IGH/CCND1 (BCL1) Translocation Probe Dual Fusion

Reciprocal translocations involving the IGH and CCND1 (Cyclin D1) loci were frequently reported in B-CLL patients. The involvement of the CCND1 gene was initially reported from a cloning study looking at the breakpoints of the translocation. However, it is likely that the initial diagnosis on the samples used for the study should have been Mantle Cell Lymphoma (MCL). The probe set for the t(11,14) translocation has been provided on the CLL panel to enable atypical B-CLL patients to be distinguished from possible MCL patients following the guidelines of the UK ACC Professional Standards Committee.

The Constant and Variable segments of the IGH gene are covered by green probe contigs. The CCND1 probe mix contains a probe 3’ of CCND1 covering a region between the two markers D11S2663 and D11S4095, measuring 157kb, (141kb from CCND1) and a second probe (161kb) covering CCND1 and the region up to the 3’ end of FGF3. Both are labelled in red.

In the normal cell, these probes will appear as discreet red and green spots, one for each homologue (resulting in a 2G 2R conformation). In a t(11:14) patient, the constant region probe of the IGH swaps with the CCND1-covering probe and vice versa resulting in two (yellow) fusion signals in addition to the red and green signals of the normal chromosomes 11 and 14 respectively (1R 1G 2Y).