BCL2, 18q21.33-q22.1, Red
BCL2, 18q21.33-q22.1, Green
The BCL2 product consists of two green 161kb, 196kb probes and two red 304kb, 176kb probes, which are positioned on each side of the BCL2 gene.
The B-cell CLL/Lymphoma 2 (BCL2) gene located at 18q21.33 encodes one of a large protein family that regulates and contributes to programmed cell death, or apoptosis, by controlling mitochondrial membrane permeability1.
Translocations of the BCL2 gene result in constant expression of the BCL2 protein. BCL2 usually translocates to the immunoglobulin (IG) heavy chain (IGH) gene via a t(14;18)(q32;q21.3) and rarely to IG light chain (IGK or IGL) loci via t(2;18)(p11;q21.3) or t(18;22)(q21.3;q11)2.
The translocation (t(14;18)(q32.33;q21.33)) is thought to be brought about by an error in the joining function of the IGH gene, mediated by the observation that both IGH and BCL2 are arranged next to each other in 3D space in normal B lymphocytes3. The translocation breakpoint at the end of the Joining (J) segment, and the subsequent fusion of the BCL2 gene to this region, results in the BCL2 gene coming under the regulatory control of those processes normally involved in maintenance of IGH gene activity4.
The t(14;18) is observed in 70-95% of Follicular Lymphoma (FL) cases and 20-30% of Diffuse Large B-cell Lymphoma (DLBCL)2. Presence of the t(14;18) translocation in DLBCL is a predictor of outcome and has a poor prognostic effect5. BCL2 translocations have also been implicated in Chronic B-cell Lymphoproliverative Disease (CLPD) and occur frequently in Chronic Lymphocytic Leukaemia (CLL)6.
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