DNA recombination and somatic hypermutation are hallmarks of the immunoglobulin (Ig) loci in developing and antigen-reactive B lymphocytes. B lymphocytes must assemble the genes encoding Ig chains, and this process begins with VH gene assembly. Somatic hypermutation (SHM), together with clonal selection, insures the development of high affinity antibodies to invading pathogens. Class-switch recombination (CSR) makes possible the development of antigen-reactive Ig's of multiple isotypes so that these Ig's can gain access to antigen wherever it resides and eliminate it through any of a number of mechanisms. These genome-damaging processes must be strictly controlled so that they act only on the Ig loci, where they are needed for normal locus function. This regulatory responsibility appears to fall on a series of cis- acting elements found within and around the Ig heavy (IgH) and light chain (IgL) loci. It has become increasingly clear that improper targeting of somatic hypermutation and class-switch recombination is a contributing factor, if not the initiating factor, in numerous neoplasms arising within the B lymphoid compartment. Not only does mis-targeting of the DNA lesions lead to undesirable chromosome translocations, but also, transposition of the Ig regulatory sequences to sites adjacent to proto-oncogenes leads to unwanted gene activity (reviewed in 36). Further study of the regulatory elements in the IgH locus, therefore, must be an essential component of any effort aimed at treating and/or preventing B-lineage cancers, as well as of efforts to harness the power of this system to more effectively combat infection. In this proposal, we seek to more precisely delineate the regulatory sequences within the IgH locus that regulate VH gene assembly (in particular, D-J joining), CSR, and SHM. We have developed bacterial artificial chromosomes (BACs) that carry an assembled VH gene and the whole of the IgH locus downstream. These BACs have been designed so that after they are integrated into the genome of transgenic animals, individual (and pairs of) elements within the 3'lgH regulatory region can be deleted at will. This experimental system will be used to further study a system of control elements that we, and others, have shown to have substantial functional redundancy. In addition, we have recently developed a mouse that lacks E mu (intronic enhancer) but carries a fully-assembled VH gene. This experimental system allows us not only to assess E mu's essential functions post-V(D)J assembly, but also its role in allelic exclusion. An understanding of the latter will contribute to models relating allelic exclusion to protection from autoimmunity.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI030653-20
Application #
7668428
Study Section
Cellular and Molecular Immunology - B Study Section (CMIB)
Program Officer
Nasseri, M Faraz
Project Start
1992-10-01
Project End
2012-08-31
Budget Start
2009-09-01
Budget End
2012-08-31
Support Year
20
Fiscal Year
2009
Total Cost
$322,801
Indirect Cost
Name
Hunter College
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
620127915
City
New York
State
NY
Country
United States
Zip Code
10065
Peng, Cheng; Eckhardt, Laurel A (2013) Role of the Igh intronic enhancer E? in clonal selection at the pre-B to immature B cell transition. J Immunol 191:4399-411
Yan, Yi; Pieretti, Joyce; Ju, Zhongliang et al. (2011) Homologous elements hs3a and hs3b in the 3' regulatory region of the murine immunoglobulin heavy chain (Igh) locus are both dispensable for class-switch recombination. J Biol Chem 286:27123-31
Li, Fubin; Yan, Yi; Pieretti, Joyce et al. (2010) Comparison of identical and functional Igh alleles reveals a nonessential role for Eýý in somatic hypermutation and class-switch recombination. J Immunol 185:6049-57
Li, Fubin; Eckhardt, Laurel A (2009) A role for the IgH intronic enhancer E mu in enforcing allelic exclusion. J Exp Med 206:153-67
Zhang, Buyi; Alaie-Petrillo, Adrienne; Kon, Maria et al. (2007) Transcription of a productively rearranged Ig VDJC alpha does not require the presence of HS4 in the IgH 3'regulatory region. J Immunol 178:6297-306
Yan, Yi; Park, Sung Sup; Janz, Siegfried et al. (2007) In a model of immunoglobulin heavy-chain (IGH)/MYC translocation, the Igh 3'regulatory region induces MYC expression at the immature stage of B cell development. Genes Chromosomes Cancer 46:950-9
Garrett, Francine E; Emelyanov, Alexander V; Sepulveda, Manuel A et al. (2005) Chromatin architecture near a potential 3' end of the igh locus involves modular regulation of histone modifications during B-Cell development and in vivo occupancy at CTCF sites. Mol Cell Biol 25:1511-25
Shi, X; Eckhardt, L A (2001) Deletional analyses reveal an essential role for the hs3b/hs4 IgH 3' enhancer pair in an Ig-secreting but not an earlier-stage B cell line. Int Immunol 13:1003-12
Stevens, S; Ong, J; Kim, U et al. (2000) Role of OCA-B in 3'-IgH enhancer function. J Immunol 164:5306-12
Ong, J; Stevens, S; Roeder, R G et al. (1998) 3' IgH enhancer elements shift synergistic interactions during B cell development. J Immunol 160:4896-903

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