Transcription factor Tox2 is required for metabolic adaptation and tissue residency of ILC3 in the gut

Group 3 innate lymphoid cells (ILC3) are the major subset of gut-resident ILC with essential roles in infections and tissue repair, but how they adapt to the gut environment to maintain tissue residency is unclear. We report that Tox2 is critical for gut ILC3 maintenance and function. Gut ILC3 highly expressed Tox2, and depletion of Tox2 markedly decreased ILC3 in gut but not at central sites, resulting in defective control of Citrobacter rodentium infection. Single-cell transcriptional profiling revealed decreased expression of Hexokinase-2 in Tox2-deficient gut ILC3. Consistent with the requirement for hexokinases in glycolysis, Tox2-/- ILC3 displayed decreased ability to utilize glycolysis for protein translation. Ectopic expression of Hexokinase-2 rescued Tox2-/- gut ILC3 defects. Hypoxia and interleukin (IL)-17A each induced Tox2 expression in ILC3, suggesting a mechanism by which ILC3 adjusts to fluctuating environments by programming glycolytic metabolism. Our results reveal the requirement for Tox2 to support the metabolic adaptation of ILC3 within the gastrointestinal tract.

Expression of the transcription factor Klf6 by thymic epithelial cells is required for thymus development

Thymic epithelial cells (TEC) control T cell development and play essential roles in establishing self-tolerance. By using Foxn1-Cre-driven ablation of Klf6 gene in TEC, we identified Klf6 as a critical factor in TEC development. Klf6 deficiency resulted in a hypoplastic thymus-evident from fetal stages into adulthood-in which a dramatic increase in the frequency of apoptotic TEC was observed. Among cortical TEC (cTEC), a previously unreported cTEC population expressing the transcription factor Sox10 was relatively expanded. Within medullary TEC (mTEC), mTEC I and Tuft-like mTEC IV were disproportionately decreased. Klf6 deficiency altered chromatin accessibility and affected TEC chromatin configuration. Consistent with these defects, naïve conventional T cells and invariant natural killer T cells were reduced in the spleen. Late stages of T cell receptor-dependent selection of thymocytes were affected, and mice exhibited autoimmunity. Thus, Klf6 has a prosurvival role and affects the development of specific TEC subsets contributing to thymic function.

Revelations in Thymic Epithelial Cell Biology and Heterogeneity from Single-Cell RNA Sequencing and Lineage Tracing Methodologies

Thymic epithelial cells (TECs) make up the thymic microenvironments that support the generation of a functionally competent and self-tolerant T-cell repertoire. Cortical (c)TECs, present in the cortex, are essential for early thymocyte development including selection of thymocytes expressing functional TCRs (positive selection). Medullary (m)TECs, located in the medulla, play a key role in late thymocyte development, including depletion of self-reactive T cells (negative selection) and selection of regulatory T cells. In recent years, transcriptomic analysis by single-cell (sc)RNA sequencing (Seq) has revealed TEC heterogeneity previously masked by population-level RNA-Seq or phenotypic studies. We summarize the discoveries made possible by scRNA-Seq, including the identification of novel mTEC subsets, advances in understanding mTEC promiscuous gene expression, and TEC alterations from embryonic to adult stages. Whereas pseudotime analyses of scRNA-Seq data can suggest relationships between TEC subsets, experimental methods such as lineage tracing and reaggregate thymic organ culture (RTOC) are required to test these hypotheses. Lineage tracing - namely, of β5t or Aire expressing cells - has exposed progenitor and parent-daughter cellular relationships within TEC.

Epstein-Barr Virus-associated Gastric Cancer and Potential Mechanisms of Oncogenesis

INTRODUCTION

EBV-associated Gastric Cancer (EBVaGC) comprises about 9% of all cases of GC and constitutes a distinct clinicopathological and molecular entity. The pattern of viral expression in EBVaGC cannot be set to any of the previously EBV-associated malignancies. Several lines of evidence support that viral expression in EBVaGC is characterized by high transcription of the BamH1- A rightward transcript (BART), low-levels of EBNA-1 and lack of LMP1. The high transcription activity of the BamH1-A region is importantly directed to express BART miRNAs, supporting a critical role for these miRNAs during epithelial cell infection and carcinogenesis. Several studies have shown that promoter hypermethylation is also a prominent feature of EBVaGC. Based on the recent TCGA report, the specific fingerprint of genomic alterations in EBVaGC is marked by mutations in PIK3CA, ARID1A and BCOR genes, and amplification of 9p24.1 that harbors the genes for the JAK2, PD-L1 and PD-L2 proteins. The specific programs of viral gene expression, promoter methylation and genomic mutations found in EBVaGC target cell signaling pathways leading to increased proliferation, increased cell survival, immune evasion, augmented EMT and acquisition of stemness features. Less understood is the participation of EBV in chronic gastric inflammation, but some studies argue that EBV, similar to and together with Helicobacter pylori, is an early participant in the GC oncogenic process through promoting chronic inflammation and increased tissue damage.

CONCLUSION

Here, we discuss the principal and distinctive carcinogenic routes promoted by EBV in the gastric epithelium.