MOLECULAR-CLONING OF 19P13 BREAKPOINT REGION IN INFANTILE LEUKEMIA WITH T(11-19)(Q23-P13) TRANSLOCATION

We studied the breakpoint regions involved in t(11;19)(q23;p13) transl ocation associated with infantile leukemias. Southern blot analysis wi th the partial cDNA clone for the MLL gene at 11q23 which we had isola ted previously detected gene rearrangements in all three cell lines an d three leukemia samples from the patients with t(11;19) translocation , indicating that these breakpoints were clustered within the 8.5 kb B amHI germline fragment detected by the probe. To study the breakpoint region, a genomic library of one of the cell lines, KOCL-33, was made. We have isolated the der(19) allele containing the breakpoint as well as the germline alleles at 19p13 and 11q23. Using the genomic probes on chromosome 19 near the breakpoint, Southern blot analysis was perfo rmed. The breakpoints at 19p13 of the two other cell lines and the thr ee leukemia samples were not located within 36 kilobases of the KOCL-3 3 breakpoint, although pulsed-field gel electrophoresis showed that th e breakpoints of all three cell lines were on the same NruI fragment o f 230 kilobases. These results showed that the breakpoints at 19p13 we re not clustered like those at 11q23 in t(11;19) translocation.