The transcriptional cofactor Tle3 reciprocally controls effector and central memory CD8+ T cell fates.

Antigen-experienced CD8+ T cells form effector and central memory T cells (TEM and TCM cells, respectively); however, the mechanism(s) controlling their lineage plasticity remains incompletely understood. Here we show that the transcription cofactor Tle3 critically regulates TEM and TCM cell fates and lineage stability through dynamic redistribution in antigen-responding CD8+ T cell genome. Genetic ablation of Tle3 promoted CD8+ TCM cell formation at the expense of CD8+ TEM cells. Lineage tracing showed that Tle3-deficient CD8+ TEM cells underwent accelerated conversion into CD8+ TCM cells while retaining robust recall capacity. Tle3 acted as a coactivator for Tbet to increase chromatin opening at CD8+ TEM cell-characteristic sites and to activate CD8+ TEM cell signature gene transcription, while engaging Runx3 and Tcf1 to limit CD8+ TCM cell-characteristic molecular features. Thus, Tle3 integrated functions of multiple transcription factors to guard lineage fidelity of CD8+ TEM cells, and manipulation of Tle3 activity could favor CD8+ TCM cell production.

Antigen exposure reshapes chromatin architecture in central memory CD8+ T cells and imprints enhanced recall capacity.

CD62L+ central memory CD8+ T (TCM) cells provide enhanced protection than naive cells; however, the underlying mechanism, especially the contribution of higher-order genomic organization, remains unclear. Systematic Hi-C analyses reveal that antigen-experienced CD8+ T cells undergo extensive rewiring of chromatin interactions (ChrInt), with TCM cells harboring specific interaction hubs compared with naive CD8+ T cells, as observed at cytotoxic effector genes such as Ifng and Tbx21. TCM cells also acquire de novo CTCF (CCCTC-binding factor) binding sites, which are not only strongly associated with TCM-specific hubs but also linked to increased activities of local gene promoters and enhancers. Specific ablation of CTCF in TCM cells impairs rapid induction of genes in cytotoxic program, energy supplies, transcription, and translation by recall stimulation. Therefore, acquisition of CTCF binding and ChrInt hubs by TCM cells serves as a chromatin architectural basis for their transcriptomic dynamics in primary response and for imprinting the code of "recall readiness" against secondary challenge.

CTCF mediates CD8+ effector differentiation through dynamic redistribution and genomic reorganization.

Differentiation of effector CD8+ T cells is instructed by stably and dynamically expressed transcription regulators. Here we show that naive-to-effector differentiation was accompanied by dynamic CTCF redistribution and extensive chromatin architectural changes. Upon CD8+ T cell activation, CTCF acquired de novo binding sites and anchored novel chromatin interactions, and these changes were associated with increased chromatin accessibility and elevated expression of cytotoxic program genes including Tbx21, Ifng, and Klrg1. CTCF was also evicted from its ex-binding sites in naive state, with concomitantly reduced chromatin interactions in effector cells, as observed at memory precursor-associated genes including Il7r, Sell, and Tcf7. Genetic ablation of CTCF indeed diminished cytotoxic gene expression, but paradoxically elevated expression of memory precursor genes. Comparative Hi-C analysis revealed that key memory precursor genes were harbored within insulated neighborhoods demarcated by constitutive CTCF binding, and their induction was likely due to disrupted CTCF-dependent insulation. CTCF thus promotes cytotoxic effector differentiation by integrating local chromatin accessibility control and higher-order genomic reorganization.

The Interplay of Transcription and Genome Topology Programs T Cell Development and Differentiation.

T cells are essential for mounting defense against various pathogens and malignantly transformed cells. Thymic development and peripheral T cell differentiation are highly orchestrated biological processes that require precise gene regulation. Higher-order genome organization on multiple scales, in the form of chromatin loops, topologically associating domains and compartments, provides pivotal control of T cell gene expression. CTCF and the cohesin machinery are ubiquitously expressed architectural proteins responsible for establishing chromatin structures. Recent studies indicate that transcription factors, such as T lineage-defining Tcf1 and TCR-induced Batf, may have intrinsic ability and/or engage CTCF to shape chromatin architecture. In this article, we summarize current knowledge on the dynamic changes in genome topology that underlie normal or leukemic T cell development, CD4+ helper T cell differentiation, and CD8+ cytotoxic T cell functions. The knowledge lays a solid foundation for elucidating the causative link of spatial chromatin configuration to transcriptional and functional output in T cells.

Tcf1-CTCF cooperativity shapes genomic architecture to promote CD8+ T cell homeostasis.

CD8+ T cell homeostasis is maintained by the cytokines IL-7 and IL-15. Here we show that transcription factors Tcf1 and Lef1 were intrinsically required for homeostatic proliferation of CD8+ T cells. Multiomics analyses showed that Tcf1 recruited the genome organizer CTCF and that homeostatic cytokines induced Tcf1-dependent CTCF redistribution in the CD8+ T cell genome. Hi-C coupled with network analyses indicated that Tcf1 and CTCF acted cooperatively to promote chromatin interactions and form highly connected, dynamic interaction hubs in CD8+ T cells before and after cytokine stimulation. Ablating CTCF phenocopied the proliferative defects caused by Tcf1 and Lef1 deficiency. Tcf1 and CTCF controlled a similar set of genes that regulated cell cycle progression and promoted CD8+ T cell homeostatic proliferation in vivo. These findings identified CTCF as a Tcf1 cofactor and uncovered an intricate interplay between Tcf1 and CTCF that modulates the genomic architecture of CD8+ T cells to preserve homeostasis.

Tcf1 preprograms the mobilization of glycolysis in central memory CD8+ T cells during recall responses.

The mechanisms underlying the heightened protection mediated by central memory CD8+ T (TCM) cells remain unclear. Here we show that the transcription factor Tcf1 was required in resting TCM cells to generate secondary effector CD8+ T cells and to clear pathogens during recall responses. Recall stimulation of CD8+ TCM cells caused extensive reprogramming of the transcriptome and chromatin accessibility, leading to rapid induction of glycolytic enzymes, cell cycle regulators and transcriptional regulators, including Id3. This cluster of genes did not require Tcf1 in resting CD8+ TCM cells, but depended on Tcf1 for optimal induction and chromatin opening in recall-stimulated CD8+ TCM cells. Tcf1 bound extensively to these recall-induced gene loci in resting CD8+ TCM cells and mediated chromatin interactions that positioned these genes in architectural proximity with poised enhancers. Thus, Tcf1 preprogramed a transcriptional program that supported the bioenergetic and proliferative needs of CD8+ TCM cells in case of a secondary challenge.

Tcf1 and Lef1 provide constant supervision to mature CD8+ T cell identity and function by organizing genomic architecture.

T cell identity is established during thymic development, but how it is maintained in the periphery remains unknown. Here we show that ablating Tcf1 and Lef1 transcription factors in mature CD8+ T cells aberrantly induces genes from non-T cell lineages. Using high-throughput chromosome-conformation-capture sequencing, we demonstrate that Tcf1/Lef1 are important for maintaining three-dimensional genome organization at multiple scales in CD8+ T cells. Comprehensive network analyses coupled with genome-wide profiling of chromatin accessibility and Tcf1 occupancy show the direct impact of Tcf1/Lef1 on the T cell genome is to promote formation of extensively interconnected hubs through enforcing chromatin interaction and accessibility. The integrative mechanisms utilized by Tcf1/Lef1 underlie activation of T cell identity genes and repression of non-T lineage genes, conferring fine control of various T cell functionalities. These findings suggest that Tcf1/Lef1 control global genome organization and help form intricate chromatin-interacting hubs to facilitate promoter-enhancer/silencer contact, hence providing constant supervision of CD8+ T cell identity and function.

HDAC10 Regulates Cancer Stem-Like Cell Properties in KRAS-Driven Lung Adenocarcinoma.

Activation of oncogenic KRAS is the most common driving event in lung adenocarcinoma development. Despite the existing rationale for targeting activated KRAS and its downstream effectors, the failure of clinical trials to date indicates that the mechanism of KRAS-driven malignancy remains poorly understood. Here we report that histone deacetylase 10 (HDAC10) might function as a putative tumor suppressor in mice carrying a spontaneously activated oncogenic Kras allele. Hdac10 deletion accelerated KRAS-driven early-onset lung adenocarcinomas, increased macrophage infiltration in the tumor microenvironment, and shortened survival time in mice. Highly tumorigenic and stem-like lung adenocarcinoma cells were increased in Hdac10-deleted tumors compared with Hdac10 wild-type tumors. HDAC10 regulated the stem-like properties of KRAS-expressing tumor cells by targeting SOX9. Expression of SOX9 was significantly increased in Hdac10-deleted tumor cells and depletion of SOX9 in Hdac10 knockout (KO) lung adenocarcinoma cells inhibited growth of tumorspheres. The genes associated with TGFß pathway were enriched in Hdac10 KO tumor cells, and activation of TGFß signaling contributed to SOX9 induction in Hdac10 KO lung adenocarcinoma cells. Overall, our study evaluates the functions and mechanisms of action of HDAC10 in lung carcinogenesis that will inform the rationale for targeting its related regulatory signaling as an anticancer strategy. SIGNIFICANCE: These findings linking HDAC10 and lung tumorigenesis identify potential novel strategies for targeting HDAC10 as a treatment for lung cancer.

Roles of energy eigenstates and eigenvalues in equilibration of isolated quantum systems.

We show that eigenenergies and energy eigenstates play different roles in the equilibration process of an isolated quantum system. Their roles are revealed numerically by exchanging the eigenenergies between an integrable model and a nonintegrable model. We find that the structure of eigenenergies of a nonintegrable model characterized by nondegeneracy ensures that quantum revival occurs rarely whereas the energy eigenstates of a nonintegrable model suppress the fluctuations for the equilibrated quantum state. Our study is aided with a quantum entropy that describes how randomly a wave function is distributed in quantum phase space. We also demonstrate with this quantum entropy the validity of Berry's conjecture for energy eigenstates. This implies that the energy eigenstates of a nonintegrable model appear indeed random.