Variant translocation of the bcl-2 gene to immunoglobulin λ light chain gene in chronic lymphocytic leukemia

The bcl-2 gene has been identified as a gene directly involved in the consistent chromosome translocation t(14;18), which is found in ∼ 90% of human follicular lymphoma cases, and is a prime candidate for the oncogene playing a crucial role in follicular lymphomagenesis. In this paper, the authors describe a case of chronic lymphocytic leukemia showing the juxtaposition of the bcl-2 gene on chromosome 18 to immunoglobulin λ light chain (Igλ) gene on chromosome 22 in a head-to-head configuration. Sequencing analysis of the joining site of the bcl-2 gene and Igλ gene has shown that the breakpoint is within the 5' flanking region of the bcl-2 gene and about 2.2 kilobases 5' to the joining segment of Igλ locus in a germ-line configuration. The extranucleotide, commonly appearing at the joining site of the t(14;18) translocation involving the IgH locus, is absent from the joining site of bcl-2 and Igλ. The lack of extranucleotide suggests that the juxtaposition of the bcl-2 and Igλ genes occurred during physiological rearrangement of the Igλ gene since it has been shown that the rearrangement of the Igλ locus is not accompanied by extranucleotides