The Bcl6 locus is not mutated in mouse B-cell lineage lymphomas.

In normal human germinal centre (GC) B-cells and post-GC B-cell lymphomas, a region in the first intron of the BCL6 gene, termed the major mutations cluster (MMC) exhibits somatic point mutations and deletions with patterns very similar to those seen in the variable regions of immunoglobulin (Ig) genes. In studies of mouse post-GC diffuse large cell lymphoma, Burkitt lymphomas, and plasmacytomas, direct sequencing or cold SSCP analyses revealed no mutations within a 686-bp region in Bcl6 intron 1 with 72% identity to the human MMC. The mouse Bcl6 locus must be inaccessible to the mutational machinery responsible for somatic mutations of Ig and BCL6 in humans.