title: Activation-induced cytidine deaminase fails to induce a mutator phenotype in the human pre-B cell line Nalm-6.
abstract: Activation-induced cytidine deaminase (AID) plays a key role in the induction of somatic hypermutation and class switching at the immunoglobulin loci of B lymphocytes. AID overexpression can induce a mutator phenotype in lymphoid and nonlymphoid cell lines, suggesting that AID by itself is sufficient to trigger hypermutation and class switching. AID expression in vivo is considered to be restricted to germinal center B lymphocytes, yet AID expression is also seen in many B cell lymphomas, hinting at a potential role for the development of these malignancies. We used a GFP-based reversion assay to efficiently evaluate the activation of mutator phenotypes. As expected, AID overexpression in the human Burkitt lymphoma cell line BL70 caused hypermutation. Surprisingly, AID overexpression in the human pre-B cell line Nalm-6 failed to induce a detectable mutator phenotype, indicating that Nalm-6 cells are probably lacking an essential factor(s) to confer AID-induced mutagenesis. This finding supports the concept that AID overexpression by itself must not automatically lead to the onset of a mutator phenotype. In addition, treating Nalm-6 transfectants with thymidine, a potential mutagenic drug, caused profound mutation rates on the GFP transgene. Thus, the GFP-based mutation assay might prove a powerful tool to study protein- and chemical-induced mutator phenotypes in cell lines.
authors.affiliation: GSF-National Research Centre for Environment and Health, Institute of Clinical Molecular Biology and Tumor Genetics, D-81377 Munich, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Rückerl
authors.forename: Jurgen
authors.initials: J
authors.lastname: Bachl
mesh_terms: D001402:B-Lymphocytes / Q000201:enzymology; D001483:Base Sequence; D002051:Burkitt Lymphoma / Q000201:enzymology / Q000235:genetics; D002460:Cell Line; D045744:Cell Line, Tumor; D018388:Codon, Terminator / Q000235:genetics; D003564:Cytidine Deaminase; D043525:Cytosine Deaminase / Q000235:genetics* / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics; D015870:Gene Expression / Q000187:drug effects; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006412:Hematopoietic Stem Cells / Q000201:enzymology; D006801:Humans; D016296:Mutagenesis; D009154:Mutation; D010641:Phenotype; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013936:Thymidine / Q000494:pharmacology; D014162:Transfection; D000098830:AICDA (Activation-Induced Cytidine Deaminase)
chemical_list: D018388:Codon, Terminator; D018076:DNA, Complementary; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D000098830:AICDA (Activation-Induced Cytidine Deaminase); D043525:Cytosine Deaminase; D003564:Cytidine Deaminase; D013936:Thymidine