RESUMEN
OBJECTIVE: T1-weighted MRI images are commonly used for volumetric assessment of brain structures. Magnetization prepared 2 rapid gradient echo (MP2RAGE) sequence offers superior gray (GM) and white matter (WM) contrast. This study aimed to quantitatively assess the agreement of whole brain tissue and deep GM (DGM) volumes obtained from MP2RAGE compared to the widely used MP-RAGE sequence. METHODS: Twenty-nine healthy participants were included in this study. All subjects underwent a 3T MRI scan acquiring high-resolution 3D MP-RAGE and MP2RAGE images. Twelve participants were re-scanned after one year. The whole brain, as well as DGM segmentation, was performed using CAT12, volBrain, and FSL-FAST automatic segmentation tools based on the acquired images. Finally, contrast-to-noise ratio between WM and GM (CNRWG), the agreement between the obtained tissue volumes, as well as scan-rescan variability of both sequences were explored. RESULTS: Significantly higher CNRWG was detected in MP2RAGE vs. MP-RAGE (Mean ± SD = 0.97 ± 0.04 vs. 0.8 ± 0.1 respectively; p<0.0001). Significantly higher total brain GM, and lower cerebrospinal fluid volumes were obtained from MP2RAGE vs. MP-RAGE based on all segmentation methods (p<0.05 in all cases). Whole-brain voxel-wise comparisons revealed higher GM tissue probability in the thalamus, putamen, caudate, lingual gyrus, and precentral gyrus based on MP2RAGE compared with MP-RAGE. Moreover, significantly higher WM probability was observed in the cerebellum, corpus callosum, and frontal-and-temporal regions in MP2RAGE vs. MP-RAGE. Finally, MP2RAGE showed a higher mean percentage of change in total brain GM compared to MP-RAGE. On the other hand, MP-RAGE demonstrated a higher overtime percentage of change in WM and DGM volumes compared to MP2RAGE. CONCLUSIONS: Due to its higher CNR, MP2RAGE resulted in reproducible brain tissue segmentation, and thus is a recommended method for volumetric imaging biomarkers for the monitoring of neurological diseases.
Asunto(s)
Encéfalo/diagnóstico por imagen , Sustancia Gris/diagnóstico por imagen , Imagen por Resonancia Magnética , Sustancia Blanca/diagnóstico por imagen , Amígdala del Cerebelo/diagnóstico por imagen , Amígdala del Cerebelo/ultraestructura , Encéfalo/ultraestructura , Mapeo Encefálico , Sistema Nervioso Central/diagnóstico por imagen , Sistema Nervioso Central/ultraestructura , Líquido Cefalorraquídeo/metabolismo , Femenino , Sustancia Gris/ultraestructura , Voluntarios Sanos , Hipocampo/diagnóstico por imagen , Hipocampo/ultraestructura , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , Masculino , Persona de Mediana Edad , Manejo de Especímenes , Tálamo/diagnóstico por imagen , Tálamo/ultraestructura , Sustancia Blanca/ultraestructuraRESUMEN
Myelin insulates neuronal axons and enables fast signal transmission, constituting a key component of brain development, aging and disease. Yet, myelin-specific imaging of macroscopic samples remains a challenge. Here, we exploit myelin's nanostructural periodicity, and use small-angle X-ray scattering tensor tomography (SAXS-TT) to simultaneously quantify myelin levels, nanostructural integrity and axon orientations in nervous tissue. Proof-of-principle is demonstrated in whole mouse brain, mouse spinal cord and human white and gray matter samples. Outcomes are validated by 2D/3D histology and compared to MRI measurements sensitive to myelin and axon orientations. Specificity to nanostructure is exemplified by concomitantly imaging different myelin types with distinct periodicities. Finally, we illustrate the method's sensitivity towards myelin-related diseases by quantifying myelin alterations in dysmyelinated mouse brain. This non-destructive, stain-free molecular imaging approach enables quantitative studies of myelination within and across samples during development, aging, disease and treatment, and is applicable to other ordered biomolecules or nanostructures.
Asunto(s)
Sistema Nervioso Central/metabolismo , Sistema Nervioso Central/ultraestructura , Vaina de Mielina/metabolismo , Vaina de Mielina/ultraestructura , Tomografía Computarizada por Rayos X/métodos , Animales , Axones/metabolismo , Axones/ultraestructura , Encéfalo/metabolismo , Encéfalo/ultraestructura , Sistema Nervioso Central/diagnóstico por imagen , Preescolar , Femenino , Humanos , Imagen por Resonancia Magnética/métodos , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Proteínas de la Mielina/metabolismo , Nanoestructuras/química , Nanoestructuras/ultraestructura , Neuroimagen/métodos , Prueba de Estudio Conceptual , Dispersión del Ángulo Pequeño , Médula Espinal/metabolismo , Médula Espinal/ultraestructuraRESUMEN
The brain vasculature has several specific features, one of them being the blood-brain barrier (BBB), which supports and protects the brain by allowing for the passage of oxygen and nutrients, while at the same time preventing passage of pathogens and toxins. The BBB also prevents efficient delivery of drugs to the brain, e.g. for treatment of brain tumors. In the murine brain, perivascular fibroblasts were recently identified as a novel potential constituent of the BBB. Here we present the existence of human cells that could be the equivalent to the murine brain perivascular fibroblasts. Using RNA sequencing, we show a similar transcriptomic profile of cultured human brain cells and murine perivascular fibroblasts. These data open up a window for new hypotheses on cell types involved in human CNS diseases.
Asunto(s)
Encéfalo/ultraestructura , Linaje de la Célula/genética , Sistema Nervioso Central/ultraestructura , Fibroblastos/metabolismo , Animales , Transporte Biológico/genética , Barrera Hematoencefálica/ultraestructura , Encéfalo/irrigación sanguínea , Encéfalo/metabolismo , Sistema Nervioso Central/irrigación sanguínea , Sistema Nervioso Central/metabolismo , Sistemas de Liberación de Medicamentos , Humanos , RatonesRESUMEN
Although it is now established that neurons in crustacea contain multiple transmitter substances, little is know about patterns of expression and co-expression or about the functional effects of such co-transmission. The present study was designed to characterize the distributions and potential colocalization of choline acetyltransferase (ChAT), serotonin (5-HT) and neuropeptide H-Phe-Met-Arg-Phe-NH2 (FMRFamide) in the central nervous system (CNS) of the Asian shore crab, Hemigrapsus sanguineus using immunohistochemical analyses in combination with laser scanning confocal microscopy. ChAT was found to be expressed by small, medium-sized, and large neurons in all regions of the brain and ventral nerve cord (VNC). For the most part, ChAT, FMRFamide, and 5-HT are expressed in different neurons, although some colocalization of ChAT- with FMRFamide- or 5-HT-LIR is observed in small and medium-sized cells, mostly neurons that immunostain only weakly. In the brain, such double immunolabeling is observed primarily in neurons of the protocerebrum and, to a particularly great extent, in local olfactory interneurons of the deutocerebrum. The clusters of neurons in the VNC that stain most intensely for ChAT, FMRFamide, and 5-HT, with colocalization in some cases, are located in the subesophageal ganglia. This colocalization appears to be related to function, since it is present in regions of the CNS characterized by multiple afferent projections and outputs to a variety of functionally related centers involved in various physiological and behavioral processes. Further elucidation of the functional significance of these neurons and of the widespread process of co-transmission in the crustaceans should provide fascinating new insights.
Asunto(s)
Braquiuros , Sistema Nervioso Central , Ganglios de Invertebrados , Neuronas , Animales , Braquiuros/metabolismo , Braquiuros/ultraestructura , Sistema Nervioso Central/metabolismo , Sistema Nervioso Central/ultraestructura , Colina O-Acetiltransferasa/metabolismo , FMRFamida/metabolismo , Ganglios de Invertebrados/metabolismo , Ganglios de Invertebrados/ultraestructura , Neuronas/metabolismo , Neuronas/ultraestructura , Serotonina/metabolismoRESUMEN
GluD2 receptor belongs to the orphan delta family of glutamate receptor ion channels. These receptors play key roles in synaptogenesis and synaptic plasticity and are associated with multiple neuronal disorders like schizophrenia, autism spectrum disorder, cerebellar ataxia, intellectual disability, paraplegia, retinal dystrophy, etc. Despite the importance of these receptors in CNS, insights into full-length GluD2 receptor structure is missing till-date. Here we report cryo-electron microscopy structure of the rat GluD2 receptor in the presence of calcium ions and the ligand 7-chlorokynurenic acid, elucidating its 3D architecture. The structure reveals a non-swapped architecture at the extracellular amino-terminal (ATD), and ligand-binding domain (LBD) interface similar to that observed in GluD1; however, the organization and arrangement of the ATD and LBD domains in GluD2 are unique. While our results demonstrate that non-swapped architecture is conserved in the delta receptor family, they also highlight the differences that exist between the two member receptors; GluD1 and GluD2.
Asunto(s)
Microscopía por Crioelectrón , Neuronas/ultraestructura , Receptores de Glutamato/ultraestructura , Receptores Ionotrópicos de Glutamato/ultraestructura , Animales , Sistema Nervioso Central/patología , Sistema Nervioso Central/ultraestructura , Humanos , Ligandos , Plasticidad Neuronal/genética , Neuronas/metabolismo , Neuronas/patología , Dominios Proteicos/genética , Ratas , Receptores de Glutamato/genética , Receptores Ionotrópicos de Glutamato/genéticaRESUMEN
At presynaptic active zones, arrays of large conserved scaffold proteins mediate fast and temporally precise release of synaptic vesicles (SVs). SV release sites could be identified by clusters of Munc13, which allow SVs to dock in defined nanoscale relation to Ca2+ channels. We here show in Drosophila that RIM-binding protein (RIM-BP) connects release sites physically and functionally to the ELKS family Bruchpilot (BRP)-based scaffold engaged in SV recruitment. The RIM-BP N-terminal domain, while dispensable for SV release site organization, was crucial for proper nanoscale patterning of the BRP scaffold and needed for SV recruitment of SVs under strong stimulation. Structural analysis further showed that the RIM-BP fibronectin domains form a "hinge" in the protein center, while the C-terminal SH3 domain tandem binds RIM, Munc13, and Ca2+ channels release machinery collectively. RIM-BPs' conserved domain architecture seemingly provides a relay to guide SVs from membrane far scaffolds into membrane close release sites.
Asunto(s)
Proteínas Portadoras/química , Sistema Nervioso Central/metabolismo , Proteínas del Citoesqueleto/química , Proteínas de Drosophila/química , Drosophila melanogaster/metabolismo , Sinapsis/metabolismo , Vesículas Sinápticas/metabolismo , Proteínas de Unión al GTP rab3/química , Animales , Animales Modificados Genéticamente , Sitios de Unión , Canales de Calcio/genética , Canales de Calcio/metabolismo , Proteínas Portadoras/genética , Proteínas Portadoras/metabolismo , Sistema Nervioso Central/ultraestructura , Clonación Molecular , Proteínas del Citoesqueleto/genética , Proteínas del Citoesqueleto/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Drosophila melanogaster/ultraestructura , Escherichia coli/genética , Escherichia coli/metabolismo , Femenino , Regulación de la Expresión Génica , Vectores Genéticos/química , Vectores Genéticos/metabolismo , Larva/genética , Larva/metabolismo , Larva/ultraestructura , Masculino , Proteínas de la Membrana/química , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Proteínas del Tejido Nervioso/química , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Unión Proteica , Conformación Proteica en Lámina beta , Dominios y Motivos de Interacción de Proteínas , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Sinapsis/ultraestructura , Transmisión Sináptica , Vesículas Sinápticas/ultraestructura , Proteínas de Unión al GTP rab3/genética , Proteínas de Unión al GTP rab3/metabolismoRESUMEN
The brain's complex microconnectivity underlies its computational abilities and vulnerability to injury and disease. It has been challenging to illuminate the features of this synaptic network due to the small size and dense packing of its elements. Here, we describe a rapid, accessible super-resolution imaging and analysis workflow-SEQUIN-that quantifies central synapses in human tissue and animal models, characterizes their nanostructural and molecular features, and enables volumetric imaging of mesoscale synaptic networks without the production of large histological arrays. Using SEQUIN, we identify cortical synapse loss resulting from diffuse traumatic brain injury, a highly prevalent connectional disorder. Similar synapse loss is observed in three murine models of Alzheimer-related neurodegeneration, where SEQUIN mesoscale mapping identifies regional synaptic vulnerability. These results establish an easily implemented and robust nano-to-mesoscale synapse quantification and characterization method. They furthermore identify a shared mechanism-synaptopathy-between Alzheimer neurodegeneration and its best-established epigenetic risk factor, brain trauma.
Asunto(s)
Lesiones Traumáticas del Encéfalo/patología , Sistema Nervioso Central/diagnóstico por imagen , Nanoestructuras/ultraestructura , Vías Nerviosas/diagnóstico por imagen , Vías Nerviosas/ultraestructura , Neuroimagen/métodos , Sinapsis/ultraestructura , Animales , Mapeo Encefálico , Sistema Nervioso Central/ultraestructura , Corteza Cerebral/patología , Humanos , Mamíferos , RatonesRESUMEN
Translational readthrough (TRT) of aquaporin-4 (AQP4) has remarkably expanded the importance of this new post-transcriptional mechanism, as well as the regulation potential of AQP4. The TRT isoform of AQP4, named AQP4ex, is central for both AQP4 polarization and water channel activity in the central nervous system (CNS). Here we evaluate the relevance of the TRT mechanism by analyzing whether AQP4ex is also expressed in peripheral tissues and whether the expression of AQP4ex is necessary for its polarized expression as it occurs in perivascular astrocyte processes. To this purpose, AQP4ex null mice were used, and analysis was performed by immunolocalization and immunoblot. The results demonstrate that AQP4ex is expressed in kidney, stomach, trachea and skeletal muscle with the same localization pattern as the canonical AQP4 isoforms. AQP4ex protein levels vary from 6% to about 13% of the total AQP4 protein levels in peripheral tissues. Immunogold electron microscopy experiments demonstrated the localization of AQP4ex at the astrocytic endfeet, and experiments conducted on AQP4ex null mice CNS confirmed that the expression of AQP4ex is necessary for anchoring of the perivascular AQP4. Without the readthrough isoform, AQP4 assemblies are mis-localized, being uniformly distributed on the astrocyte processes facing the neuropile. No alteration of AQP4 polarization was found in AQP4ex null kidney, stomach, trachea or skeletal muscle, suggesting that AQP4ex does not have a role for proper membrane localization of AQP4 in peripheral tissues. We conclude that a dual role for AQP4ex is limited to the CNS.
Asunto(s)
Acuaporina 4/genética , Astrocitos/metabolismo , Sistema Nervioso Central/metabolismo , Regulación de la Expresión Génica , Animales , Acuaporina 4/metabolismo , Astrocitos/ultraestructura , Sistema Nervioso Central/ultraestructura , Immunoblotting , Riñón/metabolismo , Ratones , Ratones Noqueados , Microscopía Inmunoelectrónica , Músculo Esquelético/metabolismo , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Estómago/química , Tráquea/metabolismo , Proteína Tumoral Controlada Traslacionalmente 1RESUMEN
Multiple sclerosis (MS) is a neurodegenerative autoimmune disease with many known structural and functional changes in the central nervous system. A well-recognized, but poorly understood, complication of MS is chronic pain. Little is known regarding the influence of sex on the development and maintenance of MS-related pain. This is important to consider, as MS is a predominantly female disease. Using the experimental autoimmune encephalomyelitis (EAE) mouse model of MS, we demonstrate sex differences in measures of spinal cord inflammation and plasticity that accompany tactile hypersensitivity. Although we observed substantial inflammatory activity in both sexes, only male EAE mice exhibit robust staining of axonal injury markers and increased dendritic arborisation in morphology of deep dorsal horn neurons. We propose that tactile hypersensitivity in female EAE mice may be more immune-driven, whereas pain in male mice with EAE may rely more heavily on neurodegenerative and plasticity-related mechanisms. Morphological and inflammatory differences in the spinal cord associated with pain early in EAE progression supports the idea of differentially regulated pain pathways between the sexes. Results from this study may indicate future sex-specific targets that are worth investigating for their functional role in pain circuitry.
Asunto(s)
Sistema Nervioso Central/fisiopatología , Encefalomielitis Autoinmune Experimental/complicaciones , Plasticidad Neuronal/fisiología , Dolor/etiología , Dolor/patología , Animales , Axones/patología , Axones/ultraestructura , Proteínas de Unión al Calcio/metabolismo , Sistema Nervioso Central/patología , Sistema Nervioso Central/ultraestructura , Modelos Animales de Enfermedad , Encefalomielitis Autoinmune Experimental/inducido químicamente , Ciclo Estral/fisiología , Femenino , Adyuvante de Freund/toxicidad , Hiperalgesia/fisiopatología , Masculino , Ratones , Ratones Endogámicos C57BL , Proteínas de Microfilamentos/metabolismo , Actividad Motora/fisiología , Glicoproteína Mielina-Oligodendrócito/inmunología , Glicoproteína Mielina-Oligodendrócito/toxicidad , Umbral del Dolor/fisiología , Fragmentos de Péptidos/inmunología , Fragmentos de Péptidos/toxicidad , Toxina del Pertussis/toxicidad , Estimulación Física/efectos adversos , Factores SexualesRESUMEN
We reconstructed, from a whole CNS EM volume, the synaptic map of input and output neurons that underlie food intake behavior of Drosophila larvae. Input neurons originate from enteric, pharyngeal and external sensory organs and converge onto seven distinct sensory synaptic compartments within the CNS. Output neurons consist of feeding motor, serotonergic modulatory and neuroendocrine neurons. Monosynaptic connections from a set of sensory synaptic compartments cover the motor, modulatory and neuroendocrine targets in overlapping domains. Polysynaptic routes are superimposed on top of monosynaptic connections, resulting in divergent sensory paths that converge on common outputs. A completely different set of sensory compartments is connected to the mushroom body calyx. The mushroom body output neurons are connected to interneurons that directly target the feeding output neurons. Our results illustrate a circuit architecture in which monosynaptic and multisynaptic connections from sensory inputs traverse onto output neurons via a series of converging paths.
Asunto(s)
Sistema Nervioso Central/fisiología , Drosophila melanogaster/fisiología , Larva/fisiología , Neuronas Motoras/fisiología , Sinapsis/fisiología , Transmisión Sináptica/fisiología , Animales , Sistema Nervioso Central/ultraestructura , Conectoma/métodos , Drosophila melanogaster/ultraestructura , Ingestión de Alimentos/fisiología , Conducta Alimentaria/fisiología , Interneuronas/citología , Interneuronas/fisiología , Larva/ultraestructura , Potenciales de la Membrana/fisiología , Neuronas Motoras/citología , Cuerpos Pedunculados/citología , Cuerpos Pedunculados/fisiología , Red Nerviosa/fisiología , Red Nerviosa/ultraestructura , Plasticidad Neuronal/fisiología , Sinapsis/ultraestructuraRESUMEN
Arachidonic acid and docosahexaenoic acid (DHA) released by the action of phospholipases A2 (PLA2) on membrane phospholipids may be metabolized by lipoxygenases to the anti-inflammatory mediators lipoxin A4 (LXA4) and resolvin D1 (RvD1), and these can bind to a common receptor, formyl-peptide receptor 2 (FPR2). The contribution of this receptor to axonal or dendritic outgrowth is unknown. The present study was carried out to elucidate the distribution of FPR2 in the rat CNS and its role in outgrowth of neuronal processes. FPR2 mRNA expression was greatest in the brainstem, followed by the spinal cord, thalamus/hypothalamus, cerebral neocortex, hippocampus, cerebellum and striatum. The brainstem and spinal cord also contained high levels of FPR2 protein. The cerebral neocortex was moderately immunolabelled for FPR2, with staining mostly present as puncta in the neuropil. Dentate granule neurons and their axons (mossy fibres) in the hippocampus were very densely labelled. The cerebellar cortex was lightly stained, but the deep cerebellar nuclei, inferior olivary nucleus, vestibular nuclei, spinal trigeminal nucleus and dorsal horn of the spinal cord were densely labelled. Electron microscopy of the prefrontal cortex showed FPR2 immunolabel mostly in immature axon terminals or 'pre-terminals', that did not form synapses with dendrites. Treatment of primary hippocampal neurons with the FPR2 inhibitors, PBP10 or WRW4, resulted in reduced lengths of axons and dendrites. The CNS distribution of FPR2 suggests important functions in learning and memory, balance and nociception. This might be due to an effect of FPR2 in mediating arachidonic acid/LXA4 or DHA/RvD1-induced axonal or dendritic outgrowth.
Asunto(s)
Axones/metabolismo , Encéfalo/metabolismo , Dendritas/metabolismo , Receptores de Lipoxina/biosíntesis , Médula Espinal/metabolismo , Animales , Axones/química , Axones/ultraestructura , Encéfalo/ultraestructura , Química Encefálica/fisiología , Supervivencia Celular/fisiología , Sistema Nervioso Central/química , Sistema Nervioso Central/metabolismo , Sistema Nervioso Central/ultraestructura , Dendritas/química , Dendritas/ultraestructura , Masculino , Ratas , Ratas Wistar , Receptores de Lipoxina/análisis , Médula Espinal/química , Médula Espinal/ultraestructuraRESUMEN
In this study, we analyze the neuropathological and biochemical alterations involved in the pathogenesis of a neurodegenerative/movement disorder during different developmental stages in juvenile rats with a mutant Myosin5a (Myo5a). In mutant rats, a spontaneous autosomal recessive mutation characterized by the absence of Myo5a protein expression in the brain is associated with a syndrome of locomotor dysfunction, altered coat color, and neuroendocrine abnormalities. Myo5a encodes a myosin motor protein required for transport and proper distribution of subcellular organelles in somatodendritic processes in neurons. Here we report marked hyperphosphorylation of alpha-synuclein and tau, as well as region-specific buildup of the autotoxic dopamine metabolite, 3,4-dihydroxyphenyl-acetaldehyde (DOPAL), related to decreased aldehyde dehydrogenases activity and neurodegeneration in mutant rats. Alpha-synuclein accumulation in mitochondria of dopaminergic neurons is associated with impaired enzymatic respiratory complex I and IV activity. The behavioral and biochemical lesions progress after 15â¯days postnatal, and by 30-40â¯days the animals must be euthanized because of neurological impairment. Based on the obtained results, we propose a pleiotropic pathogenesis that links the Myo5a gene mutation to deficient neuronal development and progressive neurodegeneration. This potential model of a neurodevelopmental disorder with neurodegeneration and motor deficits may provide further insight into molecular motors and their associated proteins responsible for altered neurogenesis and neuronal disease pathogenesis.
Asunto(s)
Sistema Nervioso Central/metabolismo , Sistema Nervioso Central/patología , Trastornos Heredodegenerativos del Sistema Nervioso , Mutación/genética , Cadenas Pesadas de Miosina/genética , Miosina Tipo V/genética , Proteínas tau/metabolismo , Ácido 3,4-Dihidroxifenilacético/análogos & derivados , Ácido 3,4-Dihidroxifenilacético/metabolismo , Animales , Sistema Nervioso Central/ultraestructura , Modelos Animales de Enfermedad , Proteínas del Complejo de Cadena de Transporte de Electrón/metabolismo , Trastornos Heredodegenerativos del Sistema Nervioso/genética , Trastornos Heredodegenerativos del Sistema Nervioso/metabolismo , Trastornos Heredodegenerativos del Sistema Nervioso/patología , Microscopía Electrónica de Transmisión , Cadenas Pesadas de Miosina/metabolismo , Miosina Tipo V/metabolismo , Fosforilación/genética , Ratas , Ratas Mutantes , alfa-Sinucleína/genética , alfa-Sinucleína/metabolismo , alfa-Sinucleína/ultraestructura , Proteínas tau/genética , Proteínas tau/ultraestructuraRESUMEN
Dendritic spines are the postsynaptic receptive regions of most excitatory synapses in the central nervous system. Thus, spines are supposed to act as a fundamental unit for information processing of the brains. Previous studies have demonstrated the roles of drebrin in the formation of dendritic spines and in the recruitment of synaptic proteins to postsynaptic sites. Further, a live imaging study has revealed the unique dynamics of drebrin in dendritic spines, which help to understand how drebrin is involved in dendritic spine formation. This review will provide a basic knowledge about dendritic spine and overview recent progresses in understanding of the roles of drebrin in dendritic spine morphogenesis and synaptogenesis.
Asunto(s)
Sistema Nervioso Central/metabolismo , Espinas Dendríticas/metabolismo , Neuropéptidos/metabolismo , Animales , Sistema Nervioso Central/ultraestructura , Espinas Dendríticas/ultraestructura , Hipocampo/metabolismo , Hipocampo/ultraestructura , Neuropéptidos/genética , Sinapsis/genética , Sinapsis/metabolismoRESUMEN
The cerebrospinal fluid (CSF) is circulating around the entire central nervous system (CNS). The main function of the CSF has been thought to insure the global homeostasis of the CNS. Recent evidence indicates that the CSF also dynamically conveys signals modulating the development and the activity of the nervous system. The later observation implies that cues from the CSF could act on neurons in the brain and the spinal cord via bordering receptor cells. Candidate neurons to enable such modulation are the cerebrospinal fluid-contacting neurons (CSF-cNs) that are located precisely at the interface between the CSF and neuronal circuits. The atypical apical extension of CSF-cNs bears a cluster of microvilli bathing in the CSF indicating putative sensory or secretory roles in relation with the CSF. In the brainstem and spinal cord, CSF-cNs have been described in over two hundred species by Kolmer and Agduhr, suggesting an important function within the spinal cord. However, the lack of specific markers and the difficulty to access CSF-cNs hampered their physiological investigation. The transient receptor potential channel PKD2L1 is a specific marker of spinal CSF-cNs in vertebrate species. The transparency of zebrafish at early stages eases the functional characterization of pkd2l1+ CSF-cNs. Recent studies demonstrate that spinal CSF-cNs detect spinal curvature via the channel PKD2L1 and modulate locomotion and posture by projecting onto spinal interneurons and motor neurons in vivo. In vitro recordings demonstrated that spinal CSF-cNs are sensing pH variations mainly through ASIC channels, in combination with PKD2L1. Altogether, neurons contacting the CSF appear as a novel sensory modality enabling the detection of mechanical and chemical stimuli from the CSF and modulating the excitability of spinal circuits underlying locomotion and posture.
Asunto(s)
Sistema Nervioso Central/fisiología , Líquido Cefalorraquídeo/citología , Líquido Cefalorraquídeo/fisiología , Actividad Motora/fisiología , Neuronas/clasificación , Neuronas/fisiología , Animales , Sistema Nervioso Central/ultraestructura , Humanos , Neuronas/ultraestructura , VertebradosRESUMEN
Neurologic phenotypes of cathepsin D (CTSD)-deficient mice, a murine model of neuronal ceroid lipofuscinoses, indicate the importance of CTSD for the maintenance of metabolism in central nervous system neurons. To further understand the role of CTSD in central nervous system neurons, we generated mice with a CTSD deficiency specifically in the Purkinje cells (PCs) (CTSDFlox/Flox;GRID2-Cre) and compared their phenotypes with those of PC-selective Atg7-deficient (Atg7Flox/Flox;GRID2-Cre) mice. In both strains of mice, PCs underwent degeneration, but the CTSD-deficient PCs disappeared more rapidly than their Atg7-deficient counterparts. When CTSD-deficient PCs died, the neuronal cell bodies became shrunken, filled with autophagosomes and autolysosomes, and had nuclei with dispersed small chromatin fragments. The dying Atg7-deficient PCs also showed similar ultrastructures, indicating that the neuronal cell death of CTSD- and Atg7-deficient PCs was distinct from apoptosis. Immunohistochemical observations showed the formation of calbindin-positive axonal spheroids and the swelling of vesicular GABA transporter-positive presynaptic terminals that were more pronounced in Atg7-deficient PCs than in CTSD-deficient PCs. An accumulation of tubular vesicles may have derived from the smooth endoplasmic reticulum; nascent autophagosome-like structures with double membranes was a common feature in the swollen axons of these PCs. These results suggested that PCs were more vulnerable to CTSD deficiency in lysosomes than to autophagy impairment, and this vulnerability does not depend on the severity of axonal swelling.
Asunto(s)
Proteína 7 Relacionada con la Autofagia/genética , Catepsina D/genética , Lipofuscinosis Ceroideas Neuronales/genética , Animales , Autofagia , Proteína 7 Relacionada con la Autofagia/metabolismo , Axones/metabolismo , Axones/ultraestructura , Catepsina D/metabolismo , Sistema Nervioso Central/metabolismo , Sistema Nervioso Central/ultraestructura , Inmunohistoquímica , Lisosomas/metabolismo , Lisosomas/ultraestructura , Masculino , Ratones , Lipofuscinosis Ceroideas Neuronales/metabolismo , Lipofuscinosis Ceroideas Neuronales/patología , Neuronas/metabolismo , Neuronas/ultraestructura , Fagosomas/metabolismo , Fagosomas/ultraestructura , Células de Purkinje/metabolismo , Células de Purkinje/patología , Células de Purkinje/ultraestructuraRESUMEN
Injured neurons in the adult mammalian central nervous system (CNS) have a very limited capacity for axonal regeneration and neurite outgrowth. This inability to grow new axons or to regrow injured axons is due to the presence of molecules that inhibit axonal growth, and age related changes in the neuron's innate growth capabilities. Available levels of cAMP are thought to have an important role in linking both of these factors. Elevated levels of cAMP in the developing nervous system are important for the guidance and stability of growth cones. As the nervous system matures, cAMP levels decline and the growth promoting effects of cAMP diminish. It has frequently been demonstrated that increasing neuronal cAMP can enhance neurite growth and regeneration. Some methods used to increase cAMP include administration of cAMP agonists, conditioning lesions, or electrical stimulation. Furthermore, it has been proposed that multiple stages of cAMP induced growth exist, one directly caused by its downstream effector Protein Kinase A (PKA) and one caused by the eventual upregulation of gene transcription. Although the role cAMP in promoting axon growth is well accepted, the downstream pathways that mediate cAMP-mediated axonal growth are less clear. This is partly because various key studies that explored the link between PKA and axonal outgrowth relied on the PKA inhibitors KT5720 and H89. More recent studies have shown that both of these drugs are less specific than initially thought and can inhibit a number of other signalling molecules including the Exchange Protein Activated by cAMP (EPAC). Consequently, it has recently been shown that a number of intracellular signalling pathways previously attributed to PKA can now be attributed solely to activation of EPAC specific pathways, or the simultaneous co-activation of PKA and EPAC specific pathways. These new studies open the door to new potential treatments for repairing the injured spinal cord.
Asunto(s)
Sistema Nervioso Central/metabolismo , AMP Cíclico/metabolismo , Neuritas/fisiología , Animales , Sistema Nervioso Central/lesiones , Sistema Nervioso Central/ultraestructura , Proteínas Quinasas Dependientes de AMP Cíclico/metabolismo , Estimulación Eléctrica , Humanos , Factores de Crecimiento Nervioso/metabolismo , Regeneración Nerviosa , Traumatismos de la Médula Espinal/metabolismo , Traumatismos de la Médula Espinal/patología , Traumatismos de la Médula Espinal/terapiaRESUMEN
Mitochondria are dynamically active organelles, regulated through fission and fusion events to continuously redistribute them across axons, dendrites, and synapses of neurons to meet bioenergetics requirements and to control various functions, including cell proliferation, calcium buffering, neurotransmission, oxidative stress, and apoptosis. However, following acute or chronic injury to CNS, altered expression and function of proteins that mediate fission and fusion lead to mitochondrial dynamic imbalance. Particularly, if the fission is abnormally increased through pro-fission mediators such as Drp1, mitochondrial function will be impaired and mitochondria will become susceptible to insertion of proapototic proteins. This leads to the formation of mitochondrial transition pore, which eventually triggers apoptosis. Thus, mitochondrial dysfunction is a major promoter of neuronal death and secondary brain damage after an insult. This review discusses the implications of mitochondrial dynamic imbalance in neuronal death after acute and chronic CNS insults.
Asunto(s)
Lesiones Encefálicas/etiología , Sistema Nervioso Central/lesiones , Dinámicas Mitocondriales , Sistema Nervioso Central/ultraestructura , HumanosRESUMEN
We aimed to identify new cell-membrane antigens implicated in opsoclonus-myoclonus with neuroblastoma. The sera of 3 out of 14 patients showed IgG electron-microscopy immunogold reactivity on SH-SY5Y neuroblastoma cells. Immunoprecipitation experiments using rat brain synaptosomes and SH-SY5Y cells led to the identification of: (1) thirty-one nuclear/cytoplasmic proteins (including antigens HuB, HuC); (2) seven neuronal membrane proteins, including the Shaw-potassium channel Kv3.3 (KCNC3), whose genetic disruption in mice causes ataxia and generalized muscle twitching. Although cell-based assays did not demonstrate direct antigenicity, our findings point to Shaw-related subfamily of the potassium voltage-gated channels complexed proteins as hypothetical antigenic targets.
Asunto(s)
Neoplasias Encefálicas , Sistema Nervioso Central/metabolismo , Neuroblastoma , Síndrome de Opsoclonía-Mioclonía , Animales , Neoplasias Encefálicas/complicaciones , Neoplasias Encefálicas/inmunología , Neoplasias Encefálicas/patología , Moléculas de Adhesión Celular Neuronal/metabolismo , Línea Celular Tumoral , Sistema Nervioso Central/ultraestructura , Niño , Bases de Datos Factuales/estadística & datos numéricos , Encefalitis/complicaciones , Encefalitis/inmunología , Femenino , Células HEK293 , Humanos , Masculino , Proteínas de la Membrana/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Proteínas del Tejido Nervioso/ultraestructura , Neuroblastoma/complicaciones , Neuroblastoma/inmunología , Neuroblastoma/patología , Proteínas Nucleares/metabolismo , Proteínas Nucleares/ultraestructura , Síndrome de Opsoclonía-Mioclonía/complicaciones , Síndrome de Opsoclonía-Mioclonía/inmunología , Síndrome de Opsoclonía-Mioclonía/patología , Ratas , Ratas Wistar , Canales de Potasio Shaw/inmunología , Canales de Potasio Shaw/metabolismo , Canales de Potasio Shaw/ultraestructura , Sinaptosomas/metabolismo , Sinaptosomas/ultraestructura , Timoma/complicacionesRESUMEN
Anatomical, molecular, and physiological interactions between astrocytes and neuronal synapses regulate information processing in the brain. The fruit fly Drosophila melanogaster has become a valuable experimental system for genetic manipulation of the nervous system and has enormous potential for elucidating mechanisms that mediate neuron-glia interactions. Here, we show the first electrophysiological recordings from Drosophila astrocytes and characterize their spatial and physiological relationship with particular synapses. Astrocyte intrinsic properties were found to be strongly analogous to those of vertebrate astrocytes, including a passive current-voltage relationship, low membrane resistance, high capacitance, and dye-coupling to local astrocytes. Responses to optogenetic stimulation of glutamatergic premotor neurons were correlated directly with anatomy using serial electron microscopy reconstructions of homologous identified neurons and surrounding astrocytic processes. Robust bidirectional communication was present: neuronal activation triggered astrocytic glutamate transport via excitatory amino acid transporter 1 (Eaat1), and blocking Eaat1 extended glutamatergic interneuron-evoked inhibitory postsynaptic currents in motor neurons. The neuronal synapses were always located within 1 µm of an astrocytic process, but none were ensheathed by those processes. Thus, fly astrocytes can modulate fast synaptic transmission via neurotransmitter transport within these anatomical parameters. J. Comp. Neurol. 524:1979-1998, 2016. © 2016 Wiley Periodicals, Inc.
Asunto(s)
Astrocitos/fisiología , Sistema Nervioso Central/citología , Proteínas de Drosophila/metabolismo , Neuronas/fisiología , Sinapsis/fisiología , Factores de Transcripción/metabolismo , Animales , Animales Modificados Genéticamente , Ácido Aspártico/farmacología , Astrocitos/ultraestructura , Cloruro de Cadmio/farmacología , Moléculas de Adhesión Celular Neuronal/metabolismo , Sistema Nervioso Central/fisiología , Sistema Nervioso Central/ultraestructura , Colina O-Acetiltransferasa/metabolismo , Drosophila , Proteínas de Drosophila/antagonistas & inhibidores , Proteínas de Drosophila/genética , Transportador 1 de Aminoácidos Excitadores/metabolismo , Regulación de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica/genética , Potenciales Postsinápticos Inhibidores/efectos de los fármacos , Potenciales Postsinápticos Inhibidores/genética , Larva , Locomoción/genética , Red Nerviosa/fisiología , Red Nerviosa/ultraestructura , Neuronas/ultraestructura , Bloqueadores de los Canales de Sodio/farmacología , Sinapsis/genética , Sinapsis/ultraestructura , Tetrodotoxina/farmacología , Factores de Transcripción/antagonistas & inhibidores , Factores de Transcripción/genética , Proteínas del Transporte Vesicular de Aminoácidos Inhibidores/metabolismoRESUMEN
In the present study, we reveal myelin-specific expression and targeting of mRNA and biochemical pools of HspB5 in the mouse CNS. Our observations are based on in situ hybridization, electron microscopy and co-localization with 2',3'-Cyclic-Nucleotide 3'-Phosphodiesterase (CNPase), reinforcing this myelin-selective expression. HspB5 mRNA might be targeted to these structures based on its presence in discrete clusters resembling RNA granules and the presence of a putative RNA transport signal. Further, sub-cellular fractionation of myelin membranes reveals a distinct sub-compartment-specific association and detergent solubility of HspB5. This is akin to other abundant myelin proteins and is consistent with HspB5's association with cytoskeletal/membrane assemblies. Oligodendrocytes have a pivotal role in supporting axonal function via generating and segregating the ensheathing myelin. This specialization places extreme structural and metabolic demands on this glial cell type. Our observations place HspB5 in oligodendrocytes which may require selective and specific chaperone capabilities to maintain normal function and neuronal support.