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Blimp1 controls plasma cell physiology and function

ABSTRACT: Antibody-secreting plasma cells are the terminal stage of the B-cell lineage. Plasma cell differentiation requires a major resetting of gene expression to silence the B cell transcriptional program, whilst establishing secretory function and long-term survival. The transcription factors Blimp1 and Irf4 are essential for the initial differentiation of activated B cells to antibody-secreting cells, however their function in mature plasma cells remains elusive. We have found that while Irf4 was essential for plasma cell survival, Blimp1 was dispensable. Blimp1-deficient cells retained the unique plasma cell transcriptional signature, but lost the ability to secrete antibody or to maintain the characteristic size and ultrastructure of plasma cells. Blimp1 was required for full expression of many components of the unfolded protein response (UPR), including Xbp1 and Atf6, as well as for the appropriate processing of Igh mRNA. The overlap of Blimp1 and Xbp1 function was restricted to the UPR genes, with Blimp1 uniquely regulating activity of the mTOR pathway, plasma cell size and morphology. These studies establish Blimp1 as a major regulator of the UPR pathway that is also required for the unique metabolic requirements of plasma cells enabling the secretion of protective antibody.

ORGANISM(S): Mus musculus

PROVIDER: GSE70981 | GEO | 2016/01/18

SECONDARY ACCESSION(S): PRJNA290087

REPOSITORIES: GEO

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Blimp1 controls plasma cell physiology and function

Project description:Antibody-secreting plasma cells are the terminal stage of the B-cell lineage. Plasma cell differentiation requires a major resetting of gene expression to silence the B cell transcriptional program, whilst establishing secretory function and long-term survival. The transcription factors Blimp1 and Irf4 are essential for the initial differentiation of activated B cells to antibody-secreting cells, however their function in mature plasma cells remains elusive. We have found that while Irf4 was essential for plasma cell survival, Blimp1 was dispensable. Blimp1-deficient cells retained the unique plasma cell transcriptional signature, but lost the ability to secrete antibody or to maintain the characteristic size and ultrastructure of plasma cells. Blimp1 was required for full expression of many components of the unfolded protein response (UPR), including Xbp1 and Atf6, as well as for the appropriate processing of Igh mRNA. The overlap of Blimp1 and Xbp1 function was restricted to the UPR genes, with Blimp1 uniquely regulating activity of the mTOR pathway, plasma cell size and morphology. These studies establish Blimp1 as a major regulator of the UPR pathway that is also required for the unique metabolic requirements of plasma cells enabling the secretion of protective antibody. RNA-seq was performed on wild type, Blimp1-/- and Xbp1-/- mouse plasma cells. Between two to four biological replicates were generated and sequenced for each sample.

2016-01-18 | E-GEOD-70981 | biostudies-arrayexpress

Transcriptomic analysis of in-vitro plasma cell generation from follicular B cells lacking Xbp1 [Xbp1_PC_stim]

Project description:During plasma cell differentiation there is activation of UPR gene expression that has been termed the physiological UPR of plasma cell differentiation. This is canonically thought to be downstream of Blimp1-mediated increases in immunoglobulin gene production and activation of the Xbp1 transcription factor by the RNA splicing activity of the ER-stress sensor IRE1α. Having observed UPR-affiliated gene expression prior to upregulation of Blimp1 as reported in the companion linked series, we endeavored to determine the necessity of Xbp1 activity in the early remodeling of the ER in nascent plasma cells. To this end, we mated mice harboring a floxed exon 2 of the Xbp1 gene (Xbp1flox) to mice expressing a tamoxifen-inducible cre recombinase under the control of the human CD20 promoter (hCD20-TamCre). These mice and their hCD20-TamCre-Xbp1wt litermates were fed oral tamoxifen in their diet for two weeks and follicular B cells were prepared for in-vitro plasma cell differentiation studies. We report here that prior to plasma cell differentiation as measured by CD138 expression, which coincides temporally with Blimp1 expression, there is no defect in UPR-affiliated gene expression in cells lacking Xbp1.

2019-12-05 | GSE141422 | GEO

An inter-chromosomal transcription hub activates the unfolded protein response in plasma cells

Project description:Previous studies have indicated that the transcription signature of antibody-secreting cells is closely associated with the induction of the unfolded protein response pathway (UPR). Here we have used genome-wide and single cell analyses to examine the folding patterns of plasma cell genomes. We found that plasma cells adopt a cartwheel configuration and undergo large-scale changes in chromatin folding at genomic regions associated with a plasma cell specific transcription signature. During plasma cell differentiation, Blimp1 assembles into an inter-chromosomal transcription hub with genes associated with the UPR, biosynthesis of the endoplasmic reticulum (ER) as well as a cluster of genes linked with Alzheimer’s disease. We suggest that the assembly of the Blimp1-UPR-ER transcription hub permits the coordinate activation of a wide spectrum of genes that collectively establish plasma cell identity.

2019-04-10 | GSE113014 | GEO

A dichotomy of gene regulatory associations during the activated B-cell to plasmablast transition [ChIP-seq]

Project description:The activated B-cell (ABC) to plasmablast transition is the cusp of antibody secreting cell (ASC) differentiation but is incompletely defined. We apply expression time-courses, parsimonious gene correlation network analysis, and ChIP-seq to explore this in human cells. The transition initiates with input signal loss leading within hours from cell growth dominant programs to enhanced proliferation, accompanied from 24h by ER-stress response, secretory optimization and upregulation of ASC features. Clustering of genomic occupancy for ASC transcription factors (TFs) IRF4, BLIMP1 and XBP1 with CTCF and histone marks defines distinct patterns for each factor in plasmablasts. Integrating TF-associated clusters and modular gene expression identifies a dichotomy: XBP1 and IRF4 significantly link to gene modules induced in plasmablasts, but not to modules of repressed genes, while BLIMP1 links to modules of ABC genes repressed in plasmablasts but is not significantly associated with modules induced in plasmablasts. Pharmacological inhibition of the G9A (EHMT2) histone-methytransferase, a BLIMP1 co-factor that catalyzes repressive H3K9me2 marks, leaves functional ASC differentiation intact but de-represses ABC-state genes. Thus, in human plasmablasts IRF4 and XBP1 emerge as the dominant association with ASC gene expression, while BLIMP1 links to repressed modules with particular focus in repression of the B-cell activation state.

2020-08-24 | GSE142493 | GEO

A dichotomy of gene regulatory associations during the activated B-cell to plasmablast transition [Microarray]

2020-08-24 | GSE142492 | GEO

A CRISPR/Cas9-mediated screen identifies regulators of early plasma cell differentiation

Project description:The differentiation of B cells into antibody-secreting cells depends on cell division-coupled, epigenetic and other cellular processes that are incompletely understood. We have developed a CRISPR/Cas9-based screen that models an early stage of T cell-dependent plasma cell differentiation and measures B cell survival or proliferation versus the formation of CD138+ plasmablasts. Here, we refined and extended this screen to more than 500 candidate genes that are highly expressed in plasma cells. Among known genes whose deletion preferentially affected plasmablast formation were the transcriptional regulators Prdm1, Irf4 and Pou2af1, and the Ern1 gene encoding the ER stress sensor IRE1a. Moreover, we newly identified several genes involved in NF-kB or p38 signaling (Pim2, Nfkbia, Mapk14), vesicle trafficking (Arf4, Preb) and epigenetic regulators that form part of the NuRD complexes (Hdac1, Mta2, Mbd2). Defective plasmablast formation caused by Ern1 deletion could not be rescued by spliced XBP1 (XBP1s), a transcription factor dependent on and downstream of IRE1a, suggesting that in early plasma cell differentiation IRE1a acts independently of XBP1s. The deletion of ARF4, a small GTPase required for ER-to-Golgi transport, impaired plasmablast formation by blocking antibody secretion. Plasmablast formation after Hdac1 deletion was consistently reduced by about 50%, while deletion of the closely related Hdac2 gene had no effect. Hdac1 knock-out led to strongly perturbed protein expression of antagonistic transcription factors that specify plasma cell versus B cell identity (by decreasing IRF4 and BLIMP1 and increasing BACH2 and PAX5). Taken together, our results highlight specific and non-redundant roles for Ern1, Arf4 and Hdac1 in the early steps of plasma cell differentiation.

2022-12-22 | PXD038201 | Pride

The Xbp1-regulated transcription factor Mist1 restricts antibody secretion by restraining Blimp1 expression in plasma cells

Project description:Antibody secretion by plasma cells provides acute and long-term protection against pathogens. The high secretion potential of plasma cells depends on the unfolded protein response, which is controlled by the transcription factor Xbp1. Here, we analyzed the Xbp1-dependent gene expression program of plasma cells and identified Bhlha15 (Mist1) as the most strongly activated Xbp1 target gene. As Mist1 plays an important role in other secretory cell types, we analyzed in detail the phenotype of Mist1-deficient plasma cells in Cd23-Cre Bhlha15(fl/fl) mice under steady-state condition or upon NP-KLH immunization. Under both conditions, Mist1-deficient plasma cells were 1.4-fold reduced in number and exhibited increased IgM production and antibody secretion compared to control plasma cells. At the molecular level, Mist1 regulated a largely different set of target genes compared to Xbp1. Notably, expression of the Blimp1 protein, which is known to activate immunoglobulin gene expression and to contribute to antibody secretion, was 1.3-fold upregulated in Mist1-deficient plasma cells, which led to a moderate downregulation of most Blimp1-repressed target genes in the absence of Mist1. Importantly, a 2-fold reduction of Blimp1 (Prdm1) expression was sufficient to restore the cell number and antibody expression of plasma cells in Prdm1(Gfp/+) Cd23-Cre Bhlha15(fl/fl) mice to the same level seen in control mice. Together, these data indicate that Mist1 restricts antibody secretion by restraining Blimp1 expression, which likely contributes to the viability of plasma cells.

2022-10-18 | GSE190591 | GEO

Transcriptomic analysis of naïve B cells and antigen-specific activated B cells and plasma cells from 4dpi NP-LPS immunized mice [NPLPS_PC]

Project description:Little is known about the earliest transcriptomic events in plasma cell differentiation. Indeed, activation of UPR-affiliated gene expression is seen in in-vitro plasma cell differentiation prior to Blimp1 upregulation and in the absence of Xbp1 as we show in linked companion series. In this study, Blimp1 reporter mice were immunized with the T-independent antigen NP-LPS four days prior to spleen harvest and naïve B cells, NP-binding activated B cells and NP-binding plasma cells were analyzed by bulk RNA-seq. Here we report the activation of ER remodeling gene expression in antigen-specific activated B cells in-vivo prior to upregulation of Blimp1 transcription.

2019-12-05 | GSE141420 | GEO

Transcriptomic analysis of in-vitro plasma cell generation from follicular B cells lacking Raptor [Raptor_PC_stim]

Project description:Early UPR-affiliated gene expression occurs before Blimp1 upregulation and independent of canonical ER-stress activated Xbp1. In linked companion studies we detailed how Xbp1-independent activation of early plasma cell specific UPR-affiliated gene expression occurs prior to Blimp1 upregulation. Having observed that these genes overlapped with canonical mTORC1 signature genes and that PC-poised marginal zone B cells have higher base line mTORC1 signaling we designed this experiment to assess the dependence of early ER-remodeling on mTORC1 signaling in plasma cell differentiation. To this end we mated mice harboring a floxed allele for the mTORC1 adapter Raptor (B6.Rptor-flox) to mice expressing a tamoxifen-inducible cre recombinase under the control of the human CD20 promoter (B6.hCD20-TamCre). These mice and their hCD20-TamCre-Rptor-wt litermates were fed oral tamoxifen in their diet for two weeks and follicular B cells were prepared for in-vitro plasma cell differentiation studies. We report here that as early as 24 hours of stimulation in culture we see a marked defect in the ability of Rptor null B cells to upregulate UPR-affiliated genes associated with plasma cell differentiation.

2019-12-05 | GSE141421 | GEO

Transcriptomic analysis of naïve B cells and plasma cells as well as in vitro stimulated B cells from Blimp1-GFP reporter mice [Blimp1_reporter_PC_stim]

Project description:Though it is known that plasma cells utilize the unfolded protein response to remodel their ER it is generally believed that this follows Blimp1-mediated transcriptional and translational increases in immunoglobulin protein. In this study we utilize Blimp1 reporter mice to examine the earliest activation of UPR-affiliated gene expression in plasma cell inductive stimulation of B cells. We combine in-vivo gene expression of follicular B cells, marginal zone B cells from spleen and short and long lived plasma cells from bone marrow with in-vivo generated activated B cells and plasma cells from the same mice to examine gene expression before and after Blimp1-upregulation. Using a novel in-vitro stimulation approach we separate those UPR-affiliated genes activated by B cell activation and those requiring a plasma cell inductive stimulus. We report here that these plasma cell specific UPR-affiliated genes are activated in absence of ER-stress prior to upregulation of Blimp1.

2019-12-05 | GSE141419 | GEO

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