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Assessing Somatic Hypermutation in Ramos B Cells after Overexpression or Knockdown of Specific Genes
Published on: November 1, 2011
Ablation of XRCC2/3 transforms immunoglobulin V gene conversion into somatic hypermutation
J E Sale1, D M Calandrini, M Takata
1Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK. jes@mrc-lmb.cam.ac.uk
Nature
|August 31, 2001
Summary
Ablating RAD51 paralogues in chicken B cells shifts immunoglobulin V gene diversification from gene conversion to somatic hypermutation. This provides a model for studying hypermutation pathways and their repair mechanisms.
Area of Science:
- Immunology
- Molecular Biology
- Genetics
Background:
- Immunoglobulin V genes diversify through somatic hypermutation or gene conversion.
- Somatic hypermutation involves non-templated nucleotide substitutions, while gene conversion is templated by pseudogenes.
- RAD51 paralogues are involved in DNA repair and recombination pathways.
Purpose of the Study:
- To investigate the role of RAD51 paralogues (XRCC2, XRCC3, RAD51B) in immunoglobulin V gene diversification.
- To determine if ablating these paralogues affects the balance between gene conversion and somatic hypermutation.
- To establish a model system for dissecting immunoglobulin hypermutation.
Main Methods:
- Gene editing to ablate RAD51 paralogues (XRCC2, XRCC3, RAD51B) in chicken DT40 B-cell lymphoma line.
- Analysis of immunoglobulin V gene diversification patterns in mutant cell lines.
- Characterization of nucleotide substitution patterns and hotspots.
Main Results:
- Ablation of RAD51 paralogues induced a significant shift from gene conversion to somatic hypermutation.
- High-frequency, non-templated single-nucleotide substitutions were observed in the V domain, with G/C preference and hotspots.
- The results support distinct pathways for gene conversion and somatic hypermutation processing of DNA lesions.
Conclusions:
- RAD51 paralogues play a crucial role in suppressing somatic hypermutation and promoting gene conversion in immunoglobulin V genes.
- Ablating RAD51 paralogues modifies recombination-mediated repair, leading to induced somatic hypermutation.
- Mutant DT40 cell lines offer a valuable tool for understanding the genetic basis of immunoglobulin hypermutation.
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