RESUMO
Disturbances of lipid homeostasis in cells provoke human diseases. The elucidation of the underlying mechanisms and the development of efficient therapies represent formidable challenges for biomedical research. Exemplary cases are two rare, autosomal recessive, and ultimately fatal lysosomal diseases historically named "Niemann-Pick" honoring the physicians, whose pioneering observations led to their discovery. Acid sphingomyelinase deficiency (ASMD) and Niemann-Pick type C disease (NPCD) are caused by specific variants of the sphingomyelin phosphodiesterase 1 (SMPD1) and NPC intracellular cholesterol transporter 1 (NPC1) or NPC intracellular cholesterol transporter 2 (NPC2) genes that perturb homeostasis of two key membrane components, sphingomyelin and cholesterol, respectively. Patients with severe forms of these diseases present visceral and neurologic symptoms and succumb to premature death. This synopsis traces the tortuous discovery of the Niemann-Pick diseases, highlights important advances with respect to genetic culprits and cellular mechanisms, and exposes efforts to improve diagnosis and to explore new therapeutic approaches.
Assuntos
Doença de Niemann-Pick Tipo C , Esfingolipídeos , Humanos , Esfingolipídeos/metabolismo , Doença de Niemann-Pick Tipo C/diagnóstico , Doença de Niemann-Pick Tipo C/genética , Doença de Niemann-Pick Tipo C/metabolismo , Metabolismo dos Lipídeos , Lisossomos/metabolismo , Colesterol/metabolismoRESUMO
Cell-cell interactions in the central nervous system are based on the release of molecules mediating signal exchange and providing structural and trophic support through vesicular exocytosis and the formation of extracellular vesicles. The specific mechanisms employed by each cell type in the brain are incompletely understood. Here, we explored the means of communication used by Müller cells, a type of radial glial cells in the retina, which forms part of the central nervous system. Using immunohistochemical, electron microscopic, and molecular analyses, we provide evidence for the release of distinct extracellular vesicles from endfeet and microvilli of retinal Müller cells in adult mice in vivo. We identify VAMP5 as a Müller cell-specific SNARE component that is part of extracellular vesicles and responsive to ischemia, and we reveal differences between the secretomes of immunoaffinity-purified Müller cells and neurons in vitro. Our findings suggest extracellular vesicle-based communication as an important mediator of cellular interactions in the retina.
Assuntos
Vesículas Extracelulares , Neuroglia , Animais , Células Ependimogliais/metabolismo , Camundongos , Neuroglia/metabolismo , Neurônios/metabolismo , Retina/metabolismoRESUMO
Liraglutide, an anti-diabetic drug and agonist of the glucagon-like peptide one receptor (GLP1R), has recently been approved to treat obesity in individuals with or without type 2 diabetes. Despite its extensive metabolic benefits, the mechanism and site of action of liraglutide remain unclear. Here, we demonstrate that liraglutide is shuttled to target cells in the mouse hypothalamus by specialized ependymoglial cells called tanycytes, bypassing the blood-brain barrier. Selectively silencing GLP1R in tanycytes or inhibiting tanycytic transcytosis by botulinum neurotoxin expression not only hampers liraglutide transport into the brain and its activation of target hypothalamic neurons, but also blocks its anti-obesity effects on food intake, body weight and fat mass, and fatty acid oxidation. Collectively, these striking data indicate that the liraglutide-induced activation of hypothalamic neurons and its downstream metabolic effects are mediated by its tanycytic transport into the mediobasal hypothalamus, strengthening the notion of tanycytes as key regulators of metabolic homeostasis.
Assuntos
Diabetes Mellitus Tipo 2 , Liraglutida , Animais , Barreira Hematoencefálica , Diabetes Mellitus Tipo 2/metabolismo , Células Ependimogliais , Hipotálamo/metabolismo , Liraglutida/farmacologia , Camundongos , Obesidade/tratamento farmacológico , Obesidade/metabolismoRESUMO
Neurodegenerative diseases, namely Alzheimer's (AD), Parkinson's (PD), and Huntington's disease (HD) together with amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS), devastate millions of lives per year worldwide and impose an increasing socio-economic burden across nations. Consequently, these diseases occupy a considerable portion of biomedical research aiming to understand mechanisms of neurodegeneration and to develop efficient treatments. A potential culprit is cholesterol serving as an essential component of cellular membranes, as a cofactor of signaling pathways, and as a precursor for oxysterols and hormones. This article uncovers the workforce studying research on neurodegeneration and cholesterol using the TeamTree analysis. This new bibliometric approach reveals the history and dynamics of the teams and exposes key players based on citation-independent metrics. The team-centered view reveals the players on an important field of biomedical research.
RESUMO
Niemann-Pick type C disease is a rare and fatal lysosomal storage disorder presenting severe neurovisceral symptoms. Disease-causing mutations in genes encoding either NPC1 or NPC2 protein provoke accumulation of cholesterol and other lipids in specific structures of the endosomal-lysosomal system and degeneration of specific cells, notably neurons in the central nervous system (CNS). 2-hydroxypropyl-beta-cyclodextrin (CD) emerged as potential therapeutic approach based on animal studies and clinical data, but the mechanism of action in neurons has remained unclear. To address this topic in vivo, we took advantage of the retina as highly accessible part of the CNS and intravitreal injections as mode of drug administration. Coupling CD to gold nanoparticles allowed us to trace its intracellular location. We report that CD enters the endosomal-lysosomal system of neurons in vivo and enables the release of lipid-laden lamellar inclusions, which are then removed from the extracellular space by specific types of glial cells. Our data suggest that CD induces a concerted action of neurons and glial cells to restore lipid homeostasis in the central nervous system.
Assuntos
Colesterol/metabolismo , Ciclodextrinas/farmacologia , Neuroglia/efeitos dos fármacos , Neurônios/metabolismo , Proteína C1 de Niemann-Pick/genética , Animais , Ouro , Corpos de Inclusão/metabolismo , Metabolismo dos Lipídeos/efeitos dos fármacos , Metabolismo dos Lipídeos/genética , Masculino , Nanopartículas Metálicas , Camundongos , Camundongos Endogâmicos BALB C , Neurônios/efeitos dos fármacos , Retina/efeitos dos fármacosRESUMO
Advances in science and technology depend on the work of research teams and the publication of results through peer-reviewed articles representing a growing socio-economic resource. Current methods to mine the scientific literature regarding a field of interest focus on content, but the workforce credited by authorship remains largely unexplored. Notably, appropriate measures of scientific production are debated. Here, a new bibliometric approach named TeamTree analysis is introduced that visualizes the development and composition of the workforce driving a field. A new citation-independent measure that scales with the H index estimates impact based on publication record, genealogical ties and collaborative connections. This author-centered approach complements existing tools to mine the scientific literature and to evaluate research across disciplines.
Assuntos
Autoria , Bibliometria , Eficiência , Ciência , Estudos de Avaliação como Assunto , Humanos , Editoração , Recursos HumanosRESUMO
Biomedical research aims to understand the molecular mechanisms causing human diseases and to develop curative therapies. So far, these goals have been achieved for a small fraction of diseases, limiting factors being the availability, validity, and use of experimental models. Niemann-Pick type C (NPC) is a prime example for a disease that lacks a curative therapy despite substantial breakthroughs. This rare, fatal, and autosomal-recessive disorder is caused by defects in NPC1 or NPC2. These ubiquitously expressed proteins help cholesterol exit from the endosomal-lysosomal system. The dysfunction of either causes an aberrant accumulation of lipids with patients presenting a large range of disease onset, neurovisceral symptoms, and life span. Here, we note general aspects of experimental models, we describe the line-up used for NPC-related research and therapy development, and we provide an outlook on future topics.
Assuntos
Modelos Biológicos , Doença de Niemann-Pick Tipo C/patologia , Animais , Modelos Animais de Doenças , Humanos , Mamíferos , Doença de Niemann-Pick Tipo C/terapia , Células-Tronco/metabolismoRESUMO
Astrocytes are a major type of glial cell in the mammalian brain, essentially regulating neuronal development and function. Quantitative imaging represents an important approach to study astrocytic signaling in neural circuits. Focusing on astrocytic Ca2+ activity, a key pathway implicated in astrocye-neuron interaction, we here report a strategy combining fast light sheet fluorescence microscopy (LSFM) and correlative screening-based time series analysis, to map activity domains in astrocytes in living mammalian nerve tissue. Light sheet of micron-scale thickness enables wide-field optical sectioning to image astrocytes in acute mouse brain slices. Using both chemical and genetically encoded Ca2+ indicators, we demonstrate the complementary advantages of LSFM in mapping Ca2+ domains in astrocyte populations as compared to epifluorescence and two-photon microscopy. Our approach then revealed distinct kinetics of Ca2+ signals between cortical and hypothalamic astrocytes in resting conditions and following the activation of adrenergic G protein coupled receptor (GPCR). This observation highlights the activity heterogeneity across regionally distinct astrocyte populations, and indicates the potential of our method for investigating dynamic signals in astrocytes.
Assuntos
Astrócitos/fisiologia , Encéfalo/fisiologia , Sinalização do Cálcio/fisiologia , Cálcio/metabolismo , Animais , Camundongos , Microscopia de Fluorescência , Neurônios/fisiologiaRESUMO
Astrocytes are the most abundant cell type in the central nervous system (CNS). They provide trophic support for neurons, modulate synaptic transmission and plasticity, and contribute to neuronal dysfunction. Many transgenic mouse lines have been generated to obtain astrocyte-specific expression of inducible Cre recombinase for functional studies; however, the expression patterns of inducible Cre recombinase in these lines have not been systematically characterized. We generated a new astrocyte-specific Aldh1l1-CreERT2 knock-in mouse line and compared the expression pattern of Cre recombinase between this and five widely-used transgenic lines (hGfap-CreERT2 from The Jackson Laboratory and The Mutant Mouse Resource and Research Center, Glast-CreERT2, Cx30-CreERT2, and Fgfr3-iCreERT2) by crossing with Ai14 mice, which express tdTomato fluorescence following Cre-mediated recombination. In adult Aldh1l1-CreERT2:Ai14 transgenic mice, tdTomato was detected throughout the CNS, and five novel morphologically-defined types of astrocyte were described. Among the six evaluated lines, the specificity of Cre-mediated recombination was highest when driven by Aldh1l1 and lowest when driven by hGfap; in the latter mice, co-staining between tdTomato and NeuN was observed in the hippocampus and cortex. Notably, evident leakage was noted in Fgfr3-iCreERT2 mice, and the expression level of tdTomato was low in the thalamus when Cre recombinase expression was driven by Glast and in the capsular part of the central amygdaloid nucleus when driven by Cx30. Furthermore, tdTomato was clearly expressed in peripheral organs in four of the lines. Our results emphasize that the astrocyte-specific CreERT2 transgenic lines used in functional studies should be carefully selected.
Assuntos
Astrócitos/citologia , Astrócitos/metabolismo , Integrases/genética , Integrases/metabolismo , Animais , Camundongos , Camundongos Transgênicos , NeurôniosRESUMO
The mevalonate (MVA)/cholesterol pathway is crucial for central nervous system (CNS) development and function and consequently, any dysfunction of this fundamental metabolic pathway is likely to provoke pathologic changes in the brain. Mutations in genes directly involved in MVA/cholesterol metabolism cause a range of diseases, many of which present neurologic and psychiatric symptoms. This raises the question whether other diseases presenting similar symptoms are related albeit indirectly to the MVA/cholesterol pathway. Here, we summarized the current literature suggesting links between MVA/cholesterol dysregulation and specific diseases, namely autism spectrum disorder and Rett syndrome.
Assuntos
Transtorno do Espectro Autista/metabolismo , Encéfalo/metabolismo , Colesterol/metabolismo , Homeostase , Ácido Mevalônico/metabolismo , Síndrome de Rett/metabolismo , Animais , HumanosRESUMO
The precise contribution of astrocytes in neuroinflammatory process occurring in Parkinson's disease (PD) is not well characterized. In this study, using GRCx30CreERT2 mice that are conditionally inactivated for glucocorticoid receptor (GR) in astrocytes, we have examined the actions of astrocytic GR during dopamine neuron (DN) degeneration triggered by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). The results show significantly augmented DN loss in GRCx30CreERT2 mutant mice in substantia nigra (SN) compared to controls. Hypertrophy of microglia but not of astrocytes was greatly enhanced in SN of these astrocytic GR mutants intoxicated with MPTP, indicating heightened microglial reactivity compared to similarly-treated control mice. In the SN of GR astrocyte mutants, specific inflammation-associated transcripts ICAM-1, TNF-α and Il-1ß as well as TNF-α protein levels were significantly elevated after MPTP neurotoxicity compared to controls. Interestingly, this paralleled increased connexin hemichannel activity and elevated intracellular calcium levels in astrocytes examined in acute midbrain slices from control and mutant mice treated with MPP+ . The increased connexin-43 hemichannel activity was found in vivo in MPTP-intoxicated mice. Importantly, treatment of MPTP-injected GRCx30CreERT2 mutant mice with TAT-Gap19 peptide, a specific connexin-43 hemichannel blocker, reverted both DN loss and microglial activation; in wild-type mice there was partial but significant survival effect. In the SN of post-mortem PD patients, a significant decrease in the number of astrocytes expressing nuclear GR was observed, suggesting the participation of astrocytic GR deregulation of inflammatory process in PD. Overall, these data provide mechanistic insights into GR-modulated processes in vivo, specifically in astrocytes, that contribute to a pro-inflammatory state and dopamine neurodegeneration in PD pathology.
Assuntos
Astrócitos/metabolismo , Conexinas/metabolismo , Neurônios Dopaminérgicos/metabolismo , Doença de Parkinson/genética , Animais , Humanos , Masculino , Camundongos , Doença de Parkinson/patologiaRESUMO
Amyotrophic lateral sclerosis (ALS) is a late-onset devastating degenerative disease mainly affecting motor neurons. Motor neuron degeneration is accompanied and aggravated by oligodendroglial pathology and the presence of reactive astrocytes and microglia. We studied the role of the Notch signaling pathway in ALS, as it is implicated in several processes that may contribute to this disease, including axonal retraction, microgliosis, astrocytosis, oligodendrocyte precursor cell proliferation and differentiation, and cell death. We observed abnormal activation of the Notch signaling pathway in the spinal cord of SOD1G93A mice, a well-established model for ALS, as well as in the spinal cord of patients with sporadic ALS (sALS). This increased activation was particularly evident in reactive GFAP-positive astrocytes. In addition, one of the main Notch ligands, Jagged-1, was ectopically expressed in reactive astrocytes in spinal cord from ALS mice and patients, but absent in resting astrocytes. Astrocyte-specific inactivation of Jagged-1 in presymptomatic SOD1G93A mice further exacerbated the activation of the Notch signaling pathway and aggravated the course of the disease in these animals without affecting disease onset. These data suggest that aberrant Notch signaling activation contributes to the pathogenesis of ALS, both in sALS patients and SOD1G93A mice, and that it is mitigated in part by the upregulation of astrocytic Jagged-1.
Assuntos
Esclerose Lateral Amiotrófica/metabolismo , Astrócitos/metabolismo , Proteína Jagged-1/metabolismo , Receptor Notch1/metabolismo , Transdução de Sinais/fisiologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Esclerose Lateral Amiotrófica/genética , Esclerose Lateral Amiotrófica/patologia , Animais , Astrócitos/patologia , Feminino , Humanos , Proteína Jagged-1/genética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Pessoa de Meia-Idade , Receptor Notch1/genética , Medula Espinal/metabolismo , Medula Espinal/patologia , Superóxido Dismutase/genética , Superóxido Dismutase/metabolismoRESUMO
Eukaryotic cells employ distinct means to release specific signals and material. Research within the last decade has identified different types of membrane-enclosed structures collectively called extracellular vesicles (EVs) as one of them. EVs fall into two categories depending on their subcellular origin. Exosomes are generated within the endosomal system and reach the extracellular space upon fusion of multivesicular bodies. Microvesicles or microparticles are generated by shedding of the plasma membrane. Sterols are essential components of eukaryotic membranes and serve as precursors or cofactors of numerous signaling molecules; their content and subcellular distribution are tightly controlled. The prominent roles of sterols in cells raise the question of whether and how these components impact EVs. In this review, we compile evidence for cholesterol accumulation in EVs and discuss its possible contribution to their biogenesis, release, and uptake. We also consider potential implications of EVs in cellular sterol homeostasis and in cholesterol-related diseases.
Assuntos
Colesterol/metabolismo , Vesículas Extracelulares/metabolismo , Animais , Micropartículas Derivadas de Células/metabolismo , Humanos , Transporte Proteico/fisiologia , Transdução de Sinais/fisiologiaRESUMO
Autism spectrum disorders (ASDs) present a wide range of symptoms characterized by altered sociability, compromised communication and stereotypic/repetitive behaviors. These symptoms are caused by developmental changes, but the mechanisms remain largely unknown. Some lines of evidence suggest an impairment of the cholesterol/isoprenoid metabolism in the brain as a possible cause, but systematic analyses in rodent models of ASDs are lacking. Prenatal exposure to the antiepileptic drug valproate (VPA) is a risk factor for ASDs in humans and generates a well-established model for the disease in rodents. Here, we studied cholesterol/isoprenoid metabolism in different brain areas of infant, adolescent and adult rats prenatally exposed to VPA. VPA-treated rats present autistic-like symptoms, they show changes in cholesterol/isoprenoid homeostasis in some brain areas, a decreased number of oligodendrocytes and impaired myelination in the hippocampus. Together, our data suggest a relation between brain cholesterol/isoprenoid homeostasis and ASDs.
Assuntos
Transtorno do Espectro Autista/metabolismo , Encéfalo/metabolismo , Colesterol/metabolismo , Terpenos/metabolismo , Adenilato Quinase/metabolismo , Animais , Transtorno do Espectro Autista/patologia , Encéfalo/crescimento & desenvolvimento , Encéfalo/patologia , Modelos Animais de Doenças , Feminino , Fígado/metabolismo , Masculino , Oligodendroglia/metabolismo , Oligodendroglia/patologia , Gravidez , Efeitos Tardios da Exposição Pré-Natal , Ratos Wistar , Ácido ValproicoRESUMO
Nervous tissue is characterized by a tight structural association between glial cells and neurons. It is well known that glial cells support neuronal functions, but their role under pathologic conditions is less well understood. Here, we addressed this question in vivo using an experimental model of retinal ischemia and transgenic mice for glia-specific inhibition of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)-dependent exocytosis. Transgene expression reduced glutamate, but not ATP release from single Müller cells, impaired glial volume regulation under normal conditions and reduced neuronal dysfunction and death in the inner retina during the early stages of ischemia. Our study reveals that the SNARE-dependent exocytosis in glial cells contributes to neurotoxicity during ischemia in vivo and suggests glial exocytosis as a target for therapeutic approaches.
Assuntos
Exocitose/genética , Isquemia/complicações , Degeneração Neural/etiologia , Retina/patologia , Células Ganglionares da Retina/metabolismo , Proteínas SNARE/metabolismo , Animais , Proteínas de Ligação ao Cálcio/metabolismo , Modelos Animais de Doenças , Doxiciclina/uso terapêutico , Células Ependimogliais/metabolismo , Proteína Glial Fibrilar Ácida/genética , Proteína Glial Fibrilar Ácida/metabolismo , Ácido Glutâmico/metabolismo , Filamentos Intermediários/metabolismo , Isquemia/patologia , Luz , Camundongos , Camundongos Transgênicos , Proteínas dos Microfilamentos/metabolismo , Proteína Quinase C-alfa/metabolismo , Receptores Purinérgicos P2Y1/deficiência , Receptores Purinérgicos P2Y1/genética , Proteínas SNARE/genética , Fator A de Crescimento do Endotélio Vascular/metabolismoRESUMO
Sensory processing requires proper alignment of neural maps throughout the brain. In the superficial layers of the superior colliculus of the midbrain, converging projections from retinal ganglion cells and neurons in visual cortex must be aligned to form a visuotopic map, but the basic mechanisms mediating this alignment remain elusive. In a new mouse model, ectopic expression of ephrin-A3 (Efna3) in a subset of retinal ganglion cells, quantitatively altering the retinal EFNAs gradient, disrupts cortico-collicular map alignment onto the retino-collicular map, creating a visuotopic mismatch. Genetic inactivation of ectopic EFNA3 restores a wild-type cortico-collicular map. Theoretical analyses using a new mapping algorithm model both map formation and alignment, and recapitulate our experimental observations. The algorithm is based on an initial sensory map, the retino-collicular map, which carries intrinsic topographic information, the retinal EFNAs, to the superior colliculus. These EFNAs subsequently topographically align ingrowing visual cortical axons to the retino-collicular map.
Assuntos
Axônios/fisiologia , Células Ganglionares da Retina/fisiologia , Colículos Superiores/fisiologia , Córtex Visual/fisiologia , Vias Visuais/fisiologia , Animais , Mapeamento Encefálico , Camundongos , Colículos Superiores/anatomia & histologia , Córtex Visual/anatomia & histologia , Vias Visuais/anatomia & histologiaRESUMO
During differentiation, neurons acquire their typical shape and functional properties. At present, it is unclear, whether this important developmental step involves metabolic changes. Here, we studied the contribution of the mevalonate (MVA) pathway to neuronal differentiation using the mouse neuroblastoma cell line N1E-115 as experimental model. Our results show that during differentiation, the activity of 3-hydroxy 3-methylglutaryl Coenzyme A reductase (HMGR), a key enzyme of MVA pathway, and the level of Low Density Lipoprotein receptor (LDLr) decrease, whereas the level of LDLr-related protein-1 (LRP1) and the dimerization of Scavanger Receptor B1 (SRB-1) rise. Pharmacologic inhibition of HMGR by simvastatin accelerated neuronal differentiation by modulating geranylated proteins. Collectively, our data suggest that during neuronal differentiation, the activity of the MVA pathway decreases and we postulate that any interference with this process impacts neuronal morphology and function. Therefore, the MVA pathway appears as an attractive pharmacological target to modulate neurological and metabolic symptoms of developmental neuropathologies. J. Cell. Biochem. 117: 2036-2044, 2016. © 2016 Wiley Periodicals, Inc.
Assuntos
Diferenciação Celular/fisiologia , Colesterol/biossíntese , Neurônios/metabolismo , Terpenos/metabolismo , Animais , Diferenciação Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Colesterol/genética , Hidroximetilglutaril-CoA-Redutases NADP-Dependentes/genética , Hidroximetilglutaril-CoA-Redutases NADP-Dependentes/metabolismo , Proteína-1 Relacionada a Receptor de Lipoproteína de Baixa Densidade , Camundongos , Receptores de LDL/genética , Receptores de LDL/metabolismo , Receptores Depuradores Classe B/genética , Receptores Depuradores Classe B/metabolismo , Sinvastatina/farmacologia , Proteínas Supressoras de Tumor/genética , Proteínas Supressoras de Tumor/metabolismoRESUMO
UNLABELLED: Aging and pathologic conditions cause intracellular aggregation of macromolecules and the dysfunction and degeneration of neurons, but the mechanisms are largely unknown. Prime examples are lysosomal storage disorders such as Niemann-Pick type C (NPC) disease, where defects in the endosomal-lysosomal protein NPC1 or NPC2 cause intracellular accumulation of unesterified cholesterol and other lipids leading to neurodegeneration and fatal neurovisceral symptoms. Here, we investigated the impact of NPC1 deficiency on rodent neurons using pharmacologic and genetic models of the disease. Improved ultrastructural detection of lipids and correlative light and electron microscopy identified lamellar inclusions as the subcellular site of cholesterol accumulation in neurons with impaired NPC1 activity. Immunogold labeling combined with transmission electron microscopy revealed the presence of CD63 on internal lamellae and of LAMP1 on the membrane surrounding the inclusions, indicating their origins from intraluminal vesicles of late endosomes and of a lysosomal compartment, respectively. Lamellar inclusions contained cell-intrinsic cholesterol and surface-labeled GM1, indicating the incorporation of plasma membrane components. Scanning electron microscopy revealed that the therapeutic drug candidate ß-cyclodextrin induces the subplasmalemmal location of lamellar inclusions and their subsequent release to the extracellular space. In parallel, ß-cyclodextrin mediated the NPC1-independent redistribution of cholesterol within neurons and thereby abolished a deleterious cycle of enhanced cholesterol synthesis and its intracellular accumulation, which was indicated by neuron-specific transcript analysis. Our study provides new mechanistic insight into the pathologic aggregation of macromolecules in neurons and suggests exocytosis as cellular target for its therapeutic reversal. SIGNIFICANCE STATEMENT: Many neurodegenerative diseases involve pathologic accumulation of molecules within neurons, but the subcellular location and the cellular impact are often unknown and therapeutic approaches lacking. We investigated these questions in the lysosomal storage disorder Niemann-Pick type C (NPC), where a defect in intracellular cholesterol transport causes loss of neurons and fatal neurovisceral symptoms. Here, we identify lamellar inclusions as the subcellular site of lipid accumulation in neurons, we uncover a vicious cycle of cholesterol synthesis and accretion, which may cause gradual neurodegeneration, and we reveal how ß-cyclodextrin, a potential therapeutic drug, reverts these changes. Our study provides new mechanistic insight in NPC disease and uncovers new targets for therapeutic approaches.
Assuntos
Corpos de Inclusão/metabolismo , Transtornos do Metabolismo dos Lipídeos/metabolismo , Metabolismo dos Lipídeos , Proteína 1 de Membrana Associada ao Lisossomo/metabolismo , Neurônios/metabolismo , Proteínas/metabolismo , Animais , Células Cultivadas , Feminino , Peptídeos e Proteínas de Sinalização Intracelular , Transtornos do Metabolismo dos Lipídeos/prevenção & controle , Masculino , Glicoproteínas de Membrana/metabolismo , Camundongos , Camundongos Endogâmicos BALB C , Neurônios/patologia , Proteína C1 de Niemann-Pick , Ratos , Células Ganglionares da RetinaRESUMO
Adult neurogenesis is regulated by the neurogenic niche, through mechanisms that remain poorly defined. Here, we investigated whether niche-constituting astrocytes influence the maturation of adult-born hippocampal neurons using two independent transgenic approaches to block vesicular release from astrocytes. In these models, adult-born neurons but not mature neurons showed reduced glutamatergic synaptic input and dendritic spine density that was accompanied with lower functional integration and cell survival. By taking advantage of the mosaic expression of transgenes in astrocytes, we found that spine density was reduced exclusively in segments intersecting blocked astrocytes, revealing an extrinsic, local control of spine formation. Defects in NMDA receptor (NMDAR)-mediated synaptic transmission and dendrite maturation were partially restored by exogenous D-serine, whose extracellular level was decreased in transgenic models. Together, these results reveal a critical role for adult astrocytes in local dendritic spine maturation, which is necessary for the NMDAR-dependent functional integration of newborn neurons.
Assuntos
Astrócitos/fisiologia , Hipocampo/citologia , Neurogênese/fisiologia , Neurônios/fisiologia , Sinapses/fisiologia , Animais , Astrócitos/ultraestrutura , Clostridium botulinum tipo B/genética , Clostridium botulinum tipo B/metabolismo , Espinhas Dendríticas/fisiologia , Espinhas Dendríticas/ultraestrutura , Transportador 1 de Aminoácido Excitatório/metabolismo , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Potenciais Pós-Sinápticos Excitadores/genética , Proteína Glial Fibrilar Ácida/genética , Proteína Glial Fibrilar Ácida/metabolismo , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Camundongos , Camundongos Transgênicos , Neurogênese/genética , Neurônios/ultraestrutura , Fosfopiruvato Hidratase/metabolismo , Receptores de N-Metil-D-Aspartato/genética , Receptores de N-Metil-D-Aspartato/metabolismo , Proteínas SNARE/genética , Proteínas SNARE/metabolismo , Serina/farmacologia , Cloreto de Sódio/farmacologia , Sinapses/genética , Sinapses/ultraestrutura , Transmissão Sináptica/efeitos dos fármacos , Transmissão Sináptica/genética , Tamoxifeno/farmacologiaRESUMO
In the neocortex, higher-order areas are essential to integrate sensory-motor information and have expanded in size during evolution. How higher-order areas are specified, however, remains largely unknown. Here, we show that the migration and distribution of early-born neurons, the Cajal-Retzius cells (CRs), controls the size of higher-order areas in the mouse somatosensory, auditory, and visual cortex. Using live imaging, genetics, and in silico modeling, we show that subtype-specific differences in the onset, speed, and directionality of CR migration determine their differential invasion of the developing cortical surface. CR migration speed is cell autonomously modulated by vesicle-associated membrane protein 3 (VAMP3), a classically non-neuronal mediator of endosomal recycling. Increasing CR migration speed alters their distribution in the developing cerebral cortex and leads to an expansion of postnatal higher-order areas and congruent rewiring of thalamo-cortical input. Our findings thus identify novel roles for neuronal migration and VAMP3-dependent vesicular trafficking in cortical wiring.