scholarly journals Loop Extrusion Mediates Physiological Locus Contraction for V(D)J Recombination

2020 ◽  
Author(s):  
Hai-Qiang Dai ◽  
Hongli Hu ◽  
Jiangman Lou ◽  
Adam Yongxin Ye ◽  
Aimee M. Chapdelaine-Williams ◽  
...  
Keyword(s):  
B Cells ◽  
Heavy Chain ◽  
Factor Versus ◽  
Signal Sequence ◽  
Recombination Center ◽  
Recombination Signal Sequence ◽  
Opposite Orientation ◽  
Contraction Process ◽  
Per Se ◽  
B Lines

AbstractImmunoglobulin heavy chain locus (Igh) VH, D, and JH gene segments are developmentally assembled into V(D)J exons. RAG endonuclease initiates V(D)J recombination by binding a JH-recombination signal sequence (RSS) within a chromatin-based recombination center (RC) and then, in an orientation-dependent process, scans upstream D-containing chromatin presented by cohesin-mediated loop extrusion for convergent D-RSSs to initiate DJH-RC formation1,2. In primary pro-B cells, 100s of upstream VH-associated RSSs, embedded in convergent orientation to the DJH-RC-RSS, gain proximity to the DJH-RC for VH-to-DJH joining via a mechanistically-undefined VH-locus contraction process3-7. Here, we report that a 2.4 mega-base VH locus inversion in primary pro-B cells nearly abrogates rearrangements of normally convergent VH-RSSs and cryptic RSSs, even though locus contraction per se is maintained. Moreover, this inversion activated rearrangement of both cryptic VH-locus RSSs normally in the opposite orientation and, unexpectedly, of normally-oriented cryptic RSSs within multiple, sequential upstream convergent-CBE domains. Primary pro-B cells had significantly reduced transcription of Wapl8, a cohesin-unloading factor, versus levels in v-Abl pro-B lines that lack marked locus contraction or distal VH rearrangements2,9-11. Correspondingly, Wapl depletion in v-Abl lines activated VH-locus contraction and orientation-specific RAG-scanning across the VH-locus. Our findings indicate that locus contraction and physiological VH-to-DJH joining both are regulated via circumvention of CBE scanning impediments.

scholarly journals Critical roles of the immunoglobulin intronic enhancers in maintaining the sequential rearrangement of IgH and Igk loci

2006 ◽  
Vol 203 (7) ◽  
pp. 1721-1732 ◽  
Author(s):  
Matthew A. Inlay ◽  
Tongxiang Lin ◽  
Heather H. Gao ◽  
Yang Xu
Keyword(s):  
B Cells ◽  
Developmental Stage ◽  
Heavy Chain ◽  
Light Chain ◽  
Matrix Attachment Region ◽  
Cis Elements ◽  
Wild Type ◽  
Intronic Enhancer ◽  
Attachment Region

V(D)J recombination of immunoglobulin (Ig) heavy (IgH) and light chain genes occurs sequentially in the pro– and pre–B cells. To identify cis-elements that dictate this order of rearrangement, we replaced the endogenous matrix attachment region/Igk intronic enhancer (MiEκ) with its heavy chain counterpart (Eμ) in mice. This replacement, denoted EμR, substantially increases the accessibility of both Vκ and Jκ loci to V(D)J recombinase in pro–B cells and induces Igk rearrangement in these cells. However, EμR does not support Igk rearrangement in pre–B cells. Similar to that in MiEκ−/− pre–B cells, the accessibility of Vκ segments to V(D)J recombinase is considerably reduced in EμR pre–B cells when compared with wild-type pre–B cells. Therefore, Eμ and MiEκ play developmental stage-specific roles in maintaining the sequential rearrangement of IgH and Igk loci by promoting the accessibility of V, D, and J loci to the V(D)J recombinase.

scholarly journals Positive and negative selection of antigen-specific B cells in transgenic mice expressing variant forms of the VH1 (T15) heavy chain

2000 ◽  
Vol 12 (6) ◽  
pp. 873-885 ◽  
Author(s):  
James J. Kenny ◽  
Eric G. Derby ◽  
Jeffrey A. Yoder ◽  
Shawn A. Hill ◽  
Randy T. Fischer ◽  
...  
Keyword(s):  
B Cells ◽  
Transgenic Mice ◽  
Heavy Chain ◽  
Negative Selection ◽  
Selection Of

scholarly journals Characterization of B-cell Receptor Heavy Chain Complementarity-determining Region 3 Repertoire Based on the Differences of Symbiotic Microorganisms in the Gut of Mice

2021 ◽  
Author(s):  
Jun Li ◽  
Yurong Pan ◽  
Qingqing Ma ◽  
Long Ma ◽  
Bin Shi ◽  
...  
Keyword(s):  
Small Intestine ◽  
B Cells ◽  
B Cell ◽  
Heavy Chain ◽  
Intestinal Microflora ◽  
Cell Receptor ◽  
Memory B Cells ◽  
B Cell Receptor ◽  
Positive Effects ◽  
Significant Difference

Abstract Background Colonization of gut microorganism is related to maturation of B cells in peripheral immune organs. This study aims to investigate the effect of intestinal microflora in Germ-free (GF), Specific Pathogen-free (SPF) and Clean (CL) BALB/C mice to small intestine total B-cell and memory B-cell receptor (BCR) complementary-determining region 3 (CDR3) repertoire. Results The composition and characteristics of intestinal microflora were analyzed by 16S rDNA sequencing. Genomic DNA extracted from small intestine tissue and memory B-cells of GF, SPF and CL mice were conducted via high-throughput DNA sequencing methods. As expected, significant differences of gut microflora diversity were observed in the three mice groups. CL group showed the most diversity, followed by SPF group, and GF group had the lowest diversity. Moreover, anormogenesis of intestinal lymphoid tissue were observed in GF mice. Diversity of the BCR heavy chain CDR3 repertoire in memory B cells were significant difference among three groups, but not in total B cells. The nucleotide polymorphism, usage frequency of gene segments (V, D, J, V–J gene segments) and amino acid of total B cells and memory B cells CDR3 were comparable among three mice groups, and there was significant difference between CL and GF mice groups. Conclusions The results of this study advocate that the colonization of intestinal microorganisms affect the diversity of B cells CDR3 repertoire. Elucidating mechanism of microbiome participated in the function of intestinal mucosal immune system may have positive effects on human health, and it requires further investigation.

scholarly journals T-independent antigen induces humoral memory through germinal centers

2022 ◽  
Vol 219 (3) ◽  
Author(s):  
Xin Liu ◽  
Yongshan Zhao ◽  
Hai Qi
Keyword(s):  
B Cells ◽  
Immune Responses ◽  
Germinal Center ◽  
Plasma Cells ◽  
Underlying Mechanism ◽  
Memory B Cells ◽  
Antigen B ◽  
Per Se ◽  
Humoral Responses ◽  
Human And Mouse

T-dependent humoral responses generate long-lived memory B cells and plasma cells (PCs) predominantly through germinal center (GC) reaction. In human and mouse, memory B cells and long-lived PCs are also generated during immune responses to T-independent antigen, including bacterial polysaccharides, although the underlying mechanism for such T-independent humoral memory is not clear. While T-independent antigen can induce GCs, they are transient and thought to be nonproductive. Unexpectedly, by genetic fate-mapping, we find that these GCs actually output memory B cells and PCs. Using a conditional BCL6 deletion approach, we show memory B cells and PCs fail to last when T-independent GCs are precluded, suggesting that the GC experience per se is important for programming longevity of T-independent memory B cells and PCs. Consistent with the fact that infants cannot mount long-lived humoral memory to T-independent antigen, B cells from young animals intrinsically fail to form T-independent GCs. Our results suggest that T-independent GCs support humoral memory, and GC induction may be key to effective vaccines with T-independent antigen.

scholarly journals Immunoglobulin gene rearrangements in normal mouse B cells

1982 ◽  
Vol 2 (7) ◽  
pp. 829-836
Author(s):  
P Early ◽  
C Nottenburg ◽  
I Weissman ◽  
L Hood
Keyword(s):  
B Cells ◽  
Heavy Chain ◽  
Germ Line ◽  
Gene Segment ◽  
Immunoglobulin M ◽  
Chain Gene ◽  
Allelic Exclusion ◽  
Immunoglobulin Gene ◽  
Spleen Cells ◽  
Surface Immunoglobulin

We have analyzed the structure of rearranged mu heavy-chain genes obtained from the genomic DNA of normal BALB/c mouse spleen cells expressing surface immunoglobulin M. Examples were found of two types of nonproductive rearrangements, which may be responsible for allelic exclusion in normal B cells. In one of these rearrangements, a germ line D gene segment has joined to the JH4 gene segment but no V/D joining has occurred. We present evidence that D gene segments lie as a cluster between V and J gene segments in the germ line. A comparison of conserved sequences in V and D gene segments suggests that the D gene segments, which are found only in the heavy-chain gene family, may have evolved from V gene segments similar to the Vk family.

scholarly journals Altered BCR and TLR signals promote enhanced positive selection of autoreactive transitional B cells in Wiskott-Aldrich syndrome

2015 ◽  
Vol 212 (10) ◽  
pp. 1663-1677 ◽  
Author(s):  
Nikita S. Kolhatkar ◽  
Archana Brahmandam ◽  
Christopher D. Thouvenel ◽  
Shirly Becker-Herman ◽  
Holly M. Jacobs ◽  
...  
Keyword(s):  
B Cells ◽  
Positive Selection ◽  
B Cell ◽  
Heavy Chain ◽  
High Throughput Sequencing ◽  
Cell Stage ◽  
Wiskott Aldrich Syndrome ◽  
Transitional B Cells ◽  
Selection Of

Wiskott-Aldrich syndrome (WAS) is an X-linked immunodeficiency disorder frequently associated with systemic autoimmunity, including autoantibody-mediated cytopenias. WAS protein (WASp)–deficient B cells have increased B cell receptor (BCR) and Toll-like receptor (TLR) signaling, suggesting that these pathways might impact establishment of the mature, naive BCR repertoire. To directly investigate this possibility, we evaluated naive B cell specificity and composition in WASp-deficient mice and WAS subjects (n = 12). High-throughput sequencing and single-cell cloning analysis of the BCR repertoire revealed altered heavy chain usage and enrichment for low-affinity self-reactive specificities in murine marginal zone and human naive B cells. Although negative selection mechanisms including deletion, anergy, and receptor editing were relatively unperturbed, WASp-deficient transitional B cells showed enhanced proliferation in vivo mediated by antigen- and Myd88-dependent signals. Finally, using both BCR sequencing and cell surface analysis with a monoclonal antibody recognizing an intrinsically autoreactive heavy chain, we show enrichment in self-reactive cells specifically at the transitional to naive mature B cell stage in WAS subjects. Our combined data support a model wherein modest alterations in B cell–intrinsic, BCR, and TLR signals in WAS, and likely other autoimmune disorders, are sufficient to alter B cell tolerance via positive selection of self-reactive transitional B cells.

scholarly journals Recombination may occur in the absence of transcription in the immunoglobulin heavy chain recombination centre

2020 ◽  
Vol 48 (7) ◽  
pp. 3553-3566
Author(s):  
Chloé Oudinet ◽  
Fatima-Zohra Braikia ◽  
Audrey Dauba ◽  
Ahmed Amine Khamlichi
Keyword(s):  
B Cells ◽  
Single Cell ◽  
Chromatin Remodeling ◽  
Heavy Chain ◽  
Single Cell Level ◽  
Mouse Line ◽  
Cell Level ◽  
Igh Locus ◽  
Chromatin Remodeling Complexes ◽  
Mechanistic Basis

Abstract Developing B cells undergo V(D)J recombination to generate a vast repertoire of Ig molecules. V(D)J recombination is initiated by the RAG1/RAG2 complex in recombination centres (RCs), where gene segments become accessible to the complex. Whether transcription is the causal factor of accessibility or whether it is a side product of other processes that generate accessibility remains a controversial issue. At the IgH locus, V(D)J recombination is controlled by Eμ enhancer, which directs the transcriptional, epigenetic and recombinational events in the IgH RC. Deletion of Eμ enhancer affects both transcription and recombination, making it difficult to conclude if Eμ controls the two processes through the same or different mechanisms. By using a mouse line carrying a CpG-rich sequence upstream of Eμ enhancer and analyzing transcription and recombination at the single-cell level, we found that recombination could occur in the RC in the absence of detectable transcription, suggesting that Eμ controls transcription and recombination through distinct mechanisms. Moreover, while the normally Eμ-dependent transcription and demethylating activities were impaired, recruitment of chromatin remodeling complexes was unaffected. RAG1 was efficiently recruited, thus compensating for the defective transcription-associated recruitment of RAG2, and providing a mechanistic basis for RAG1/RAG2 assembly to initiate V(D)J recombination.

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