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 5

Positively selected LZ B cells gain antiapoptotic signals via miR-155.

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Positively selected LZ B cells gain antiapoptotic signals via miR-155. (...
(A) Splenic B cells derived from Mycgfp/gfp SWHEL Mir155+/+ or Mycgfp/gfp SWHEL Mir155–/– mice were adoptively transferred into CD45.1+ congenic recipients, which were injected with HEL3X-SRBC. Four days later, spleen cells from these mice were analyzed. The graph shows the percentage of AnnexinV+7-AAD– cells determined by flow cytometry in DZ and LZ B cells further divided on the basis of c-MYC expression. The mean ± SEM from 2 independent experiments is shown (Mycgfp/gfp Mir155+/+, n = 13; Mycgfp/gfp Mir155–/–, n = 13). *P < 0.05 using 1-way ANOVA followed by a Tukey’s multiple comparisons post-test. (B) SWHEL Mir155LacZ/+ or SWHEL Mir155LacZ/– B cells were adoptively transferred into CD45.1+ congenic recipients, which were injected with HEL3X-SRBC. Spleen cells from these mice were analyzed 5 days later. The graph shows the percentage of AnnexinV+7-AAD– cells determined by flow cytometry in DZ and LZ B cells further divided on the basis of LacZ positivity. The mean ± SEM from 2 independent experiments is shown (Mir155LacZ/+, n = 10; Mir155LacZ/–, n = 11). ***P < 0.001 using 1-way ANOVA followed by a Tukey’s multiple comparisons post-test. (C) Using the same HEL3X-SRBC injection as in B, IgG1+ donor–derived GC B cells were analyzed for their binding ability against HEL3X and HEL. Two independent experiments were performed, and the mean ± SEM of a representative experiment is shown (Mir155LacZ/+, n = 7; Mir155LacZ/–, n = 6). *P < 0.05, **P < 0.005 using 2-tailed unpaired t test (C). (D) Summary illustrations showing the role of miR-155 in the GC response. The absence of miR-155 expression in positively selected c-MYC+ LZ B cells increase apoptosis in the population. Consequently, GC cellularity is decreased, and concomitantly, affinity maturation is abrogated.