Local translation is engaged to sustain synaptic function in impaired Wallerian degeneration
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ABSTRACT:
PROVIDER: PRJNA1124852 | ENA |
REPOSITORIES: ENA
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Project description:After injury, severed axons separated from their somas activate programmed axon degeneration, a conserved pathway to initiate their degeneration within a day. Conversely, severed projections deficient in programmed axon degeneration remain morphologically preserved with functional synapses for weeks to months after injury. How this synaptic function is sustained remains currently unknown. Here, we demonstrate that dNmnat-mediated over-expression attenuates programmed axon degeneration in distinct neuronal populations. Severed projections remain morphologically preserved for weeks. When evoked, they elicit a postsynaptic behavior which is a readout for preserved synaptic function. We used ribosomal pulldown to isolate translatomes from these projections. Transcriptional profiling revealed several enriched biological classes. Identified candidates were validated in a screen using a novel automated system to detect evoked antennal grooming as a proxy for preserved synaptic function. We used RNAi-mediated knockdown to identify mTOR as a mediator of protein synthesis, and candidates involved in protein ubiquitination and calcium homeostasis, required for preserved synaptic function. Our dataset uncovered several uncharacterized genes linked to human diseases. It may offer insights into novel avenues for therapeutic treatments.
2024-10-24 | GSE270011 | GEO
Project description:After injury, severed axons separated from their somas activate programmed axon degeneration, a conserved pathway to initiate their degeneration within a day. Conversely, severed projections deficient in programmed axon degeneration remain morphologically preserved with functional synapses for weeks to months after axotomy. How this synaptic function is sustained remains currently unknown. Here, we show that dNmnat over-expression attenuates programmed axon degeneration in distinct neuronal populations. Severed projections remain morphologically preserved for weeks. When evoked, they elicit a postsynaptic behavior, a readout for preserved synaptic function. We used ribosomal pulldown to isolate the translatome from these projections one week after axotomy. Translatome candidates of enriched biological classes identified by transcriptional profiling are validated in a screen using a novel automated system to detect evoked antennal grooming as a proxy for preserved synaptic function. RNAi-mediated knockdown reveals that transcripts of mTOR, a mediator of protein synthesis, and of candidate genes involved in protein ubiquitination and Ca2+ homeostasis are required for preserved synaptic function. Our translatome dataset also uncovers several uncharacterized Drosophila genes associated with human disease. It may offer insights into novel avenues for therapeutic treatments.
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Project description:As synapse degeneration is an early event in Alzheimer’s disease (AD) pathophysiology, a biofluid marker of synapse loss in living patients could be a surrogate marker of disease prognosis and therefore would be an excellent addition to the AD biomarker arsenal. With direct access to the brain interstitial fluid, the cerebrospinal fluid (CSF) is a potential source of synapse-derived proteins that could be potential biomarkers of underlying synapse degeneration. The aim of this study was to identify, verify and evaluate a set of synaptic proteins as surrogate CSF markers of underlying synapse loss in AD patients. In the Discovery Stage, we combined high-throughput shotgun proteomics of the CSF with an exhaustive search of the literature and public databases for proteomic studies of the CSF and synapse.
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Project description:Synapse degeneration is an early and invariant feature of neurodegenerative diseases. Indeed, synapse loss occurs prior to neuronal degeneration and correlates with the symptom severity of these diseases. However, the molecular mechanisms that trigger synaptic loss remain poorly understood. Here we demonstrate that deficient Wnt signalling elicits synaptic degeneration in the adult striatum. Inducible expression of the secreted Wnt antagonist Dickkopf1 (Dkk1) in adult mice (iDkk1) decreases the number of cortico-striatal glutamatergic synapses and of D1 and D2 dopamine receptor clusters. Synapse loss occurs in the absence of axon retraction or cell death. The remaining excitatory terminals contain fewer synaptic vesicles and have a reduced probability of evoked transmitter release. IDkk1 mice show impaired motor coordination and are irresponsive to amphetamine. These studies identify Wnts as key endogenous regulators of synaptic maintenance and suggest that dysfunction in Wnt signalling contributes to synaptic degeneration at early stages in neurodegenerative diseases.
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Project description:Chromatin is highly condensed and transcriptionally repressed during mitosis. Although it is established that some general transcription factors are inactivated by phosphorylation at mitosis, many details of mitotic transcriptional repression and its underlying mechanisms are largely unknown. Here, we provide evidence that as cells enter mitosis, genes with transcriptionally engaged RNA Polymerase II (Pol II) can continue transcription until the end of the gene to clear Pol II from mitotic chromatin. Using ChIP-Seq, we find that the transcriptional reinitiation process is globally impaired in early mitosis (prophase/prometaphase), with loss of TFIIB occupancy and nucleosome-free regions at promoters. Pretreatment of nocodazole-arrested mitotic cells with the P-TEFb inhibitor flavopiridol prevents the release of promoter-proximal engaged Pol II. Global nascent RNA sequencing and RNA fluorescence in situ hybridization (FISH) of individual genes demonstrate the existence of transcriptionally engaged Pol II in early mitosis. Chemical and mutational inhibition of P-TEFb in mitosis leads to delays in the progression of cell division. Together, our study reveals a novel mechanism for mitotic transcriptional repression whereby transcriptionally engaged Pol II can progress into productive elongation and finish transcription to allow proper cellular division.
2015-10-30 | GSE71848 | GEO
Project description:s synapse degeneration is an early event in Alzheimer’s disease (AD) pathophysiology, a biofluid marker of synapse loss in living patients could be a surrogate marker of disease prognosis and therefore would be an excellent addition to the AD biomarker arsenal. With direct access to the brain interstitial fluid, the cerebrospinal fluid (CSF) is a potential source of synapse-derived proteins that could be potential biomarkers of underlying synapse degeneration. The aim of this study was to identify, verify and evaluate a set of synaptic proteins as surrogate CSF markers of underlying synapse loss in AD patients. In the Discovery Stage, we combined high-throughput shotgun proteomics of the CSF with an exhaustive search of the literature and public databases for proteomic studies of the CSF and synapse. A thorough characterization of the synaptic component of the CSF identified 210 synaptic proteins that are detectable in human CSF. We selected an initial panel of 22 candidate biomarkers for evaluation. In the Verification Stage, 12 proteins were discarded due to poor detection by targeted mass spectrometry (Selected Reaction Monitoring, SRM). We confirmed the expression of the remaining 10 proteins either directly at (Calsynytenin-1, GluR2, GluR4, Neurexins 2A and 3A, Neuroligin-2, Syntaxin-1B, Thy-1 and Vamp-2), or surrounding (Tenascin-R), the human synapse using Array Tomography microscopy and biochemical fractionation methods. We quantified the synaptic panel by SRM in CSF samples from 2 independent clinical cohorts of cognitively normal controls and all clinical stages of AD (n=140). A set of the panel proteins demonstrated a non-linear profile distinct to that of existing biomarkers whereby the CSF levels were decreased at the earliest preclinical stage of AD, reflecting reduced synaptic density in these asymptomatic individuals and elevated at later symptomatic stages when neurodegeneration is widespread. In conclusion, we have identified a set of novel synapse-specific proteins that could have clinical value for assessing disease progression in individuals at-risk for AD and potentially in other neurological disorders characterized by early synapse loss.
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