Activation Induced Deaminase defines a mature Burkitt-like lymphoma in the mouse
Germinal centers (GCs) are the sites of secondary antibody diversification and underlie the mechanism of action of many vaccination strategies. Activation-induced deaminase (AID) triggers secondary antibody diversification through the introduction of somatic changes in immunoglobulin genes which lead to the generation of antibodies of higher affinity and more specialized effector functions. However, AID can also target other genomic regions, giving rise to mutations and chromosome translocations with oncogenic potential. Many human lymphomas originate from mature B cells that have undergone the GC reaction, such as the diffuse large B cell lymphoma, the follicular lymphoma and Burkitt lymphoma, and carry chromosome translocations. Mature B cell lymphomagenesis has been modeled in the mouse by the genetic introduction of chromosome translocations. Here, we present the first in-depth characterization of one such model, ?-MYC mice. We found that young pre-tumor stage mice had a prominent block in early B cell differentiation that resulted in the generation of very aggressive tumors lacking surface B cell receptor (BCR) expression, indicating that a large fraction of tumors in ?-MYC mice arise from B cell precursors rather than from mature B cells. Further, we assessed the contribution of AID to B cell lymphomagenesis in ?-MYC mice by using a genetic tracer of AID expression. Only a fraction of tumors contained GC-experienced cells defined by AID expression. AID-expressing tumors associated with longer survival and resembled mature Burkitt lymphomas. Thus, AID expression defines Burkitt lymphomagenesis in ?-MYC mice. Overall design: Lymphoma cells were isolated by FACS from two independent ?-MYC mice based on Tom+ protein (AID historical expression). The four samples (B220+ IgM+ Tom+/-) were subjected to bulk RNA-sequencing for differential expression analysis.