FLT3 N676K mutations identified in CBFB/MYH11-rearranged AML. (A) Exome data sets of a CBFB/MYH11-positive AML sample (upper panels) and the corresponding follow-up sample from the same patient (lower panels) are displayed using the integrative genomics viewer.24 Horizontal gray bars symbolize the 76-bp reads aligned to the reference sequence. The frequency of 24% of the mutant nucleotide T in the diagnostic leukemia sample indicates a heterozygous point mutation causing an amino acid substitution (NM_004119.2:c.2028C>A; p.N676K), whereas in the follow-up sample, only the wild-type nucleotide G is detected at this position. Read depth and base count are indicated for the affected positions, respectively. (B) Sanger sequencing confirmed the FLT3 N676K mutation found initially by exome sequencing. Chromatograms are shown for both the diagnostic AML sample and the corresponding follow-up sample at complete remission (CR) from the same patient. (C) The structure of the human FLT3 protein includes the transmembrane domain (TM), the juxtamembrane domain (JM), and TKD1 and TKD2. Amino acid positions targeted by known recurrent mutations in AML are indicated in green above the corresponding domains. N676 is indicated in blue below the TKD1 domain. (D) Frequency distribution of additional genetic aberrations in 84 CBFB/MYH11-rearranged patients. Each column indicates one patient. Dark gray boxes indicate patients who are positive for the respective mutation; light gray boxes indicate wild-type status. Missing information is shown as a white space (N/A, not available). Gene names and types of mutations are indicated on the left. Mutation frequencies are indicated on the right. MLL-PTD, partial tandem duplications in the MLL gene.
