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The neurite outgrowth inhibitor Nogo-A promotes denervation in an amyotrophic lateral sclerosis model.

ABSTRACT: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by motor neuron loss and muscle wasting. In muscles of ALS patients, Nogo-A-a protein known to inhibit axon regeneration-is ectopically expressed at levels that correlate with the severity of the clinical symptoms. We now show that the genetic ablation of Nogo-A extends survival and reduces muscle denervation in a mouse model of ALS. In turn, overexpression of Nogo-A in wild-type muscle fibres leads to shrinkage of the postsynapse and retraction of the presynaptic motor ending. This suggests that the expression of Nogo-A occurring early in ALS skeletal muscle could cause repulsion and destabilization of the motor nerve terminals, and subsequent dying back of the axons and motor neurons.

SUBMITTER: Jokic N

PROVIDER: S-EPMC1679784 | biostudies-literature | 2006 Nov

REPOSITORIES: biostudies-literature

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The neurite outgrowth inhibitor Nogo-A promotes denervation in an amyotrophic lateral sclerosis model.

Jokic Natasa N Gonzalez de Aguilar Jose-Luis JL Dimou Leda L Lin Shuo S Fergani Anissa A Ruegg Markus A MA Schwab Martin E ME Dupuis Luc L Loeffler Jean-Philippe JP

EMBO reports 20061013 11

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by motor neuron loss and muscle wasting. In muscles of ALS patients, Nogo-A-a protein known to inhibit axon regeneration-is ectopically expressed at levels that correlate with the severity of the clinical symptoms. We now show that the genetic ablation of Nogo-A extends survival and reduces muscle denervation in a mouse model of ALS. In turn, overexpression of Nogo-A in wild-type muscle fibres leads to shrinkage of ...[more]

PMID: 17039253

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Endplate denervation correlates with Nogo-A muscle expression in amyotrophic lateral sclerosis patients.

Project description:Data from mouse models of amyotrophic lateral sclerosis (ALS) suggest early morphological changes in neuromuscular junctions (NMJs), with loss of nerve-muscle contact. Overexpression of the neurite outgrowth inhibitor Nogo-A in muscle may play a role in this loss of endplate innervation.We used confocal and electron microscopy to study the structure of the NMJs in muscle samples collected from nine ALS patients (five early-stage patients and four long-term survivors). We correlated the morphological results with clinical and electrophysiological data, and with Nogo-A muscle expression level.Surface electromyography assessment of neuromuscular transmission was abnormal in 3/9 ALS patients. The postsynaptic apparatus was morphologically altered for almost all NMJs (n = 430) analyzed using confocal microscopy. 19.7% of the NMJs were completely denervated (fragmented synaptic gutters and absence of nerve terminal profile). The terminal axonal arborization was usually sparsely branched and 56.8% of innervated NMJs showed a typical reinnervation pattern. Terminal Schwann cell (TSC) morphology was altered with extensive cytoplasmic processes. A marked intrusion of TSCs in the synaptic cleft was seen in some cases, strikingly reducing the synaptic surface available for neuromuscular transmission. Finally, high-level expression of Nogo-A in muscle was significantly associated with higher extent of NMJ denervation and negative functional outcome.Our results support the hypothesis that morphological alterations of NMJs are present from early-stage disease and may significantly contribute to functional motor impairment in ALS patients. Muscle expression of Nogo-A is associated with NMJ denervation and thus constitutes a therapeutic target to slow disease progression.

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Neurite outgrowth inhibitor Nogo-A establishes spatial segregation and extent of oligodendrocyte myelination.

Project description:A requisite component of nervous system development is the achievement of cellular recognition and spatial segregation through competition-based refinement mechanisms. Competition for available axon space by myelinating oligodendrocytes ensures that all relevant CNS axons are myelinated properly. To ascertain the nature of this competition, we generated a transgenic mouse with sparsely labeled oligodendrocytes and establish that individual oligodendrocytes occupying similar axon tracts can greatly vary the number and lengths of their myelin internodes. Here we show that intercellular interactions between competing oligodendroglia influence the number and length of myelin internodes, referred to as myelinogenic potential, and identify the amino-terminal region of Nogo-A, expressed by oligodendroglia, as necessary and sufficient to inhibit this process. Exuberant and expansive myelination/remyelination is detected in the absence of Nogo during development and after demyelination, suggesting that spatial segregation and myelin extent is limited by microenvironmental inhibition. We demonstrate a unique physiological role for Nogo-A in the precise myelination of the developing CNS. Maximizing the myelinogenic potential of oligodendrocytes may offer an effective strategy for repair in future therapies for demyelination.

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Proteolytic control of neurite outgrowth inhibitor NOGO-A by the cAMP/PKA pathway.

Project description:Protein kinase A (PKA) controls major aspects of neurite outgrowth and morphogenesis and plays an essential role in synaptic plasticity and memory. However, the molecular mechanism(s) of PKA action on neurite sprouting and activity are still unknown. Here, we report that in response to neurotrophin or cAMP stimulation the RING ligase praja2 ubiquitinates and degrades NOGO-A, a major inhibitor of neurite outgrowth in mammalian brain. Genetic silencing of praja2 severely inhibited neurite extension of differentiating neuroblastoma cells and mesencephalic neurons and axon outgrowth and sprouting of striatal terminals in developing rat brain. This phenotype was rescued when both praja2 and NOGO-A were depleted, suggesting that NOGO-A is, indeed, a biologically relevant target of praja2 in neuronal cells. Our findings unveil a novel mechanism that functionally couples cAMP signaling with the proteolytic turnover of NOGO-A, positively impacting on neurite outgrowth in mammalian brain.

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Nogo Receptor Antagonist LOTUS Promotes Neurite Outgrowth through Its Interaction with Teneurin-4.

Project description:Neurite outgrowth is a crucial process for organizing neuronal circuits in neuronal development and regeneration after injury. Regenerative failure in the adult mammalian central nervous system (CNS) is attributed to axonal growth inhibitors such as the Nogo protein that commonly binds to Nogo receptor-1 (NgR1). We previously reported that lateral olfactory tract usher substance (LOTUS) functions as an endogenous antagonist for NgR1 in forming neuronal circuits in the developing brain and improving axonal regeneration in the adult injured CNS. However, another molecular and cellular function of LOTUS remains unknown. In this study, we found that cultured retinal explant neurons extend their neurites on the LOTUS-coating substrate. This action was also observed in cultured retinal explant neurons derived from Ngr1-deficient mouse embryos, indicating that the promoting action of LOTUS on neurite outgrowth may be mediated by unidentified LOTUS-binding protein(s). We therefore screened the binding partner(s) of LOTUS by using a liquid chromatography-tandem mass spectrometry (LC-MS/MS). LC-MS/MS analysis and pull-down assay showed that LOTUS interacts with Teneurin-4 (Ten-4), a cell adhesion molecule. RNAi knockdown of Ten-4 inhibited neurite outgrowth on the LOTUS substrate in retinoic acid (RA)-treated Neuro2A cells. Furthermore, a soluble form of Ten-4 attenuates the promoting action on neurite outgrowth in cultured retinal explant neurons on the LOTUS substrate. These results suggest that LOTUS promotes neurite outgrowth by interacting with Ten-4. Our findings may provide a new molecular mechanism of LOTUS to contribute to neuronal circuit formation in development and to enhance axonal regeneration after CNS injury.

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Amyotrophic lateral sclerosis: SOD1 mouse model

Project description:Identification of familial amyotrophic lateral sclerosis (fALS) related genes. Material from three hSOD1(G93A) transgenic mice was compared to material from three non-transgenic control mice using an alternating loop design on two-colour cDNA microarrays. Statistical data management and analysis: postgreSQL relational database (www.postgresql.org), Perl, and R (www.r-project.org); pin-wise lowess-regression based normalisation (Yang et al., 2002 [PMID: 11842121]); mixed ANOVA-model. Keywords = amyotrophic lateral sclerosis, ALS, SOD1 mouse model

2010-06-05 | E-GEOD-2400 | biostudies-arrayexpress

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2005-12-31 | GSE2400 | GEO

Lateral olfactory tract usher substance (LOTUS), an endogenous Nogo receptor antagonist, ameliorates disease progression in amyotrophic lateral sclerosis model mice.

Project description:Nogo-Nogo receptor 1 (NgR1) signaling is significantly implicated in neurodegeneration in amyotrophic lateral sclerosis (ALS). We previously showed that lateral olfactory tract usher substance (LOTUS) is an endogenous antagonist of NgR1 that prevents all myelin-associated inhibitors (MAIs), including Nogo, from binding to NgR1. Here we investigated the role of LOTUS in ALS pathogenesis by analyzing G93A-mutated human superoxide dismutase 1 (SOD1) transgenic (Tg) mice, as an ALS model, as well as newly generated LOTUS-overexpressing SOD1 Tg mice. We examined expression profiles of LOTUS and MAIs and compared motor functions and survival periods in these mice. We also investigated motor neuron survival, glial proliferation in the lumbar spinal cord, and neuromuscular junction (NMJ) morphology. We analyzed downstream molecules of NgR1 signaling such as ROCK2, LIMK1, cofilin, and ataxin-2, and also neurotrophins. In addition, we investigated LOTUS protein levels in the ventral horn of ALS patients. We found significantly decreased LOTUS expression in both SOD1 Tg mice and ALS patients. LOTUS overexpression in SOD1 Tg mice increased lifespan and improved motor function, in association with prevention of motor neuron loss, reduced gliosis, increased NMJ innervation, maintenance of cofilin phosphorylation dynamics, decreased levels of ataxin-2, and increased levels of brain-derived neurotrophic factor (BDNF). Reduced LOTUS expression may enhance neurodegeneration in SOD1 Tg mice and ALS patients by activating NgR1 signaling, and in this study LOTUS overexpression significantly ameliorated ALS pathogenesis. LOTUS might serve as a promising therapeutic target for ALS.

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Amyotrophic lateral sclerosis and denervation alter sphingolipids and up-regulate glucosylceramide synthase.

Project description:Amyotrophic lateral sclerosis (ALS) is a fatal adult-onset disease characterized by upper and lower motor neuron degeneration, muscle wasting and paralysis. Growing evidence suggests a link between changes in lipid metabolism and ALS. Here, we used UPLC/TOF-MS to survey the lipidome in SOD1(G86R) mice, a model of ALS. Significant changes in lipid expression were evident in spinal cord and skeletal muscle before overt neuropathology. In silico analysis also revealed appreciable changes in sphingolipids including ceramides and glucosylceramides (GlcCer). HPLC analysis showed increased amounts of GlcCer and downstream glycosphingolipids (GSLs) in SOD1(G86R) muscle compared with wild-type littermates. Glucosylceramide synthase (GCS), the enzyme responsible for GlcCer biosynthesis, was up-regulated in muscle of SOD1(G86R) mice and ALS patients, and in muscle of wild-type mice after surgically induced denervation. Conversely, inhibition of GCS in wild-type mice, following transient peripheral nerve injury, reversed the overexpression of genes in muscle involved in oxidative metabolism and delayed motor recovery. GCS inhibition in SOD1(G86R) mice also affected the expression of metabolic genes and induced a loss of muscle strength and morphological deterioration of the motor endplates. These findings suggest that GSLs may play a critical role in ALS muscle pathology and could lead to the identification of new therapeutic targets.

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