mpo (C-D), and cebpα (E-F) in the uninjected embryos treated with DMSO and AC220 from 6 to 36 hpf, respectively. (G-L) WISH showing the expression of pu.1 (G-H), mpo (I-J), and cebpα (K-L) in the FLT3-ITD embryos treated with DMSO and AC220 from 6 to 36 hpf. (M-R) WISH showing pu.1 (M-N), mpo (O-P), and cebpα (Q-R) expression in the FLT3-TKD embryos treated with DMSO and AC220 treatment from 6 to 36 hpf. (S-U) Percentage of FLT3-ITD, FLT3-TKD embryos showing the myeloid-committed cell expansion as shown by pu.1 (S), mpo (T), and cebpα (U) expansion after DMSO or AC220 treatment from 6 to 36 hpf. AC220 significantly ameliorated the expansion of myeloid expression based on pu.1, mpo, and cebpα expression (P < .01) in FLT3-ITD but not FLT3-TKD embryos (P > .05). Scale bars represent 500 μm.