Nucleotide and protein sequences of the FLT3-ITD-N676K mutation. (A-B) Genomic sequence shows the exchange of cytosine to guanine leading to an amino acid exchange at position 676 from asparagine to lysine. The N676K mutation was detectable in the larger FLT3-ITD band only, and not in the smaller wild-type allele, as confirmed by gel extraction and direct sequencing and by sequencing of FLT3-cDNA clones (data not shown).