RESUMO
Sensory axons degenerate following separation from their cell body, but partial injury to peripheral nerves may leave the integrity of damaged axons preserved. We show that an endogenous ligand for the natural killer (NK) cell receptor NKG2D, Retinoic Acid Early 1 (RAE1), is re-expressed in adult dorsal root ganglion neurons following peripheral nerve injury, triggering selective degeneration of injured axons. Infiltration of cytotoxic NK cells into the sciatic nerve by extravasation occurs within 3 days following crush injury. Using a combination of genetic cell ablation and cytokine-antibody complex stimulation, we show that NK cell function correlates with loss of sensation due to degeneration of injured afferents and reduced incidence of post-injury hypersensitivity. This neuro-immune mechanism of selective NK cell-mediated degeneration of damaged but intact sensory axons complements Wallerian degeneration and suggests the therapeutic potential of modulating NK cell function to resolve painful neuropathy through the clearance of partially damaged nerves.
Assuntos
Células Matadoras Naturais/fisiologia , Proteínas Associadas à Matriz Nuclear/metabolismo , Proteínas de Transporte Nucleocitoplasmático/metabolismo , Traumatismos dos Nervos Periféricos/metabolismo , Animais , Axônios , Gânglios Espinais/citologia , Gânglios Espinais/metabolismo , Células Matadoras Naturais/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Subfamília K de Receptores Semelhantes a Lectina de Células NK/metabolismo , Regeneração Nervosa , Neurônios/citologia , Neurônios Aferentes/imunologia , Neurônios Aferentes/metabolismo , Proteínas Associadas à Matriz Nuclear/fisiologia , Proteínas de Transporte Nucleocitoplasmático/fisiologia , Dor , Traumatismos dos Nervos Periféricos/imunologia , Doenças do Sistema Nervoso Periférico , Nervo Isquiático , Células Receptoras Sensoriais/metabolismoRESUMO
Guillain-Barré syndrome (GBS) is a rare heterogenous disorder of the peripheral nervous system, which is usually triggered by a preceding infection, and causes a potentially life-threatening progressive muscle weakness1. Although GBS is considered an autoimmune disease, the mechanisms that underlie its distinct clinical subtypes remain largely unknown. Here, by combining in vitro T cell screening, single-cell RNA sequencing and T cell receptor (TCR) sequencing, we identify autoreactive memory CD4+ cells, that show a cytotoxic T helper 1 (TH1)-like phenotype, and rare CD8+ T cells that target myelin antigens of the peripheral nerves in patients with the demyelinating disease variant. We characterized more than 1,000 autoreactive single T cell clones, which revealed a polyclonal TCR repertoire, short CDR3ß lengths, preferential HLA-DR restrictions and recognition of immunodominant epitopes. We found that autoreactive TCRß clonotypes were expanded in the blood of the same patient at distinct disease stages and, notably, that they were shared in the blood and the cerebrospinal fluid across different patients with GBS, but not in control individuals. Finally, we identified myelin-reactive T cells in the nerve biopsy from one patient, which indicates that these cells contribute directly to disease pathophysiology. Collectively, our data provide clear evidence of autoreactive T cell immunity in a subset of patients with GBS, and open new perspectives in the field of inflammatory peripheral neuropathies, with potential impact for biomedical applications.
Assuntos
Autoimunidade , Linfócitos T CD8-Positivos , Síndrome de Guillain-Barré , Nervos Periféricos , Doenças do Sistema Nervoso Periférico , Células Th1 , Humanos , Biópsia , Linfócitos T CD8-Positivos/imunologia , Linfócitos T CD8-Positivos/patologia , Síndrome de Guillain-Barré/sangue , Síndrome de Guillain-Barré/líquido cefalorraquidiano , Síndrome de Guillain-Barré/etiologia , Síndrome de Guillain-Barré/imunologia , Antígenos HLA-DR/imunologia , Epitopos Imunodominantes/imunologia , Bainha de Mielina/imunologia , Nervos Periféricos/imunologia , Nervos Periféricos/patologia , Doenças do Sistema Nervoso Periférico/complicações , Doenças do Sistema Nervoso Periférico/imunologia , Doenças do Sistema Nervoso Periférico/patologia , Receptores de Antígenos de Linfócitos T/imunologia , Células Th1/imunologia , Células Th1/patologia , Linfócitos T Citotóxicos/imunologia , Linfócitos T Citotóxicos/patologia , Memória ImunológicaRESUMO
The immune system has a critical role in orchestrating tissue healing. As a result, regenerative strategies that control immune components have proved effective1,2. This is particularly relevant when immune dysregulation that results from conditions such as diabetes or advanced age impairs tissue healing following injury2,3. Nociceptive sensory neurons have a crucial role as immunoregulators and exert both protective and harmful effects depending on the context4-12. However, how neuro-immune interactions affect tissue repair and regeneration following acute injury is unclear. Here we show that ablation of the NaV1.8 nociceptor impairs skin wound repair and muscle regeneration after acute tissue injury. Nociceptor endings grow into injured skin and muscle tissues and signal to immune cells through the neuropeptide calcitonin gene-related peptide (CGRP) during the healing process. CGRP acts via receptor activity-modifying protein 1 (RAMP1) on neutrophils, monocytes and macrophages to inhibit recruitment, accelerate death, enhance efferocytosis and polarize macrophages towards a pro-repair phenotype. The effects of CGRP on neutrophils and macrophages are mediated via thrombospondin-1 release and its subsequent autocrine and/or paracrine effects. In mice without nociceptors and diabetic mice with peripheral neuropathies, delivery of an engineered version of CGRP accelerated wound healing and promoted muscle regeneration. Harnessing neuro-immune interactions has potential to treat non-healing tissues in which dysregulated neuro-immune interactions impair tissue healing.
Assuntos
Peptídeo Relacionado com Gene de Calcitonina , Macrófagos , Neutrófilos , Nociceptores , Cicatrização , Animais , Camundongos , Comunicação Autócrina , Peptídeo Relacionado com Gene de Calcitonina/metabolismo , Peptídeo Relacionado com Gene de Calcitonina/farmacologia , Diabetes Mellitus Experimental/complicações , Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Experimental/patologia , Eferocitose , Macrófagos/citologia , Macrófagos/metabolismo , Monócitos/citologia , Monócitos/metabolismo , Músculo Esquelético , Canal de Sódio Disparado por Voltagem NAV1.8/deficiência , Canal de Sódio Disparado por Voltagem NAV1.8/genética , Canal de Sódio Disparado por Voltagem NAV1.8/metabolismo , Neutrófilos/citologia , Neutrófilos/metabolismo , Nociceptores/metabolismo , Comunicação Parácrina , Doenças do Sistema Nervoso Periférico/complicações , Proteína 1 Modificadora da Atividade de Receptores/metabolismo , Regeneração/efeitos dos fármacos , Pele , Trombospondina 1/metabolismo , Cicatrização/efeitos dos fármacos , Cicatrização/imunologia , Humanos , Masculino , FemininoRESUMO
CLP1 is a RNA kinase involved in tRNA splicing. Recently, CLP1 kinase-dead mice were shown to display a neuromuscular disorder with loss of motor neurons and muscle paralysis. Human genome analyses now identified a CLP1 homozygous missense mutation (p.R140H) in five unrelated families, leading to a loss of CLP1 interaction with the tRNA splicing endonuclease (TSEN) complex, largely reduced pre-tRNA cleavage activity, and accumulation of linear tRNA introns. The affected individuals develop severe motor-sensory defects, cortical dysgenesis, and microcephaly. Mice carrying kinase-dead CLP1 also displayed microcephaly and reduced cortical brain volume due to the enhanced cell death of neuronal progenitors that is associated with reduced numbers of cortical neurons. Our data elucidate a neurological syndrome defined by CLP1 mutations that impair tRNA splicing. Reduction of a founder mutation to homozygosity illustrates the importance of rare variations in disease and supports the clan genomics hypothesis.
Assuntos
Doenças do Sistema Nervoso Central/genética , Mutação de Sentido Incorreto , Proteínas Nucleares/metabolismo , Doenças do Sistema Nervoso Periférico/genética , Fosfotransferases/metabolismo , RNA de Transferência/metabolismo , Fatores de Transcrição/metabolismo , Anormalidades Múltiplas/genética , Anormalidades Múltiplas/patologia , Animais , Doenças do Sistema Nervoso Central/patologia , Cérebro/patologia , Pré-Escolar , Endorribonucleases/metabolismo , Feminino , Fibroblastos/metabolismo , Humanos , Lactente , Masculino , Camundongos , Camundongos Endogâmicos CBA , Microcefalia/genética , Doenças do Sistema Nervoso Periférico/patologia , RNA de Transferência/genética , Proteínas de Ligação a RNARESUMO
Diabetes represents a spectrum of disease in which metabolic dysfunction damages multiple organ systems including liver, kidneys and peripheral nerves1,2. Although the onset and progression of these co-morbidities are linked with insulin resistance, hyperglycaemia and dyslipidaemia3-7, aberrant non-essential amino acid (NEAA) metabolism also contributes to the pathogenesis of diabetes8-10. Serine and glycine are closely related NEAAs whose levels are consistently reduced in patients with metabolic syndrome10-14, but the mechanistic drivers and downstream consequences of this metabotype remain unclear. Low systemic serine and glycine are also emerging as a hallmark of macular and peripheral nerve disorders, correlating with impaired visual acuity and peripheral neuropathy15,16. Here we demonstrate that aberrant serine homeostasis drives serine and glycine deficiencies in diabetic mice, which can be diagnosed with a serine tolerance test that quantifies serine uptake and disposal. Mimicking these metabolic alterations in young mice by dietary serine or glycine restriction together with high fat intake markedly accelerates the onset of small fibre neuropathy while reducing adiposity. Normalization of serine by dietary supplementation and mitigation of dyslipidaemia with myriocin both alleviate neuropathy in diabetic mice, linking serine-associated peripheral neuropathy to sphingolipid metabolism. These findings identify systemic serine deficiency and dyslipidaemia as novel risk factors for peripheral neuropathy that may be exploited therapeutically.
Assuntos
Diabetes Mellitus Experimental , Insulina , Metabolismo dos Lipídeos , Doenças do Sistema Nervoso Periférico , Serina , Animais , Camundongos , Diabetes Mellitus Experimental/complicações , Diabetes Mellitus Experimental/metabolismo , Glicina/metabolismo , Insulina/metabolismo , Doenças do Sistema Nervoso Periférico/metabolismo , Serina/metabolismo , Dieta Hiperlipídica , Adiposidade , Esfingolipídeos/metabolismo , Neuropatia de Pequenas Fibras , DislipidemiasRESUMO
BACKGROUND: Notalgia paresthetica is a neuropathic disorder characterized by pruritus in a circumscribed region of the upper back. Difelikefalin, a selective kappa opioid receptor agonist, has shown efficacy in other chronic pruritic conditions and is being investigated for the treatment of notalgia paresthetica. METHODS: In this phase 2, double-blind, placebo-controlled trial, we randomly assigned, in a 1:1 ratio, patients with moderate-to-severe pruritus caused by notalgia paresthetica to receive 2 mg of oral difelikefalin or placebo twice daily for 8 weeks. The primary outcome was the change from baseline at week 8 in the weekly mean score on the daily Worst Itch Numeric Rating Scale (WI-NRS; scores range from 0 [no itch] to 10 [worst itch imaginable]). The secondary clinical outcomes were itch-related quality-of-life and itch-related sleep measures. RESULTS: A total of 126 patients were enrolled; 62 patients were assigned to receive difelikefalin, and 63 were assigned to receive placebo. One patient who had been assigned to receive difelikefalin withdrew consent before the first dose and is not included in the main analyses. The mean baseline WI-NRS score was 7.6 (indicating severe itch) in each group. The change from baseline in the weekly mean WI-NRS score at week 8 was -4.0 points in the difelikefalin group and -2.4 points in the placebo group (difference in change, -1.6 points; 95% confidence interval, -2.6 to -0.6; P = 0.001). The results for the secondary outcomes generally did not support those of the primary analysis. Headache, dizziness, constipation, and increased urine output occurred more frequently in the difelikefalin group than in the placebo group. CONCLUSIONS: Among patients with notalgia paresthetica, oral treatment with difelikefalin resulted in modestly greater reductions in itch intensity scores than placebo over a period of 8 weeks but was associated with adverse events. Larger and longer trials are needed to assess the efficacy and safety of difelikefalin treatment in this disorder. (Funded by Cara Therapeutics; KOMFORT ClinicalTrials.gov number, NCT04706975.).
Assuntos
Doenças do Sistema Nervoso Periférico , Piperidinas , Prurido , Receptores Opioides kappa , Humanos , Método Duplo-Cego , Piperidinas/efeitos adversos , Piperidinas/uso terapêutico , Prurido/tratamento farmacológico , Prurido/etiologia , Resultado do Tratamento , Receptores Opioides kappa/agonistas , Doenças do Sistema Nervoso Periférico/complicações , Doenças do Sistema Nervoso Periférico/tratamento farmacológico , Dorso/inervaçãoRESUMO
The sympathetic nervous system prepares the body for 'fight or flight' responses and maintains homeostasis during daily activities such as exercise, eating a meal or regulation of body temperature. Sympathetic regulation of bodily functions requires the establishment and refinement of anatomically and functionally precise connections between postganglionic sympathetic neurons and peripheral organs distributed widely throughout the body. Mechanistic studies of key events in the formation of postganglionic sympathetic neurons during embryonic and early postnatal life, including axon growth, target innervation, neuron survival, and dendrite growth and synapse formation, have advanced the understanding of how neuronal development is shaped by interactions with peripheral tissues and organs. Recent progress has also been made in identifying how the cellular and molecular diversity of sympathetic neurons is established to meet the functional demands of peripheral organs. In this Review, we summarize current knowledge of signalling pathways underlying the development of the sympathetic nervous system. These findings have implications for unravelling the contribution of sympathetic dysfunction stemming, in part, from developmental perturbations to the pathophysiology of peripheral neuropathies and cardiovascular and metabolic disorders.
Assuntos
Axônios/fisiologia , Dendritos/fisiologia , Neurônios/fisiologia , Doenças do Sistema Nervoso Periférico/fisiopatologia , Sistema Nervoso Simpático/crescimento & desenvolvimento , Sistema Nervoso Simpático/fisiopatologia , Animais , Axônios/patologia , Dendritos/patologia , Humanos , Plasticidade Neuronal/fisiologia , Neurônios/patologia , Doenças do Sistema Nervoso Periférico/patologia , Sistema Nervoso Simpático/citologiaRESUMO
Chemotherapy-induced peripheral neuropathy (CIPN) is a persistent and irreversible side effect of antineoplastic agents. Patients with CIPN usually show chronic pain and sensory deficits with glove-and-stocking distribution. However, whether spinal neuronal microRNA (miR)-124 is involved in cisplatin-induced peripheral neuropathy remains to be studied. In this study, miR-124 was significantly reduced in the spinal dorsal horn in CIPN mice. Overexpression of neuronal miR-124 induced by injecting adeno-associated virus with neuron-specific promoter into the spinal cord of mice prevented the development of mechanical allodynia, sensory deficits, and the loss of intraepidermal nerve fibers induced by cisplatin. Meanwhile, cisplatin-induced M1 microglia activation and the release of proinflammatory cytokines were significantly inhibited by overexpression of neuronal miR-124. Furthermore, electroacupuncture (EA) treatment upregulated miR-124 expression in the spinal dorsal horn of CIPN mice. Interestingly, downregulation of spinal neuronal miR-124 significantly inhibited the regulatory effect of EA on CIPN and microglia activity as well as spinal neuroinflammation induced by cisplatin. These results demonstrate that spinal neuronal miR-124 is involved in the prevention and treatment of EA on cisplatin-induced peripheral neuropathy in mice. Our findings suggest that spinal neuronal miR-124 might be a potential target for EA effect, and we provide, to our knowledge, a new experimental basis for EA prevention of CIPN.
Assuntos
Antineoplásicos , Eletroacupuntura , MicroRNAs , Doenças do Sistema Nervoso Periférico , Humanos , Camundongos , Animais , Cisplatino/toxicidade , Microglia , Paclitaxel/efeitos adversos , Antineoplásicos/toxicidade , Doenças do Sistema Nervoso Periférico/induzido quimicamente , Doenças do Sistema Nervoso Periférico/genética , Doenças do Sistema Nervoso Periférico/prevenção & controle , Neurônios/metabolismo , MicroRNAs/genética , MicroRNAs/metabolismoRESUMO
CANVAS is a recently characterized repeat expansion disease, most commonly caused by homozygous expansions of an intronic (A2G3)n repeat in the RFC1 gene. There are a multitude of repeat motifs found in the human population at this locus, some of which are pathogenic and others benign. In this study, we conducted structure-functional analyses of the pathogenic (A2G3)n and nonpathogenic (A4G)n repeats. We found that the pathogenic, but not the nonpathogenic, repeat presents a potent, orientation-dependent impediment to DNA polymerization in vitro. The pattern of the polymerization blockage is consistent with triplex or quadruplex formation in the presence of magnesium or potassium ions, respectively. Chemical probing of both repeats in vitro reveals triplex H-DNA formation by only the pathogenic repeat. Consistently, bioinformatic analysis of S1-END-seq data from human cell lines shows preferential H-DNA formation genome-wide by (A2G3)n motifs over (A4G)n motifs. Finally, the pathogenic, but not the nonpathogenic, repeat stalls replication fork progression in yeast and human cells. We hypothesize that the CANVAS-causing (A2G3)n repeat represents a challenge to genome stability by folding into alternative DNA structures that stall DNA replication.
Assuntos
Ataxia Cerebelar , Expansão das Repetições de DNA , Replicação do DNA , Doenças do Sistema Nervoso Periférico , Doenças Vestibulares , Humanos , DNA/metabolismo , DNA/química , DNA/genética , Expansão das Repetições de DNA/genética , Replicação do DNA/genética , Conformação de Ácido Nucleico , Proteína de Replicação C/genética , Proteína de Replicação C/metabolismo , Ataxia Cerebelar/genética , Doenças do Sistema Nervoso Periférico/genética , Doenças Vestibulares/genéticaRESUMO
An expansion of AAGGG pentanucleotide repeats in the replication factor C subunit 1 (RFC1) gene is the genetic cause of cerebellar ataxia, neuropathy, and vestibular areflexia syndrome (CANVAS), and it also links to several other neurodegenerative diseases including the Parkinson's disease. However, the pathogenic mechanism of RFC1 AAGGG repeat expansion remains enigmatic. Here, we report that the pathogenic RFC1 AAGGG repeats form DNA and RNA parallel G-quadruplex (G4) structures that play a role in impairing biological processes. We determine the first high-resolution nuclear magnetic resonance (NMR) structure of a bimolecular parallel G4 formed by d(AAGGG)2AA and reveal how AAGGG repeats fold into a higher-order structure composed of three G-tetrad layers, and further demonstrate the formation of intramolecular G4s in longer DNA and RNA repeats. The pathogenic AAGGG repeats, but not the nonpathogenic AAAAG repeats, form G4 structures to stall DNA replication and reduce gene expression via impairing the translation process in a repeat-length-dependent manner. Our results provide an unprecedented structural basis for understanding the pathogenic mechanism of AAGGG repeat expansion associated with CANVAS. In addition, the high-resolution structures resolved in this study will facilitate rational design of small-molecule ligands and helicases targeting G4s formed by AAGGG repeats for therapeutic interventions.
Assuntos
Ataxia Cerebelar , DNA , Repetições de Microssatélites , Doenças do Sistema Nervoso Periférico , Doenças Vestibulares , Proteína de Replicação C/genética , DNA/genética , DNA/química , RNA , Expressão GênicaRESUMO
Chronic pain and alcohol use disorder (AUD) are highly comorbid, and patients with chronic pain are more likely to meet the criteria for AUD. Evidence suggests that both conditions alter similar brain pathways, yet this relationship remains poorly understood. Prior work shows that the anterior insular cortex (AIC) is involved in both chronic pain and AUD. However, circuit-specific changes elicited by the combination of pain and alcohol use remain understudied. The goal of this work was to elucidate the converging effects of binge alcohol consumption and chronic pain on AIC neurons that send projections to the dorsolateral striatum (DLS). Here, we used the Drinking-in-the-Dark (DID) paradigm to model binge-like alcohol drinking in mice that underwent spared nerve injury (SNI), after which whole-cell patch-clamp electrophysiological recordings were performed in acute brain slices to measure intrinsic and synaptic properties of AICâDLS neurons. In male, but not female, mice, we found that SNI mice with no prior alcohol exposure consumed less alcohol compared with sham mice. Electrophysiological analyses showed that AICâDLS neurons from SNI-alcohol male mice displayed increased neuronal excitability and increased frequency of miniature excitatory postsynaptic currents. However, mice exposed to alcohol prior to SNI consumed similar amounts of alcohol compared with sham mice following SNI. Together, our data suggest that the interaction of chronic pain and alcohol drinking have a direct effect on both intrinsic excitability and synaptic transmission onto AICâDLS neurons in mice, which may be critical in understanding how chronic pain alters motivated behaviors associated with alcohol.
Assuntos
Alcoolismo , Consumo Excessivo de Bebidas Alcoólicas , Dor Crônica , Doenças do Sistema Nervoso Periférico , Humanos , Camundongos , Animais , Masculino , Dor Crônica/metabolismo , Córtex Insular , Consumo Excessivo de Bebidas Alcoólicas/metabolismo , Etanol/farmacologia , Neurônios/metabolismo , Alcoolismo/metabolismo , Doenças do Sistema Nervoso Periférico/metabolismoRESUMO
We recently demonstrated that transient attenuation of Toll-like receptor 4 (TLR4) in dorsal root ganglion (DRG) neurons, can both prevent and reverse pain associated with chemotherapy-induced peripheral neuropathy (CIPN), a severe side effect of cancer chemotherapy, for which treatment options are limited. Given the reduced efficacy of opioid analgesics to treat neuropathic, compared with inflammatory pain, the cross talk between nociceptor TLR4 and mu-opioid receptors (MORs), and that MOR and TLR4 agonists induce hyperalgesic priming (priming), which also occurs in CIPN, we determined, using male rats, whether (1) antisense knockdown of nociceptor MOR attenuates CIPN, (2) and attenuates the priming associated with CIPN, and (3) CIPN also produces opioid-induced hyperalgesia (OIH). We found that intrathecal MOR antisense prevents and reverses hyperalgesia induced by oxaliplatin and paclitaxel, two common clinical chemotherapy agents. Oxaliplatin-induced priming was also markedly attenuated by MOR antisense. Additionally, intradermal morphine, at a dose that does not affect nociceptive threshold in controls, exacerbates mechanical hyperalgesia (OIH) in rats with CIPN, suggesting the presence of OIH. This OIH associated with CIPN is inhibited by interventions that reverse Type II priming [the combination of an inhibitor of Src and mitogen-activated protein kinase (MAPK)], an MOR antagonist, as well as a TLR4 antagonist. Our findings support a role of nociceptor MOR in oxaliplatin-induced pain and priming. We propose that priming and OIH are central to the symptom burden in CIPN, contributing to its chronicity and the limited efficacy of opioid analgesics to treat neuropathic pain.
Assuntos
Antineoplásicos , Hiperalgesia , Doenças do Sistema Nervoso Periférico , Receptores Opioides mu , Animais , Masculino , Ratos , Analgésicos Opioides/farmacologia , Antineoplásicos/efeitos adversos , Antineoplásicos/toxicidade , Gânglios Espinais/metabolismo , Gânglios Espinais/efeitos dos fármacos , Hiperalgesia/induzido quimicamente , Hiperalgesia/metabolismo , Compostos Organoplatínicos/efeitos adversos , Compostos Organoplatínicos/toxicidade , Oxaliplatina/toxicidade , Oxaliplatina/efeitos adversos , Paclitaxel/toxicidade , Paclitaxel/efeitos adversos , Dor/induzido quimicamente , Dor/tratamento farmacológico , Dor/metabolismo , Doenças do Sistema Nervoso Periférico/induzido quimicamente , Doenças do Sistema Nervoso Periférico/metabolismo , Ratos Sprague-Dawley , Receptores Opioides mu/metabolismo , Receptor 4 Toll-Like/metabolismoRESUMO
Short tandem repeats are inherently unstable during DNA replication depending on repeat length, and the expansion of the repeat length in the human genome is responsible for repeat expansion disorders. Pentanucleotide AAGGG and ACAGG repeat expansions in intron 2 of the gene encoding replication factor C subunit 1 (RFC1) cause cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS) and other phenotypes of late-onset cerebellar ataxia. Herein, we reveal the structural polymorphism of the RFC1 repeats associated with CANVAS in vitro. Single-stranded AAGGG repeat DNA formed a hybrid-type G-quadruplex, whereas its RNA formed a parallel-type G-quadruplex with three layers. The RNA of the ACAGG repeat formed hairpin structure comprising C-G and G-C base pairs with A:A and GA:AG mismatched repeats. Furthermore, both pathogenic repeat RNAs formed more rigid structures than those of the nonpathogenic repeat RNAs. These findings provide novel insights into the structural polymorphism of the RFC1 repeats, which may be closely related to the disease mechanism of CANVAS.
Assuntos
Ataxia Cerebelar , Expansão das Repetições de DNA , Doenças do Sistema Nervoso Periférico , Proteína de Replicação C , Doenças Vestibulares , Humanos , Ataxia Cerebelar/genética , Ataxia Cerebelar/metabolismo , Quadruplex G , Repetições de Microssatélites , Polimorfismo Genético , Proteína de Replicação C/genética , Proteína de Replicação C/metabolismo , Proteína de Replicação C/química , RNA/química , RNA/genética , RNA/metabolismo , Doenças do Sistema Nervoso Periférico/genética , Doenças do Sistema Nervoso Periférico/metabolismo , Doenças Vestibulares/genética , Doenças Vestibulares/metabolismoRESUMO
Aminoacyl-tRNA synthetases (ARSs) are essential enzymes that ligate tRNA molecules to cognate amino acids. Heterozygosity for missense variants or small in-frame deletions in six ARS genes causes dominant axonal peripheral neuropathy. These pathogenic variants reduce enzyme activity without significantly decreasing protein levels and reside in genes encoding homo-dimeric enzymes. These observations raise the possibility that neuropathy-associated ARS variants exert a dominant-negative effect, reducing overall ARS activity below a threshold required for peripheral nerve function. To test such variants for dominant-negative properties, we developed a humanized yeast assay to co-express pathogenic human alanyl-tRNA synthetase (AARS1) mutations with wild-type human AARS1. We show that multiple loss-of-function AARS1 mutations impair yeast growth through an interaction with wild-type AARS1, but that reducing this interaction rescues yeast growth. This suggests that neuropathy-associated AARS1 variants exert a dominant-negative effect, which supports a common, loss-of-function mechanism for ARS-mediated dominant peripheral neuropathy.
Assuntos
Alanina-tRNA Ligase , Aminoacil-tRNA Sintetases , Doenças do Sistema Nervoso Periférico , Humanos , Alanina-tRNA Ligase/genética , Doenças do Sistema Nervoso Periférico/patologia , Mutação , Aminoacil-tRNA Sintetases/genética , Nervos Periféricos/metabolismoRESUMO
Recessive mutations in the DNAJB2 gene, encoding the J-domain co-chaperones DNAJB2a and DNAJB2b, have previously been reported as the genetic cause of progressive peripheral neuropathies, rarely involving pyramidal signs, parkinsonism and myopathy. We describe here a family with the first dominantly acting DNAJB2 mutation resulting in a late-onset neuromyopathy phenotype. The c.832 T > G p.(*278Glyext*83) mutation abolishes the stop codon of the DNAJB2a isoform resulting in a C-terminal extension of the protein, with no direct effect predicted on the DNAJB2b isoform of the protein. Analysis of the muscle biopsy showed reduction of both protein isoforms. In functional studies, the mutant protein mislocalized to the endoplasmic reticulum due to a transmembrane helix in the C-terminal extension. The mutant protein underwent rapid proteasomal degradation and also increased the turnover of co-expressed wild-type DNAJB2a, potentially explaining the reduced protein amount in the patient muscle tissue. In line with this dominant negative effect, both wild-type and mutant DNAJB2a were shown to form polydisperse oligomers.
Assuntos
Doenças Neuromusculares , Doenças do Sistema Nervoso Periférico , Humanos , Chaperonas Moleculares/genética , Mutação , Isoformas de Proteínas/genética , Proteínas Mutantes/genética , Proteínas de Choque Térmico HSP40/genéticaRESUMO
Cell adhesion molecules are membrane-bound proteins predominantly expressed in the central nervous system along principal axonal pathways with key roles in nervous system development, neural cell differentiation and migration, axonal growth and guidance, myelination, and synapse formation. Here, we describe ten affected individuals with bi-allelic variants in the neuronal cell adhesion molecule NRCAM that lead to a neurodevelopmental syndrome of varying severity; the individuals are from eight families. This syndrome is characterized by developmental delay/intellectual disability, hypotonia, peripheral neuropathy, and/or spasticity. Computational analyses of NRCAM variants, many of which cluster in the third fibronectin type III (Fn-III) domain, strongly suggest a deleterious effect on NRCAM structure and function, including possible disruption of its interactions with other proteins. These findings are corroborated by previous in vitro studies of murine Nrcam-deficient cells, revealing abnormal neurite outgrowth, synaptogenesis, and formation of nodes of Ranvier on myelinated axons. Our studies on zebrafish nrcamaΔ mutants lacking the third Fn-III domain revealed that mutant larvae displayed significantly altered swimming behavior compared to wild-type larvae (p < 0.03). Moreover, nrcamaΔ mutants displayed a trend toward increased amounts of α-tubulin fibers in the dorsal telencephalon, demonstrating an alteration in white matter tracts and projections. Taken together, our study provides evidence that NRCAM disruption causes a variable form of a neurodevelopmental disorder and broadens the knowledge on the growing role of the cell adhesion molecule family in the nervous system.
Assuntos
Transtornos do Neurodesenvolvimento , Doenças do Sistema Nervoso Periférico , Animais , Axônios/metabolismo , Adesão Celular/genética , Moléculas de Adesão Celular/genética , Moléculas de Adesão Celular/metabolismo , Moléculas de Adesão Celular Neuronais , Humanos , Camundongos , Hipotonia Muscular/genética , Hipotonia Muscular/metabolismo , Espasticidade Muscular/metabolismo , Transtornos do Neurodesenvolvimento/genética , Transtornos do Neurodesenvolvimento/metabolismo , Peixe-Zebra/genética , Peixe-Zebra/metabolismoRESUMO
Cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS) is a late-onset, autosomal recessive neurodegenerative disorder caused by biallelic AAGGG/ACAGG repeat expansion (AAGGG-exp/ACAGG-exp) in RFC1. The recent identification of patients with CANVAS exhibiting compound heterozygosity for AAGGG-exp and truncating variants supports the loss-of-function of RFC1 in CANVAS patients. We investigated the pathological changes in 2 autopsied patients with CANVAS harboring biallelic ACAGG-exp and AAGGG-exp. RNA fluorescence in situ hybridization of the 2 patients revealed CCTGT- and CCCTT-containing RNA foci, respectively, in neuronal nuclei of tissues with neuronal loss. Our findings suggest that RNA toxicity may be involved in the pathogenesis of CANVAS. ANN NEUROL 2024;95:607-613.
Assuntos
Vestibulopatia Bilateral , Ataxia Cerebelar , Doenças do Sistema Nervoso Periférico , Humanos , Ataxia Cerebelar/genética , Hibridização in Situ Fluorescente , RNA , SíndromeRESUMO
Biallelic SORD mutations cause one of the most frequent forms of recessive hereditary neuropathy, estimated to affect â¼10 000 patients in North America and Europe alone. Pathogenic SORD loss-of-function changes in the encoded enzyme sorbitol dehydrogenase result in abnormally high sorbitol levels in cells and serum. How sorbitol accumulation leads to peripheral neuropathy remains to be elucidated. A reproducible animal model for SORD neuropathy is essential to illuminate the pathogenesis of SORD deficiency and for preclinical studies of potential therapies. Therefore, we have generated a Sord knockout (KO), Sord-/-, Sprague Dawley rat, to model the human disease and to investigate the pathophysiology underlying SORD deficiency. We have characterized the phenotype in these rats with a battery of behavioural tests as well as biochemical, physiological and comprehensive histological examinations. Sord-/- rats had remarkably increased levels of sorbitol in serum, CSF and peripheral nerve. Moreover, serum from Sord-/- rats contained significantly increased levels of neurofilament light chain, an established biomarker for axonal degeneration. Motor performance significantly declined in Sord-/- animals starting at â¼7 months of age. Gait analysis evaluated with video motion-tracking confirmed abnormal gait patterns in the hindlimbs. Motor nerve conduction velocities of the tibial nerves were slowed. Light and electron microscopy of the peripheral nervous system revealed degenerating myelinated axons, de- and remyelinated axons, and a likely pathognomonic finding-enlarged 'ballooned' myelin sheaths. These findings mainly affected myelinated motor axons; myelinated sensory axons were largely spared. In summary, Sord-/- rats develop a motor-predominant neuropathy that closely resembles the human phenotype. Our studies revealed novel significant aspects of SORD deficiency, and this model will lead to an improved understanding of the pathophysiology and the therapeutic options for SORD neuropathy.
Assuntos
Modelos Animais de Doenças , Animais , Feminino , Masculino , Ratos , L-Iditol 2-Desidrogenase/deficiência , L-Iditol 2-Desidrogenase/metabolismo , Condução Nervosa , Doenças do Sistema Nervoso Periférico/fisiopatologia , Doenças do Sistema Nervoso Periférico/patologia , Doenças do Sistema Nervoso Periférico/genética , Ratos Sprague-Dawley , Sorbitol/metabolismoRESUMO
Maintaining functional adipose innervation is critical for metabolic health. We found that subcutaneous white adipose tissue (scWAT) undergoes peripheral neuropathy (PN) with obesity, diabetes, and aging (reduced small-fiber innervation and nerve/synaptic/growth-cone/vesicle markers, altered nerve activity). Unlike with nerve injuries, peripheral nerves do not regenerate with PN, and therefore new therapies are needed for treatment of this condition affecting 20-30 million Americans. Here, we validated a gene therapy approach using an adipocyte-tropic adeno-associated virus (AAV; serotype Rec2) to deliver neurotrophic factors (brain-derived neurotrophic factor [BDNF] and nerve growth factor [NGF]) directly to scWAT to improve tissue-specific PN as a proof-of-concept approach. AAVRec2-BDNF intra-adipose delivery improved tissue innervation in obese/diabetic mice with PN, but after longer periods of dietary obesity there was reduced efficacy, revealing a key time window for therapies. AAVRec2-NGF also increased scWAT innervation in obese mice and was more effective than BDNF, likely because Rec2 targeted adipocytes, the tissue's endogenous NGF source. AAVRec2-NGF also worked well even after 25 weeks of dietary obesity, unlike BDNF, which likely needs a vector that targets its physiological cellular source (stromal vascular fraction cells). Given the differing effects of AAVs carrying NGF versus BDNF, a combined therapy may be ideal for PN.
Assuntos
Adipócitos , Fator Neurotrófico Derivado do Encéfalo , Dependovirus , Terapia Genética , Vetores Genéticos , Obesidade , Gordura Subcutânea , Animais , Dependovirus/genética , Obesidade/terapia , Obesidade/metabolismo , Camundongos , Terapia Genética/métodos , Adipócitos/metabolismo , Vetores Genéticos/administração & dosagem , Vetores Genéticos/genética , Gordura Subcutânea/metabolismo , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Fator Neurotrófico Derivado do Encéfalo/genética , Modelos Animais de Doenças , Fator de Crescimento Neural/metabolismo , Fator de Crescimento Neural/genética , Fatores de Crescimento Neural/metabolismo , Fatores de Crescimento Neural/genética , Técnicas de Transferência de Genes , Humanos , Masculino , Doenças do Sistema Nervoso Periférico/terapia , Doenças do Sistema Nervoso Periférico/etiologia , Doenças do Sistema Nervoso Periférico/metabolismo , Doenças do Sistema Nervoso Periférico/genética , Transdução GenéticaRESUMO
Type 2 diabetes mellitus is a global epidemic that due to its increasing prevalence worldwide will likely become the most common debilitating health condition. Even if diabetes is primarily a metabolic disorder, it is now well established that key aspects of the pathogenesis of diabetes are associated with nervous system alterations, including deleterious chronic inflammation of neural tissues, referred here as neuroinflammation, along with different detrimental glial cell responses to stress conditions and neurodegenerative features. Moreover, diabetes resembles accelerated aging, further increasing the risk of developing age-linked neurodegenerative disorders. As such, the most common and disabling diabetic comorbidities, namely diabetic retinopathy, peripheral neuropathy, and cognitive decline, are intimately associated with neurodegeneration. As described in aging and other neurological disorders, glial cell alterations such as microglial, astrocyte, and Müller cell increased reactivity and dysfunctionality, myelin loss and Schwann cell alterations have been broadly described in diabetes in both human and animal models, where they are key contributors to chronic noxious inflammation of neural tissues within the PNS and CNS. In this review, we aim to describe in-depth the common and unique aspects underlying glial cell changes observed across the three main diabetic complications, with the goal of uncovering shared glial cells alterations and common pathological mechanisms that will enable the discovery of potential targets to limit neuroinflammation and prevent neurodegeneration in all three diabetic complications. Diabetes and its complications are already a public health concern due to its rapidly increasing incidence, and thus its health and economic impact. Hence, understanding the key role that glial cells play in the pathogenesis underlying peripheral neuropathy, retinopathy, and cognitive decline in diabetes will provide us with novel therapeutic approaches to tackle diabetic-associated neurodegeneration.