Resting innate-like B cells leverage sustained Notch2/mTORC1 signaling to achieve rapid and mitosis-independent plasma cell differentiation
Brian T. Gaudette, … , Ivan Maillard, David Allman
Brian T. Gaudette, … , Ivan Maillard, David Allman
Published September 2, 2021
Citation Information: J Clin Invest. 2021;131(20):e151975. https://doi.org/10.1172/JCI151975.
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Research Article Immunology

Resting innate-like B cells leverage sustained Notch2/mTORC1 signaling to achieve rapid and mitosis-independent plasma cell differentiation

Abstract

Little is known about how cells regulate and integrate distinct biosynthetic pathways governing differentiation and cell division. For B lineage cells it is widely accepted that activated cells must complete several rounds of mitosis before yielding antibody-secreting plasma cells. However, we report that marginal zone (MZ) B cells, innate-like naive B cells known to generate plasma cells rapidly in response to blood-borne bacteria, generate functional plasma cells despite cell-cycle arrest. Further, short-term Notch2 blockade in vivo reversed division-independent differentiation potential and decreased transcript abundance for numerous mTORC1- and Myc-regulated genes. Myc loss compromised plasma cell differentiation for MZ B cells, and reciprocally induced ectopic mTORC1 signaling in follicular B cells enabled division-independent differentiation and plasma cell–affiliated gene expression. We conclude that ongoing in situ Notch2/mTORC1 signaling in MZ B cells establishes a unique cellular state that enables rapid division-independent plasma cell differentiation.

Authors

Brian T. Gaudette, Carly J. Roman, Trini A. Ochoa, Daniela Gómez Atria, Derek D. Jones, Christian W. Siebel, Ivan Maillard, David Allman

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Figure 5

Sustained Notch2 signaling maintains function-related gene expression for MZ B cells.

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Sustained Notch2 signaling maintains function-related gene expression fo...
C57BL/6 mice were treated with anti–Notch2 (N2) blocking or isotype control antibodies (Iso) for up to 96 hours. Splenocytes were analyzed by flow cytometry at the indicated time points. (A) Shown is the relative proportion of mature splenic B cells (live, singlet CD19+, AA4.1–) consisting of CD23–, CD1d+, IgMhi MZ B cells. Symbols represent data from individual mice with means indicated by horizontal lines. Individual values, mean ± SEM. ***P < 0.001 1-way ANOVA, Dunnett’s multiple comparison to isotype control (t = 0). (B–D) RNAseq was performed with the indicated sorted splenic B cell populations at 12, 24, and 48 hours after anti-Notch2 administration versus at 48 hours for isotype controls. (B) Volcano plots displaying the fold change in log2 TPM versus significance (–log10 adjusted P value, eBayes method with Benjamini-Hochberg correction) for all gene expression changes between Notch-deprived MZ (top) and follicular (FO, bottom) B cells and their respective isotype controls at the indicated time points. Genes are color-coded as follows: red: down in Notch2 blockade versus isotype control, adjusted P < 0.05, lfc > 1; blue: up in Notch2 blockade versus isotype control, adjusted P < 0.05, lfc > 1. Canonical Notch targets are indicated. (C) Log2 TPM data for canonical Notch target gene transcripts showing the mean (bar) and 75% CI (box) and 95% CI (whisker). (D) GSEA for ChIP-seq verified human Notch targets at 12, 24, or 48 hours after giving anti–N2 antibodies (top, left to right) (34), as well as for Myc targets and gene sets affiliated with plasma cell function and/or the cell cycle at 48 hours. NES: Normalized Enrichment Score; Nom.p.val: Nominal P value; and FDR.q.val: FDR q value are shown. FDR-q computed using 1000 gene-set permutations. All RNAseq data are compiled from 4 animals per treatment group and time point.