DETECTION OF MYC TRANSLOCATIONS IN LYMPHOMA-CELLS BY FLUORESCENCE IN-SITU HYBRIDIZATION WITH YEAST ARTIFICIAL CHROMOSOMES

Translocations involving chromosome 8 at band q24 and one of the Ig lo ci on chromosomes 14q32, 22q11, and 2p11 are the hallmark of Burkitt's lymphoma (BL). It has been previously observed that the exact localiz ation of the breakpoints at chromosome 8q24 can vary significantly fro m patient to patient, scattering over a distance of more than 300 kb u pstream of c-myc and about 300 kb downstream of c-myc. To generate pro bes for fluorescence in situ hybridization (FISH) that detect most c-m yc translocations, we screened a yeast artificial chromosome (YAC) lib rary from normal human lymphocytes by colony hybridization, using thre e markers surrounding the c-myc gene as probes. We obtained 10 YAC clo nes ranging in size between 500 and 200 kb. Two nonchimeric clones wer e used for FISH on several BL cell lines and patient samples with diff erent breakpoints at 8q24. Our results show that the YAC clones detect ed translocations scattered along approximately 200 kb in both metapha se chromosomes and interphase nuclei. The sensitivity, rapidity, and f easibility in nondividing cells render FISH an important diagnostic to ol. Furthermore, the use of large DNA fragments such as YACs greatly s implifies the detection of translocations with widely scattered breakp oints such as these seen in BL. (C) 1995 by The American Society of He matology.