FISH analysis of

Tcrα/δ, Tcl1 and c-myc genes inAtm^−/− lymphomas. (A, B) FISH analysis of the Tcrα/δ locus on mouse chromosome 14 with BAC probes to constant region alpha (TcrCα) and variable region alpha (TcrVα). TcrCα signals are shown in green and the TcrVα signal in red for all panels A-D as depicted in D. Chromosomes and DNA are counterstained with DAPI (blue). Structural aberrations were identified by SKY (not shown). At least 10 nuclei were examined and the presence of the same pattern of FISH signals was confirmed in the majority of nuclei. Representative metaphase nuclei are shown for tumors AT-7 (A) and AT-11 (B). (C) FISH analysis of AT-13 with BAC probes to the T-cell receptor constant region TcrCα (red) and the Tcl1 locus (green).TcrCα on chromosome 14 is translocated into the vicinity of the Tcl1 gene on chromosome 12 (T12;14). TheTcl1 locus appears to be amplified compared with the second FISH signal on a normal chromosome 12 allele. One allele of chromosome 14 with the second TcrCα has undergone deletion of theTcrVα region (Del(14); Table 1). The second allele of chromosome 14, T(14;15), has lost the TcrCα region and therefore shows no hybridization signal. Chromosomes are counterstained with DAPI (blue). (D) FISH analysis of chromosome 15 and thec-myc locus in thymic lymphoma AT-7. The AT-7 lymphoma has gained an extra copy of chromosome 15 (chromosome painted in red), along with an additional copy of the c-myc allele (green). Note the 3 c-myc FISH signals captured in the interphase nuclei above and below the metaphase plate. Chromosomes and DNA are counterstained with DAPI (blue).