LOCALIZATION OF THE 8-13 TRANSLOCATION BREAKPOINT ASSOCIATED WITH MYELOPROLIFERATIVE DISEASE TO A 1.5 MBP REGION OF CHROMOSOME-13

There are five reported cases of an atypical myeloproliferative disord er in which the leukemia cells have a consistent t(8;13)(p11;q12) tran slocation. We analyzed the breakpoint in metaphases from two of these patients by fluorescence in situ hybridization using a series of yeast artificial chromosomes (YACs) derived from the 13q 12 region. We foun d that a YAC containing the FLT1 and FLT3 oncogenes was localized dist al to the 13q 12 breakpoint and was not rearranged. YAC 66, a YAC that lies immediately adjacent to the chromosome 13 centromere, was locali zed proximal to the 13q 12 breakpoint and was not rearranged. A third YAC, which is located between FLT1 and YAC 66, was unrearranged in nor mal metaphase chromosomes, but showed hybridization signals on both de rivative chromosomes in both cases. Thus, the breakpoints in these two cases are localized to the same 1.5 Mbp region of 13q12. This may be the site of an unidentified gene involved in the pathogenesis of some types of leukemia. (C) 1995 Wiley-Liss, Inc.