Analysis of the inv(11)(p15q23) in 2 patients with acute myeloid leukemia. (A) Partial karyotype of patient 1. Breakpoints are indicated by arrows. Chr indicates chromosome. (B) Fluorescence in situ hybridization on metaphase chromosomes of patient 1 shows split of the NUP98 (green) and MLL (red) loci. The bacterial artificial chromosomes used as probes are indicated on the Figure. (C) Reverse transcription–polymerase chain reaction with primers corresponding to NUP98 exon 11 and MLL exon 3 amplified an NUP98-MLL fusion transcript in samples with inv(11) but not in those from control. (D) Sequence analysis of amplified cDNA showed an in-frame fusion between exon 13 of NUP98 and exon 2 of MLL. (E) Schematic of the wild-type and fusion proteins. Some identified domains are indicated. The location of the majority of the MLL breakpoints is indicated by an arrowhead, and the taspase cleavage site is shown by a double-headed arrow.