Targeting the NuRD Component, CHD4, Impairs Foxp3+ Treg Cell Production and Function and Promotes Anti-Tumor Immunity

H3.3 chaperone Hira primes the effector program and function of regulatory T cells

It is shown that the histone variant H3.3 is enriched in tissue Tregs compared to splenic Tregs and its chaperone Hira is a critical regulator of Treg effector program, revealing a previously unreported epigenetic mechanism critical for Treg effector differentiation and function.

Defining the Role of HDAC3 Enzymatic vs. Adaptor Function in T Cells 2258602

Generation of T cells requires dynamic epigenetic alteration of histones to control gene expression at each developmental stage. Histone acetyltransferases (HATs) and histone deacetylases (HDACs) facilitate addition or removal of various acyl groups from lysine residues, including acetylation (KAc) and crotonylation (KCr). The Class I deacetylases HDAC1, HDAC2, and HDAC3 have been shown to have 3 functions: adaptor, decrotonylase, and deacetylase activity. The relative importance of each function in T cells is not known. Genetic knockout of HDAC3 in mice using CD2icre results in a severe block in T cell development and spontaneous development of severe colitis. Our lab determined that HDAC3 is required for three different aspects of this process: CD4+CD8 + (DP) cell survival, positive selection, and CD4+ lineage commitment. We generated a novel mouse model with CD2icre-mediated deletion of endogenous HDAC3 and linked re-expression of HDAC3 “VRPP” mutant mice, which maintained adaptor function but lacks enzymatic activity. Strikingly, these mice do not develop spontaneous colitis even up to one year of age. We used flow cytometry to assess T cell development and maturation in the thymus, spleen, mLN, and colon of HDAC3 cKO vs. HDAC3 VRPP mice. CUT&RUN was utilized to determine differences in H3K9Ac, H3K27Ac, and H3K18Cr across CD8 and CD4 lineage genes. H&E was utilized to assess structural changes in thymus and colon. Similar to CD2icre HDAC3 cKO mice, HDAC3 VRPP mice have a block in positive selection due to failure to down regulate RORγt and decreased DP cell survival due to increased expression of P2RX7. Although fewer T cells are produced in HDAC3 VRPP mice, CD4+ lineage commitment is restored, likely mitigating the development of spontaneous colitis. Our results demonstrate that HDAC3 enzymatic activity is necessary for several aspects of T cell development, while HDAC3 adaptor function is sufficient to restore CD4+ lineage commitment. NIAID RO1 AI150100, T32 AI170478 Hematopoiesis and Immune System Development (HEM)

Targeting the FOXP3-T-bet interaction to restore Treg stability in IFN-γ-driven autoimmunity.

Targeting the FOXP3—T-bet interaction to restore Treg stability in IFN-γ—driven autoimmunity 2254306

Regulatory T cells (Tregs) maintain immune homeostasis through FOXP3-centered transcriptional complexes that tightly control lineage stability and suppressive function. However, how specific FOXP3 mutations disturb this complex and drive pathogenic Treg reprogramming in IPEX syndrome remains unclear. We identified a distinctive mechanism by which the FOXP3 V408M mutation promotes Th1-skewed inflammation and also explored a pharmacological strategy to restore Treg stability. We generated FOXP3 V408M knock-in mice and performed immunophenotyping, transcriptomic, and chromatin conformation analyses to determine how the mutation affects FOXP3—T-bet interaction and Ifng transcription. An AI-driven virtual screening strategy integrating sequence- and structure-based modeling was applied to identify compounds that stabilize FOXP3—T-bet interaction. Functional validation was performed in vitro and in multiple in vivo mouse models. FOXP3 V408M mutation disrupted the FOXP3—T-bet interaction, thereby releasing T-bet from FOXP3-mediated repression and enhancing Ifng transcription. This defect reprogrammed Tregs toward an IFN-γ—producing phenotype that promoted Th1 inflammation. Among the AI-driven screening hits, 430C10 emerged as a first-in-class FOXP3-targeting stabilizer binding an allosteric pocket within the FKH domain. 430C10 reinforced the FOXP3—T-bet interaction and suppressed T-bet—driven IFN-γ production by Tregs. Oral 430C10 treatment markedly alleviated IFN-γ+ Treg—driven inflammation in FOXP3 V408M mice and improved disease outcomes in an acute colitis model under FOXP3 WT settings. Our findings define the FOXP3—T-bet interaction as a tunable checkpoint controlling Treg stability and IFN-γ—driven autoimmunity. Pharmacological stabilization of this interaction with 430C10 provides a proof-of-concept therapeutic strategy for restoring immune homeostasis in IPEX syndrome and related autoimmune diseases. Our research is supported by National Natural Science Foundation of China (82271829, 32130041, 82441047, 82241222); The Innovation Program of Shanghai Municipal Education Commission (21140902900); Noncommunicable Chronic Diseases-National Science and Tech Therapeutic Approaches to Autoimmunity (THER)

Targeting genome organizer Satb1 in regulatory T cells safely and potently enhances cancer immunity 2309560

Deletion of Satb1 specifically in Tregs impaired the function of Satb1+ pro-tumorigenic Tregs, leading to enhanced CD8+ T cell antitumor immune responses, and complete tumor eradication without any systemic autoimmune conditions.

RACK1 maintains mouse hematopoietic stem cells by directly binding to and stabilizing LDB1

Single-cell RNA sequencing indicates that adulthood Rack1 deletion in type I interferon-I-responsive cells leads to aberrant lineage-geneset-scores of transcriptional HSCs and the emergence of stressed HSCs, and Mechanistically, RACK1 prevents HSC loss through maintaining the protein level of LDB1.