The immunoglobulin heavy chain 3' regulatory region superenhancer controls mouse B1 B-cell fate and late VDJ repertoire diversity

International audienceThe immunoglobulin heavy chain (IgH) 3' regulatory region (3'RR) superenhancer controls B2 B-cell IgH transcription and cell fate at the mature stage but not early repertoire diversity. B1 B cells represent a small percentage of total B cells differing from B2 B cells by several points such as precursors, development, functions, and regulation. B1 B cells act at the steady state to maintain homeostasis in the organism and during the earliest phases of an immune response, setting them at the interface between innate and acquired immunity. We investigated the role of the 3'RR superenhancer on B1 B-cell fate. Similar to B2 B cells, the 3'RR controls mu transcription and cell fate in B1 B cells. In contrast to B2 B cells, 3'RR deletion affects B1 B-cell late repertoire diversity. Thus, differences exist for B1 and B2 B-cell 3'RR control during B-cell maturation. For the first time, these results highlight the contribution of the 3'RR superenhancer at this interface between innate and acquired immunity

The IgH 3 ' regulatory region super-enhancer does not control IgA class switch recombination in the B1 lineage

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Homozygous iMycCα transgenic mice as a model of plasma B-cell lymphomas

International audienceThe 3' regulatory region (3'RR) located downstream from the Cα gene is the conductor of transcription, accessibility, and remodeling of the IgH locus at mature B-cell stages. Convincing demonstrations of the essential contributions of the 3'RR in B-cell lymphomagenesis have been provided by mouse models which bring the oncogene c-Myc under the 3'RR transcriptional control. In this study, we developed a mouse model of CD138+ plasma B-cell lymphomas. If the KI of c-myc directly into Cα just 5' to the 3'RR in iMycCα mice produced B-cell lymphomas with low kinetics, we enforced c-myc production in iMycCα mice by the generation of homozygous c-myc transgenic mice. Our results show that homozygous iMycCα mice lead to a mouse model of plasma CD138+ B-cell lymphomas with interesting and wide transcriptomic similarities to human multiple myeloma and appropriated emergence kinetics that can be used to test new experimental therapeutic approaches

CD95L concatemers highlight different stoichiometries of CD95‐mediated apoptotic and non‐apoptotic pathways

International audienceTo better understand the stoichiometry of CD95L required to trigger apoptotic and nonapoptotic signals, we generated several concatemers from dimer hexamer conjugated via a flexible link (GGGGS)2 . These ligands reveal that although hexameric structure is best cell death, sufficient induce response in CD95-sensitive Jurkat cells. Interestingly, only trimeric forms can implement potent Ca2+ response, suggesting while CD95 aggregation controls implementation signal, both conformation are pathway

The IgH 3' regulatory region governs μ chain transcription in mature B lymphocytes and the B cell fate.

International audienceWe report that the IgH 3' regulatory region (3'RR) has no role on μ chain transcription and pre-BCR expression in B cell progenitors. In contrast, analysis of heterozygous IgH aΔ3'RR/bwt mice indicated that the 3'RR controls μ chain transcripts in mature splenocytes and impacts membrane IgM density without obvious effect on BCR signals (colocalisation with lipid rafts and phosphorylation of Erk and Akt after BCR crosslinking). Deletion of the 3'RR modulates the B cell fate to less marginal zone B cells. In conclusion, the 3'RR is dispensable for pre-BCR expression and necessary for optimal commitments toward the marginal zone B cell fate. These results reinforce the concept of a dual regulation of the IgH locus transcription and accessibility by 5' elements at immature B cell stages, and by the 3'RR as early as the resting mature B cell stage and then along further activation and differentiation

Targeting IgE polyadenylation signal with antisense oligonucleotides decreases IgE secretion and plasma cell viability

International audienceBACKGROUND: Allergy regroups numerous complex and various diseases classified as IgE-dependent or non-IgE-dependent hypersensitivities. IgEs are expressed as membrane and secreted forms by B cells and plasma cells, respectively. In IgE-mediated hypersensitivity, IgE secretion and binding to the high-affinity IgE receptor FcεRI on effector cells are responsible for the onset of allergic symptoms; in contrast, surface IgE expression as a B-cell receptor is barely detectable. OBJECTIVE: Our aim was to test an innovative antisense approach to reducing IgE secretion. METHODS: We designed an antisense oligonucleotide (ASO) targeting the polyadenylation signal of human secreted IgE to redirect IgE transcript polyadenylation from the secreted form to the membrane form. ASO treatments were performed on B cells from transgenic mice expressing humanized IgE (InEps mice), as well as on human primary B cells and myeloma cells. In vivo ASO delivery was tested by using an InEps mouse model. RESULTS: We demonstrated that treatment with a morpholino ASO targeting the secreted IgE polyadenylation signal drastically decreased IgE secretion and inversely increased membrane IgE mRNA expression. In addition, ASO treatment induced apoptosis of IgE-expressing U266 myeloma cells, and RNA sequencing revealed attenuation of their plasma cell phenotype. Remarkably, systemic administration of an ASO coupled with Pip6a as an arginine-rich cell-penetrating peptide decreased IgE secretion in vivo. CONCLUSION: Altogether, this ASO strategy could be an effective way to decrease IgE secretion and allergic symptoms in patients with IgE-dependent allergies, and it could also promote allergen tolerance through apoptosis of IgE(+) antibody-secreting cells

Caractéristiques des IgA promptes à se déposer dans le mésangium

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A mouse model recapitulating human monoclonal heavy chain deposition disease evidences the relevance of proteasome inhibitor therapy.

International audienceRandall-type heavy chain deposition disease (HCDD) is a rare disorder characterized by glomerular and peritubular amorphous deposits of a truncated monoclonal immunoglobulin heavy chain (HC) bearing a deletion of the first constant domain (CH1). We created a transgenic mouse model of HCDD using targeted insertion in the immunoglobulin κ locus of a human HC extracted from a HCDD patient. Our strategy allows the efficient expression of the human HC in mouse B and plasma cells, and conditional deletion of the CH1 domain reproduces the major event underlying HCDD. We show that the deletion of the CH1 domain dramatically reduced serum HC levels. Strikingly, even with very low serum level of truncated monoclonal HC, histologic studies revealed typical Randall-type renal lesions that were absent in mice expressing the complete human HC. Bortezomib-based treatment resulted in a strong decrease of renal deposits. We further demonstrated that this efficient response to proteasome inhibitors mostly relies on the presence of the isolated truncated HC that sensitizes plasma cells to bortezomib through an elevated unfolded protein response (UPR). This new transgenic model of HCDD efficiently recapitulates the pathophysiologic features of the disease and demonstrates that the renal damage in HCDD relies on the production of an isolated truncated HC, which, in the absence of a LC partner, displays a high propensity to aggregate even at very low concentration. It also brings new insights into the efficacy of proteasome inhibitor-based therapy in this pathology