The Ig heavy chain intronic enhancer core region is necessary and sufficient to promote efficient class switch recombination

Sakai, Eiko; Bottaro, Andrea; Alt, Frederick W.

doi:10.1093/intimm/11.10.1709

Cited by 38 publications

(36 citation statements)

References 45 publications

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“…Although some noticeable effects of Em deletion on CSR efficiency have been previously reported, it is admitted that Em is dispensable for such a process in vivo (13,19,20,58). Because our full-length Em KO model modified peripheral B cell fate, we expected Ab responses to be affected.…”

Section: Discussionmentioning

confidence: 92%

The Eμ Enhancer Region Influences H Chain Expression and B Cell Fate without Impacting IgVH Repertoire and Immune Response In Vivo

Marquet

Garot

Bender

et al. 2014

The Journal of Immunology

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The IgH intronic enhancer region Eμ is a combination of both a 220-bp core enhancer element and two 310–350-bp flanking scaffold/matrix attachment regions named MARsEμ. In the mouse, deletion of the core-enhancer Eμ element mainly affects VDJ recombination with minor effects on class switch recombination. We carried out endogenous deletion of the full-length Eμ region (core plus MARsEμ) in the mouse genome to study VH gene repertoire and IgH expression in developing B-lineage cells. Despite a severe defect in VDJ recombination with partial blockade at the pro–B cell stage, Eμ deletion (core or full length) did not affect VH gene usage. Deletion of this regulatory region induced both a decrease of pre–B cell and newly formed B cell compartments and a strong orientation toward the marginal zone B cell subset. Because Igμ H chain expression was decreased in Eμ-deficient pre–B cells, we propose that modification of B cell homeostasis in deficient animals was caused by “weak” pre–B cell and BCR expression. Besides imbalances in B cell compartments, Ag-specific Ab responses were not impaired in animals carrying the Eμ deletion. In addition to its role in VDJ recombination, our study points out that the full-length Eμ region does not influence VH segment usage but ensures efficient Igμ-chain expression required for strong signaling through pre–B cells and newly formed BCRs and thus participates in B cell inflow and fate.

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Section: Discussionmentioning

confidence: 92%

The Eμ Enhancer Region Influences H Chain Expression and B Cell Fate without Impacting IgVH Repertoire and Immune Response In Vivo

Marquet

Garot

Bender

et al. 2014

The Journal of Immunology

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“…The activity of enhancer elements within the 3Ј IgH RR (hs3b and hs4) is required to activate transcription from promoters flanking S regions (I promoters) of downstream C H genes and, thereby, regulates CSR (2,18). Based on location, iE was a candidate to transcriptionally activate S during CSR; correspondingly, deletion of this element appeared to result in a decrease in IgH CSR (19,20). However, the exact mechanism by which deletion of iE affects CSR remains unclear.…”

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confidence: 99%

Elucidation of IgH intronic enhancer functions via germ-line deletion

Perlot

Alt

Bassing

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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Studies of chimeric mice demonstrated that the core Ig heavy chain (IgH) intronic enhancer (iE) functions in V(D)J and class switch recombination at the IgH locus. To more fully evaluate the role of this element in these and other processes, we generated mice homozygous for germ-line mutations in which the core sequences of iE (cE) were either deleted (cE ⌬/⌬ mice) or replaced with a pgk-Neo R cassette (cE N/N mice). The cE ⌬/⌬ mice had reduced B cell numbers, in association with impaired D to JH and VH to DJH rearrangement, whereas cE N/N mice had a complete block in IgH V(D)JH recombination, confirming that additional cis elements cooperate with iE to enforce D to JH recombination. In addition, developing cE ⌬/⌬ and cE N/N B lineage cells had correspondingly decreased levels of germ-line transcripts from the JH region of the IgH locus (0 and I transcripts); although both had normal levels of germ-line VH transcripts, suggesting that cE may influence IgH locus V(D)J recombination by influencing accessibility of JH proximal regions of the locus. Consistent with chimera studies, peripheral cE ⌬/⌬ B cells had normal surface Ig and relatively normal class switch recombination. However, cE ⌬/⌬ B cells also had relatively normal somatic hypermutation of their IgH variable region genes, showing unexpectedly that the cE is not required for this process. The availability of mice with the iE mutation in their germ line will facilitate future studies to elucidate the roles of iE in VH(D)JH recombination in the context of IgH chromatin structure and germ-line transcription.germ-line transcription ͉ immunoglobulin heavy chain ͉ somatic hypermutation ͉ VDJ recombination ͉ class switch recombination T he mouse Ig heavy chain (IgH) locus can be divided into two principal regions: an Ϸ2.2-Mb 5Ј region containing clusters of variable (V H ), diversity (D H ) and joining (J H ) segments and an Ϸ200-kb region downstream region harboring the sets of constant region exons (C, C␦, C␥3, C␥1, C␥2b, C␥2a, C, and C␣) referred as C H genes. Generation of an Ig heavy chain protein, which is first expressed in B cell development, involves assembly of a V H DJ H exon upstream of C via the V(D)J recombination reaction (1). In antigen-stimulated peripheral B cells, expression of downstream IgH isotypes (such as IgG, IgE, or IgA) can occur via a class switch recombination (CSR) reaction that replaces C with a downstream set of C H exons (2). Somatic hypermutation (SHM) of the variable region exon, which allows selection of higher affinity antibodies, also occurs in antigen-stimulated B cells (3). V(D)J recombination is initiated by the RAG endonuclease, whereas CSR and SHM are initiated by activation induced deaminase (4). The overall mechanisms that control these processes in the context of B cell development and activation are still being elucidated; however, many studies have implicated a role for transcriptional control elements (5). Major known control elements in the IgH locus include the transcriptional enhancer that lies within the intr...

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“…1A). The first of these to be identified was the ϳ1-kb intronic enhancer E, which is situated in the intron between J H and C Targeted deletion studies with mice have revealed that E is important for VDJ joining (1,29,32,36).A 3Ј regulatory region (3Ј RR) extends ϳ35 kb downstream of the C␣ gene and includes multiple DNase I-hypersensitive (hs) sites. The murine 3Ј RR contains modules (Fig.…”

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confidence: 99%

Pax5 and Linker Histone H1 Coordinate DNA Methylation and Histone Modifications in the 3′ Regulatory Region of the Immunoglobulin Heavy Chain Locus

Giambra

Volpi

Emelyanov

et al. 2008

Molecular and Cellular Biology

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The 3 regulatory region (3 RR) of the murine immunoglobulin heavy chain (IgH) locus contains multiple DNase I-hypersensitive (hs) sites. Proximal sites hs3A, hs1.2, and hs3B are located in an extensive palindromic region and together with hs4 are associated with enhancers involved in the expression and class switch recombination of IgH genes. Distal hs5, -6, and -7 sites located downstream of hs4 comprise a potential insulator for the IgH locus. In pro-B cells, hs4 to -7 are associated with marks of active chromatin, while hs3A, hs1.2, and hs3B are not. Our analysis of DNA methylation-sensitive restriction sites of the 3 RR has revealed a similar modular pattern in pro-B cells; hs4 to -7 sites are unmethylated, while the palindromic region is methylated. This modular pattern of DNA methylation and histone modifications appears to be determined by at least two factors: the B-cell-specific transcription factor Pax5 and linker histone H1. In pre-B cells, a region beginning downstream of hs4 and extending into hs5 showed evidence of allele-specific demethylation associated with the expressed heavy chain allele. Palindromic enhancers become demethylated later in B-cell differentiation, in B and plasma cells.The immunoglobulin heavy chain (IgH) gene locus undergoes a panoply of regulated DNA events during B-cell development, including VDJ joining to construct variable-region genes; class switch recombination (CSR) to achieve the production of non-IgM classes, such as IgG, IgE, and IgA; and somatic hypermutation (reviewed in reference 23). The identification of the specific cis regulatory regions that regulate these processes is of considerable interest. Candidates include promoters that are locally associated with V and D segments and also with I regions upstream of each constant-region gene, except for C␦. In addition, regulators capable of acting at considerable distances from their target sequences flank the C H genes (Fig. 1A). The first of these to be identified was the ϳ1-kb intronic enhancer E, which is situated in the intron between J H and C Targeted deletion studies with mice have revealed that E is important for VDJ joining (1,29,32,36).A 3Ј regulatory region (3Ј RR) extends ϳ35 kb downstream of the C␣ gene and includes multiple DNase I-hypersensitive (hs) sites. The murine 3Ј RR contains modules (Fig. 1A) that are developmentally regulated, as assessed by DNase I hypersensitivity, reporter assays, and engagement with active chromatin marks. The three most proximal sites, i.e., hs3A, hs1.2, and hs3B, form a 25-kb palindromic region by virtue of almost identical hs3A and hs3B sequences in inverted orientation at either end of this segment and by intervening families of locally repetitive sequences flanking the central hs1.2 enhancer (4, 34). hs3A, hs1.2, and hs3B are DNase I hypersensitive at later stages of B-cell development, i.e., in plasma cells (14,20). A second unit contains hs4, which appears to be active beginning in pro-B cells and continuing throughout B-cell development (14,20,24). A third 3Ј RR m...

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The Ig heavy chain intronic enhancer core region is necessary and sufficient to promote efficient class switch recombination

Cited by 38 publications

References 45 publications

The Eμ Enhancer Region Influences H Chain Expression and B Cell Fate without Impacting IgVH Repertoire and Immune Response In Vivo

The Eμ Enhancer Region Influences H Chain Expression and B Cell Fate without Impacting IgVH Repertoire and Immune Response In Vivo

Elucidation of IgH intronic enhancer functions via germ-line deletion

Pax5 and Linker Histone H1 Coordinate DNA Methylation and Histone Modifications in the 3′ Regulatory Region of the Immunoglobulin Heavy Chain Locus

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