Identification and validation of the KMT2E-ASNS fusion transcripts in 2 relapsed childhood ETP-ALL patients. (A) Fusion transcripts KMT2E-ASNS containing KMT2E exon 1 (5′UTR) linked to the entire coding sequence of ASNS identified in the relapse material of both childhood ETP-ALL patients (TC0002 and TC0022) by RNA sequencing (RNA-seq). The dotted lines indicate observed exon junctions. Filled boxes correspond to coding sequences and small unfilled boxes correspond to UTRs (the first 23 bp of ASNS exon 3 are part of the 5′ UTR). (B) Complementary DNA (cDNA) sequence at exon junctions for the 2 transcript isoforms identified from RNA-seq data. (C) Validation of the fusion transcripts by RT-PCR and Sanger sequencing for both patients. (D) RT-PCR performed on the different time points of 4 samples taken from TC0002s patient on diagnosis, during and after treatment (W5, W16, W108, and W136), and on relapse showing the evolution of the KMT2E-ASNS alteration. KMT2E-ASNS is not detected until relapse (154 weeks after treatment end). D, diagnosis; R, relapse; Tx, treatment; W, week.