The 2p breakpoint of a 2;8 translocation in Burkitt lymphoma interrupts the V kappa locus.

摘要

The majority of chromosomal rearrangements observed in Burkitt lymphomas involve a translocation between 8q and 14q, while the remaining minority carry variant translocations between chromosome 8 and either 2 or 22. We have studied the JI Burkitt lymphoma cell line carrying the variant 2;8 chromosome translocation using a combination of high-resolution and molecular cytogenetic techniques. We have determined that the chromosome 2 breakpoint of the 2;8 translocation in these cells is in the distal portion of 2p11.2. In situ hybridization of a DNA probe for kappa light chain variable (V kappa) region demonstrated that this 2p11.2 breakpoint is within the V kappa region. There was significant hybridization of the probe to both the 2p- and 8q+ chromosomes, with 23% of all grains considered to be specific for V kappa located over the middle one-third of the long arm of the 8q+ chromosome. Thus, there is translocation of the entire kappa constant (C kappa) region and a portion of the region carrying V kappa genes from 2p to a region 3' of the c-myc oncogene on the involved chromosome 8, resulting in transcriptional activation of the c-myc that is quite distant from the 5' end of the C kappa gene. These results provide direct evidence for translocation-related rearrangement of the kappa immunoglobulin gene cluster in this Burkitt lymphoma and for the assignment of the V kappa locus to 2p11.2.