Polyclonal hyper-IgE mouse model reveals mechanistic insights into antibody class switch recombination (original) (raw)
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Journal of Experimental Medicine, 2014
Classical class-switch recombination (cCSR) substitutes the C gene with C , C , or C , thereby generating IgG, IgE, or IgA classes, respectively. This activation-induced deaminase (AID)-driven process is controlled by the IgH 3 regulatory region (3RR). Regulation of rare IgD CSR events has been enigmatic. We show that CSR occurs in mouse mesenteric lymph node (MLN) B cells and is AID-dependent. AID attacks differ from those in cCSR because they are not accompanied by extensive somatic hypermutation (SHM) of targeted regions and because repaired junctions exhibit features of the alternative end-joining (A-EJ) pathway. In contrast to cCSR and SHM, CSR is 3RR-independent, as its absence affects neither breakpoint locations in S -and S -like ( ) nor mutation patterns at S - junctions. Although mutations occur in the immediate proximity of the junctions, SHM is absent distal to the junctions within both S and rearranged VDJ regions. In conclusion, CSR is active in MLNs, occurs independently of 3RR-driven assembly, and is even dramatically increased in 3RRdeficient mice, further showing that its regulation differs from cCSR.
Class-Switch Recombination in the Absence of the IgH 39 Regulatory Region
The ∼28-kb 39 regulatory region (39RR), which is located at the most distal 39 region of the Ig H chain locus, has multiple regulatory functions that control IgH expression, class-switch recombination (CSR), and somatic hypermutation. In this article, we report that deletion of the entire 39RR in a mouse B cell line that is capable of robust cytokine-dependent CSR to IgA results in reduced, but not abolished, CSR. These data suggest that 39RR is not absolutely required for CSR and, thus, is not essential for targeting activation-induced cytidine deaminase to S regions, as was suggested. Moreover, replacing 39RR with a DNA fragment including only its four DNase I hypersensitive sites (lacking the large spacer regions) restores CSR to a level equivalent to or even higher than in wild-type cells, suggesting that the four hypersensitive sites contain most of the CSR-promoting functions of 39RR. Stimulated cells express abundant germline transcripts, with the presence or absence of 39RR, providing evidence that 39RR has a role in promoting CSR that is unique from enhancing S region transcription.
Increased Targeting of Donor Switch Region and IgE in S 1-Deficient B Cells
The Journal of Immunology, 2010
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Immunity, 2001
proteins, which altogether may either mediate repres-CNRS UMR6101 sion of the 3Ј elements in lymphocytes or activation in Faculté de Mé decine plasma cells (Muto et al., 1998). By contrast, the distant Limoges hs4 enhancer, lying some 26 kb downstream of the 2 Centre de Dé veloppement des Techniques Avancé es ␣ gene, seems to be active throughout B cell differentiapour l'Expé rimentation Animale tion (Michaelson et al., 1995). Its activity in pre-B cells UPS CNRS 44 may rely on the presence of oct and B sites; BSAP Orlé ans binds hs4 in a differential manner, apparently repressing France the enhancer in pre-B cells and boosting its activity in mature B cells (Michaelson et al., 1996). Based on transient transfection experiments, it was Summary concluded that the four enhancers are rather weak when they individually drive transcription of reporter genes. Four transcriptional enhancers lie downstream of the However, their combinations displayed strong transcripimmunoglobulin heavy chain locus: C␣3/hs3a, hs1,2,
European Journal of Immunology, 2006
The predominant path of immunoglobulin class switch recombination follows the paradigm of intra-chromosomal deletion enabling expression of another heavy chain instead of l and d. This was, however, challenged by observations of inter-allelic class switch recombination in rabbit or mouse IgG3-or IgA-producing B cells. Assuming that the conditions of inter-chromosomal exchange are likely present at any target S regions in stimulated B cells, we explored trans-association of VH and C genes in a model allowing all C genes to be checked simultaneously. Heterozygous mutant mice are thus studied, which carry one non-functional IgH allele inactivated by a non-translatable mutation of VDJ-CH transcripts, while the functional allele is deficient for class switching due to a truncated 3 0 regulatory region. A fair level of switching to all Ig classes is restored in heterozygous mice despite the fact that cis-recombination is either non productive on one allele or deficient on the other. Molecular evidence at the DNA level of trans-CSR to IgG3 was demonstrated by cloning and sequencing Sl-Sc3 hybrid junctions. These data demonstrate that inter-allelic recombination may broadly rescue the production of various class-switched isotypes and allow complementation between mutations located at both ends of the IgH constant gene cluster.
Journal of Biological Chemistry, 2011
Immunoglobulin heavy chain (IgH) genes are formed, tested, and modified to yield diverse, specific, and high affinity antibody responses to antigen. The processes involved must be regulated, however, to avoid unintended damage to chromosomes. The 3 regulatory region of the Igh locus plays a major role in regulating class-switch recombination (CSR), the process by which antibody effector functions are modified during an immune response. Loss of all known enhancer-like elements in this region dramatically impairs CSR, but individual element deletions have no effect on this process. In the present study, we explored the hypothesis that an underlying functional redundancy in the homologous elements hs3a and hs3b was masking the importance of either element to CSR. Several transgenic mouse lines were generated, each carrying a bacterial artificial chromosome transgene that mimicked Igh locus structure but in which hs3a was missing and hs3b was flanked by loxP sites. Matings to Cyclization Recombination Enzyme-expressing mice established "pairs" of lines that differed only in the presence or absence of hs3b. Remarkably, CSR remained robust in the absence of both hs3a and hs3b, suggesting that the remaining two elements of the 3 regulatory region, hs1.2 and hs4, although individually dispensable for CSR, are, together, sufficient to support CSR.
IgH 3’ regulatory region increases ectopic class switch recombination
PLOS Genetics, 2021
DNA lesions inflicted by activation-induced deaminase (AID) instrumentally initiate the processes reshaping immunoglobulin genes in mature B-cells, from local somatic hypermutation (SHM) to junctions of distant breaks during class switch recombination (CSR). It remains incompletely understood how these divergent outcomes of AID attacks are differentially and temporally focused, with CSR strictly occurring in the Ig heavy chain (IgH) locus while SHM concentrates on rearranged V(D)J regions in the IgH and Ig light chain loci. In the IgH locus, disruption of either the 3’Regulatory Region (3’RR) super-enhancer or of switch (S) regions preceding constant genes, profoundly affects CSR. Reciprocally, we now examined if these elements are sufficient to induce CSR in a synthetic locus based on the Igκ locus backbone. Addition of a surrogate “core 3’RR” (c3’RR) and of a pair of transcribed and spliced Switch regions, together with a reporter system for “κ-CSR” yielded a switchable Igκ locus....