Project description:Purpose was to identify transcriptomic changes in whole liver and isolated hepatocytes from 2 week old wild type and Cdk1 liver-specific knock-out (Cdk1 Liv-/-) mice.
Project description:Liver fibrosis is a strong predictor of long-term mortality in patients with non-alcoholic fatty liver disease; yet the mechanisms underlying the progression from the comparatively benign fatty liver state to advanced non-alcoholic steatohepatitis (NASH) and liver fibrosis are incompletely under-stood. Using a cell type-resolved genomics approach, we show that comprehensive alterations in hepatocyte genomic and transcriptional settings during NASH progression, led to a partial loss of hepatocyte identity. The hepatocyte reprogramming was under tight cooperative control of a net-work of NASH-activated transcription factors (TFs), as exemplified by Elf3 and Glis2. Indeed, Elf3 and Glis2 controlled hepatocyte identity and fibrosis-dependent hepatokine genes targeting disease-associated hepatic stellate cell (HSC) gene programs. Thus, interconnected TF networks not only promoted hepatocyte dysfunction, but also directed the intra-hepatic crosstalk with HSCs necessary for NASH and fibrosis progression implying molecular “hub-centered” targeting strategies to be superior to existing mono-target approaches as currently used in NASH therapy.
Project description:Transforming growth factor beta-activated kinase1 (TAK1) encoded by the gene MAP3K7 regulates multiple important downstream effectors involved in immune response, cell death and carcinogenesis. Hepatocyte-specific deletion of TAK1 in Tak1_Hep mice promotes liver fibrosis and hepatocellular carcinoma (HCC) formation. Here, we report that genetic inactivation of RIPK1 kinase using kinase dead knock-in D138N mutation in Tak1_Hep mice inhibits the expression of liver tumor biomarkers, liver fibrosis and HCC formation. Inhibition of RIPK1, however, has no or minimum effect on hepatocyte loss and compensatory proliferation, which are the recognized factors important for liver fibrosis and HCC development. Using single cell RNA-seq, we discover that inhibition of RIPK1 strongly suppresses inflammation induced by hepatocyte-specific loss of TAK1. Activation of RIPK1 promotes the transcription of key proinflammatory cytokines, such as CCL2, and CCR2+ macrophage infiltration. Our study demonstrates the role and mechanism of RIPK1 kinase in promoting inflammation, both cell-autonomously and cell-non-autonomously, in the development of liver fibrosis and HCC, independent of cell death and compensatory proliferation. We suggest the possibility of inhibiting RIPK1 kinase as a therapeutic strategy for reducing liver fibrosis and HCC development by inhibiting inflammation.
Project description:Objective: The rs641738C>T variant located near the membrane-bound O-acyltransferase domain containing 7 (MBOAT7) locus is associated with fibrosis in liver diseases, including non-alcoholic fatty liver disease (NAFLD), alcohol-related liver disease, hepatitis B and C. We aim to understand the mechanism by which the rs641738C>T variant contributes to pathogenesis of NAFLD. Design: Mice with hepatocyte-specific deletion of MBOAT7 (Mboat7 Δhep) were generated and livers were characterised by histology, flow cytometry, qPCR, RNA sequencing and lipidomics. We analysed the association of rs641738C>T genotype with liver inflammation and fibrosis in 846 NAFLD patients and obtained genotype-specific liver lipidomes from 280 human biopsies. Results: Allelic imbalance analysis of heterozygous human liver samples pointed to lower expression of the MBOAT7 transcript on the rs641738C>T haplotype. Mboat7 Δhep mice showed spontaneous steatosis characterised by increased hepatic cholesterol ester content after 10 weeks. After 6 weeks on a high fat, methionine-low, choline-deficient diet, mice developed increased hepatic fibrosis as measured by picrosirius staining (p<0.05), hydroxyproline content (p<0.05) and transcriptomics, while the inflammatory cell populations and inflammatory mediators were minimally affected. In a human biopsied NAFLD cohort, MBOAT7 rs641738C>T was associated with fibrosis (p=0.004) independent of the presence of histological inflammation. Liver lipidomes of Mboat7 Δhep mice and human rs641738TT carriers with fibrosis showed increased total lysophosphatidylinositol (LPI) levels. The altered LPI and phosphatidylinositol subspecies in MBOAT7 Δhep livers and humans rs641738TT carriers were similar. Conclusion: Mboat7 deficiency in mice and human points to an inflammation-independent pathway of liver fibrosis that may be mediated by lipid signalling and a potentially targetable treatment option in NAFLD.
Project description:Non-alcoholic fatty liver disease (NAFLD) is characterized by excess lipid accumulation in hepatocytes and reprepresents a huge public health problem owing to its propensity to progress to non-alcoholic steatohepatitis (NASH), fibrosis, and liver failure. The lipids stored in hepatic steatosis are primarily triglycerides (TGs) synthesized by two acyl CoA:diacylglycerol acyltransferase (DGAT) enzymes. Either DGAT1 or DGAT2 catalyzes this reaction, and these enzymes have been suggested to differentially utilize exogenous or endogenously synthesized fatty acids, with DGAT2 being linked to storage of fatty acids from de novo lipogenesis, a process that is increased in NAFLD. However, whether DGAT2 is more responsible for lipid accumulation in NAFLD and the progression to fibrosis is currently unknown. Also, it is unresolved whether DGAT2 can be safely inhibited as a therapy for NAFLD. Here we induced NAFLD-like disease in mice by feeding a diet rich in fructose, saturated fat, and cholesterol and found that hepatocyte-specfici Dgat2 deficiency reduced expression of de novo lipogenesis genes and lowered liver TGs by ~70%. Importantly, the reduction of steatosis was not accompanied by increased inflammation or fibrosis, and insulin and glucose metabolism were unchanged. Conclusion: This study suggests that hepatic DGAT2 deficiency successfully reduced diet-induced hepatic steatosis and supports the development of DGAT2 inhibitors as a therapeutic strategy for treating NAFLD and preventing downstream consequences.
Project description:Background and Aims: The activation of stimulator of interferon genes (STING) and NOD-like receptors protein 3 (NLRP3) inflammasomes-mediated pyroptosis signaling pathways represent two distinct central mechanisms in liver disease. However, the interconnection between these two pathways and the epigenetic regulation of the STING-NLRP3 axis in hepatocyte pyroptosis during liver fibrosis remain unknown and is the focus of this study. Approach and Results: Liver fibrosis was induced in Sting knockout, Gasdermin D (Gsdmd) knockout mice, and in mice with hepatocyte-specific Nlrp3 deletion. RNA-sequencing, metabolomics, epigenetic compound screening system, and chromatin immunoprecipitation were utilized. STING and NLRP3 inflammasome signaling pathways were activated in cirrhotic livers but were suppressed by Sting knockout. Sting knockout also ameliorated hepatic pyroptosis, inflammation, and fibrosis in the murine cirrhotic model. In vitro, STING induced pyroptosis in primary murine hepatocytes via activating the NLRP3 inflammasome. H3K4-specific histone methyltransferase WD repeat-containing protein 5 (WDR5) and DOT1-like histone H3K79 methyltransferase (DOT1L) were identified to regulate NLRP3 expression in STING-overexpressed AML12 hepatocytes. WDR5/DOT1L-mediated histone methylation enhanced interferon regulatory transcription factor 3 (IRF3) binding to the Nlrp3 promoter and promoted STING-induced Nlrp3 transcription in hepatocytes. The RNA-sequencing and metabolomics analysis in murine livers and primary hepatocytes showed that metabolic reprogramming might participate in NLRP3-mediated hepatocyte pyroptosis and liver fibrosis. Moreover, hepatocyte-specific Nlrp3 deletion and downstream Gsdmd knockout attenuated hepatic pyroptosis, inflammation, and fibrosis in murine cirrhotic models. Conclusions: This study describes a novel epigenetic mechanism by which the STING-WDR5/DOT1L/IRF3-NLRP3 signaling pathway enhances hepatocyte pyroptosis and hepatic inflammation in liver fibrosis.
Project description:Cell proliferation is tightly controlled by inhibitors that block cell cycle progression until growth signals relieve this inhibition, allowing cells to divide. In several tissues including the liver, cell proliferation is inhibited at mitosis by the transcriptional repressors E2F7 and E2F8, leading to formation of polyploid cells. Whether growth factors promote mitosis and cell cycle progression by relieving the E2F7/E2F8-mediated inhibition is unknown. We report here on a new mechanism of cell division control in the postnatal liver, in which Wnt/βcatenin signaling maintains active hepatocyte cell division through Tbx3, a Wnt target gene. Tbx3 directly represses transcription of E2F7 and E2F8, thereby promoting mitosis. This cascade of sequential transcriptional repressors, initiated by Wnt signals, provides a new paradigm for exploring how commonly active developmental signals impact cell cycle completion.