t(2;8) variant translocation in burkitt's lymphoma: Mapping of chromosomal breakpoints by in situ hybridization

In 6 different Burkitt lymphoma cell lines with t(2;8) variant translocations (JI. LY66, LY9I, BL21, BL64, JBL2) the breakpoints on chromosome 8q + were mapped in relation to each other and to c‐myc by in situ hybridization. The probes used were derived from chromosome 8q24 and comprised a c‐myc probe, a probe located 48 kb downstream of c‐myc , 3 probes adjacent to the chromosomal breakpoints of BL64, LY91 and JBL2, respectively, and 2 probes located in the 5′ and 3′ part of the thyroglobulin gene. The breakpoints of LY91 and JBL2 lie <200 kb and>200 kb downstream of c‐myc , whereas the distance to c‐myc of the BL64 breakpoint and of the thyroglobulin probes is unknown. By recording the hybridization signals specific for these probes on chromosomes 2p − and 8q + of each cell line it was possible to establish the order of breakpoints on band 8q24 relative to the c‐myc and thyroglobulin genes as follows: centromere—c‐myc—JI—BL64—BL21— LY91—JBL2—LY66—thyroglobulin—telomere. This information is essential for further mapping of this important chromosomal region.