Systems spatiotemporal dynamics of traumatic brain injury at single cell resolution
Ontology highlight
ABSTRACT: The etiology of mild traumatic brain injury (mTBI) remains elusive due to the tissue and cellular heterogeneity of the affected brain regions that underlie cognitive impairments and subsequent neurological disorders. This complexity is further exacerbated by disrupted circuits within and between cell populations across brain regions and the periphery, which occur at different timescales and in spatial domains. We profiled three tissues (hippocampus, frontal cortex, and blood leukocytes) at the acute (24hr) and chronic (7days) phases of mTBI at single cell resolution and demonstrated that the coordinated gene expression patterns across cell types were disrupted and re-organized by TBI at different timescales with distinct regional and cellular patterns. Gene expression-based network modeling identified astrocytes as a key regulator of the cell-cell coordination following mTBI in both hippocampus and frontal cortex across timepoints, and mt-Rnr2, which encodes the mitochondrial peptide humanin, as a potential target for intervention based on its broad regional and dynamic dysregulation following mTBI. Treatment of a murine mTBI model with humanin reversed cognitive impairment caused by mTBI through the restoration of metabolic pathways within astrocytes. Our results offer a systems-level understanding of the dynamic and spatial regulation of gene programs by mTBI and pinpoint key target genes, pathways, and cell circuits that are amenable to therapeutics.
Project description:Astrocytes within specific brain regions contribute uniquely to regional circuits for higher-order brain function through interactions with local neurons. The regional diversification of astrocytes is dictated by their embryonic origin, yet the mechanisms governing their regional allocation remain unknown. Here we show that allocation of astrocytes to specific brain regions requires the transcription factor 4 (Tcf4) mediated fate restriction during brain development. Loss of Tcf4 in ventral telencephalic neural progenitors alters the fate of oligodendrocyte precursors to transient intermediate astrocyte precursor cells, resulting in mislocated astrocytes in the dorsal neocortex. These ectopic astrocytes originated from the ventral telencephalon engage with neurons and acquire features reminiscent of local neocortical astrocytes. Furthermore, Tcf4 functions as a suppressor of astrocyte fate during differentiation of oligodendrocyte precursors, thereby restricting the fate to oligodendrocyte lineage. Our study reveals that fate restriction governs regional astrocyte allocation, contributing to astrocyte diversification across brain regions.
Project description:Traumatic brain injury (TBI) is a global problem reaching near epidemic numbers that manifests clinically with cognitive problems that decades later may result in dementias like Alzheimer’s disease (AD). Presently, little can be done to prevent ensuing neurological dysfunctions by pharmacological means. Recently, it has become apparent that several CNS diseases share common terminal features of neuronal cell death. The effects of exendin-4 (Ex-4), a neuroprotective agent delivered via a subcutaneous micro-osmotic pump, were examined in the setting of mild TBI (mTBI). Utilizing a model of mTBI, where cognitive disturbances occur over time, animals were subjected to four treatments: sham; Ex-4; mTBI and Ex-4/mTBI. mTBI mice displayed deficits in novel object recognition, while Ex-4/mTBI mice performed similar to sham. Hippocampal gene expression, assessed by gene array methods, showed significant differences with little overlap in co-regulated genes between groups. Importantly, changes in gene expression induced by mTBI, including genes associated with AD were largely prevented by Ex-4. These data suggest a strong beneficial action of Ex-4 in managing secondary events induced by a traumatic brain injury.
Project description:Around 25% of stroke survivors over 65 years old develop progressive cognitive decline more than 3 months post-stroke, with features of vascular dementia. Poststroke dementia (PSD) is associated with pathology in frontal brain regions, in particular dorsal lateral prefrontal cortex (DLPFC) neurons and white matter, remote from the infarct, implicating damage to anterior cognitive circuits (ACC) involved in impaired executive function. We hypothesised that PSD results from progressive neuronal damage in the DLPFC and that this is associated with alterations in the gliovascular unit (GVU) of frontal white matter. We aimed to identify the cellular and molecular basis of PSD by investigating the transcriptomic profile of the neurons and white matter GVU cells previously implicated in pathology. Laser capture microdissected neurons, astrocytes and endothelial cells were obtained from the Cognitive Function After Stroke (COGFAST) cohort. Gene expression was assessed using microarrays and pathways analysis to compare changes in PSD with controls and with poststroke non-dementia (PSND). Laser captured microdissected neurons were obtained from the bilateral carotid artery stenosis (BCAS) model and equivalent SHAM animals
Project description:Frontotemporal dementia is a debilitating neurodegenerative disorder characterized by frontal and temporal lobe degeneration, resulting in behavioral changes, language difficulties, and cognitive decline. In this study, smallRNA sequencing was conducted on postmortem brain tissues obtained from FTD patients with GRN, MAPT, or C9ORF mutations, focusing on the frontal and temporal lobes. Our analysis identified miR-129-5p as consistently deregulated across all mutation conditions and brain regions. Functional investigations revealed a novel role of miR-129-5p in astrocytes, where its loss led to neuroinflammation and impaired neuronal support functions, including glutamate uptake. Depletion of miR-129-5p in astrocytes resulted in the loss of neuronal spines and altered neuronal network activity. These findings highlight miR-129-5p as a potential therapeutic target in neurodegenerative diseases and also sheds light on the role of astrocytes in Frontotemporal dementia pathogenesis.
Project description:Patients with an inflammatory disease of the central nervous system known as neuromyelitis optica (NMO) experience increased levels of depression. These patients have an antibody that recognizes a type of cell in the brain called astrocytes – binding of this antibody to astrocytes triggers a stress response in the cell that results in the development of brain lesions that cause disability and cognitive disturbances. We recently observed a change in the level of glutamate in a part of the brain involved in depression in patients with NMO. Glutamate is a chemical that is used in the brain for communication between neurons – reduced levels of glutamate are thought to trigger depression by reducing neuronal activity in specific circuits. Based on this observation and the known role of astrocytes in maintaining glutamate levels in the brain, we hypothesize that the NMO antibody disturbs metabolic activity in astrocytes and thereby reduces glutamate and triggers depression. We intend to trace the metabolic response induced in astrocytes by the NMO antibody using TCA isotopomers. It is our hope that we will not only learn something about the mechanisms of astrocyte dysregulation in neuromyelitis optica, but that we will learn something about the mechanisms of depression in general that may lead to new therapies for this disease.
Project description:Patients with an inflammatory disease of the central nervous system known as neuromyelitis optica (NMO) experience increased levels of depression. These patients have an antibody that recognizes a type of cell in the brain called astrocytes – binding of this antibody to astrocytes triggers a stress response in the cell that results in the development of brain lesions that cause disability and cognitive disturbances. We recently observed a change in the level of glutamate in a part of the brain involved in depression in patients with NMO. Glutamate is a chemical that is used in the brain for communication between neurons – reduced levels of glutamate are thought to trigger depression by reducing neuronal activity in specific circuits. Based on this observation and the known role of astrocytes in maintaining glutamate levels in the brain, we hypothesize that the NMO antibody disturbs metabolic activity in astrocytes and thereby reduces glutamate and triggers depression. We intend to measure TCA concentration in NMO astrocytes. It is our hope that we will not only learn something about the mechanisms of astrocyte dysregulation in neuromyelitis optica, but that we will learn something about the mechanisms of depression in general that may lead to new therapies for this disease.
Project description:Vanishing white matter (VWM) is a leukodystrophy that primarily manifests in young children. In this disease, the brain white matter is differentially affected in a predictable pattern with telencephalic brain areas being more severely affected, while others remain allegedly completely spared. Using high-resolution mass spectrometry-based proteomics, we investigated the proteome patterns of the severely affected white matter in the frontal lobe and normal appearing pons in VWM and control cases to identify molecular bases underlying regional vulnerability. By comparing VWM patients to controls, we identified disease-specific proteome patterns. We showed substantial pathogenic changes in both the frontal white matter and pons at the protein level. Side-by-side comparison of brain region-specific proteome patterns further revealed regional differences. We found that different cell types are affected in the VWM frontal white matter than in the pons. Gene ontology and pathway analyses identified involvement of region distinct biological processes, of which pathways implicated in cellular respiratory metabolism were overarching features. In the VWM frontal white matter, proteome changes were associated with decrease in glycolysis/gluconeogenesis and metabolism of various amino acids. By contrast, in the VWM pons white matter, we found a decrease in oxidative phosphorylation. Taken together, our data show that brain regions are affected in parallel in VWM, but to different degrees. We found region-specific involvement of different cell types and discovered that cellular respiratory metabolism is differently affected across white matter regions in VWM. These region-specific changes help explain regional vulnerability to pathology in VWM.
Project description:Repetitive mild traumatic brain injury (mTBI) in children and adolescents leads to acute and chronic neurological sequelae and is linked by epidemiological data to later life neurodegenerative disease. However, the biological mechanisms connecting early life mTBI to neurodegeneration remain unknown. Using an adolescent mouse repetitive closed head injury (CHI) model that induces progressive cognitive impairment in the absence of overt histopathology, we examined transcriptional and translational changes in neurons isolated from sham and injured brain in the chronic phase after injury. At 14 months, single nuclei RNA sequencing of cortical brain tissue identified disruption of genes associated with neuronal proteostasis in injured mice. Western blot analysis of neurons isolated by immunopanning showed evidence of inflammasome activation, accumulation of misfolded, hyperphosphorylated Tau, and changes in expression of proteins suggestive of impaired translation. Compared to injured wild type, injured interleukin-1 receptor 1 knockout mice, which are protected from post-injury cognitive deficits, had reduced microgliosis and decreased accumulation of pro-interleukin-1 beta and misfolded tau in cortex and cerebellum at six months. Taken together, our findings provide evidence for neuronal inflammasome activation and impaired proteostasis as key mechanisms linking repetitive mTBI in adolescence to later life neurological dysfunction and neurodegeneration.
Project description:The subventricular zone (SVZ) is a neurogenetic niche that contributes to homeostasis and repair after brain injury. However, effects of mild traumatic brain injury (mTBI) on genomewide gene expression in the SVZ remain largely unexplored. To address this issue, we investigated the single-nucleus transcriptomic profiles of the SVZ after mTBI. 18 distinct clusters were yielded via unsupervised clustering of the transcriptomic profiles. Cell type specific gene expression responding to mTBI were revealed, some of which were closely associated with pathogenesis post-injury. Furthermore, the diverse cell to cell interaction networks uncovered an array of cellular processes under mTBI. Also, we reported novel lineage trajectories and molecular hallmarks that govern the neurogenesis. Our gene expression atlas provides extensive resources for future researches regarding mTBI induced pathogenesis, its therapeutic interventions or diagnostic tests.
Project description:The relationship between repetitive mild traumatic brain injury (r-mTBI) and Alzheimer’s disease (AD) is well-recognized. However, the precise nature of how r-mTBI leads to or precipitates AD pathogenesis is currently not understood. Part A: Plasma biomarkers potentially provide non-invasive tools for detecting neurological changes in the brain, and can reveal overlaps between long-term consequences of r-mTBI and AD. In this study we address this by generating time-dependent molecular profiles of response to r-mTBI and AD pathogenesis in mouse models using unbiased proteomic analyses. To model AD, we used the well-validated hTau and PSAPP(APP/PS1) mouse models that develop age-related tau and amyloid pathological features respectively, and our well-established model of r-mTBI in C57BL/6 mice. Plasma were collected at different ages (3, 9, and 15 months-old for hTau and PSAPP mice), encompassing pre-, peri- and post-“onset” of the cognitive and neuropathological phenotypes, or at different timepoints after r-mTBI (24hrs, 3, 6, 9 and 12 months post-injury). Liquid chromatography/mass spectrometry (LC-MS) approaches coupled with Tandem Mass Tag labeling technology were applied to develop molecular profiles of protein species that were significantly differentially expressed as a consequence of mTBI or AD. Mixed model ANOVA after Benjamini-Hochberg correction, and a stringent cut-off identified 31 proteins significantly changing in r-mTBI groups over time and, when compared with changes over time in sham mice, 13 of these were unique to the injured mice. The canonical pathways predicted to be modulated by these changes were LXR/RXR activation, production of nitric oxide and reactive oxygen species and complement systems. We identified 18 proteins significantly changing in PSAPP mice and 19 proteins in hTau mice compared to their wildtype littermates with ageing. Six proteins were found to be significantly regulated in all three models i.e. r-mTBI, hTau and PSAPP mice compared to their controls. The top canonical pathways coincidently changing in all three models were LXR/RXR activation, and production of nitric oxide and reactive oxygen species. This work suggests potential biomarkers for TBI and AD pathogenesis and for the overlap between these two, and warrant targeted investigation in human populations. Part B: In this study we also address the aformention gap in the field by utilizing our unbiased proteomic approach to generate detailed time-dependent brain molecular profiles of response to repetitive mTBI and AD pathogenesis in established mouse models. Methods: We used the well-validated hTau and PSAPP(APP/PS1) mouse models that develops age-related tau and amyloid pathological features respectively, and our well-established model of repetitive-mTBI in C57BL/6 mice. Brain tissue from these animals were collected at different time points after repetitive mTBI (24hrs -12 months post-injury) and at different ages (3-15 months-old for hTau and PSAPP mice), encompassing pre-, peri- and post-“onset” of the cognitive and neuropathological phenotypes previously described in all models. Liquid chromatography/mass spectrometry (LC-MS) approach coupled with Tandem Mass Tag labeling technology were applied to reveal molecular profiles of proteins and pathways that are significantly altered as a consequence of AD or repetitive mTBI. Results: Mixed model ANOVA after Benjamin Hochberg correction identified 30 and 47 proteins that were specifically unique and changing in the hippocampus and cortex, respectively, within the r-mTBI group alone when compared with changes overtime in sham mice. PI3K/AKT signaling, Protein Kinase A signaling and PPAR/RXR activation in the hippocampus, and Protein Kinase A signaling, GNRH signaling and B cell receptor signaling in the cortex were the top canonical systems significantly altered in injury groups compared to sham mice. Mixed model AONVA identified 19 proteins significantly changing in the cortex of PSAPP mice and 7 proteins in hTau mice compared to their relative wildtype littermates respectively. In addition to the heterogeneous changes observed in the TBI and AD mouse models, there was a notable convergence and coincidental change in 6 unique proteins identified in the repetitive mTBI model and the hTau and PSAPP model. These proteins ostensibly indicate significant common pathobiological responses involving alterations in mitochondrial bioenergetics and energy metabolism, aberrant cytoskeletal reorganization and alterations in intracellular signaling transduction cascades. Conclusion: We believe that this work could help identify the common molecular substrates responsible for the precipitation of AD pathogenesis following repetitive mTBI, and also help to identify novel biological targets for therapeutic modulation in mTBI and AD.