Identification of the MLL-EDC4 fusion and accompanying mutations. (A) In-frame fusion of MLL exon 13 (red bar) to EDC4 exon 6 (green bar) linked by 19 nucleotides from EDC4 intron 5, resulting in the predicted amino acid sequence ALNTLLR inserted between MLL p.K1565 and EDC4 p.E215. (B) Gel electrophoresis of the polymerase chain reaction on reverse-transcribed MLL-EDC4 mRNA at the indicated time points. (C) Patient-derived xenograft model of the MLL-EDC4⁺ AML. Survival of NOG mice after injection of primary patient blasts (P1) collected at t2 and after serial transplantation (P2-P6). (D) VAFs (derived from exome sequencing) of the mutations in STAG2 (NM_006603: c.463-1G>C), NRAS (p.G12C), KRAS (p.G13D), and FLT3 (p.D835V) at t1, t2, and t3, displaying the presence of the NRAS and KRAS mutations before the start of decitabine and the increase of the FLT3-mutated clone toward t3. FISH, fluorescence in situ hybridization; NTC, no template control; P, passage; pos., positive; VAF, variant allele frequency.