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:We conducted transcriptome analysis of TFAM-depleted HepG2 cells and HeLa cells as a mitochondrial stress model. We found that mitochondrial dysfunction upregulated unique secretory proteins such as amphiregulin (AREG) and thrombospondin 1 in hepatic cells.
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: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:SIRT3 is a NAD+-dependent mitochondrial protein deacetylase participating in the regulation of central metabolism and mitochondrial proteostasis. SIRT3 is downregulated in clear cell renal cell carcinoma (ccRCC), a main type of renal cancers, but the function of SIRT3 in tumorigenesis and development of ccRCC remains unknown. In this study, we established a SIRT3 overexpressed cell line to explore the changes of proteomics and metabolomics regulated by SIRT3 expression. Both the results of quantitative proteomics, metabolomics and acetylome showed overexpression of SIRT3 increased mitochondrial biogenesis and reversed the mitochondrial dysfunctions in ccRCC. We found SIRT3 could increase the activity of TFAM through modulation of TFAM transcription, degradation and acetylation level. The acetylation of TFAM K154 decreased while TFAM protein expression increased after SIRT3 overexpression. Further study revealed that SIRT3 could bind with TFAM, and decrease the acetylation of TFAM, promoting TFAM activity in mitochondrial biogenesis. Overall, our results present a new mechanism of SIRT3 in regulating mitochondrial functions, and the downregulation of SIRT3 in ccRCC lowers the activity of TFAM, subsequently inhibits the transcription of mitochondrial genes and mitochondrial biogenesis.
Project description:Langerhans cells (LCs) are skin-resident professional antigen-presenting dendritic cells (DCs) to maintain skin homeostasis. The number and function of LCs are significantly reduced during the skin aging processes, which is closely related to the aging-associated skin disorders. However, the reasons underlying the changes of LC features with age are uncertain. Mitochondria are well known to be the main powerhouse to regulate cell fitness and function, and a decline in mitochondrial quality and activity was associated with normal aging and correlated with the development of a wide range of age-related diseases. So far, it is unknown if mitochondrial abnormality is involved in skin disorders by regulating LC homeostasis. The mitochondrial transcription factor A (Tfam) acts as a nuclear-encoded transcription factor and plays a critical role in mitochondrial stabilization. To explore the role of mitochondrial quality in LC homeostasis, we generated the mice with conditional deletion of Tfam in LC lineage. We found that Tfam-deficient LCs exhibits mitochondrial abnormality including morphology and membrane permeability of mitochondria, decreased cell number as well as maturation, whereas increased phagocytosis and inflammatory response of LCs. Interestingly, age-LCs from human skin have lower Tfam expression compared to young-LCs, and have the similar features with Tfam-deficient LCs analyzed by scRNA sequence (HRA000395). Thus, our data highlight that Tfam-mediated mitochondrial stability is essential for epidermal LC maintenance and function, which might be explain the states of increased susceptible to skin infections and rising incidence of cutaneous tumor in the elder. This is the first time to investigate the effect of mitochondria abnormality on LC homeostasis, which might be helpful for therapeutic interventions in aging-associated skin pathologies.
Project description:Mammalian mitochondrial DNA (mtDNA) is coated with mitochondrial transcription factor A (TFAM) and compacted into nucleoids. TFAM is not only the main component of mitochondrial nucleoids but its levels can also control mtDNA copy number. Here we show that the TFAM-to-mtDNA ratio is critical for maintaining normal mtDNA expression in different tissues of the mouse. BAC transgenic mice with a 1.5-fold increase in TFAM protein levels maintain a normal TFAM-to-mtDNA ratio in different tissues and as a consequence mitochondrial gene expression, nucleoid distribution and whole animal metabolism are all unaltered. In contrast, mice expressing TFAM from the CAG promoter in the ROSA26 locus have 4.5-fold increase of TFAM protein levels in heart and skeletal muscle and develop pathology leading to early postnatal lethality. The TFAM-to-mtDNA ratio varies widely between tissues in these mice and is very high in skeletal muscle where it causes strong repression of mtDNA expression and deficient oxidative phosphorylation (OXPHOS) despite normal mtDNA levels. In heart, mtDNA copy number is increased leading to a near normal TFAM-to-mtDNA ratio and maintained OXPHOS capacity. In the liver, mtDNA expression is maintained despite increased TFAM levels and normal mtDNA levels. Here, tissue-specific induction of the LONP1 protease and mitochondrial RNA polymerase (POLRMT) expression counteracts the silencing effect of high TFAM levels. We conclude that the TFAM-to-mtDNA ratio has an important role in maintaining mtDNA expression in vivo. TFAM acts as a general repressor of mtDNA expression and this effect can be counterbalance by tissue-specific expression of regulatory factors.
Project description:Mitochondrial transcription factor A (TFAM) was deleted in renal epithelial cells using the Six2-Cre transgene. To characterize gene expression in TFAM-deficient renal epithelial cells, renal cortices from mutant and Cre-negative control mice were compared.
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.