RESUMO
Alpha-synuclein (αSyn) and tau are abundant multifunctional neuronal proteins, and their intracellular deposits have been linked to many neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease. Despite the disease relevance, their physiological roles remain elusive, as mice with knock-out of either of these genes do not exhibit overt phenotypes. To reveal functional cooperation, we generated αSyn-/-tau-/- double-knock-out mice and characterized the functional cross talk between these proteins during brain development. Intriguingly, deletion of αSyn and tau reduced Notch signaling and accelerated interkinetic nuclear migration of G2 phase at early embryonic stage. This significantly altered the balance between the proliferative and neurogenic divisions of progenitor cells, resulting in an overproduction of early born neurons and enhanced neurogenesis, by which the brain size was enlarged during the embryonic stage in both sexes. On the other hand, a reduction in the number of neural progenitor cells in the middle stage of corticogenesis diminished subsequent gliogenesis in the αSyn-/-tau-/- cortex. Additionally, the expansion and maturation of macroglial cells (astrocytes and oligodendrocytes) were suppressed in the αSyn-/-tau-/- postnatal brain, which in turn reduced the male αSyn-/-tau-/- brain size and cortical thickness to less than the control values. Our study identifies important functional cooperation of αSyn and tau during corticogenesis.SIGNIFICANCE STATEMENT Correct understanding of the physiological functions of αSyn and tau in CNS is critical to elucidate pathogenesis involved in the etiology of neurodegenerative diseases including Alzheimer's disease and Parkinson's disease. We show here that αSyn and tau are cooperatively involved in brain development via maintenance of progenitor cells. αSyn and tau double-knock-out mice exhibited an overproduction of early born neurons and accelerated neurogenesis at early corticogenesis. Furthermore, loss of αSyn and tau also perturbed gliogenesis at later embryonic stage, as well as the subsequent glial expansion and maturation at postnatal brain. Our findings provide new mechanistic insights and extend therapeutic opportunities for neurodegenerative diseases caused by aberrant αSyn and tau.
Assuntos
Doença de Alzheimer , Doenças Neurodegenerativas , Doença de Parkinson , Doença de Alzheimer/metabolismo , Animais , Feminino , Masculino , Camundongos , Camundongos Knockout , Doenças Neurodegenerativas/metabolismo , Doença de Parkinson/patologia , alfa-Sinucleína/genética , alfa-Sinucleína/metabolismoRESUMO
Neural progenitor cells (NPCs), which are apicobasally elongated and densely packed in the developing brain, systematically move their nuclei/somata in a cell cycle-dependent manner, called interkinetic nuclear migration (IKNM): apical during G2 and basal during G1. Although intracellular molecular mechanisms of individual IKNM have been explored, how heterogeneous IKNMs are collectively coordinated is unknown. Our quantitative cell-biological and in silico analyses revealed that tissue elasticity mechanically assists an initial step of basalward IKNM. When the soma of an M-phase progenitor cell rounds up using actomyosin within the subapical space, a microzone within 10 µm from the surface, which is compressed and elastic because of the apical surface's contractility, laterally pushes the densely neighboring processes of non-M-phase cells. The pressed processes then recoil centripetally and basally to propel the nuclei/somata of the progenitor's daughter cells. Thus, indirect neighbor-assisted transfer of mechanical energy from mother to daughter helps efficient brain development.
Assuntos
Divisão do Núcleo Celular/fisiologia , Núcleo Celular/fisiologia , Células-Tronco Neurais/fisiologia , Células Neuroepiteliais/fisiologia , Actomiosina/química , Actomiosina/metabolismo , Animais , Fenômenos Biomecânicos , Ciclo Celular/efeitos dos fármacos , Ciclo Celular/fisiologia , Núcleo Celular/efeitos dos fármacos , Núcleo Celular/ultraestrutura , Divisão do Núcleo Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Córtex Cerebral/citologia , Córtex Cerebral/fisiologia , Elasticidade , Embrião de Mamíferos , Transferência de Energia , Compostos Heterocíclicos de 4 ou mais Anéis/farmacologia , Camundongos , Camundongos Endogâmicos ICR , Movimento/fisiologia , Células-Tronco Neurais/citologia , Células-Tronco Neurais/efeitos dos fármacos , Células Neuroepiteliais/citologia , Células Neuroepiteliais/efeitos dos fármacos , Imagem com Lapso de TempoRESUMO
Morphogenesis and organ development should be understood based on a thorough description of cellular dynamics. Recent studies have explored the dynamic behaviors of mammalian neural progenitor cells (NPCs) using slice cultures in which three-dimensional systems conserve in vivo-like environments to a considerable degree. However, live observation of NPCs existing truly in vivo, as has long been performed for zebrafish NPCs, has yet to be established in mammals. Here, we performed intravital two-photon microscopic observation of NPCs in the developing cerebral cortex of H2B-EGFP or Fucci transgenic mice in utero. Fetuses in the uterine sac were immobilized using several devices and were observed through a window made in the uterine wall and the amniotic membrane while monitoring blood circulation. Clear visibility was obtained to the level of 300 µm from the scalp surface of the fetus, which enabled us to quantitatively assess NPC behaviors, such as division and interkinetic nuclear migration, within a neuroepithelial structure called the ventricular zone at embryonic day (E) 13 and E14. In fetuses undergoing healthy monitoring in utero for 60 min, the frequency of mitoses observed at the apical surface was similar to those observed in slice cultures and in freshly fixed in vivo specimens. Although the rate and duration of successful in utero observations are still limited (33% for ≥10 min and 14% for 60 min), further improvements based on this study will facilitate future understanding of how organogenetic cellular behaviors occur or are pathologically influenced by the systemic maternal condition and/or maternal-fetal relationships.
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Microscopia/métodos , Neocórtex/embriologia , Células-Tronco Neurais/citologia , Animais , Divisão Celular/fisiologia , Células CultivadasRESUMO
To achieve highly sensitive and comprehensive assessment of the morphology and dynamics of cells committed to the neuronal lineage in mammalian brain primordia, we generated two transgenic mouse lines expressing a destabilized (d4) Venus controlled by regulatory elements of the Neurogenin2 (Neurog2) or Gadd45g gene. In mid-embryonic neocortical walls, expression of Neurog2-d4Venus mostly overlapped with that of Neurog2 protein, with a slightly (1 h) delayed onset. Although Neurog2-d4Venus and Gadd45g-d4Venus mice exhibited very similar labeling patterns in the ventricular zone (VZ), in Gadd45g-d4Venus mice cells could be visualized in more basal areas containing fully differentiated neurons, where Neurog2-d4Venus fluorescence was absent. Time-lapse monitoring revealed that most d4Venus(+) cells in the VZ had processes extending to the apical surface; many of these cells eventually retracted their apical process and migrated basally to the subventricular zone, where neurons, as well as the intermediate neurogenic progenitors that undergo terminal neuron-producing division, could be live-monitored by d4Venus fluorescence. Some d4Venus(+) VZ cells instead underwent nuclear migration to the apical surface, where they divided to generate two d4Venus(+) daughter cells, suggesting that the symmetric terminal division that gives rise to neuron pairs at the apical surface can be reliably live-monitored. Similar lineage-committed cells were observed in other developing neural regions including retina, spinal cord, and cerebellum, as well as in regions of the peripheral nervous system such as dorsal root ganglia. These mouse lines will be useful for elucidating the cellular and molecular mechanisms underlying development of the mammalian nervous system.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Encéfalo/citologia , Encéfalo/embriologia , Proteínas de Transporte/metabolismo , Linhagem da Célula , Movimento Celular , Mitose , Proteínas do Tecido Nervoso/metabolismo , Neurônios/citologia , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Proteínas de Transporte/genética , Diferenciação Celular , Células Cultivadas , Peptídeos e Proteínas de Sinalização Intracelular , Camundongos , Camundongos Transgênicos , Mitose/genética , Proteínas do Tecido Nervoso/genética , Neurônios/metabolismo , Imagem com Lapso de TempoRESUMO
The Delta-Notch system plays a vital role in many areas of biology and typically forms a salt and pepper pattern in which cells strongly expressing Delta and cells strongly expressing Notch are alternately aligned via lateral inhibition. In this study, we consider cell rearrangement events, such as cell mixing and proliferation, that alter the spatial structure itself and affect the pattern dynamics. We model cell rearrangement events by a Poisson process and analyze the model while preserving the discrete properties of the spatial structure. We investigate the effects of the intermittent perturbations arising from these cell rearrangement events on the discrete spatial structure itself in the context of pattern formation and by using an analytical approach, coupled with numerical simulation. We find that the homogeneous expression pattern is stabilized if the frequency of cell rearrangement events is sufficiently large. We analytically obtain the balanced frequencies of the cell rearrangement events where the decrease of the pattern amplitude, as a result of cell rearrangement, is balanced by the increase in amplitude due to the Delta-Notch interaction dynamics. Our framework, while applied here to the specific case of the Delta-Notch system, is applicable more widely to other pattern formation mechanisms.
Assuntos
Receptores Notch , Transdução de Sinais , Receptores Notch/metabolismo , Proteínas de Membrana/metabolismo , Comunicação Celular/fisiologia , Diferenciação CelularRESUMO
Correct neuronal migration is crucial for brain architecture and function. During cerebral cortex development (corticogenesis), excitatory neurons generated in the proliferative zone of the dorsal telencephalon (mainly ventricular zone) move through the intermediate zone and migrate past the neurons previously located in the cortical plate and come to rest just beneath the marginal zone. The in utero electroporation technique is a powerful method for rapid gain- and loss-of-function studies of neuronal development, especially neuronal migration. This method enabled us to introduce genes of interest into ventricular zone progenitor cells of mouse embryos and to observe resulting phenotypes such as proliferation, migration, and cell morphology at later stages. In this Award Lecture Review, we focus on the application of the in utero electroporation method to functional analyses of cytoskeleton-related protein septin. We then refer to, as an advanced technique, the in utero electroporation-based real-time imaging method for analyses of cell signaling regulating neuronal migration. The in utero electroporation method and its application would contribute to medical molecular morphology through identification and characterization of the signaling pathways disorganized in various neurological and psychiatric disorders.
Assuntos
Encéfalo/embriologia , Movimento Celular/fisiologia , Eletroporação/métodos , Embrião de Mamíferos/metabolismo , Neurônios/fisiologia , Útero/metabolismo , Animais , Embrião de Mamíferos/fisiologia , Feminino , Humanos , Camundongos , Gravidez , Septinas/genética , Septinas/metabolismoRESUMO
Schizophrenia is a complex mental disorder with fairly high level of heritability. Dystrobrevin binding protein 1, a gene encoding dysbindin protein, is a susceptibility gene for schizophrenia that was identified by family-based association analysis. Recent studies revealed that dysbindin is involved in the exocytosis and/or formation of synaptic vesicles. However, the molecular function of dysbindin in synaptic transmission is largely unknown. To investigate the signaling pathway in which dysbindin is involved, we isolated dysbindin-interacting molecules from rat brain lysate by combining ammonium sulfate precipitation and dysbindin-affinity column chromatography, and identified dysbindin-interacting proteins by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and liquid chromatography-tandem mass spectrometry. Proteins involved in protein localization process, including Munc18-1, were identified as dysbindin-interacting proteins. Munc18-1 was co-immunoprecipitated with dysbindin from rat brain lysate, and directly interacted with dysbindin in vitro. In primary cultured rat hippocampal neurons, a part of dysbindin was co-localized with Munc18-1 at pre-synaptic terminals. Our result suggests a role for dysbindin in synaptic vesicle exocytosis via interaction with Munc18-1.
Assuntos
Proteínas de Transporte/metabolismo , Proteômica/métodos , Esquizofrenia/metabolismo , Animais , Proteínas de Transporte/genética , Disbindina , Proteínas Associadas à Distrofina , Exocitose/genética , Hipocampo/metabolismo , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Proteínas Munc18/genética , Proteínas Munc18/metabolismo , Ligação Proteica/genética , Ratos , Esquizofrenia/genéticaRESUMO
Despite recent studies elucidating the molecular mechanisms underlying cortical patterning and map formation, very little is known about how the embryonic pallium expands ventrally to form the future cortex and the nature of the underlying force-generating events. We find that neurons born at embryonic day 10 (E10) in the mouse dorsal pallium ventrally stream until E13, thereby superficially spreading the preplate, and then constitute the subplate from E14. From E11 to E12, the preplate neurons migrate, exerting pulling and pushing forces at the process and the soma, respectively. At E13, they are morphologically heterogeneous, with â¼40% possessing corticofugal axons, which are found to be in tension. Ablation of these E10-born neurons attenuates both deflection of radial glial fibers (by E13) and extension of the cortical plate (by E14), which should occur ventrally, and subsequently shrinks the postnatal neocortical map dorsally. Thus, the preplate stream physically primes neocortical expansion and arealization.
Assuntos
Axônios/fisiologia , Córtex Cerebral/embriologia , Células Ependimogliais/citologia , Neocórtex/embriologia , Neurônios/fisiologia , Animais , Axônios/metabolismo , Movimento Celular , Córtex Cerebral/citologia , Córtex Cerebral/fisiologia , Embrião de Mamíferos/embriologia , Embrião de Mamíferos/metabolismo , Desenvolvimento Embrionário , Células Ependimogliais/metabolismo , Células Ependimogliais/fisiologia , Camundongos , Camundongos Knockout , Neocórtex/citologia , Neocórtex/metabolismo , Neocórtex/fisiologia , Neurônios/citologia , Córtex Somatossensorial/citologia , Córtex Somatossensorial/embriologia , Córtex Somatossensorial/metabolismoRESUMO
Disrupted-in-Schizophrenia-1 (DISC1) is a candidate gene for susceptibility of schizophrenia. In the accompanying paper (Taya et al., 2006), we report that DISC1 acts as a linker between Kinesin-1 and DISC1-interacting molecules, such as NudE-like, lissencephaly-1, and 14-3-3epsilon. Here we identified growth factor receptor bound protein 2 (Grb2) as a novel DISC1-interacting molecule. Grb2 acts as an adaptor molecule that links receptor tyrosine kinases and the Ras-extracellular signal-regulated kinase (ERK) pathway. DISC1 formed a ternary complex with Grb2 and kinesin heavy chain KIF5A of Kinesin-1. In cultured rat hippocampal neurons, both DISC1 and Grb2 partially colocalized at the distal part of axons. Knockdown of DISC1 or kinesin light chains of Kinesin-1 by RNA interference inhibited the accumulation of Grb2 from the distal part of axons. Knockdown of DISC1 also inhibited the neurotrophin-3 (NT-3)-induced phosphorylation of ERK-1/2 at the distal part of axons and inhibited NT-3-induced axon elongation. These results suggest that DISC1 is required for NT-3-induced axon elongation and ERK activation at the distal part of axons by recruiting Grb2 to axonal tips.
Assuntos
Axônios/metabolismo , Axônios/ultraestrutura , Proteína Adaptadora GRB2/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Neurotrofina 3/administração & dosagem , Animais , Axônios/efeitos dos fármacos , Transporte Biológico Ativo/efeitos dos fármacos , Encéfalo/citologia , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Células COS , Crescimento Celular , Células Cultivadas , Chlorocebus aethiops , Relação Dose-Resposta a Droga , Homeostase/efeitos dos fármacos , Homeostase/fisiologia , Mapeamento de Interação de Proteínas , RatosRESUMO
Disrupted-In-Schizophrenia 1 (DISC1) is a candidate gene for susceptibility to schizophrenia. DISC1 is reported to interact with NudE-like (NUDEL), which forms a complex with lissencephaly-1 (LIS1) and 14-3-3epsilon. 14-3-3epsilon is involved in the proper localization of NUDEL and LIS1 in axons. Although the functional significance of this complex in neuronal development has been reported, the transport mechanism of the complex into axons and their functions in axon formation remain essentially unknown. Here we report that Kinesin-1, a motor protein of anterograde axonal transport, was identified as a novel DISC1-interacting molecule. DISC1 directly interacted with kinesin heavy chain of Kinesin-1. Kinesin-1 interacted with the NUDEL/LIS1/14-3-3epsilon complex through DISC1, and these molecules localized mainly at cell bodies and partially in the distal part of the axons. DISC1 partially colocalized with Kinesin family member 5A, NUDEL, LIS1, and 14-3-3epsilon in the growth cones. The knockdown of DISC1 by RNA interference or the dominant-negative form of DISC1 inhibited the accumulation of NUDEL, LIS1, and 14-3-3epsilon at the axons and axon elongation. The knockdown or the dominant-negative form of Kinesin-1 inhibited the accumulation of DISC1 at the axons and axon elongation. Furthermore, the knockdown of NUDEL or LIS1 inhibited axon elongation. Together, these results indicate that DISC1 regulates the localization of NUDEL/LIS1/14-3-3epsilon complex into the axons as a cargo receptor for axon elongation.
Assuntos
Proteínas 14-3-3/metabolismo , Axônios/metabolismo , Axônios/ultraestrutura , Cisteína Endopeptidases/metabolismo , Cinesinas/metabolismo , Proteínas Motores Moleculares/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Animais , Transporte Biológico Ativo , Células COS , Crescimento Celular , Chlorocebus aethiops , Homeostase/fisiologia , Células PC12 , RatosRESUMO
Human mutations in KATNB1 (p80) cause severe congenital cortical malformations, which encompass the clinical features of both microcephaly and lissencephaly. Although p80 plays critical roles during brain development, the underlying mechanisms remain predominately unknown. Here, we demonstrate that p80 regulates microtubule (MT) remodeling in combination with NuMA (nuclear mitotic apparatus protein) and cytoplasmic dynein. We show that p80 shuttles between the nucleus and spindle pole in synchrony with the cell cycle. Interestingly, this striking feature is shared with NuMA. Importantly, p80 is essential for aster formation and maintenance in vitro. siRNA-mediated depletion of p80 and/or NuMA induced abnormal mitotic phenotypes in cultured mouse embryonic fibroblasts and aberrant neurogenesis and neuronal migration in the mouse embryonic brain. Importantly, these results were confirmed in p80-mutant harboring patient-derived induced pluripotent stem cells and brain organoids. Taken together, our findings provide valuable insights into the pathogenesis of severe microlissencephaly, in which p80 and NuMA delineate a common pathway for neurogenesis and neuronal migration via MT organization at the centrosome/spindle pole.
Assuntos
Adenosina Trifosfatases/metabolismo , Fibroblastos/fisiologia , Células-Tronco Pluripotentes Induzidas/fisiologia , Katanina/metabolismo , Microtúbulos/metabolismo , Malformações do Sistema Nervoso/metabolismo , Neurônios/fisiologia , Proteínas Nucleares/metabolismo , Adenosina Trifosfatases/genética , Animais , Proteínas de Ciclo Celular , Dineínas/metabolismo , Células HeLa , Humanos , Katanina/genética , Camundongos , Camundongos Endogâmicos , Mitose/genética , Mutação/genética , Malformações do Sistema Nervoso/genética , Neurogênese/genética , Proteínas Nucleares/genética , RNA Interferente Pequeno/genéticaRESUMO
It has been proposed that four members of the plexin A subfamily (plexin-As; plexin-A1, -A2, -A3, and -A4) and two neuropilins (neuropilin-1 and neuropilin-2) form complexes and serve as receptors for class 3 secreted semaphorins (Semas), potent neural chemorepellents. The roles of given plexin-As in semaphorin signaling and axon guidance, however, are mostly unknown. Here, to elucidate functions of plexin-A4 in semaphorin signaling and axon guidance events in vivo, we generated plexin-A4 null mutant mice by targeted disruption of the plexin-A4 gene. Plexin-A4 mutant mice were defective in the trajectory and projection of peripheral sensory axons and sympathetic ganglion (SG) axons and the formation of the anterior commissure and the barrels. The defects in peripheral sensory and SG axons were fundamentally related to those of neuropilin-1 or Sema3A mutant embryos reported but were more moderate than the phenotype in these mutants. The growth cone collapse assay showed that dorsal root ganglion axons and SG axons of plexin-A4 mutant embryos partially lost their responsiveness to Sema3A. These results suggest that plexin-A4 plays roles in the propagation of Sema3A activities and regulation of axon guidance and that other members of the plexin-A subfamily are also involved in the propagation of Sema3A activities. Plexin-A4-deficient SG axons did not lose their responsiveness to Sema3F, suggesting that plexin-A4 serves as a Sema3A-specific receptor, at least in SG axons. In addition, the present study showed that plexin-A4 bound class 6 transmembrane semaphorins, Sema6A and Sema6B, and mediated their axon-repulsive activities, independently of neuropilin-1. Our results imply that plexin-A4 mediates multiple semaphorin signals and regulates axon guidance in vivo.
Assuntos
Axônios/fisiologia , Fibras Nervosas/fisiologia , Proteínas do Tecido Nervoso/fisiologia , Neurônios/citologia , Receptores de Superfície Celular/fisiologia , Semaforinas/metabolismo , Animais , Animais Recém-Nascidos , Moléculas de Adesão Celular Neuronais/metabolismo , Células Cultivadas , Clonagem Molecular/métodos , Contactina 2 , Relação Dose-Resposta a Droga , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Embrião de Mamíferos , Gânglios Espinais/citologia , Gânglios Espinais/metabolismo , Regulação da Expressão Gênica no Desenvolvimento/genética , Imuno-Histoquímica/métodos , Hibridização In Situ/métodos , Camundongos , Camundongos Knockout , Proteínas do Tecido Nervoso/deficiência , Neuritos/metabolismo , Neurônios/metabolismo , Neuropilina-1/metabolismo , Prosencéfalo/embriologia , Prosencéfalo/metabolismo , Receptores de Superfície Celular/deficiência , Proteínas Recombinantes/metabolismo , Semaforinas/farmacocinética , Sistema Nervoso Simpático/metabolismo , Tubulina (Proteína)/metabolismo , Tirosina 3-Mono-Oxigenase/metabolismoRESUMO
Cell-producing events in developing tissues are mechanically dynamic throughout the cell cycle. In many epithelial systems, cells are apicobasally tall, with nuclei and somata that adopt different apicobasal positions because nuclei and somata move in a cell cycle-dependent manner. This movement is apical during G2 phase and basal during G1 phase, whereas mitosis occurs at the apical surface. These movements are collectively referred to as interkinetic nuclear migration, and such epithelia are called "pseudostratified." The embryonic mammalian cerebral cortical neuroepithelium is a good model for highly pseudostratified epithelia, and we previously found differences between mice and ferrets in both horizontal cellular density (greater in ferrets) and nuclear/somal movements (slower during G2 and faster during G1 in ferrets). These differences suggest that neuroepithelial cells alter their nucleokinetic behavior in response to physical factors that they encounter, which may form the basis for evolutionary transitions toward more abundant brain-cell production from mice to ferrets and primates. To address how mouse and ferret neuroepithelia may differ physically in a quantitative manner, we used atomic force microscopy to determine that the vertical stiffness of their apical surface is greater in ferrets (Young's modulus = 1700 Pa) than in mice (1400 Pa). We systematically analyzed factors underlying the apical-surface stiffness through experiments to pharmacologically inhibit actomyosin or microtubules and to examine recoiling behaviors of the apical surface upon laser ablation and also through electron microscopy to observe adherens junction. We found that although both actomyosin and microtubules are partly responsible for the apical-surface stiffness, the mouse
RESUMO
In the olfactory epithelium (OE), olfactory cells (OCs) and supporting cells (SCs), which express different cadherins, are arranged in a characteristic mosaic pattern in which OCs are enclosed by SCs. However, the mechanism underlying this cellular patterning is unclear. Here, we show that the cellular pattern of the OE is established by cellular rearrangements during development. In the OE, OCs express nectin-2 and N-cadherin, and SCs express nectin-2, nectin-3, E-cadherin, and N-cadherin. Heterophilic trans-interaction between nectin-2 on OCs and nectin-3 on SCs preferentially recruits cadherin via α-catenin to heterotypic junctions, and the differential distributions of cadherins between junctions promote cellular intercalations, resulting in the formation of the mosaic pattern. These observations are confirmed by model cell systems, and various cellular patterns are generated by the combinatorial expression of nectins and cadherins. Collectively, the synergistic action of nectins and cadherins generates mosaic pattern, which cannot be achieved by a single mechanism.
Assuntos
Caderinas/metabolismo , Moléculas de Adesão Celular/metabolismo , Mucosa Olfatória/citologia , Mucosa Olfatória/metabolismo , Animais , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , NectinasRESUMO
Disrupted-in-schizophrenia 1 (DISC1) is a susceptibility gene for major psychiatric disorders, including schizophrenia. DISC1 has been implicated in neurodevelopment in relation to scaffolding signal complexes. Here we used proteomic analysis to screen for DISC1 interactors and identified several RNA-binding proteins, such as hematopoietic zinc finger (HZF), that act as components of RNA-transporting granules. HZF participates in the mRNA localization of inositol-1,4,5-trisphosphate receptor type 1 (ITPR1), which plays a key role in synaptic plasticity. DISC1 colocalizes with HZF and ITPR1 mRNA in hippocampal dendrites and directly associates with neuronal mRNAs, including ITPR1 mRNA. The binding potential of DISC1 for ITPR1 mRNA is facilitated by HZF. Studies of Disc1-knockout mice have revealed that DISC1 regulates the dendritic transport of Itpr1 mRNA by directly interacting with its mRNA. The DISC1-mediated mRNA regulation is involved in synaptic plasticity. We show that DISC1 binds ITPR1 mRNA with HZF, thereby regulating its dendritic transport for synaptic plasticity.
Assuntos
Hipocampo/metabolismo , Receptores de Inositol 1,4,5-Trifosfato/genética , Proteínas do Tecido Nervoso/fisiologia , Plasticidade Neuronal/fisiologia , Proteínas/fisiologia , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA/fisiologia , Regiões 3' não Traduzidas/genética , Animais , Transporte Biológico , Grânulos Citoplasmáticos/metabolismo , Dendritos/metabolismo , Dendritos/ultraestrutura , Hipocampo/citologia , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Proteínas do Tecido Nervoso/deficiência , Proteínas do Tecido Nervoso/genética , Plasticidade Neuronal/genética , Ligação Proteica , Mapeamento de Interação de Proteínas , Interferência de RNA , Proteínas de Ligação a RNA/genética , Proteínas Recombinantes de Fusão/metabolismoRESUMO
The neuroepithelium (NE) or ventricular zone (VZ), from which multiple types of brain cells arise, is pseudostratified. In the NE/VZ, neural progenitor cells are elongated along the apicobasal axis, and their nuclei assume different apicobasal positions. These nuclei move in a cell cycle-dependent manner, i.e., apicalward during G2 phase and basalward during G1 phase, a process called interkinetic nuclear migration (INM). This review will summarize and discuss several topics: the nature of the INM exhibited by neural progenitor cells, the mechanical difficulties associated with INM in the developing cerebral cortex, the community-level mechanisms underlying collective and efficient INM, the impact on overall brain formation when NE/VZ is overcrowded due to loss of INM, and whether and how neural progenitor INM varies among mammalian species. These discussions will be based on recent findings obtained in live, three-dimensional specimens using quantitative and mechanical approaches. Experiments in which overcrowding was induced in mouse neocortical NE/VZ, as well as comparisons of neocortical INM between mice and ferrets, have revealed that the behavior of NE/VZ cells can be affected by cellular densification. A consideration of the physical aspects in the NE/VZ and the mechanical difficulties associated with high-degree pseudostratification (PS) is important for achieving a better understanding of neocortical development and evolution.
RESUMO
The thick outer subventricular zone (OSVZ) is characteristic of the development of human neocortex. How this region originates from the ventricular zone (VZ) is largely unknown. Recently, we showed that over-proliferation-induced acute nuclear densification and thickening of the VZ in neocortical walls of mice, which lack an OSVZ, causes reactive delamination of undifferentiated progenitors and invasion by these cells of basal areas outside the VZ. In this study, we sought to determine how VZ cells behave in non-rodent animals that have an OSVZ. A comparison of mid-embryonic mice and ferrets revealed: (1) the VZ is thicker and more pseudostratified in ferrets. (2) The soma and nuclei of VZ cells were horizontally and apicobasally denser in ferrets. (3) Individual endfeet were also denser on the apical (ventricular) surface in ferrets. (4) In ferrets, apicalward nucleokinesis was less directional, whereas basalward nucleokinesis was more directional; consequently, the nuclear density in the periventricular space (within 16 µm of the apical surface) was smaller in ferrets than in mice, despite the nuclear densification seen basally in ferrets. These results suggest that species-specific differences in nucleokinesis strategies may have evolved in close association with the magnitudes and patterns of nuclear stratification in the VZ.
Assuntos
Transporte Ativo do Núcleo Celular/fisiologia , Núcleo Celular/fisiologia , Ventrículos Laterais/citologia , Neocórtex/anatomia & histologia , Células-Tronco Neurais/fisiologia , Animais , Animais Geneticamente Modificados , Ciclo Celular , Embrião de Mamíferos , Proteínas do Olho/metabolismo , Feminino , Furões , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Proteínas de Homeodomínio/metabolismo , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/metabolismo , Camundongos , Camundongos Endogâmicos ICR , Neocórtex/embriologia , Fator de Transcrição PAX6 , Fatores de Transcrição Box Pareados/metabolismo , Gravidez , Proteínas Repressoras/metabolismo , Especificidade da Espécie , Estatísticas não Paramétricas , Proteína da Zônula de Oclusão-1/metabolismoRESUMO
Neural progenitors exhibit cell cycle-dependent interkinetic nuclear migration (INM) along the apicobasal axis. Despite recent advances in understanding its underlying molecular mechanisms, the processes to which INM contributes mechanically and the regulation of INM by the apicobasally elongated morphology of progenitors remain unclear. We found that knockdown of the cell-surface molecule TAG-1 resulted in retraction of neocortical progenitors' basal processes. Highly shortened stem-like progenitors failed to undergo basalward INM and became overcrowded in the periventricular (subapical) space. Surprisingly, the overcrowded progenitors left the apical surface and migrated into basal neuronal territories. These observations, together with the results of in toto imaging and physical tests, suggest that progenitors may sense and respond to excessive mechanical stress. Although, unexpectedly, the heterotopic progenitors remained stem-like and continued to sequentially produce neurons until the late embryonic period, histogenesis was severely disrupted. Thus, INM is essential for preventing overcrowding of nuclei and their somata, thereby ensuring normal brain histogenesis.
Assuntos
Ciclo Celular/fisiologia , Núcleo Celular/metabolismo , Contactina 2/metabolismo , Células-Tronco Neurais/ultraestrutura , Animais , Ciclo Celular/genética , Membrana Celular/metabolismo , Núcleo Celular/genética , Proliferação de Células , Córtex Cerebral/citologia , Simulação por Computador , Contactina 2/genética , Embrião de Mamíferos , Epitélio/embriologia , Epitélio/fisiologia , Histonas/metabolismo , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , Camundongos , Camundongos Endogâmicos ICR , Camundongos Transgênicos , Modelos Biológicos , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Células-Tronco Neurais/fisiologia , Técnicas de Cultura de Órgãos , Interferência de RNA/fisiologia , RNA Interferente Pequeno/metabolismo , Proteína Wnt3A/genética , Proteína Wnt3A/metabolismoRESUMO
Septins are a family of conserved guanosine triphosphate/guanosine diphosphate-binding proteins implicated in a variety of cellular functions such as cell cycle control and cytokinesis. Although several members of septin family, including Septin 14 (Sept14), are abundantly expressed in nervous tissues, little is known about their physiological functions, especially in neuronal development. Here, we report that Sept14 is strongly expressed in the cortical plate of developing cerebral cortex. Knockdown experiments by using the method of in utero electroporation showed that reduction of Sept14 caused inhibition of cortical neuronal migration. Whereas cDNA encoding RNA interference-resistant Sept14 rescued the migration defect, the C-terminal deletion mutant of Sept14 did not. Biochemical analyses revealed that C-terminal coiled-coil region of Sept14 interacts with Septin 4 (Sept4). Knockdown experiments showed that Sept4 is also involved in cortical neuronal migration in vivo. In addition, knockdown of Sept14 or Sept4 inhibited leading process formation in migrating cortical neurons. These results suggest that Sept14 is involved in neuronal migration in cerebral cortex via interaction with Sept4.