Immunoglobulin repertoires in mice carrying a knock-in human Cµ gene downstream of the IGH 3' regulatory region
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ABSTRACT: To in-depth analyze the repertoire of B cells after the occurrence of recombination events joining SÙ to the IgH downstream regulatory region (3'RR)
Project description:Class Switch Recombination (CSR) is a DNA recombination reaction that diversifies the effector component of antibody responses. CSR is initiated by activation-induced cytidine deaminase (AID), which targets transcriptionally active immunoglobulin heavy chain (Igh) switch donor and acceptor DNA. The 3’ Igh super-enhancer, 3’ Regulatory Region (3’RR), is essential for acceptor region transcription, but how this function is regulated is unknown. Here we identify the chromatin reader ZMYND8 as an essential regulator of the 3’RR and CSR. In B cells, ZMYND8 binds promoters and super-enhancers, including the 3’RR, and controls its activity by modulating the enhancer transcriptional status. In its absence, there is increased 3’RR polymerase loading, and decreased acceptor region transcription and CSR. In addition to CSR, ZMYND8 deficiency impairs somatic hypermutation (SHM) of Igh, which is also dependent on the 3’RR. Thus ZMYND8 controls Igh diversification in mature B lymphocytes by regulating the activity of the 3’ Igh super-enhancer.
Project description:The IgH 3â?? regulatory region (3â??RR) controls class switch recombination (CSR) and somatic hypermutation (SHM) in B cells. The mouse 3â??RR contains four enhancer elements with hs1,2 flanked by inverted repeated sequences and the center of a 25-kb palindrome bounded by two hs3 enhancer inverted copies (hs3a and hs3b). hs4 lies downstream of the palindrome. Evolution maintained in mammals this unique palindromic arrangement suggesting that it is functionally significant. We report that deconstructing the palindromic IgH 3â??RR strongly impacts its function even when enhancers are preserved. CSR and IgH transcription appear poorly dependent from the 3â??RR architecture and are more or less preserved provided 3â??RR enhancers are present. By contrast, an â??architectural effectâ?? significantly lowers VH germline transcription, AID recruitment and SHM. In conclusion, this work indicates that the IgH 3â??RR does not simply pile up enhancer units but also optimally expose them into a functional architecture of crucial importance. RNAseq analysis of B-cell splenocytes with (S=stimulated) or without (R=resting) LPS activation from wt, delta2leftPAL, and deltaIRIS mice.
Project description:The IgH 3’ regulatory region (3’RR) controls class switch recombination (CSR) and somatic hypermutation (SHM) in B cells. The mouse 3’RR contains four enhancer elements with hs1,2 flanked by inverted repeated sequences and the center of a 25-kb palindrome bounded by two hs3 enhancer inverted copies (hs3a and hs3b). hs4 lies downstream of the palindrome. Evolution maintained in mammals this unique palindromic arrangement suggesting that it is functionally significant. We report that deconstructing the palindromic IgH 3’RR strongly impacts its function even when enhancers are preserved. CSR and IgH transcription appear poorly dependent from the 3’RR architecture and are more or less preserved provided 3’RR enhancers are present. By contrast, an “architectural effect” significantly lowers VH germline transcription, AID recruitment and SHM. In conclusion, this work indicates that the IgH 3’RR does not simply pile up enhancer units but also optimally expose them into a functional architecture of crucial importance.
Project description:We used 454 sequencing to assess the repertoire of B cell subsets from bone marrow, spleen, and small intestinal lamina propria from two mouse strains. We used a RAG2-GFP reporter mouse strain (129Sve background) to isolate CD19+ RAG2+ B lineage cells from bone marrow and small intestinal lamina propria and total splenic B cells. We used 5' RACE to amplify cDNA libraries using primers specific for the mu constant region of IgH and the Ig kappa constant region. We also used this technique to analyze total B cell libraries from Swiss Webster germ-free mice to compare to littermate controls that were cohoused with regular specific pathogen free (SPF) mice for 7 days. Examination of the Ig kappa repertoire and IgH repertoire in RAG2+ bone marrow B lineage cells compared to RAG2+ small intestinal lamina propria B lineage cells or total splenic B cells. There are 8 (Ig kappa) or 4 (IgH) independent experiments comparing repertoires in RAG2-GFP mice. Each experiment in RAG2-GFP+ mice consisted of a pool of 8-12 mice. There are 3 experiments comparing germ-free to colonized mouse total B cell repertoires, each consisting of one mouse per condition.
Project description:Numerous B-cell lymphomas feature translocations linking oncogenes with the IgH locus and epigenetic drugs such as histone deacetylase inhibitors (HDACi) have been approved to treat some of them. In this study we investigated IgH locus transcription in B-cell splenocytes stimulated with LPS and the HDACi SAHA. B-cell development is spatially and temporally regulated with the 3'RR enhancer of the IgH locus as a conductor. 3'RR is composed of 4 enhancer elements with a palindromic structure of great significance. We investigated the role of this palindrome with KOKI mice where the 30Kb structure of the 3'RR has been deleted of its palindromic structure.
Project description:We used 454 sequencing to assess the repertoire of B cell subsets from bone marrow, spleen, and small intestinal lamina propria from two mouse strains. We used a RAG2-GFP reporter mouse strain (129Sve background) to isolate CD19+ RAG2+ B lineage cells from bone marrow and small intestinal lamina propria and total splenic B cells. We used 5' RACE to amplify cDNA libraries using primers specific for the mu constant region of IgH and the Ig kappa constant region. We also used this technique to analyze total B cell libraries from Swiss Webster germ-free mice to compare to littermate controls that were cohoused with regular specific pathogen free (SPF) mice for 7 days.