Immunoglobulin gene conversion or hypermutation: that's the question.

Chicken B cells develop their primary immunoglobulin (Ig) gene repertoire by pseudogene templated gene conversion within the bursa of Fabricius. The DT40 cell line is derived from bursal B cells and continues to diversify its rearranged Ig light chain in cell culture. Ig gene conversion of DT40 requires expression of the AID gene which was earlier shown to be needed for Ig hypermutation and switch recombination in mammalian B cells. Interestingly, Ig hypermutation can be induced in DT40, if Ig gene conversion is blocked by the disruption of RAD51 paralog genes, the deletion of the nearby pseudogene locus or the disruption of the UNG gene. The ease of gene targeting and the compactness of the chicken Ig light chain locus makes DT40 an ideal model to study the molecular mechanism of AID induced gene conversion and hypermutation.