Abstract
Antibody affinity maturation occurs in secondary lymphoid organs within germinal centers (GCs). At these sites, B cells mutate their antibody-encoding genes in the dark zone, followed by preferential selection of the high-affinity variants in the light zone by T cells. The strength of the T cell-derived selection signals is proportional to the B cell receptor affinity and to the magnitude of subsequent Myc expression. However, because the lifetime of Myc mRNA and its corresponding protein is very short, it remains unclear how T cells induce sustained Myc levels in positively selected B cells. Here, by direct visualization of mRNA and active transcription sites in situ, we found that an increase in transcriptional bursts promotes Myc expression during B cell positive selection in GCs. Elevated T cell help signals predominantly enhance the percentage of cells expressing Myc in GCs as opposed to augmenting the quantity of Myc transcripts per individual cell. Visualization of transcription start sites in situ revealed that T cell help promotes an increase in the frequency of transcriptional bursts at the Myc locus in GC B cells located primarily in the LZ apical rim. Thus, the rise in Myc, which governs positive selection of B cells in GCs, reflects an integration of transcriptional activity over time rather than an accumulation of transcripts at a specific time point.
| Original language | English |
|---|---|
| Article number | eadj7124 |
| Number of pages | 15 |
| Journal | Science immunology |
| Volume | 9 |
| Issue number | 93 |
| DOIs | |
| Publication status | Published - 29 Mar 2024 |
Bibliographical note
We thank S. Itzkovitz from the Department of Molecular Cell Biology, the Weizmann Institute of Science, for critical support and discussions. We also thank A. Nachshon from the Department of Molecular Genetics, the Weizmann Institute of Science, for advice and assistance in statistical analysis.Funding: Z.S. is supported by the European Research Council (ERC), grant no. 101001613; the Morris Kahn Institute for Human Immunology, Human Frontiers of Science Program (CDA-00023/2016); and Azrieli Foundation, Israel Science Foundation (ISF, 1090/18). Z.S. is a member of the European Molecular Biology Organization (EMBO) Young Investigator Program. Z.S. is supported by grants from the Benoziyo Endowment Fund for the Advancement of Science, the Sir Charles Clore Research Prize, Comisaroff Family Trust, Irma & Jacques Ber-Lehmsdorf Foundation, Gerald O. Mann Charitable Foundation, and David M. Polen Charitable Trust and E. Hirschfeld and S. Schlesinger.
Author contributions: S.K.B.T. planned and performed most experiments, analyzed data and prepared figures, conceptualized the study, and wrote the manuscript. N.G. performed a set of smFISH experiments. E.S. generated the GCRegions analysis tool and contributed to data presentation. D.H. contributed to experiment planning. H.H.-B. contributed to data analysis and interpretation and figure preparation. A.B. suggested experiments and contributed to data interpretation. L.M. performed a set of smFISH experiments and contributed to data interpretation and presentation. N.W. contributed to data analysis and figure preparation. A.E. contributed to experiment planning and data interpretation. A.M. contributed to figure preparation. O.G. contributed to experiment planning and data presentation. M.G. and A.T. contributed to sample collection and experiment planning. Z.S. conceived and conceptualized the study, wrote the manuscript, and supervised the study.
All Science Journal Classification (ASJC) codes
- Immunology and Allergy
- Immunology