Copy number analysis of MSX2. (A) FISH analysis of tetraploid CCRF-CEM cells, using a painting probe for chromosome 5 (green) and RP11-54H11 probe for MSX2 (red). Of note, one allele of MSX2 (located at 5q35) is deleted on der(5). FISH analysis of PEER (B) and HPB-ALL (C), using probes for MSX2 (54H11, green), NKX2-5 (fosmid1, red) and TLX3 (fosmid2, orange). Data indicate deletion of MSX2 with concomitant rearrangement of NKX2-5 (PEER) or TLX3 (HPB-ALL). (D) Quantitative analysis of MSX2 copy numbers was performed by genomic real-time PCR in 12 selected T-cell lines. The MEF2C locus was used as endogenous control as described previously . Of note, cell lines CCRF-CEM, HPB-ALL and PEER demonstrate bisected quantities, indicating deletion of one allele of MSX2.