Somatic hypermutation is the targeted process of mutagenesis which introduces single base changes into the rearranged variable regions encoding immunoglobulin heavy and light chains. Somatic hypermutation results in the production of B cell clones with affinity for antigen increased 10-fold or even 50-fold, thus enhancing the efficiency of the immune response. The rate of somatic hypermutation is one single base change per 1000 bases per generation, which is nearly one million-fold higher than the typical rate of mutation in a mammalian somatic cell. Mutations are targeted to the V regions of the rearranged heavy and light chain loci, and do not appear in constant regions, in unrearranged V regions, or elsewhere in the genome. Our long-term goal is to understand in detail the molecular mechanism and regulation of immunoglobulin gene hypermutation. Our specific experimental plans are (1) to identify regulatory elements that target hypermutation of a rearranged transgene in cis, by testing the ability of specific sequences to target mutation of a rearranged light chain gene in transgenic mice; (2) to determine what role gene conversion plays in somatic hypermutation, by assaying hypermutation of engineered substrates in transgenic mice; (3) to identify and study factors that may regulate somatic hypermutation, by searching for DNA binding proteins that are specific to or specifically induced in hypermutating B cells, and that recognize sequence elements we have shown to be critical for hypermutation; and (4) to identify genes that are actively transcribed in hypermutating B cells. These experiments address the mechanism of a fundamental process in the immune response. Furthermore, since the somatic events that diversify the cellular genome during B lymphocyte development probably occur by directed use of mechanisms common to all cells, understanding the mechanism of somatic hypermutation of the immunoglobulin loci is likely to provide insight into analogous mutation events that are central to genomic evolution, genetic disease, and oncogenesis.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM041712-08
Application #
2022289
Study Section
Mammalian Genetics Study Section (MGN)
Project Start
1989-12-01
Project End
1998-11-30
Budget Start
1996-12-01
Budget End
1997-11-30
Support Year
8
Fiscal Year
1997
Total Cost
Indirect Cost
Name
Yale University
Department
Biochemistry
Type
Schools of Medicine
DUNS #
082359691
City
New Haven
State
CT
Country
United States
Zip Code
06520
Le, Quy; Maizels, Nancy (2015) Cell Cycle Regulates Nuclear Stability of AID and Determines the Cellular Response to AID. PLoS Genet 11:e1005411
Maizels, Nancy (2013) Genome engineering with Cre-loxP. J Immunol 191:5-6
Humbert, Olivier; Davis, Luther; Maizels, Nancy (2012) Targeted gene therapies: tools, applications, optimization. Crit Rev Biochem Mol Biol 47:264-81
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Sacho, Elizabeth J; Maizels, Nancy (2011) DNA repair factor MRE11/RAD50 cleaves 3'-phosphotyrosyl bonds and resects DNA to repair damage caused by topoisomerase 1 poisons. J Biol Chem 286:44945-51
Davis, Luther; Maizels, Nancy (2011) DNA nicks promote efficient and safe targeted gene correction. PLoS One 6:e23981
Yabuki, Munehisa; Ordinario, Ellen C; Cummings, W Jason et al. (2009) E2A acts in cis in G1 phase of cell cycle to promote Ig gene diversification. J Immunol 182:408-15
Ordinario, Ellen C; Yabuki, Munehisa; Larson, Ryan P et al. (2009) Temporal regulation of Ig gene diversification revealed by single-cell imaging. J Immunol 183:4545-53
Ordinario, Ellen C; Yabuki, Munehisa; Handa, Priya et al. (2009) RAD51 paralogs promote homology-directed repair at diversifying immunoglobulin V regions. BMC Mol Biol 10:98

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