Project description:The peripheral T cell pool is maintained at dynamic homeostasis throughout life. This is achieved through fine-tuning of thymic output and self-renewal of naïve T cells. Dysregulation of T cell homeostasis has been implicated in autoimmune diseases, yet little is known about the homeostatic mechanisms. Here, we report that the replication protein A1 (RPA1) is upregulated during T cell activation. Utilizing T cell-specific Rpa1-deficient (Rpa1fl/fl Cd4-cre) mice, we find that loss of Rpa1 restrains peripheral CD8+ T cell population and limits TCR repertoire diversity. Clinical analysis reveals that the mRNA level of RPA1 is reduced in patients with ulcerative colitis. Accordingly, Rpa1fl/fl Cd4-cre mice exhibit increased susceptibility to inflammatory diseases, including colitis and hepatitis. Mechanistically, RPA1 deficiency triggers necroptotic T cell death following TCR engagement, which in turn results in damage-associated molecular patterns (DAMPs) leakage and leukocyte recruitment, consequently exacerbating inflammatory damage. These studies thus uncover that RPA1 acts as a guardian of T cell clonal expansion that is essential for T cell homeostasis.
Project description:The peripheral T cell pool is maintained at dynamic homeostasis through fine-tuning of thymic output and self-renewal of naïve T cells. Lymphopenia or reduced lymphocyte number is implicated in autoimmune diseases, yet little is known about the homeostatic mechanisms. Here, it is reported that the replication protein A1 (RPA1) plays a critical role in T cell homeostasis. Utilizing T cell-specific Rpa1-deficient (Rpa1fl/fl Cd4-cre) mice, loss of Rpa1 results in lymphopenia through restraining peripheral T cell population and limiting TCR repertoire diversity. Moreover, Rpa1fl/fl Cd4-cre mice exhibit increased susceptibility to inflammatory diseases, including colitis and hepatitis. Clinical analysis reveals that the expression of RPA1 is reduced in patients with ulcerative colitis or other autoinflammatory diseases. Mechanistically, depletion of RPA1 activates ZBP1-RIPK3 signaling through triggering the genomic DNA leakage into cytosol, consequently resulting in T cell necroptosis. This necroptotic T cell death induced by RPA1 deficiency allows the release of damage-associated molecular patterns (DAMPs), which in turn recruits leukocytes and exacerbates inflammatory response. Reciprocally, chemical or genetic inhibition of necroptosis signaling can ameliorate the Rpa1 deficiency-induced inflammatory damage. The studies thus uncover the importance of RPA1-ZBP1-RIPK3 axis in T cell homeostasis and provide a promising strategy for autoinflammatory disease treatment.
Project description:As a single strand DNA binding protein, RPA1 participates various cellular processes including DNA replication and DNA repair.However, the role of RPA1 in T cell is largely unknown. We generate a mice model in which RPA1 was specifically deleted in T cell. Through single cell RNA sequencing, we reveal the immune landscape in RPA1 conditional knockout mice.
Project description:Using tRNA-derived stress-induced RNA (tiRNA) and tRNA-derived fragment (tRF) sequencing, we identified tRF-Glu-TTC as significantly upregulated in intestinal tissues, plasma, epithelial cells, and human clinical samples. tRF-Glu-TTC levels positively correlated with the severity of intestinal injury. Functionally, tRF-Glu-TTC exacerbates intestinal mucosal damage by activating TNF pathway-mediated necroptosis in intestinal epithelial cells. Mechanistically, tRF-Glu-TTC directly binds to and suppresses the RNA-editing enzyme ADAR1, impairing adenosine-to-inosine editing of autophagy-related transcripts (ATG18 and Lamp2), thereby suppressing autophagy and concurrently triggering reactive oxygen species (ROS) accumulation. This cascade promoted TNF-α secretion, amplifying TNF pathway-mediated necroptosis.
Project description:As a single strand DNA binding protein, RPA1 participates in various cellular processes including DNA replication and DNA repair. However, the role of RPA1 in T cells is largely unknown. We generated a mouse model in which RPA1 was specifically deleted in T cells. Through single cell RNA sequencing, we reveal the immune landscape in RPA1 conditional knockout mice.
Project description:As a single strand DNA binding protein, RPA1 participates in various cellular processes including DNA replication and DNA repair. However, the role of RPA1 in T cells is largely unknown. We generated a mouse model in which RPA1 was specifically deleted in T cells. Through single cell RNA sequencing, we reveal the immune landscape in RPA1 conditional knockout mice.
Project description:Replication protein A1 (RPA1) is a single-stranded DNA binding protein that is known to participate in DNA replication, recombination and damage repair. However, little is known about RPA1’s role in controlling chromatin architecture and gene transcription. Further, physiological functions of RPA1 in mouse tissues still remain exclusive. Here we show that Rpa1 heterozygous mice developed age-depended fatty liver disease and are more susceptible to hepatic steatosis in response to high-fat diet. Liver specific deletion of Rpa1 impairs fatty acid oxidation, leading to hepatic steatosis and high incidence of hepatocellular carcinoma. Transcriptome analysis identified down-regulation of fatty acid oxidation related genes. Cleavage Under Targets and Tagmentation (CUT&Tag) and Assay for transposase-accessible chromatin using sequencing (ATAC-seq) revealed that RPA1 binds and regulates chromatin accessibility in regulatory regions of a group of genes involved in lipid metabolism in liver. Further, down-regulation of RPA1 was found in patients with fatty liver disease. Thus, our results not only established that RPA1 is critical controller of chromatin architecture and regulator of gene transcription, but also provided new insights into the epigenetic mechanism of fatty liver disease, which could inform future therapy.
Project description:Replication protein A(RPA), a ssDNA binding protein complex, participates in DNA replication, recombination and damage repair, but its physiological function remains elusive. Here, we show that heterozygous Rpa1 knockout mice were developmentally normal, but hypersensitive to ageing and high-fat-diet (HFD) induced hepatic steatosis. Liver specific deletion of Rpa1 leads to impaired lipid beta-oxidation, hepatic steatosis and subsequently hepatocellular carcinoma (HCC). Assays for RNA-seq, pull-down and transposase-accessible chromatin sequencing (ATAC-seq) reveal that RPA1 is required for transcription of a subgroup of lipid metabolic genes via altering chromatin accessibility landscape. Thus, our results suggest that RPA1 is a critical regulator of gene transcription and chromatin remodeling, linking a guardian of genome stability to lipid metabolic homeostasis.
Project description:Microglial necroptosis exacerbates neurodegenerative diseases, central nervous system injury and demonstrates a pro-inflammatory process, but its contribution to subarachnoid hemorrhage (SAH) is poorly characterized. BCL-2 homologous antagonist-killer protein (Bak1), a critical regulatory molecule of endogenous apoptosis, can be involved in the pathological process of necroptosis by regulating mitochondrial permeability. In this study, we revealed microglia undergo necroptosis after subarachnoid hemorrhage in vivo and vitro. We found that Bak1 was elevated at 24h after SAH. Knocked-down of Bak1 by adeno-associated virus attenuates microglial necroptosis, alleviates neuroinflammation, and improves neurological function after SAH. To further explore the corresponding mechanisms, oxyhemoglobin induces necroptosis in BV2 microglia, increasing Bak1 expression and mediating pro-inflammatory phenotype transformation, exacerbating oxidative stress and neuroinflammation. Abrogating BV2 Bak1 reduces necroptosis by downregulating the expression of phosphorylated pseudokinase mixed lineage kinase domain-like protein (p-MLKL), then downregulates pro-inflammatory phenotype gene expression. RNA-Seq shows that disrupting BV2 Bak1 downregulates multiple immune and inflammatory pathways and ameliorates cell injury by elevating Thrombospondin 1 (THBS1) expression. In summary, we identified a critical regulatory role for Bak1 in microglial necroptosis and neuroinflammation after SAH. Bak1 is expected to be a new therapeutic target, and it provides a new idea for the treatment strategy of SAH.