Loss of Sarm1 Mitigates Axonal Degeneration and Promotes Neuronal Regeneration After Ischemic Stroke
Ontology highlight
ABSTRACT:
PROVIDER: PRJNA1180930 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR31190700_1.fastq.gz | Fastqsanger.gz | |||
| SRR31190700_2.fastq.gz | Fastqsanger.gz | |||
| SRR31190701_1.fastq.gz | Fastqsanger.gz | |||
| SRR31190701_2.fastq.gz | Fastqsanger.gz | |||
| SRR31190702_1.fastq.gz | Fastqsanger.gz |
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Project description:Axonal degeneration is a core feature of ischemic brain injury that limits functional recovery. The pro-degenerative molecule Sarm1 is required for Wallerian axon degeneration after traumatic and chemotoxic nerve injuries, however it is unclear if a similar mechanism mediates axonal degradation after ischemic injury. Here we show that loss of Sarm1 in male mice tested results in profound attenuation of axonal degeneration after focal ischemia to the subcortical white matter. Moreover, absence of Sarm1 significantly promotes the survival of neurons distal but connected to the infarct after ischemic injuries to the subcortical white matter as well as to the cortex. To further understand the mechanism of Sarm1-/- mediated neuronal protection, we performed differential gene expression analysis of male wildtype and Sarm1-/- stroke-injured neurons and found that that loss of Sarm1 activates a pro-regenerative molecular program that promotes new axon and synapse formation after white matter ischemia. Using a functional genomics approach to recapitulate such a molecular program in Sarm1-/- neurons, we identify molecular compounds sufficient to enhance cortical neurite outgrowth in vitro, and all of which elicit a conserved epigenetic signature promoting axonogenesis. These results indicate that Sarm1 concurrently promotes axonal degeneration and inhibits a regenerative program encoded at the level of the epigenome that can be modulated pharmacologically. Our findings thus reveal a novel role for Sarm1 as a crucial regulator of both axonal degeneration and axonal remodeling after ischemic stroke.
2025-05-01 | GSE280862 | GEO
Project description:Axonal degeneration is a core feature of ischemic brain injury that limits functional recovery (1). The pro-degenerative molecule Sarm1 is required for Wallerian axon degeneration after traumatic and chemotoxic nerve injuries (2), however it is unclear if a similar mechanism mediates axonal degradation after ischemic injury. Here we show that loss of Sarm1 results in profound attenuation of axonal degeneration after focal ischemia to the subcortical white matter. Moreover, absence of Sarm1 significantly promotes the survival of neurons remote from but connected to the infarct after ischemic injuries to the subcortical white matter as well as to the cortex. To further understand the mechanism of Sarm1-/- mediated neuronal protection, we performed differential gene expression analyses of wildtype and Sarm1-/- stroke-injured neurons and found that the loss of Sarm1 activates a pro-growth molecular program that promotes new axon and synapse formation after white matter ischemia. Using a functional genomics approach to recapitulate such a molecular program in Sarm1-/- neurons, we identify molecular compounds sufficient to enhance cortical neurite outgrowth in vitro, and all of which elicit a conserved epigenetic signature promoting axonogenesis. These results indicate that Sarm1 promotes axonal degeneration and concurrently inhibits an axonal reparative program encoded at the level of the epigenome that can be modulated pharmacologically. Our findings thus reveal a novel role for Sarm1 as a crucial regulator of both axonal degeneration and axonal remodeling after ischemic stroke.
| S-EPMC11888178 | biostudies-literature
Project description:The Toll/IL-1R domain-containing adaptor protein SARM1 is expressed primarily in the brain, where it mediates axonal degeneration. Additional roles for SARM1 in a number of other processes including TLR-signaling, viral infection, chemokine expression, and XAF1 expression have also been described. Here we report defects in the induction of Ccl3, Ccl4, and Ccl5 in Sarm1-/- macrophages, for which we were unable to find mechanistic support. We instead show that the 129 congenic locus spans both the chemokine and XAF1 loci, and SNP analysis reveals other remaining 129 genomic regions in both existing knockout strains. New knockout mouse strains generated on a pure B6 genetic background using CRISPR confirmed the role of SARM1 in axonal degeneration and susceptibility WNV infection, but not in chemokine expression or susceptibility to VSV or LACV infection. We show that XAF1 expression differences are due to sequence and isoform polymorphism between B6 and 129 strains. Given its known role in apoptosis, XAF1 polymorphism may account for some phenotypes described in Sarm1-/- mice. RNAseq in the new CRISPR strains reveals changes in transcripts of the mitochondrial electron transport chain and ribosomal proteins, suggesting possible targets of SARM1.
2020-02-23 | GSE136221 | GEO
Project description:The Toll/IL-1R domain-containing adaptor protein SARM1 is expressed primarily in the brain, where it mediates axonal degeneration. Additional roles for SARM1 in a number of other processes including TLR-signaling, viral infection, chemokine expression, and XAF1 expression have also been described. Here we report defects in the induction of Ccl3, Ccl4, and Ccl5 in Sarm1-/- macrophages, for which we were unable to find mechanistic support. We instead show that the 129 congenic locus spans both the chemokine and XAF1 loci, and SNP analysis reveals other remaining 129 genomic regions in both existing knockout strains. New knockout mouse strains generated on a pure B6 genetic background using CRISPR confirmed the role of SARM1 in axonal degeneration and susceptibility WNV infection, but not in chemokine expression or susceptibility to VSV or LACV infection. We show that XAF1 expression differences are due to sequence and isoform polymorphism between B6 and 129 strains. Given its known role in apoptosis, XAF1 polymorphism may account for some phenotypes described in Sarm1-/- mice. RNAseq in the new CRISPR strains reveals changes in transcripts of the mitochondrial electron transport chain and ribosomal proteins, suggesting possible targets of SARM1.
2020-02-23 | GSE136284 | GEO
Project description:Upon axonal injury, Sterile alpha (SAM) and Toll/interleukin-1 receptor (TIR) motif containing 1 (SARM1) is activated by nicotinamide mononucleotide (NMN) to deplete NAD and consequently promote the process of axon degeneration (AxD). Currently, only the inactive form of SARM1 in its auto-inhibitory conformation has been resolved. The flexibility of the enzymatically active form of SARM1 has so far precluded its structural determination. To solve the problem, we generated a stabilizing nanobody, Nb-C6, that specifically recognized 30 only the NMN-activated form of SARM1. The conformation specificity was verified by immunoprecipitation and surface plasmon resonance. Fluorescently labeled Nb-C6 could immunostain only the activated SARM1 in cells stimulated with CZ-48, a permeant mimetic of NMN. Expression of Nb-C6 in live cells resulted in stabilization of the active form of the endogenous and exogenous SARM1, producing and elevating cellular levels of cyclic ADP-ribose, a calcium messenger. Cryo-EM of the NMN-activated SARM1 complexed by Nb-C6 showed an octameric structure resembling a “blooming lotus” with the ARM domains bending significantly inward and swinging out together with the TIR domains to form the “petals of the lotus”. Nb-C6 bound to the SAM domain of the activated SARM1 and stabilized its Armadillo repeat motif domain. Analyses using hydrogen-deuterium exchange mass spectrometry (HDX-MS), and cross-linking MS (XL-MS) indicate that the activated SARM1 is highly dynamic and flexible and the neighboring TIRs form dimers via the surface close to one BB loop. The Nanobody is thus a valuable tool for delineating the mechanism of activation of SARM1 in AxD and other cellular processes.
2022-11-29 | PXD033528 | Pride
Project description:Axon loss contributes to many common neurodegenerative disorders. In healthy axons, the axon survival factor NMNAT2 inhibits SARM1, the central executioner of programmed axon degeneration. We identified two rare NMNAT2 missense variants in two brothers afflicted with a progressive neuropathy syndrome. The polymorphisms result in amino acid substitutions, V98M and R232Q, which reduce NMNAT2 NAD+-synthetase activity. We generated a mouse model of the human syndrome and found that Nmnat2V98M/Nmnat2R232Q compound-heterozygous CRISPR mice survive to adulthood but develop progressive motor dysfunction, peripheral axon loss, and macrophage infiltration. These disease phenotypes are all SARM1-dependent. Remarkably, macrophage depletion therapy blocks and reverses neuropathic phenotypes in Nmnat2V98M/R232Q mice, identifying a SARM1-dependent neuroimmune mechanism as a key driver of disease pathogenesis. These findings demonstrate that SARM1 induces an inflammatory neuropathy and highlight the potential of immune therapy to treat this rare syndrome and other neurodegenerative conditions associated with NMNAT2 loss and SARM1 activation.
2022-10-25 | GSE210403 | GEO
Project description:The NAD hydrolase (NADase) SARM1 acts as a central executioner of programmed axon death and is a possible therapeutic target for neurodegenerative disorders. While orthosteric inhibitors of SARM1 have been described, this multi-domain enzyme is also subject to intricate forms of autoregulation, suggesting the potential for allosteric modes of inhibition. Previous studies have identified multiple cysteine residues that support SARM1 activation and catalysis, but which of these cysteines, if any, might be selectively targetable by electrophilic small molecules remains unknown. Here we describe the chemical proteomic discovery of a series of tryptoline acrylamides that site-specifically and stereoselectively modify cysteine-311 (C311) in the non-catalytic, autoregulatory armadillo repeat (ARM) domain of SARM1. These covalent compounds inhibit the NADase activity of WT-SARM1, but not C311A or C311S SARM1 mutants, show a high degree of proteome-wide selectivity for SARM1_C311, and stereoselectively block vincristine- and vacor-induced neurite degeneration in primary rodent dorsal root ganglion neurons. Our findings describe selective, covalent inhibitors of SARM1 targeting an allosteric cysteine, pointing to a potentially attractive therapeutic strategy for axon degeneration-dependent forms of neurological disease.
2022-08-22 | PXD035400 | Pride
Project description:Diabetic patients have a high risk of developing skeletal diseases accompanied by diabetic peripheral neuropathy (DPN). In this study, we isolated the role of DPN in skeletal disease with global and conditional knockout models of sterile-α and TIR-motif-containing protein-1 (Sarm1). SARM1, an NADase highly expressed in the nervous system, regulates axon degeneration upon a range of insults, including DPN. Global knockout of Sarm1 prevented DPN, but not skeletal disease, in male mice with type 1 diabetes (T1D). Female wild type mice also developed diabetic bone disease, but without DPN. Unexpectedly, global Sarm1 knockout completely protected female mice from T1D-associated bone suppression and skeletal fragility despite comparable muscle atrophy and hyperglycemia. Global Sarm1 knockout rescued bone health through sustained osteoblast function with abrogation of local oxidative stress responses. This was independent of the neural actions of SARM1, as beneficial effects on bone were lost with neural conditional Sarm1 knockout. This study demonstrates that the onset of skeletal disease occurs rapidly in both male and female mice with T1D completely independent of DPN. In addition, this reveals that clinical SARM1 inhibitors, currently being developed for treatment of neuropathy, may also have benefits for diabetic bone through actions outside of the nervous system.
2024-04-30 | GSE252292 | GEO
Project description:Several traumatic and neurodegenerative disorders of the CNS show axonal degeneration as a key and early pathological feature. Following a focal axonal lesion, an extended axonal disintegration by acute axonal degeneration (AAD) occurs within several hours. During AAD, activation of autophagic proteins including Unc-51 like autophagy activating kinase 1 (ULK1) has been demonstrated, but its role is incompletely understood. Here, we overexpressed a dominant negative of ULK1 (ULK1.DN) in primary rat cortical neurons in vitro and in the spinal cord (SC) and optic nerve (ON) in vivo. We found a significant inhibitory effect on autophagy in vitro and in vivo. While no effect on cell survival could be observed, ULK1.DN attenuated AAD after axotomy in microfluidic chambers in vitro. Models of SC injury and ON crush in vivo confirmed an attenuation of axonal degeneration by ULK1.DN. In a translational approach, we employed the selective ULK1 inhibitor SBI-0206965 (SBI) and found an attenuation of AAD after ON crush in vivo mediated by a reduction of autophagy by SBI. Quantitative proteomic profiling after ULK1.DN overexpression in vitro revealed a regulation of proteins associated with translation and splicing. A differential exon expression analysis identified the genes kinesin family member 1B (Kif1b), DNA damage inducible transcript 3 (Ddit3) and WD repeat domain 6 (Wdr6) as targets of ULK1.DN and potential mediators of its degeneration-attenuating effect. These findings reveal ULK1 as an important mediator of axonal degeneration and elucidate its function in splicing, defining it as a putative therapeutic target.
2020-09-23 | GSE123687 | GEO
Project description:Basal forebrain cholinergic neurons (BFCNs) extend long projections to multiple targets in the brain to regulate cognitive functions, and are compromised in numerous neurodegenerative disorders. Our previous study showed that injury to the target region of these neurons affects their viability in vivo. Moderate cortical injury in mice promoted a significant increase in proneurotrophins in the injured cortex, leading to the retrograde loss of BFCNs ipsilateral to the injury via the p75 neurotrophin receptor (p75NTR). We determined that stimulation of BFCN axon terminals with proNGF elicited retrograde degeneration of the axons leading to cell death of these neurons in vitro. Our current study investigates mechanisms of axonal p75NTR signaling, and shows that retrograde transport and local axonal protein synthesis are necessary for proNGF induced retrograde degeneration initiated at the axon terminal. Analysis of the nascent axonal proteome revealed numerous newly synthesized proteins after stimulation of axon terminals with proNGF. Pathway analysis showed that amyloid precursor protein (APP) was a key upstream regulator. Our results show a functional role for APP in promoting proNGF induced BFCN axonal degeneration and cell death.
2025-05-06 | PXD043846 | Pride