Analysis of TEL/AML1 translocations in concordant twin leukemias. (A) Long-distance inverse PCR analysis of an intron 5TEL HindIII fragment of normal control (CON) and leukemic (T-2850) DNA. The expected band size is 4.2 kb, patient T-2850 exhibited a 1.3-kb band. (B) Schematic of the normal TEL andAML1 genes along with the TEL/AML1 translocation in T-2850. The inv3 primers anneal to the 5′ end of the 4.2-kbHindIII fragment as shown; the translocation brought aHindIII site of AML1 closer to the inv3 primer sites than the normal HindIII site in TEL. The location of anAlu repeat sequence in TEL is shown, as well as exon 2 of AML1. A large arrow indicates the translocation breakpoint. (C) PCR analysis of the reciprocal AML1/TEL translocation in the twins. The 411-bp heminested PCR product was amplified in both twins, but not in control DNA samples. A total of 10 ng of T-2850 and 1 μL of a 1:100 dilution of DNA isolated from the T-244 slide was amplified, along with 50 ng of control DNA samples. CON-1 is DNA from a normal healthy individual, CON-2 and CON-3 are DNA samples from other pediatric leukemia patients that also had TEL/AML1translocations by RT-PCR. (D) Sequence surrounding the translocations in the twins. Normal TEL is shown at top and bottom andAML1 in the center. TEL/AML1 is indicated by der 12 andAML1/TEL by der 21. The duplicated “GTT” at the breakpoint site is shown in bold, a Y is shown at the center nucleotide in the der 21 sequence to indicate the T → C mutation in T-244. The bottom sequence of TEL is shifted 44 nucleotides to the left to indicate a 47-bp deletion on translocation.