Sequencing of t(2;7) translocations reveals a consistent breakpoint linking CDK6 to the IGK locus in indolent B-cell neoplasia.

The translocation t(2;7)(p11;q21) has repeatedly been documented in association with indolent B-cell lymphoproliferative disorders (BLPDs). However, the chromosomal breakpoints associated with this recurrent translocation have rarely been characterized. Using an approach based on long-range PCR, we mapped the t(2;7) breakpoints in five patients presenting with indolent B-cell neoplasia. The sequencing of these rearrangements revealed several striking parallels across the t(2;7) breakpoints. The junction sites on 2p11 consistently mapped to the heptamer recombination signal sequence (RSS) of an immunoglobulin kappa variable gene (IGK) within the Vκ3 family, while the breakpoints on 7q21 each localized to within 4 bp of an RSS-like element located approximately 0.5 kb upstream of the transcription start site of the cyclin-dependent kinase 6 gene (CDK6). These findings confirm the significant genetic overlap arising in BLPD-associated t(2;7) translocations, and implicate the deregulated expression of CDK6 as a common molecular mechanism involved in the emergence of clonal B-cell proliferations presenting with this recurrent abnormality. In addition, the successful mapping of the t(2;7) translocations in each of five patients using a simple PCR-based protocol highlights the potential diagnostic utility of this approach during characterization of cases harboring analogous rearrangements.