DETECTION OF CHROMOSOME 11Q23 INVOLVING TRANSLOCATIONS BY PULSED-FIELD GEL-ELECTROPHORESIS

Translocations involving chromosome band 11q23 are associated with acu te lymphocytic and myelomonocytic leukemias with poor clinical prognos is. Pulsed-field gel electrophoresis (PFGE) was used to characterize t he breakpoint region that has been mapped within a 300-kb fragment bet ween the genes CD3G and PBGD. Using CD3G as a marker on SfuI-restricte d DNA separated by PFGE, we detected a rearrangement involving 11q23 i n the cell line B1 with a t(4; 11) and in the leukemic cells of two pa tients, one with a t (2; 11) and one with a t(11; 19). In comparison, lymphoblastoid cell lines established from normal peripheral blood lym phocytes of these two patients had a normal karyotype and showed germl ine configuration, thus excluding RFL polymorphisms. Digestion of DNA with BssHII or SalI showed heterogeneity of 11q23 involving breakpoint s. A rearrangement in the t(4; 11) containing lymphoma cell line Karpa s422 was seen only with the chromosome 4 probe KIT on SalI-digested DN A. PFGE is a reliable method for the mapping and detection of complex breakpoint regions. The breakpoints on 11q23 involve different introns of the highly spliced HRX/ALL-1/MLL gene.