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1.
Nat Commun ; 11(1): 4514, 2020 09 09.
Artigo em Inglês | MEDLINE | ID: mdl-32908139

RESUMO

The velocity of nerve conduction is moderately enhanced by larger axonal diameters and potently sped up by myelination of axons. Myelination thus allows rapid impulse propagation with reduced axonal diameters; however, no myelin-dependent mechanism has been reported that restricts radial growth of axons. By label-free proteomics, STED-microscopy and cryo-immuno electron-microscopy we here identify CMTM6 (chemokine-like factor-like MARVEL-transmembrane domain-containing family member-6) as a myelin protein specifically localized to the Schwann cell membrane exposed to the axon. We find that disruption of Cmtm6-expression in Schwann cells causes a substantial increase of axonal diameters but does not impair myelin biogenesis, radial sorting or integrity of axons. Increased axonal diameters correlate with accelerated sensory nerve conduction and sensory responses and perturbed motor performance. These data show that Schwann cells utilize CMTM6 to restrict the radial growth of axons, which optimizes nerve function.


Assuntos
Axônios/metabolismo , Proteínas da Mielina/metabolismo , Nervos Periféricos/citologia , Células de Schwann/metabolismo , Células Receptoras Sensoriais/metabolismo , Animais , Axônios/ultraestrutura , Membrana Celular/metabolismo , Membrana Celular/ultraestrutura , Microscopia Crioeletrônica , Masculino , Camundongos , Camundongos Knockout , Bainha de Mielina/metabolismo , Condução Nervosa , Nervos Periféricos/metabolismo , Nervos Periféricos/ultraestrutura , Proteômica , Células de Schwann/citologia , Células de Schwann/ultraestrutura , Células Receptoras Sensoriais/citologia , Células Receptoras Sensoriais/ultraestrutura
2.
Nat Commun ; 11(1): 4067, 2020 08 13.
Artigo em Inglês | MEDLINE | ID: mdl-32792493

RESUMO

The brain is organized morphologically and functionally into a columnar structure. According to the radial unit hypothesis, neurons from the same lineage form a radial unit that contributes to column formation. However, the molecular mechanisms that link neuronal lineage and column formation remain elusive. Here, we show that neurons from the same lineage project to different columns under control of Down syndrome cell adhesion molecule (Dscam) in the fly brain. Dscam1 is temporally expressed in newly born neuroblasts and is inherited by their daughter neurons. The transient transcription of Dscam1 in neuroblasts enables the expression of the same Dscam1 splice isoform within cells of the same lineage, causing lineage-dependent repulsion. In the absence of Dscam1 function, neurons from the same lineage project to the same column. When the splice diversity of Dscam1 is reduced, column formation is significantly compromised. Thus, Dscam1 controls column formation through lineage-dependent repulsion.


Assuntos
Moléculas de Adesão Celular/metabolismo , Proteínas de Drosophila/metabolismo , Neurônios/citologia , Neurônios/metabolismo , Isoformas de Proteínas/metabolismo , Animais , Axônios/metabolismo , Moléculas de Adesão Celular/genética , Células Cultivadas , Proteínas de Drosophila/genética , Drosophila melanogaster , Células-Tronco Neurais/citologia , Células-Tronco Neurais/metabolismo , Neurogênese/genética , Neurogênese/fisiologia , Isoformas de Proteínas/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa
3.
PLoS One ; 15(8): e0236883, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32817642

RESUMO

While it is still not possible to describe the neuronal-level connections of the human brain, we can map the human connectome with several hundred vertices, by the application of diffusion-MRI based techniques. In these graphs, the nodes correspond to anatomically identified gray matter areas of the brain, while the edges correspond to the axonal fibers, connecting these areas. In our previous contributions, we have described numerous graph-theoretical phenomena of the human connectomes. Here we map the frequent complete subgraphs of the human brain networks: in these subgraphs, every pair of vertices is connected by an edge. We also examine sex differences in the results. The mapping of the frequent subgraphs gives robust substructures in the graph: if a subgraph is present in the 80% of the graphs, then, most probably, it could not be an artifact of the measurement or the data processing workflow. We list here the frequent complete subgraphs of the human braingraphs of 413 subjects (238 women and 175 men), each with 463 nodes, with a frequency threshold of 80%, and identify 812 complete subgraphs, which are more frequent in male and 224 complete subgraphs, which are more frequent in female connectomes.


Assuntos
Gráficos por Computador , Conectoma , Algoritmos , Axônios/metabolismo , Feminino , Humanos , Masculino , Rede Nervosa/citologia , Rede Nervosa/diagnóstico por imagem
4.
Proc Natl Acad Sci U S A ; 117(30): 18037-18048, 2020 07 28.
Artigo em Inglês | MEDLINE | ID: mdl-32641508

RESUMO

Axon-axon interactions are essential for axon guidance during nervous system wiring. However, it is unknown whether and how the growth cones communicate with each other while sensing and responding to guidance cues. We found that the Parkinson's disease gene, leucine-rich repeat kinase 2 (LRRK2), has an unexpected role in growth cone-growth cone communication. The LRRK2 protein acts as a scaffold and induces Frizzled3 hyperphosphorylation indirectly by recruiting other kinases and also directly phosphorylates Frizzled3 on threonine 598 (T598). In LRRK1 or LRRK2 single knockout, LRRK1/2 double knockout, and LRRK2 G2019S knockin, the postcrossing spinal cord commissural axons are disorganized and showed anterior-posterior guidance errors after midline crossing. Growth cones from either LRRK2 knockout or G2019S knockin mice showed altered interactions, suggesting impaired communication. Intercellular interaction between Frizzled3 and Vangl2 is essential for planar cell polarity signaling. We show here that this interaction is regulated by phosphorylation of Frizzled3 at T598 and can be regulated by LRRK2 in a kinase activity-dependent way. In the LRRK1/2 double knockout or LRRK2 G2019S knockin, the dopaminergic axon bundle in the midbrain was significantly widened and appeared disorganized, showing aberrant posterior-directed growth. Our findings demonstrate that LRRK2 regulates growth cone-growth cone communication in axon guidance and that both loss-of-function mutation and a gain-of-function mutation (G2019S) cause axon guidance defects in development.


Assuntos
Axônios/metabolismo , Receptores Frizzled/metabolismo , Cones de Crescimento/metabolismo , Serina-Treonina Proteína Quinase-2 com Repetições Ricas em Leucina/genética , Neurogênese/genética , Transdução de Sinais , Animais , Neurônios Dopaminérgicos/citologia , Neurônios Dopaminérgicos/metabolismo , Técnicas de Silenciamento de Genes , Humanos , Serina-Treonina Proteína Quinase-2 com Repetições Ricas em Leucina/metabolismo , Camundongos , Modelos Biológicos , Mutação , Neurônios/metabolismo , Fosforilação , Medula Espinal/citologia , Medula Espinal/metabolismo
5.
ACS Chem Neurosci ; 11(13): 1868-1870, 2020 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-32605374

RESUMO

Cytokine storm in COVID-19 is characterized by an excessive inflammatory response to SARS-CoV-2 that is caused by a dysregulated immune system of the host. We are proposing a new hypothesis that SARS-CoV-2 mediated inflammation of nucleus tractus solitarius (NTS) may be responsible for the cytokine storm in COVID 19. The inflamed NTS may result in a dysregulated cholinergic anti-inflammatory pathway and hypothalamic-pituitary-adrenal axis.


Assuntos
Betacoronavirus/metabolismo , Infecções por Coronavirus/metabolismo , Citocinas/metabolismo , Pneumonia Viral/metabolismo , Núcleo Solitário/metabolismo , Axônios/imunologia , Axônios/metabolismo , Axônios/virologia , Betacoronavirus/imunologia , Infecções por Coronavirus/imunologia , Nervos Cranianos/imunologia , Nervos Cranianos/metabolismo , Nervos Cranianos/virologia , Citocinas/imunologia , Humanos , Sistema Hipotálamo-Hipofisário/imunologia , Sistema Hipotálamo-Hipofisário/metabolismo , Sistema Hipotálamo-Hipofisário/virologia , Mediadores da Inflamação/imunologia , Mediadores da Inflamação/metabolismo , Pandemias , Sistema Hipófise-Suprarrenal/imunologia , Sistema Hipófise-Suprarrenal/metabolismo , Sistema Hipófise-Suprarrenal/virologia , Pneumonia Viral/imunologia , Núcleo Solitário/imunologia , Núcleo Solitário/virologia
6.
Proc Natl Acad Sci U S A ; 117(32): 19287-19298, 2020 08 11.
Artigo em Inglês | MEDLINE | ID: mdl-32723825

RESUMO

Retinal ganglion cell axons forming the optic nerve (ON) emerge unmyelinated from the eye and become myelinated after passage through the optic nerve lamina region (ONLR), a transitional area containing a vascular plexus. The ONLR has a number of unusual characteristics: it inhibits intraocular myelination, enables postnatal ON myelination of growing axons, modulates the fluid pressure differences between eye and brain, and is the primary lesion site in the age-related disease open angle glaucoma (OAG). We demonstrate that the human and rodent ONLR possesses a mitotically active, age-depletable neural progenitor cell (NPC) niche, with unique characteristics and culture requirements. These NPCs generate both forms of macroglia: astrocytes and oligodendrocytes, and can form neurospheres in culture. Using reporter mice with SOX2-driven, inducible gene expression, we show that ONLR-NPCs generate macroglial cells for the anterior ON. Early ONLR-NPC loss results in regional dysfunction and hypomyelination. In adulthood, ONLR-NPCs may enable glial replacement and remyelination. ONLR-NPC depletion may help explain why ON diseases such as OAG progress in severity during aging.


Assuntos
Neurônios/citologia , Nervo Óptico/citologia , Nicho de Células-Tronco , Células-Tronco/citologia , Animais , Astrócitos , Axônios/metabolismo , Diferenciação Celular , Glaucoma de Ângulo Aberto/genética , Glaucoma de Ângulo Aberto/metabolismo , Glaucoma de Ângulo Aberto/fisiopatologia , Humanos , Camundongos , Bainha de Mielina/metabolismo , Neuroglia , Neurônios/metabolismo , Oligodendroglia , Nervo Óptico/metabolismo , Fatores de Transcrição SOXB1/genética , Fatores de Transcrição SOXB1/metabolismo , Células-Tronco/metabolismo
7.
PLoS One ; 15(7): e0236090, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32702050

RESUMO

OBJECTIVES: To evaluate retinal axonal density and retinal capillary flow density (CFD) variations in patients affected by multiple sclerosis (MS) as documented by Optical Coherence Tomography Angiography (OCT-A). MATERIAL AND METHODS: A cross-sectional study was performed in a tertiary university eye hospital on 94 eyes from 48 MS patients compared to 37 eyes from 23 matched controls. MS patients were divided in two groups: those with previous episodes of optic neuritis (MS ON+, 71.4%) and those without any previous visual complaint (no optic neuritis group, MS ON, 28.6%). Patients underwent macular and optic nerve head OCT-A with Optovue XR Avanti (Optovue, Freemont, California) after that preliminary evaluation of the ganglion cell complex (GCC) and of the retinal nerve fiber layer (RNFL) was achieved for each single eye by SD-OCT. CFD was evaluated in three different retinal layers of MS patients and controls: superficial capillary plexus (SCP), deep capillary plexus (DCP) and the choriocapillaris layer (CL). Each layer was analyzed in 18 preset subregions automatically detected by the system. CFD values were then correlated to the RNFL thickness and GCC thickness in the groups: p values were computed by t-tests between each group of MS patients and controls. A p-value of <0.05 was considered significant. RESULTS: A significant difference in the overall CFD values was found between ON+ and ON- patients when compared to controls in 18 subregions of SCP. Furthermore, a significant difference was found between MS patients and controls in 16 subregions analyzed corresponding to the CL layer without difference between the two MS subgroups (ON+ and ON-). CONCLUSIONS: OCT-A when performed at the optic nerve head level and at the macular region is characterized by a reduction of retinal perfusion in a significant portion of MS patients independently if they had a previous history of optic nerve inflammation or not.


Assuntos
Esclerose Múltipla/diagnóstico por imagem , Tomografia de Coerência Óptica , Axônios/metabolismo , Capilares/diagnóstico por imagem , Capilares/metabolismo , Estudos de Casos e Controles , Estudos Transversais , Reações Falso-Positivas , Humanos , Esclerose Múltipla/patologia , Esclerose Múltipla/fisiopatologia , Fibras Nervosas/metabolismo , Retina/diagnóstico por imagem , Retina/fisiopatologia
8.
PLoS Comput Biol ; 16(6): e1007826, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32479499

RESUMO

Artificial electrical stimulation of peripheral nerves for sensory feedback restoration can greatly benefit from computational models for simulation-based neural implant design in order to reduce the trial-and-error approach usually taken, thus potentially significantly reducing research and development costs and time. To this end, we built a computational model of a peripheral nerve trunk in which the interstitial space between the fibers and the tissues was modelled using a resistor network, thus enabling distance-dependent ephaptic coupling between myelinated axons and between fascicles as well. We used the model to simulate a) the stimulation of a nerve trunk model with a cuff electrode, and b) the propagation of action potentials along the axons. Results were used to investigate the effect of ephaptic interactions on recruitment and selectivity stemming from artificial (i.e., neural implant) stimulation and on the relative timing between action potentials during propagation. Ephaptic coupling was found to increase the number of fibers that are activated by artificial stimulation, thus reducing the artificial currents required for axonal recruitment, and it was found to reduce and shift the range of optimal stimulation amplitudes for maximum inter-fascicular selectivity. During propagation, while fibers of similar diameters tended to lock their action potentials and reduce their conduction velocities, as expected from previous knowledge on bundles of identical axons, the presence of many other fibers of different diameters was found to make their interactions weaker and unstable.


Assuntos
Potenciais de Ação , Estimulação Elétrica/métodos , Modelos Neurológicos , Nervos Periféricos/fisiologia , Sistema Nervoso Periférico/fisiologia , Algoritmos , Animais , Axônios/metabolismo , Axônios/fisiologia , Simulação por Computador , Eletrodos Implantados , Humanos , Condução Nervosa , Nós Neurofibrosos/fisiologia
9.
PLoS One ; 15(6): e0234519, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32530970

RESUMO

Axonal damage leads to the release of neurofilament light chain (NFL), which enters the CSF or blood. In this work, an assay kit for plasma NFL utilizing immunomagnetic reduction (IMR) was developed. Antibodies against NFL were immobilized on magnetic nanoparticles to develop an IMR NFL kit. The preclinical properties, such as the standard curve, limit of detection (LoD), and dynamic range, were characterized. Thirty-one normal controls (NC), fifty-two patients with Parkinson's disease (PD) or PD dementia (PDD) and thirty-one patients with Alzheimer's disease (AD) were enrolled in the study evaluating the plasma NFL assay using an IMR kit. T-tests and receiver operating characteristic (ROC) curve analysis were performed to investigate the capability for discrimination among the clinical groups according to plasma NFL levels. The LoD of the NFL assay using the IMR kit was found to be 0.18 fg/ml. The dynamic range of the NFL assay reached 1000 pg/ml. The NC group showed a plasma NFL level of 7.70 ± 4.00 pg/ml, which is significantly lower than that of the PD/PDD (15.85 ± 7.82 pg/ml, p < 0.001) and AD (19.24 ± 8.99 pg/ml, p < 0.001) groups. A significant difference in plasma NFL levels was determined between the PD and AD groups (p < 0.01). Through ROC curve analysis, the cut-off value of the plasma NFL concentration for differentiating NCs from dementia patients (AD and PD/PDD) was found to be 12.71 pg/ml, with a clinical sensitivity and specificity of 73.5% and 90.3%, respectively. The AUC was 0.868. Furthermore, the cut-off value of the plasma NFL concentration for discriminating AD from PD/PDD was found to be 18.02 pg/ml, with a clinical sensitivity and specificity of 61.3% and 65.4%, respectively. The AUC was 0.630. An ultrasensitive assay for measuring plasma NFL utilizing IMR technology was developed. Clear differences in plasma NFL concentrations were observed among NCs and PD and AD patients. These results imply that the determination of plasma NFL is promising not only for screening dementia but also for differential diagnosis.


Assuntos
Peptídeos beta-Amiloides/sangue , Biomarcadores/sangue , Proteínas de Neurofilamentos/sangue , Proteínas tau/sangue , Doença de Alzheimer/sangue , Doença de Alzheimer/patologia , Axônios/metabolismo , Axônios/patologia , Disfunção Cognitiva/sangue , Disfunção Cognitiva/genética , Disfunção Cognitiva/patologia , Feminino , Humanos , Separação Imunomagnética , Filamentos Intermediários/genética , Filamentos Intermediários/patologia , Masculino , Pessoa de Meia-Idade , Doença de Parkinson/sangue , Doença de Parkinson/genética , Doença de Parkinson/patologia
10.
PLoS One ; 15(6): e0235110, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32584865

RESUMO

Programmed axonal degeneration, also known as Wallerian degeneration, occurs in immune-mediated central nervous system (CNS) inflammatory disorders such as multiple sclerosis and the animal model experimental allergic encephalomyelitis (EAE). Sterile alpha and TIR domain containing protein 1 (SARM1) functions to promote programmed axonal degeneration. To test the hypothesis that loss of SARM1 will reduce axonal degeneration in immune-mediated CNS inflammatory disorders, the course and pathology of EAE was compared in Sarm1 knockout mice and wild type littermates. The clinical course of EAE was similar in Sarm1 knockout and wild type. Analysis of EAE in mice expressing neuronal yellow fluorescent protein (YFP) showed significantly less axonal degeneration in Sarm1 knockout mice compared to wild type littermates at 14 days post-induction of EAE. At 21 days post-induction, however, difference in axonal degeneration was not significant. At 42 days post-induction, Sarm1 knockout mice were indistinguishable from wild type with respect to markers of axonal injury, and were similar with respect to axonal density in the lumbar cords. There was no significant change in peripheral immune activation or CNS inflammatory cell infiltration associated with EAE in Sarm1 knockout mice. In conclusion, Sarm1 deletion delayed axonal degeneration early in the course of CNS inflammation, but did not confer long-term protection from axonal degeneration in an animal model of immune-mediated CNS inflammation.


Assuntos
Proteínas do Domínio Armadillo , Axônios , Proteínas do Citoesqueleto , Encefalomielite Autoimune Experimental , Técnicas de Inativação de Genes , Medula Espinal , Animais , Proteínas do Domínio Armadillo/genética , Proteínas do Domínio Armadillo/metabolismo , Axônios/metabolismo , Axônios/patologia , Proteínas do Citoesqueleto/genética , Proteínas do Citoesqueleto/metabolismo , Encefalomielite Autoimune Experimental/genética , Encefalomielite Autoimune Experimental/metabolismo , Encefalomielite Autoimune Experimental/patologia , Encefalomielite Autoimune Experimental/prevenção & controle , Camundongos , Camundongos Knockout , Medula Espinal/metabolismo , Medula Espinal/patologia , Fatores de Tempo
11.
Proc Natl Acad Sci U S A ; 117(27): 15955-15966, 2020 07 07.
Artigo em Inglês | MEDLINE | ID: mdl-32554499

RESUMO

Axon regeneration is regulated by a neuron-intrinsic transcriptional program that is suppressed during development but that can be reactivated following peripheral nerve injury. Here we identify Prom1, which encodes the stem cell marker prominin-1, as a regulator of the axon regeneration program. Prom1 expression is developmentally down-regulated, and the genetic deletion of Prom1 in mice inhibits axon regeneration in dorsal root ganglion (DRG) cultures and in the sciatic nerve, revealing the neuronal role of Prom1 in injury-induced regeneration. Elevating prominin-1 levels in cultured DRG neurons or in mice via adeno-associated virus-mediated gene delivery enhances axon regeneration in vitro and in vivo, allowing outgrowth on an inhibitory substrate. Prom1 overexpression induces the consistent down-regulation of cholesterol metabolism-associated genes and a reduction in cellular cholesterol levels in a Smad pathway-dependent manner, which promotes axonal regrowth. We find that prominin-1 interacts with the type I TGF-ß receptor ALK4, and that they synergistically induce phosphorylation of Smad2. These results suggest that Prom1 and cholesterol metabolism pathways are possible therapeutic targets for the promotion of neural recovery after injury.


Assuntos
Antígeno AC133/metabolismo , Axônios/metabolismo , Colesterol/metabolismo , Regeneração Nervosa/fisiologia , Transdução de Sinais , Células-Tronco/metabolismo , Antígeno AC133/genética , Receptores de Ativinas Tipo I , Animais , Axônios/patologia , Colesterol/genética , Regulação para Baixo , Gânglios Espinais/metabolismo , Deleção de Genes , Regulação da Expressão Gênica , Camundongos , Camundongos Knockout , Neurônios/metabolismo , Traumatismos dos Nervos Periféricos/metabolismo , Receptor do Fator de Crescimento Transformador beta Tipo I/metabolismo , Nervo Isquiático
12.
Nat Commun ; 11(1): 2441, 2020 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-32415109

RESUMO

KIF21B is a kinesin protein that promotes intracellular transport and controls microtubule dynamics. We report three missense variants and one duplication in KIF21B in individuals with neurodevelopmental disorders associated with brain malformations, including corpus callosum agenesis (ACC) and microcephaly. We demonstrate, in vivo, that the expression of KIF21B missense variants specifically recapitulates patients' neurodevelopmental abnormalities, including microcephaly and reduced intra- and inter-hemispheric connectivity. We establish that missense KIF21B variants impede neuronal migration through attenuation of kinesin autoinhibition leading to aberrant KIF21B motility activity. We also show that the ACC-related KIF21B variant independently perturbs axonal growth and ipsilateral axon branching through two distinct mechanisms, both leading to deregulation of canonical kinesin motor activity. The duplication introduces a premature termination codon leading to nonsense-mediated mRNA decay. Although we demonstrate that Kif21b haploinsufficiency leads to an impaired neuronal positioning, the duplication variant might not be pathogenic. Altogether, our data indicate that impaired KIF21B autoregulation and function play a critical role in the pathogenicity of human neurodevelopmental disorder.


Assuntos
Cinesina/genética , Atividade Motora , Mutação/genética , Transtornos do Neurodesenvolvimento/genética , Transtornos do Neurodesenvolvimento/fisiopatologia , Animais , Axônios/metabolismo , Movimento Celular , Proliferação de Células , Córtex Cerebral/embriologia , Córtex Cerebral/patologia , Córtex Cerebral/fisiopatologia , Feminino , Regulação da Expressão Gênica no Desenvolvimento , Células HEK293 , Humanos , Masculino , Camundongos , Mutação de Sentido Incorreto/genética , Rede Nervosa/patologia , Rede Nervosa/fisiopatologia , Neurônios/metabolismo , Tamanho do Órgão , Organogênese/genética , Linhagem , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Peixe-Zebra/anatomia & histologia , Peixe-Zebra/genética
13.
Nat Commun ; 11(1): 2464, 2020 05 18.
Artigo em Inglês | MEDLINE | ID: mdl-32424147

RESUMO

Information within the brain travels from neuron to neuron across billions of synapses. At any given moment, only a small subset of neurons and synapses are active, but finding the active synapses in brain tissue has been a technical challenge. Here we introduce SynTagMA to tag active synapses in a user-defined time window. Upon 395-405 nm illumination, this genetically encoded marker of activity converts from green to red fluorescence if, and only if, it is bound to calcium. Targeted to presynaptic terminals, preSynTagMA allows discrimination between active and silent axons. Targeted to excitatory postsynapses, postSynTagMA creates a snapshot of synapses active just before photoconversion. To analyze large datasets, we show how to identify and track the fluorescence of thousands of individual synapses in an automated fashion. Together, these tools provide an efficient method for repeatedly mapping active neurons and synapses in cell culture, slice preparations, and in vivo during behavior.


Assuntos
Imageamento Tridimensional , Sinapses/fisiologia , Potenciais de Ação , Animais , Axônios/metabolismo , Biomarcadores/metabolismo , Células Cultivadas , Feminino , Fluorescência , Hipocampo/citologia , Luz , Masculino , Camundongos Endogâmicos C57BL , Neurônios/metabolismo , Terminações Pré-Sinápticas/metabolismo , Ratos Sprague-Dawley , Ratos Wistar , Sinaptofisina/metabolismo , Fatores de Tempo
14.
PLoS One ; 15(5): e0233700, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32469963

RESUMO

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by cognitive decline and amyloid-beta (Aß) depositions generated by the proteolysis of amyloid precursor protein (APP) in the brain. In APPNL-F mice, APP gene was humanized and contains two familial AD mutations, and APP-unlike other mouse models of AD-is driven by the endogenous mouse APP promoter. Similar to people without apparent cognitive dysfunction but with heavy Aß plaque load, we found no significant decline in the working memory of adult APPNL-F mice, but these mice showed decline in the expression of normal anxiety. Using immunohistochemistry and 3D block-face scanning electron microscopy, we found no changes in GABAA receptor positivity and size of somatic and dendritic synapses of hippocampal interneurons. We did not find alterations in the level of expression of perineuronal nets around parvalbumin (PV) interneurons or in the density of PV- or somatostatin-positive hippocampal interneurons. However, in contrast to other investigated cell types, PV interneuron axons were occasionally mildly dystrophic around Aß plaques, and the synapses of PV-positive axon initial segment (AIS)-targeting interneurons were significantly enlarged. Our results suggest that PV interneurons are highly resistant to amyloidosis in APPNL-F mice and amyloid-induced increase in hippocampal pyramidal cell excitability may be compensated by PV-positive AIS-targeting cells. Mechanisms that make PV neurons more resilient could therefore be exploited in the treatment of AD for mitigating Aß-related inflammatory effects on neurons.


Assuntos
Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Hipocampo/metabolismo , Interneurônios/metabolismo , Mutação , Rede Nervosa/metabolismo , Fragmentos de Peptídeos/metabolismo , Doença de Alzheimer/genética , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/genética , Animais , Axônios/metabolismo , Axônios/patologia , Hipocampo/patologia , Humanos , Interneurônios/patologia , Memória de Curto Prazo , Camundongos , Camundongos Transgênicos , Rede Nervosa/patologia , Fragmentos de Peptídeos/genética , Células Piramidais/metabolismo , Células Piramidais/patologia , Receptores de GABA-A/genética , Receptores de GABA-A/metabolismo
15.
J Virol ; 94(14)2020 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-32404525

RESUMO

Mouse hepatitis virus (MHV) is a murine betacoronavirus (m-CoV) that causes a wide range of diseases in mice and rats, including hepatitis, enteritis, respiratory diseases, and encephalomyelitis in the central nervous system (CNS). MHV infection in mice provides an efficient cause-effect experimental model to understand the mechanisms of direct virus-induced neural-cell damage leading to demyelination and axonal loss, which are pathological features of multiple sclerosis (MS), the most common disabling neurological disease in young adults. Infiltration of T lymphocytes, activation of microglia, and their interplay are the primary pathophysiological events leading to disruption of the myelin sheath in MS. However, there is emerging evidence supporting gray matter involvement and degeneration in MS. The investigation of T cell function in the pathogenesis of deep gray matter damage is necessary. Here, we employed RSA59 (an isogenic recombinant strain of MHV-A59)-induced experimental neuroinflammation model to compare the disease in CD4-/- mice with that in CD4+/+ mice at days 5, 10, 15, and 30 postinfection (p.i.). Viral titer estimation, nucleocapsid gene amplification, and viral antinucleocapsid staining confirmed enhanced replication of the virions in the absence of functional CD4+ T cells in the brain. Histopathological analyses showed elevated susceptibility of CD4-/- mice to axonal degeneration in the CNS, with augmented progression of acute poliomyelitis and dorsal root ganglionic inflammation rarely observed in CD4+/+ mice. Depletion of CD4+ T cells showed unique pathological bulbar vacuolation in the brain parenchyma of infected mice with persistent CD11b+ microglia/macrophages in the inflamed regions on day 30 p.i. In summary, the current study suggests that CD4+ T cells are critical for controlling acute-stage poliomyelitis (gray matter inflammation), chronic axonal degeneration, and inflammatory demyelination due to loss of protective antiviral host immunity.IMPORTANCE The current trend in CNS disease biology is to attempt to understand the neural-cell-immune interaction to investigate the underlying mechanism of neuroinflammation, rather than focusing on peripheral immune activation. Most studies in MS are targeted toward understanding the involvement of CNS white matter. However, the importance of gray matter damage has become critical in understanding the long-term progressive neurological disorder. Our study highlights the importance of CD4+ T cells in safeguarding neurons against axonal blebbing and poliomyelitis from murine betacoronavirus-induced neuroinflammation. Current knowledge of the mechanisms that lead to gray matter damage in MS is limited, because the most widely used animal model, experimental autoimmune encephalomyelitis (EAE), does not present this aspect of the disease. Our results, therefore, add to the existing limited knowledge in the field. We also show that the microglia, though important for the initiation of neuroinflammation, cannot establish a protective host immune response without the help of CD4+ T cells.


Assuntos
Axônios/imunologia , Axônios/metabolismo , Antígenos CD4/deficiência , Infecções por Coronavirus/imunologia , Infecções por Coronavirus/virologia , Vírus da Hepatite Murina/fisiologia , Poliomielite/etiologia , Animais , Axônios/patologia , Encéfalo/imunologia , Encéfalo/metabolismo , Encéfalo/patologia , Contagem de Linfócito CD4 , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD4-Positivos/metabolismo , Infecções por Coronavirus/patologia , Citocinas/metabolismo , Modelos Animais de Doenças , Suscetibilidade a Doenças/imunologia , Gânglios Espinais/imunologia , Gânglios Espinais/metabolismo , Gânglios Espinais/patologia , Imuno-Histoquímica , Mediadores da Inflamação/metabolismo , Camundongos
16.
Proc Natl Acad Sci U S A ; 117(20): 11097-11108, 2020 05 19.
Artigo em Inglês | MEDLINE | ID: mdl-32358199

RESUMO

It has been known for a long time that inositol-trisphosphate (IP3) receptors are present in the axon of certain types of mammalian neurons, but their functional role has remained unexplored. Here we show that localized photolysis of IP3 induces spatially constrained calcium rises in Purkinje cell axons. Confocal immunohistology reveals that the axon initial segment (AIS), as well as terminals onto deep cerebellar cells, express specific subtypes of Gα/q and phospholipase C (PLC) molecules, together with the upstream purinergic receptor P2Y1. By contrast, intermediate parts of the axon express another set of Gα/q and PLC molecules, indicating two spatially segregated signaling cascades linked to IP3 generation. This prompted a search for distinct actions of IP3 in different parts of Purkinje cell axons. In the AIS, we found that local applications of the specific P2Y1R agonist MRS2365 led to calcium elevation, and that IP3 photolysis led to inhibition of action potential firing. In synaptic terminals on deep cerebellar nuclei neurons, we found that photolysis of both IP3 and ATP led to GABA release. We propose that axonal IP3 receptors can inhibit action potential firing and increase neurotransmitter release, and that these effects are likely controlled by purinergic receptors. Altogether our results suggest a rich and diverse functional role of IP3 receptors in axons of mammalian neurons.


Assuntos
Potenciais de Ação/fisiologia , Axônios/metabolismo , Receptores de Inositol 1,4,5-Trifosfato/metabolismo , Inositol 1,4,5-Trifosfato/metabolismo , Células de Purkinje/metabolismo , Cálcio/metabolismo , Cerebelo/metabolismo , Neurônios/metabolismo , Terminações Pré-Sinápticas/metabolismo , Receptores Purinérgicos P2Y1 , Fosfolipases Tipo C/metabolismo
17.
PLoS One ; 15(5): e0233651, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32469980

RESUMO

Transference of RNAs and ribosomes from Schwann cell-to-axon was demonstrated in normal and regenerating peripheral nerves. Previously, we have shown that RNAs transfer is dependent on F-actin cytoskeleton and Myosin Va. Here, we explored the contribution of microtubules to newly synthesized RNAs transport from Schwann cell nuclei up to nodal microvilli in sciatic nerves. Results using immunohistochemistry and quantitative confocal FRET analysis indicate that Schwann cell-derived RNAs co-localize with microtubules in Schwann cell cytoplasm. Additionally, transport of Schwann cell-derived RNAs is nocodazole and colchicine sensitive demonstrating its dependence on microtubule network integrity. Moreover, mRNAs codifying neuron-specific proteins are among Schwann cell newly synthesized RNAs population, and some of them are associated with KIF1B and KIF5B microtubules-based motors.


Assuntos
Axônios/metabolismo , Microtúbulos/metabolismo , RNA/metabolismo , Células de Schwann/metabolismo , Nervo Isquiático/metabolismo , Animais , Masculino , Bainha de Mielina/metabolismo , Regeneração Nervosa , RNA/análise , Transporte de RNA , Ratos , Ratos Sprague-Dawley
18.
Phys Rev Lett ; 124(19): 198103, 2020 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-32469583

RESUMO

Within cells, vesicles and proteins are actively transported several micrometers along the cytoskeletal filaments. The transport along microtubules is propelled by dynein and kinesin motors, which carry the cargo in opposite directions. Bidirectional intracellular transport is performed with great efficiency, even under strong confinement, as for example in the axon. For this kind of transport system, one would expect generically cluster formation. In this Letter, we discuss the effect of the recently observed self-enhanced binding affinity along the kinesin trajectories on the microtubule. We introduce a stochastic lattice-gas model, where the enhanced binding affinity is realized via a floor field. From Monte Carlo simulations and a mean-field analysis we show that this mechanism can lead to self-organized symmetry breaking and lane formation that indeed leads to efficient bidirectional transport in narrow environments.


Assuntos
Modelos Biológicos , Proteínas Motores Moleculares/química , Proteínas Motores Moleculares/metabolismo , Animais , Axônios/metabolismo , Transporte Biológico , Dineínas/química , Dineínas/metabolismo , Humanos , Cinesina/química , Cinesina/metabolismo , Modelos Neurológicos , Método de Monte Carlo , Processos Estocásticos
19.
PLoS Genet ; 16(5): e1008767, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32357156

RESUMO

Despite the importance of dendritic targeting in neural circuit assembly, the mechanisms by which it is controlled still remain incompletely understood. We previously showed that in the developing Drosophila antennal lobe, the Wnt5 protein forms a gradient that directs the ~45˚ rotation of a cluster of projection neuron (PN) dendrites, including the adjacent DA1 and VA1d dendrites. We report here that the Van Gogh (Vang) transmembrane planar cell polarity (PCP) protein is required for the rotation of the DA1/VA1d dendritic pair. Cell type-specific rescue and mosaic analyses showed that Vang functions in the olfactory receptor neurons (ORNs), suggesting a codependence of ORN axonal and PN dendritic targeting. Loss of Vang suppressed the repulsion of the VA1d dendrites by Wnt5, indicating that Wnt5 signals through Vang to direct the rotation of the DA1 and VA1d glomeruli. We observed that the Derailed (Drl)/Ryk atypical receptor tyrosine kinase is also required for the rotation of the DA1/VA1d dendritic pair. Antibody staining showed that Drl/Ryk is much more highly expressed by the DA1 dendrites than the adjacent VA1d dendrites. Mosaic and epistatic analyses showed that Drl/Ryk specifically functions in the DA1 dendrites in which it antagonizes the Wnt5-Vang repulsion and mediates the migration of the DA1 glomerulus towards Wnt5. Thus, the nascent DA1 and VA1d glomeruli appear to exhibit Drl/Ryk-dependent biphasic responses to Wnt5. Our work shows that the final patterning of the fly olfactory map is the result of an interplay between ORN axons and PN dendrites, wherein converging pre- and postsynaptic processes contribute key Wnt5 signaling components, allowing Wnt5 to orient the rotation of nascent synapses through a PCP mechanism.


Assuntos
Antenas de Artrópodes/crescimento & desenvolvimento , Dendritos/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila/crescimento & desenvolvimento , Proteínas de Membrana/metabolismo , Proteínas Proto-Oncogênicas/metabolismo , Receptores Proteína Tirosina Quinases/metabolismo , Proteínas Wnt/metabolismo , Animais , Antenas de Artrópodes/metabolismo , Axônios/metabolismo , Padronização Corporal , Drosophila/genética , Drosophila/metabolismo , Proteínas de Drosophila/genética , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Membrana/genética , Neurônios Receptores Olfatórios/metabolismo , Proteínas Proto-Oncogênicas/genética , Receptores Proteína Tirosina Quinases/genética , Transdução de Sinais , Proteínas Wnt/genética
20.
Nat Commun ; 11(1): 2329, 2020 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-32393757

RESUMO

Impaired cognitive functioning is a core feature of schizophrenia, and is hypothesized to be due to myelination as well as interneuron defects during adolescent prefrontal cortex (PFC) development. Here we report that in the apomorphine-susceptible (APO-SUS) rat model, which has schizophrenia-like features, a myelination defect occurred specifically in parvalbumin interneurons. The adult rats displayed medial PFC (mPFC)-dependent cognitive inflexibility, and a reduced number of mature oligodendrocytes and myelinated parvalbumin inhibitory axons in the mPFC. In the developing mPFC, we observed decreased myelin-related gene expression that persisted into adulthood. Environmental enrichment applied during adolescence restored parvalbumin interneuron hypomyelination as well as cognitive inflexibility. Collectively, these findings highlight that impairment of parvalbumin interneuron myelination is related to schizophrenia-relevant cognitive deficits.


Assuntos
Cognição/fisiologia , Interneurônios/patologia , Bainha de Mielina/patologia , Esquizofrenia/patologia , Esquizofrenia/fisiopatologia , Animais , Axônios/metabolismo , Axônios/ultraestrutura , Linhagem da Célula , Modelos Animais de Doenças , Neurônios GABAérgicos/metabolismo , Regulação da Expressão Gênica , Interneurônios/ultraestrutura , Aprendizagem , Bainha de Mielina/ultraestrutura , Oligodendroglia/patologia , Parvalbuminas/metabolismo , Córtex Pré-Frontal/fisiopatologia , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos Wistar
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