MicroRNA-155 controls affinity-based selection by protecting c-MYC+ B cells from apoptosis
Rinako Nakagawa, … , Robert Brink, Elena Vigorito
Rinako Nakagawa, … , Robert Brink, Elena Vigorito
Published December 14, 2015
Citation Information: J Clin Invest. 2016;126(1):377-388. https://doi.org/10.1172/JCI82914.
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Research Article Immunology

MicroRNA-155 controls affinity-based selection by protecting c-MYC+ B cells from apoptosis

Abstract

The production of high-affinity antibodies by B cells is essential for pathogen clearance. Antibody affinity for antigen is increased through the affinity maturation in germinal centers (GCs). This is an iterative process in which B cells cycle between proliferation coupled with the acquisition of mutations and antigen-based positive selection, resulting in retention of the highest-affinity B cell clones. The posttranscriptional regulator microRNA-155 (miR-155) is critical for efficient affinity maturation and the maintenance of the GCs; however, the cellular and molecular mechanism by which miR-155 regulates GC responses is not well understood. Here, we utilized a miR-155 reporter mouse strain and showed that miR-155 is coexpressed with the proto-oncogene encoding c-MYC in positively selected B cells. Functionally, miR-155 protected positively selected c-MYC+ B cells from apoptosis, allowing clonal expansion of this population, providing an explanation as to why Mir155 deletion impairs affinity maturation and promotes the premature collapse of GCs. We determined that miR-155 directly inhibits the Jumonji family member JARID2, which enhances B cell apoptosis when overexpressed, and thereby promotes GC B cell survival. Our findings also suggest that there is cooperation between c-MYC and miR-155 during the normal GC response, a cooperation that may explain how c-MYC and miR-155 can collaboratively function as oncogenes.

Authors

Rinako Nakagawa, Rebecca Leyland, Michael Meyer-Hermann, Dong Lu, Martin Turner, Giuseppina Arbore, Tri Giang Phan, Robert Brink, Elena Vigorito

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Figure 3

miR-155 expression is associated with cell cycle progression of GC B cells.

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miR-155 expression is associated with cell cycle progression of GC B cel...
SWHEL Mir155LacZ/+ B cells were adoptively transferred into CD45.1+ congenic recipient mice, which were then injected with HEL3X-SRBC and analyzed after 5 days. LacZ reporter staining is incompatible with permeabilization and, therefore, cells were sorted first using the strategy explained in Figure 2A. Subsequently, cell cycle was analyzed in the 4 subsets of GC B cells by DAPI staining. The mean of the indicated fraction ± SEM from 3 independent experiments is shown. (A) HEL-binding vs. DAPI. (B) Forward scatter (FSC) vs. side scatter (SSC). (C) S-phase and G2/M-phase B cells for each of the sorted subsets were gated as shown in A. The upper panel shows the CXCR4/CD86 distribution of cells in S-phase cells (black dots) superimposed on DZ cells (pink) or LZ cells (light blue) of the indicated subset. The lower panel is similar to the upper panel, except that G2/M-phase cells (black) are shown. The percentage of black dots over total cell per gate is shown. A representative FACS plot of the indicated subset out of 3 independent experiments is shown (A–C). (D) The indicated subsets were sorted at day 5 after HEL3x-SRBC immunization. Aicda, Prdm1, and Myc transcripts levels were analyzed by qPCR and normalized by Hprt. Naive follicular B cells (Fo-B) were sorted as B220+AA4.1–CD21/35intCD23hi cells from 2 naive mice. The experiment shown is representative of 3 independent sorting experiments. In each experiment, cDNA was prepared from sorted cells after pooling 5–10 mice. The mean ± SEM is shown. *P < 0.05, **P < 0.01, ***P < 0.001 using 1-way ANOVA followed by a Tukey’s multiple comparisons post-test.