Project description:While Notch signaling has been proposed to play a key role in fibrosis, the direct molecular pathways targeted by Notch signaling and the precise ligand and receptor pair that are responsible for kidney disease remain poorly defined. In this study, we found that JAG1 and NOTCH2 showed the strongest correlation with the degree of interstitial fibrosis in a genome wide expression analysis of a large cohort of human kidney samples. Transcript analysis of mouse kidney disease models, including folic-acid-induced nephropathy, unilateral ureteral obstruction, or APOL1-associated kidney disease, indicated that Jag1 and Notch2 levels were higher in all analyzed kidney fibrosis models. Mice with tubule-specific deletion of Jag1 or Notch2 (Kspcre/Jag1flox/flox and Kspcre/Notch2flox/flox) had no kidney-specific alterations at baseline, but showed protection from folic acid induced kidney fibrosis. Tubule-specific genetic deletion of Notch1 and global knock-out of Notch3 had no effect on fibrosis. In vitro chromatin immunoprecipitation experiments and genome-wide expression studies identified the mitochondrial transcription factor A (Tfam) as a direct Notch target. Re-expression of Tfam in tubule cells prevented Notch-induced metabolic and profibrotic reprogramming. Kidney tubule specific deletion of Tfam resulted in fibrosis. In summary, Jag1/Notch2 plays a key role in kidney fibrosis development by regulating Tfam expression and metabolic reprogramming.
Project description:Objectives: The transcription factor TFAM is controlling the transcription of core proteins required for mitochondrial homeostasis. The aim of the current study was to investigate changes in TFAM expression in systemic sclerosis (SSc), to analyze mitochondrial function and to evaluate the consequences for fibroblast activation. Methods: The expression of TFAM was analyzed by immunofluorescence and Western blot. The effects of TFAM knockout were investigated in cultured fibroblasts and in bleomycin-induced skin and lung fibrosis and in TβRIact-induced skin fibrosis. Results: The expression of TFAM was downregulated in fibroblasts in SSc skin and in cultured SSc fibroblasts. The downregulation of TFAM was associated with decreased mitochondrial number and accumulation of damaged mitochondria with release of mtDNA, accumulation of deletions in mtDNA, metabolic alterations with impaired OXPHOS and release of the mitokine GDF15. Chronic, but not acute exposure of normal fibroblasts to TGFβ mimicked the finding in SSc fibroblasts with downregulation of TFAM and accumulation of mitochondrial damage. Downregulation of TFAM promotes fibroblast activation with upregulation of fibrosis-relevant GO-terms in RNASeq. Mice with fibroblast-specific knockout of TFAM are prone to fibrotic tissue remodeling with fibrotic responses even to NaCl instillation and enhanced sensitivity to bleomycin injection and TβRIact-overexpression. TFAM knockout fosters SMAD3 signaling to promote fibroblast activation. Conclusions: Alterations in the key mitochondrial transcription factor TFAM in response to prolonged activation of TGFβ and associated mitochondrial damage induce transcriptional programs that promote fibroblast-to-myofibroblast transition and drive tissue fibrosis.
Project description:ChIP-seq data characterizing the occupancy of TFAM over the mitochondrial and nuclear genomes in HeLa cells. Characterization of mitochondrial and nuclear genome-wide TFAM binding in HeLa cells
Project description:The goal of this analysis was to utilize microarray profiling to identify basal alterations in gene expression in response to TFAM depletion and mtDNA stress. Mitochondrial DNA (mtDNA) is normally present at thousands of copies per cell and is packaged into several hundred higher-order structures termed nucleoids. The abundant mtDNA-binding protein, TFAM (transcription factor A,mitochondrial), regulates nucleoid architecture, abundance and segregation. Complete mtDNA depletion profoundly impairs oxidative phosphorylation, triggering calcium-dependent stress signalling and adaptive metabolic responses. However, the cellular responses to mtDNA instability, a physiologically relevant stress observed in many human diseases and ageing, remain poorly defined. Here we show that moderate mtDNA stress elicited by TFAM deficiency engages cytosolic antiviral signalling to enhance the expression of a subset of interferon-stimulated genes. Mechanistically, we find that aberrant mtDNA packaging promotes escape of mtDNA into the cytosol, where it engages the DNA sensor cGAS (also known as MB21D1) and promotes STING (also known as TMEM173)–IRF3-dependent signalling to elevate interferon-stimulated gene expression, potentiate type I interferon responses and confer broad viral resistance. Furthermore, we demonstrate that herpesviruses induce mtDNA stress, which enhances antiviral signalling and type I interferon responses during infection. Our results further demonstrate that mitochondria are central participants in innate immunity, identify mtDNA stress as a cell-intrinsic trigger of antiviral signaling and suggest that cellular monitoring of mtDNA homeostasis cooperates with canonical virus sensing mechanisms to fully engage antiviral innate immunity. Murine embryonic fibroblasts were isolated from wild-type or Tfam+/- E13.5 littermate embryos. RNA from passage-matched wild-type and Tfam+/- MEF lines was extracted in duplicate and hybridized onto Affymetrix microarrays. Four arrays were performed in total with two technical replicates per genotype.
Project description:Gene expression analysis of 2-month-old Ctrl and Tfam-SCKO mice. At this age mitochondrial function is disrupted in the Schwann cells of Tfam-SCKO mice ,but their nerves display only very limited pathology. Mitochondrial dysfunction is a common cause of peripheral neuropathy. Much effort has been devoted to examining the role played by neuronal/axonal mitochondria, but how mitochondrial deficits in peripheral nerve glia (Schwann cells, SCs) contribute to peripheral nerve diseases remains unclear. Here, we investigate a mouse model of peripheral neuropathy secondary to SC mitochondrial dysfunction (Tfam-SCKOs). We show that disruption of SC mitochondria activates a maladaptive integrated stress response through actions of heme-regulated inhibitor kinase (HRI), and causes a shift in lipid metabolism away from fatty acid synthesis toward oxidation. These alterations in SC lipid metabolism result in depletion of important myelin lipid components as well as in accumulation of acylcarnitines, an intermediate of fatty acid b-oxidation. Importantly, we show that acylcarnitines are released from SCs and induce axonal degeneration. A maladaptive integrated stress response as well as altered SC lipid metabolism are thus underlying pathological mechanisms in mitochondria-related peripheral neuropathies. Total RNA samples were prepared by isolating and pooling RNA from three different 2-month-old MPZ-Tfam KO and Ctrl mice. 2 replicates per genotype were used in this experiment and they were prepared entirely independently.
Project description:miRNA expression profiles of HMECs treated with 40mM Jagged1 (JAG1) or the control peptide for 1 day Genome-wide miRNA PCR array analysis was performed using human miRNA PCR arrays (MIHS216Z, SABiosceinces) acccording to the manufacturer's instructions
Project description:Transcriptional profiling of MC3T3-E1 osteoblasts that were flow cytometry-separated from cocultures with control or Jagged1-overexpressing tumor cells and treated with either DMSO control or 1μM MRK-003 (gamma-secretase inhibitor). One cell line (MC3T3-E1) cells: four different experimental conditions: cultured with (1) control tumor cells + DMSO; (2) Jagged1-overexpressing tumor cells + DMSO; (3) control tumor cells + MRK-003; (4) Jagged1-overexpressing tumor cells + MRK-003. Each experiment has two biological replicates. Total, 8 samples.