Uncoupling between Ig somatic hypermutation and oncogene mutation in mouse lymphoma

Christelle Vincent1, Véronique Truffinet, Remi Fiancette

  • 1UMR CNRS 6101, Centre National de la Recherche Scientifique, Université de Limoges, France.

Burkitt lymphoma (BL) features translocations linking c-myc to the immunoglobulin heavy chain (IgH) locus. By inserting a c-myc gene under the control of the 3'IgH locus control region (LCR) into the mouse genome, we generated c-myc-3'LCR mice that develop clonal BL or diffuse anaplastic lymphoma. We show in the present study that while BL from c-myc-3'LCR mice would be classified as pre-germinal center (GC) cells due to the absence of both BCL-6 expression and somatic hypermutation (SHM) in V(H) sequences, they show a high level of SHM focused on the c-myc oncogene itself. This observation suggests that the c-myc-3'IgH LCR tandem association drives development of lymphoma from naïve B cells by specifically recruiting AID activity on c-myc in a process that early becomes independent from antigen selection and where the successive rounds of SHM rather rely on the selection of the most efficient mutations for oncogene deregulation. Similar to the translocated c-myc gene in human BL, mutations were found in first exon and 5' flanking sequences of transgenic c-myc and specially focused on negative regulatory elements, thus leading to high and constitutive oncogene expression. In conclusion while 3'IgH transcriptional enhancers in c-myc-3'LCR mice first simply act in cis to slightly stimulate c-myc transcription in untransformed B cells, the occurrence of lymphoma appears to result from an additional mechanism necessitating AID-driven mutations within the first exon and 5' flanking sequences which does not occur in parallel but rather circumvents antigen-driven selection.

Related Concept Videos

Mouse Models of Cancer Study02:43

Mouse Models of Cancer Study

Mice have long served as models for studying human biology and pathology because of their phylogenetic and physiological similarity with humans. They are also easy to maintain and breed in the laboratory, and hence, many inbred strains are now available for research. Studies on mice have contributed immeasurably to our understanding of cancer biology.
The development of transgenic, knockout, and knock-in mice has led to an exponential increase in their use as model organisms in research,...
Cancers Originate from Somatic Mutations in a Single Cell02:21

Cancers Originate from Somatic Mutations in a Single Cell

Cancer arises from mutations in the critical genes that allow healthy cells to escape cell cycle regulation and acquire the ability to proliferate indefinitely. Though originating from a single mutation event in one of the originator cells, cancer progresses when the mutant cell lines continue to gain more and more mutations, and finally, become malignant. For example, chronic myelogenous leukemia (CML) develops initially as a non-lethal increase in white blood cells, which progressively...
Cancers Originate from Somatic Mutations in a Single Cell02:21

Cancers Originate from Somatic Mutations in a Single Cell

Cancer arises from mutations in the critical genes that allow healthy cells to escape cell cycle regulation and acquire the ability to proliferate indefinitely. Though originating from a single mutation event in one of the originator cells, cancer progresses when the mutant cell lines continue to gain more and more mutations, and finally, become malignant. For example, chronic myelogenous leukemia (CML) develops initially as a non-lethal increase in white blood cells, which progressively...
Mismatch Repair01:20

Mismatch Repair

Organisms are capable of detecting and fixing nucleotide mismatches that occur during DNA replication. This sophisticated process requires identifying the new strand and replacing the erroneous bases with correct nucleotides. Mismatch repair is coordinated by many proteins in both prokaryotes and eukaryotes.
The Mutator Protein Family Plays a Key Role in DNA Mismatch Repair
The human genome has more than 3 billion base pairs of DNA per cell. Prior to cell division, that vast amount of genetic...
Spontaneous and Induced Mutations01:30

Spontaneous and Induced Mutations

Spontaneous mutations arise infrequently during DNA replication due to errors in the process. A key factor behind these errors is tautomeric shifts in nitrogenous bases, where bases transition from keto to enol forms or amino to imino forms. This shift can alter base-pairing rules, leading to mutations. Additionally, reactive oxygen species (ROS) arising from aerobic metabolism can damage DNA, resulting in depurination (loss of a purine base) or depyrimidination (loss of a pyrimidine base).
In-vitro Mutagenesis01:16

In-vitro Mutagenesis

To learn more about the function of a gene, researchers can observe what happens when the gene is inactivated or “knocked out,” by creating genetically engineered knockout animals. Knockout mice have been particularly useful as models for human diseases such as cancer, Parkinson’s disease, and diabetes.