Fig. 3

FLT3 of patients 36 and 20 as characterized by next-generation sequencing and fragment analysis. a NGS sequencing depth histogram for 3 amplicons covering FLT3 exons 13 to 15 at scale 0–30000X. Magnitude of drops in sequencing depth at amplicon 2 and the region of 3 bp deletion (c.1739_1741delAGG; indicated by arrow) was proportional to the deletion VAF as indicated. The amplicon 2 covered the 75 bp ITD (indicated by triangle) but was affected by the 3 bp deletion in cis. b PCR fragment analysis for FLT3 ITD detection. ITD of 54 bp, 63 bp (patient 36 initial sample), 25 bp and 119 bp (patient 20) detected by NGS and ITDseek were confirmed by the corresponding fragments. Single additional fragment detected in both initial and relapsed samples of patient 36 confirmed the additional allele, which consisted of 75 bp ITD and 3 bp deletion in cis and was not detected by NGS due to allele drop-out.