Examples of FISH and next-generation sequencing iAMP21 data. (A) Cells from a patient with iAMP21. The red signals indicate copies of RUNX1, and the green signals indicate copies of ETV6 using FISH with a dual-color probe for the detection of the ETV6-RUNX1 fusion. No fusions are present in these cells. In the metaphase, the 2 pairs of green signals indicate the normal location of ETV6 on the short arm of the 2 normal chromosome 12 homologs. The individual pair of red signals on the right-hand side of the cell shows the location of RUNX1 on the normal chromosome 21. On the left-hand side of the cell, the cluster of red signals indicates amplification of RUNX1 on the abnormal chromosome 21 (iAMP21 chromosome). In the interphase cell (inset), the 2 green signals indicate the presence of 2 copies of ETV6. The cluster of red signals indicates the amplification of RUNX1. The fact that these signals are clustered implies that they are located in close proximity on a single chromosome. These characteristics define iAMP21. (B) A typical sporadic-iAMP21 copy-number profile of the chromosome 21 derived from paired-end sequencing data.²¹  Fluctuations above and below a copy number of 2 indicate gain and deletion, respectively. The profile covers the whole of chromosome 21, from centromere (left had side) to telomere (right hand side), and the chromosome positions are indicated in Mb. The deletion of the telomeric region indicates the breakpoint from which the BFB cycle was initiated in this patient. The stepwise changes in copy number along chromosome 21 represent the typical profile generated from BFB cycles, with the most highly amplified region juxtaposed to the deleted telomeric region. There are a small number of rearrangements resulting from chromothripsis in this patient. The originally defined common region of amplification of 5.1 Mb is indicated by the red bar, and the consistently most highly amplified and overexpressed regions generated from a consensus copy-number profile²¹  are indicated by the green bars. These regions include genes important in hematologic malignancies, and some examples with their relative locations are shown in the red box.