# Novel Mechanisms of c-Rel Dependent Thymic Regulatory T Cell Development

> **NIH NIH R21** · UNIVERSITY OF PENNSYLVANIA · 2020 · $202,500

## Abstract

PROJECT SUMMARY
Natural or thymic regulatory T cells (tTregs) are a subpopulation of CD4+ lymphocytes that develop in the
thymus to maintain self-tolerance, thereby preventing the development of immune-mediated disease and
autoimmune disorders. Moreover, aberrant activity of Tregs can suppress antitumor immune activity and
exacerbate the growth and/or metastasis of certain tumors. Consequently, understanding the mechanisms that
drive tTreg development and function will inform new approaches for controlling autoimmune diseases and
immunity to certain cancers. Most autoreactive T cells that develop in the thymus die by apoptosis following
contact with high affinity antigen/agonists by a process termed negative selection. However, a small proportion
of these cells is diverted from apoptotic death to become tTregs. Development of tTregs is critically regulated
by the expression and then activation of the transcription factor c-Rel. Indeed, a block in tTreg development in
c-Rel-deficient mice is associated with defective generation of tTreg precursors. However, our inability to
visualize c-Rel expression in live cells is a major roadblock to defining how this is controlled by antigen and
performing lineage tracing experiments on c-Rel+ tTreg precursors. Therefore, in this high impact R21
application, we outline strategies to develop c-Rel reporter mice to facilitate studies of the relationship between
TCR signaling, c-Rel expression, and genetic mechanisms by which c-Rel drives commitment of autoreactive T
cell clones to tTreg development. While control of c-Rel expression represents an early checkpoint in nTreg
development, very little is known about the subsequent mechanisms that regulate c-Rel activation and
transcriptional specificity. Our exciting new data provide an original conceptual framework to explore this
question. Our unbiased mass spectrometry (MS) experiments revealed Serine 34 as a novel target on c-Rel
that undergoes TCR-induced, Ca2+-dependent phosphorylation. Furthermore, preliminary analysis of a new
mouse line with an alanine substitution at c-Rel S34 reveals a crucial role for phosphorylation of this residue in
tTreg development. Indeed, preliminary RNAseq analysis indicate that c-Rel S34 phosphorylation tunes the
pattern of gene expression in T cells. In this proposal, we outline an approach using these mice to explore
general mechanisms of tTreg development and specifically to dissect how phosphorylation of c-Rel at S34
regulates commitment to nTreg development. The conceptually and technically innovative experiments we
propose using the mice we have and will generate will yield important therapeutic insights and reveal new
targets for regulating the susceptibility to and course of immune-mediated diseases.

## Key facts

- **NIH application ID:** 9962296
- **Project number:** 5R21AI142162-02
- **Recipient organization:** UNIVERSITY OF PENNSYLVANIA
- **Principal Investigator:** BRUCE D FREEDMAN
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $202,500
- **Award type:** 5
- **Project period:** 2019-06-21 → 2022-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9962296

## Citation

> US National Institutes of Health, RePORTER application 9962296, Novel Mechanisms of c-Rel Dependent Thymic Regulatory T Cell Development (5R21AI142162-02). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9962296. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*