Gene Expression in Myeloma Cells
Principal Investigator: LAUREL ECKHARDT
Abstract: 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.
Funding Period: ----------------2010 - ---------------2011-
more information: NIH RePORT
- Transcription of a productively rearranged Ig VDJC alpha does not require the presence of HS4 in the IgH 3' regulatory regionBuyi Zhang
Department of Biological Sciences, Hunter College and Graduate Center of the City University of New York, New York, NY 10021, USA
J Immunol 178:6297-306. 2007..Thus, hs4 does not play a uniquely essential role in the transcription of a productively rearranged Ig VDJCalpha transcription unit...
- 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 developmentYi Yan
Department of Biological Sciences, Hunter College and Graduate Center of the City University of New York, New York, NY, USA
Genes Chromosomes Cancer 46:950-9. 2007..Our data show that hMYC is expressed almost exclusively in B-lineage cells and is induced to high levels as soon as bone marrow cells reach the immature B cell stage...
- A role for the IgH intronic enhancer E mu in enforcing allelic exclusionFubin Li
Hunter College and Graduate Center of the City University of New York, New York, NY 10065, USA
J Exp Med 206:153-67. 2009..These findings reveal both an important role for E mu in influencing the fate of newly arising B cells and a second checkpoint for allelic exclusion...
- Comparison of identical and functional Igh alleles reveals a nonessential role for Eμ in somatic hypermutation and class-switch recombinationFubin Li
Department of Biological Sciences, Hunter College and Graduate Center, City University of New York, New York, NY 10065, USA
J Immunol 185:6049-57. 2010..We conclude that Eμ contributes to, but is not essential for, these complex processes and that its contribution is not as a transcriptional enhancer but, rather, is at the level of recruitment and/or activation of the SHM/CSR machinery...
- Homologous elements hs3a and hs3b in the 3' regulatory region of the murine immunoglobulin heavy chain (Igh) locus are both dispensable for class-switch recombinationYi Yan
Department of Biological Sciences, Hunter College, New York, New York 10065, USA
J Biol Chem 286:27123-31. 2011..2 and hs4, although individually dispensable for CSR, are, together, sufficient to support CSR...
- Role of the Igh intronic enhancer Eμ in clonal selection at the pre-B to immature B cell transitionCheng Peng
Department of Biological Sciences, Hunter College and The Graduate Center of City University of New York, New York, NY 10065
J Immunol 191:4399-411. 2013..In summary, these studies show that Eμ's effect on IgH levels at the pre-B cell to immature B cell transition strongly influences allelic exclusion, the breadth of the mature BCR repertoire, and the emergence of autoimmune B cells...