Gene expression differences between prion-resistant and prion-susceptible cells
Ontology highlight
ABSTRACT: Prions consist of aggregates of abnormal conformers of cellular prion protein (PrPC). They propagate by recruiting host-encoded PrPC although the critical interacting proteins and the reasons for the differences in susceptibility of distinct cell lines and populations are unknown. We derived a lineage of cell lines with markedly differing susceptibilities, unexplained by PrPC expression differences, to identify such factors. We examined the transcriptomes of prion-resistant revertants, isolated from highly susceptible cells, and identified a gene expression signature associated with susceptibility. Several of these genes encode proteins with a role in extracellular matrix (ECM) remodelling, a compartment in which disease-related PrP deposits. Loss-of-function of nine of these genes significantly increased susceptibility. Remarkably, inhibition of fibronectin 1 binding to integrin α8 by RGD peptide inhibited metalloproteinases (MMP)-2/9 whilst increasing prion propagation rates. This indicates that prion replication may be controlled by MMPs at the ECM in an integrin-dependent manner.
Project description:Prions cause transmissible neurodegenerative diseases and replicate by conformational conversion of normal, benign forms of prion protein (PrPC) to disease-causing PrPSc isoforms. A systems approach to disease postulates that disease arises from the pathological perturbation (genetic and/or environmental) of one or more biological networks in the relevant organ. In this regard, we tracked global (all mRNA transcripts) gene expression in the brains of eight distinct mouse strain-prion strain combinations at 8 - 10 time points throughout the progression of the disease to capture the effects of prion strain, host genetics, and PrP concentration on disease incubation time. Data are also available from http://prion.systemsbiology.net
Project description:Prion diseases are fatal transmissible neurodegenerative conditions of humans and animals that arise through neurotoxicity induced by PrP misfolding. The cellular and molecular mechanisms of prion-induced neurotoxicity remain undefined. Understanding these processes will underpin therapeutic and control strategies for human and animal prion diseases, respectively. Prion diseases are difficult to study in their natural hosts and require the use of tractable animal models. Here we used RNA-Seq-based transcriptome analysis of prion-exposed Drosophila to probe the mechanism of prion-induced neurotoxicity. Adult Drosophila transgenic for pan neuronal expression of ovine PrP targeted to the plasma membrane exhibit a neurotoxic phenotype evidenced by decreased locomotor activity after exposure to ovine prions at the larval stage. Pathway analysis and quantitative PCR of genes differentially expressed in prion-infected Drosophila revealed up-regulation of cell cycle activity and DNA damage response, followed by down-regulation of eIF2 and mTOR signalling. Mitochondrial dysfunction was identified as the principal toxicity pathway in prion-exposed PrP transgenic Drosophila. The transcriptomic changes we observed were specific to PrP targeted to the plasma membrane since these prion-induced gene expression changes were not evident in similarly-treated Drosophila transgenic for cytosolic pan neuronal PrP expression, or in non-transgenic control flies. Collectively, our data indicate that aberrant cell cycle activity, repression of protein synthesis and altered mitochondrial function are key events involved in prion-induced neurotoxicity, and correlate with those identified in mammalian hosts undergoing prion disease. These studies highlight the use of PrP transgenic Drosophila as a genetically well-defined tractable host to study mammalian prion biology.
Project description:A key event in the pathogenic process of prion diseases is the conversion of the cellular prion protein (PrPC) to an abnormal and protease-resistant isoform (PrPSc). Mice lacking PrP are resistant to prion infection, and down-regulation of PrPC during prion infection prevents neuronal loss and the progression to clinical disease. These results are suggestive of the potential beneficial effect of silencing PrPC during prion diseases. However, the silencing of a protein that is widely expressed throughout the CNS could be detrimental to brain homeostasis. The physiological role of PrPC remains still unclear, but several putative functions have been proposed. Among these, several lines of evidence support PrPC function in neuronal development and maintenance. To assess the influence of PrPC on gene expression profile during development in the mouse brain, we undertook a microarray analysis by using RNA isolated from the hippocampus, at two different developmental stages: newborn (4-day-old) and adult (3-month-old) mice, both from Prnp+/+ and Prnp0/0 animals. The comparison of the different datasets allowed us to identify “commonly” co-regulated genes and “uniquely” de-regulated genes during postnatal development in these animal models. The lack of PrPC during neuronal development affected several biological pathways, among which the most representative were cell signaling, cell-cell communication and transduction process. In addition, the absence of PrPC influenced genes involved in calcium homeostasis, nervous system development, synaptic transmission and cell adhesion. There was only a moderate alteration of the gene expression profile during neuronal development in the animal models we studied. PrPC deficiency does not lead to a dramatic alteration of gene expression profile, and produces moderate altered gene expression levels from young to adult animals. Thus, our results may provide additional support to silencing endogenous PrPC levels as a therapeutic approach to prion diseases.
Project description:A key event in the pathogenic process of prion diseases is the conversion of the cellular prion protein (PrPC) to an abnormal and protease-resistant isoform (PrPSc). Mice lacking PrP are resistant to prion infection, and down-regulation of PrPC during prion infection prevents neuronal loss and the progression to clinical disease. These results are suggestive of the potential beneficial effect of silencing PrPC during prion diseases. However, the silencing of a protein that is widely expressed throughout the CNS could be detrimental to brain homeostasis. The physiological role of PrPC remains still unclear, but several putative functions have been proposed. Among these, several lines of evidence support PrPC function in neuronal development and maintenance. To assess the influence of PrPC on gene expression profile during development in the mouse brain, we undertook a microarray analysis by using RNA isolated from the hippocampus, at two different developmental stages: newborn (4-day-old) and adult (3-month-old) mice, both from Prnp+/+ and Prnp0/0 animals. The comparison of the different datasets allowed us to identify “commonly” co-regulated genes and “uniquely” de-regulated genes during postnatal development in these animal models. The lack of PrPC during neuronal development affected several biological pathways, among which the most representative were cell signaling, cell-cell communication and transduction process. In addition, the absence of PrPC influenced genes involved in calcium homeostasis, nervous system development, synaptic transmission and cell adhesion. There was only a moderate alteration of the gene expression profile during neuronal development in the animal models we studied. PrPC deficiency does not lead to a dramatic alteration of gene expression profile, and produces moderate altered gene expression levels from young to adult animals. Thus, our results may provide additional support to silencing endogenous PrPC levels as a therapeutic approach to prion diseases. To analyze the influence of PrPC expression on CNS gene expression profile during development, we investigated WT PrPC (Prnp+/+) and Prnp0/0 mice at two different developmental stages: in neonatal animals (postnatal day 4, P4) and in adult animals (3 months old). For each developmental stage, hippocampi of 3 (pups) or 4 (adult) animals were dissected immediately after animal sacrifice and promptly processed for RNA extraction and purification, for a total of 14 samples.
Project description:An essential and remarkable process of the biochemical and physiological features in prion diseases is the conversion of a host-encoded prion protein (PrPC) into a misfolded isoform (PrPSc). The conversion of PrPC and the replication of prions, in cases of peripheral infection, occur following the uptake and subsequent spread of prions to brain via spinal cord. We investigated the changes of gene expression profiles in the spleen, cervical spinal cord and thalamus following intraperitoneal inoculation of ME7 scrapie prion and the inter-tissue alterations of the differentially expressed genes through Venn diagram to find genes which are commonly influenced by ME7 scrapie prion spread in the three tissues.
Project description:The prion protein, PrPC, is well known as an essential susceptibility factor for neurodegenerative prion diseases, yet its function in normal, healthy cells remains uncertain. A role in synaptic function has been proposed for PrPC, supported by its cell surface expression in neurons and glia. Here, in mouse retina, we localized PrPC with synaptic proteins EAAT5, CtBP2 and PSD-95, which are present at junctions between photoreceptors and bipolar cells. PrPC localized most densely with the bipolar cell dendrites synapsing with cone photoreceptor terminals. In two coisogenic mouse strains, deletion of the gene encoding PrPC, Prnp, significantly altered the scotopic and photopic electroretinographic (ERG) responses of photoreceptor and bipolar cells. Cone-dominant pathways showed the most significant ERG changes. Retinal thickness, quantitated by high-resolution optical coherence tomography (OCT), and ribbon synapse morphology were not altered upon deletion of PrPC, suggesting that the ERG changes were driven by functional rather than structural alterations
Project description:Synapse dysfunction and synaptic loss are a central feature of neurodegenerative disorders, including prion disease. The cellular prion protein (PrPC) binds prion, amyloid-β, tau, and α-synuclein oligomers, resulting in the activation of macromolecular complexes and signaling at the post-synapse, yet the initial signaling events are unclear. Here we used a transcriptomic approach focused on the early-stage, prion-infected hippocampus of male wild type mice, and identify immediate early genes, including the synaptic activity response gene, Arc/Arg3.1, as significantly upregulated. In a longitudinal study of the prion-infected hippocampus, Arc/Arg-3.1 protein increased, from early to terminal disease. Notably, metabotropic glutamate receptor levels (mGluR5 dimers) were markedly reduced over time, while phosphorylated AMPA receptors (pGluA1-S845) levels increased. Sporadic Creutzfeldt-Jakob disease (sCJD) post-mortem cortical samples also showed low levels of mGluR5 dimers. Together, these findings suggest that prions trigger a chronic Arc response, an increase in phosphorylated GluA1, and a reduction in mGluR5 receptors beginning in early disease.
Project description:While prion infections have been extensively characterized in the laboratory mouse, little is known regarding the molecular responses to prions in other rodents. To explore these responses and make comparisons, we generated a prion disease in the laboratory rat by successive passage of mouse RML prions. Here we describe the accumulation of prions and associated pathology in the rat and describe the transcriptional impact throughout prion disease. Comparative transcriptional profiling between laboratory mice and rats suggests that similar molecular processes are unfolding in response to prion infection. At the level of individual transcripts, however, variability exists between mice and rats and many genes deregulated in mouse scrapie are not affected in rats. Notwithstanding these differences, many transcriptome responses are conserved between mice and rats infected with scrapie. Our findings highlight the usefulness of comparative approaches to understanding neurodegeneration and prion diseases in particular.
Project description:Cell culture models allow prion propagation studies ex vivo after contact with infectious brain homogenates. To date, among the neural cell lines, the mouse neuroblastoma-derived cell line N2a has been one of the most widely used model and has yet provided interesting insights into cell biology of prion propagation. Remarkably, persistently-infected N2a sublines have been set up and replicate prions without exhibiting any pathological changes. One further interesting feature of N2a is the possibility to establish by subcloning, sublines with a range of susceptibility to prions. Indeed, susceptible sublines propagate prions and accumulate the pathogenic isoform of the prion protein, PrPSc, at the opposite of resistant sublines. The aim of our study was to apply large-scale expression analysis using microarrays combined with quantitative real-time PCR to examine the gene expression profile in a persistently-infected N2a cell line, N2a58, infected with the mouse-adapted prion strain 22L, to seek for prion-specific gene transcription. We also questioned if we could observe identical variations of expression of these genes in three other 22L-infected N2a sublines. Finally, we examined the transcriptional state of a N2a subline considered as resistant when exposed to prions. Common pathways of gene transcription would disclose information on the molecular basis of the cell infection and help to identify potential therapeutic targets. Keywords: other
Project description:The molecular function of the cellular prion protein (PrPC) and the mechanism by which it may contribute to neurotoxicity in prion diseases and Alzheimer’s disease (AD) are only partially understood. Mouse neuroblastoma Neuro2a cells and, more recently, C2C12 myocytes and myotubes have emerged as popular models for investigating the cellular biology of PrP. Mouse epithelial NMuMG cells might become attractive models for studying the possible involvement of PrP in a morphogenetic program underlying epithelial-to-mesenchymal transitions. Here we describe the generation of PrP knockout clones from these cell lines using CRISPR-Cas9 knockout technology. More specifically, knockout clones were generated with two separate gRNAs targeting recognition sites on opposite strands within the first hundred nucleotides of the Prnp coding sequence. Several PrP knockout clones were isolated and genomic insertions and deletions near the CRISPR-target sites were characterized. Subsequently, deep quantitative global proteome analyses that recorded the relative abundance of > 3000 proteins were undertaken to begin to characterize the molecular consequences of PrP deficiency. The levels of ~120 proteins were shown to reproducibly correlate with the presence or absence of PrP, with most of these proteins as belonging to extracellular components, cell junctions or the cytoskeleton.