RESUMO
Cholinergic neurons in the basal forebrain play a crucial role in regulating adult hippocampal neurogenesis (AHN). However, the circuit and molecular mechanisms underlying cholinergic modulation of AHN, especially the initial stages of this process related to the generation of newborn progeny from quiescent radial neural stem cells (rNSCs), remain unclear. Here, we report that stimulation of the cholinergic circuits projected from the diagonal band of Broca (DB) to the dentate gyrus (DG) neurogenic niche promotes proliferation and morphological development of rNSCs, resulting in increased neural stem/progenitor pool and rNSCs with longer radial processes and larger busy heads. Interestingly, DG granule cells (GCs) are required for DB-DG cholinergic circuit-dependent modulation of proliferation and morphogenesis of rNSCs. Furthermore, single-nucleus RNA sequencing of DG reveals cell type-specific transcriptional changes in response to cholinergic circuit stimulation, with GCs (among all the DG niche cells) exhibiting the most extensive transcriptional changes. Our findings shed light on how the DB-DG cholinergic circuits orchestrate the key niche components to support neurogenic function and morphogenesis of rNSCs at the circuit and molecular levels.
Assuntos
Neurônios Colinérgicos , Giro Denteado , Células-Tronco Neurais , Neurogênese , Animais , Células-Tronco Neurais/metabolismo , Células-Tronco Neurais/citologia , Giro Denteado/metabolismo , Giro Denteado/citologia , Neurogênese/fisiologia , Neurônios Colinérgicos/metabolismo , Neurônios Colinérgicos/fisiologia , Camundongos , Proliferação de Células , Células-Tronco Adultas/metabolismo , Células-Tronco Adultas/fisiologia , Células-Tronco Adultas/citologia , Morfogênese , Nicho de Células-Tronco/fisiologia , MasculinoRESUMO
Developmental exposure to nonylphenol (NP) results in irreversible impairments of the central nervous system (CNS). The neural precursor cell (NPC) pool located in the subgranular zone (SGZ), a substructure of the hippocampal dentate gyrus, is critical for the development of hippocampal circuits and some hippocampal functions such as learning and memory. However, the effects of developmental exposure to NP on this pool remain unclear. Thus, our aim was to clarify the impacts of developmental exposure to NP on this pool and to explore the potential mechanisms. Animal models of developmental exposure to NP were created by treating Wistar rats with NP during pregnancy and lactation. Our data showed that developmental exposure to NP decreased Sox2-and Ki67-positive cells in the SGZ of offspring. Inhibited activation of Shh signaling and decreased levels of its downstream mediators, E2F1 and cyclins, were also observed in pups developmentally exposed to NP. Moreover, we established the in vitro model in the NE-4C cells, a neural precursor cell line, to further investigate the effect of NP exposure on NPCs and the underlying mechanisms. Purmorphamine, a small purine-derived hedgehog agonist, was used to specifically modulate the Shh signaling. Consistent with the in vivo results, exposure to NP reduced cell proliferation by inhibiting the Shh signaling in NE-4C cells, and purmorphamine alleviated this reduction in cell proliferation by restoring this signaling. Altogether, our findings support the idea that developmental exposure to NP leads to inhibition of the NPC proliferation and the NPC pool depletion in the SGZ located in the dentate gyrus. Furthermore, we also provided the evidence that suppressed activation of Shh signaling may contribute to the effects of developmental exposure to NP on the NPC pool.
Assuntos
Proliferação de Células , Giro Denteado , Proteínas Hedgehog , Células-Tronco Neurais , Fenóis , Ratos Wistar , Transdução de Sinais , Animais , Giro Denteado/efeitos dos fármacos , Giro Denteado/metabolismo , Giro Denteado/citologia , Células-Tronco Neurais/efeitos dos fármacos , Células-Tronco Neurais/metabolismo , Células-Tronco Neurais/citologia , Proteínas Hedgehog/metabolismo , Fenóis/farmacologia , Fenóis/toxicidade , Feminino , Gravidez , Ratos , Transdução de Sinais/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Purinas/farmacologia , Morfolinas/farmacologia , Efeitos Tardios da Exposição Pré-Natal/induzido quimicamente , Efeitos Tardios da Exposição Pré-Natal/metabolismo , Masculino , Fatores de Transcrição SOXB1/metabolismo , Linhagem CelularRESUMO
Real-time approaches are typically needed in studies of learning and memory, and in vivo calcium imaging provides the possibility to investigate neuronal activity in awake animals during behavior tasks. Since the hippocampus is closely associated with episodic and spatial memory, it has become an essential brain region in this field's research. In recent research, engram cells and place cells were studied by recording the neural activities in the hippocampal CA1 region using the miniature microscope in mice while performing behavioral tasks including open-field and linear track. Although the dentate gyrus is another important region in the hippocampus, it has rarely been studied with in vivo imaging due to its greater depth and difficulty for imaging. In this protocol, we present in detail a calcium imaging process, including how to inject the virus, implant a GRIN (Gradient-index) lens, and attach a base plate for imaging the dentate gyrus of the hippocampus. We further describe how to preprocess the calcium imaging data using MATLAB. Additionally, studies of other deep brain regions that require imaging may benefit from this method.
Assuntos
Cálcio , Giro Denteado , Neurônios , Animais , Giro Denteado/citologia , Giro Denteado/diagnóstico por imagem , Camundongos , Cálcio/metabolismo , Cálcio/análise , Neurônios/citologiaRESUMO
Many types of neurons exhibit a daily rhythm of intrinsic excitability. Here, we present a protocol for assessing circadian regulation of dentate granule cell excitability using a mouse model for conditional knockout of the molecular clock protein BMAL1. We describe steps for obtaining healthy oblique horizontal slices that contain the hippocampus and measuring intrinsic excitability and synaptic potentials by combining whole-cell patch-clamp recordings and perforant-path electric stimulation. We then detail procedures for validating single-cell genetic deletion of Bmal1 by immunohistochemistry. For complete details on the use and execution of this protocol, please refer to Gonzalez et al.1.
Assuntos
Ritmo Circadiano , Giro Denteado , Animais , Camundongos , Giro Denteado/citologia , Giro Denteado/metabolismo , Giro Denteado/fisiologia , Ritmo Circadiano/fisiologia , Técnicas de Patch-Clamp/métodos , Neurônios/metabolismo , Neurônios/fisiologia , Neurônios/citologia , Fatores de Transcrição ARNTL/metabolismo , Fatores de Transcrição ARNTL/genética , Camundongos Knockout , MasculinoRESUMO
Complex systems are neither fully determined nor completely random. Biological complex systems, including single neurons, manifest intermediate regimes of randomness that recruit integration of specific combinations of functionally specialized subsystems. Such emergence of biological function provides the substrate for the expression of degeneracy, the ability of disparate combinations of subsystems to yield similar function. Here, we present evidence for the expression of degeneracy in morphologically realistic models of dentate gyrus granule cells (GCs) through functional integration of disparate ion-channel combinations. We performed a 45-parameter randomized search spanning 16 active and passive ion channels, each biophysically constrained by their gating kinetics and localization profiles, to search for valid GC models. Valid models were those that satisfied 17 sub- and suprathreshold cellular-scale electrophysiological measurements from rat GCs. A vast majority (>99%) of the 15,000 random models were not electrophysiologically valid, demonstrating that arbitrarily random ion-channel combinations would not yield GC functions. The 141 valid models (0.94% of 15,000) manifested heterogeneities in and cross-dependencies across local and propagating electrophysiological measurements, which matched with their respective biological counterparts. Importantly, these valid models were widespread throughout the parametric space and manifested weak cross-dependencies across different parameters. These observations together showed that GC physiology could neither be obtained by entirely random ion-channel combinations nor is there an entirely determined single parametric combination that satisfied all constraints. The complexity, the heterogeneities in measurement and parametric spaces, and degeneracy associated with GC physiology should be rigorously accounted for while assessing GCs and their robustness under physiological and pathological conditions.NEW & NOTEWORTHY A recent study from our laboratory had demonstrated pronounced heterogeneities in a set of 17 electrophysiological measurements obtained from a large population of rat hippocampal granule cells. Here, we demonstrate the manifestation of ion-channel degeneracy in a heterogeneous population of morphologically realistic conductance-based granule cell models that were validated against these measurements and their cross-dependencies. Our analyses show that single neurons are complex entities whose functions emerge through intricate interactions among several functionally specialized subsystems.
Assuntos
Giro Denteado , Modelos Neurológicos , Neurônios , Giro Denteado/fisiologia , Giro Denteado/citologia , Animais , Neurônios/fisiologia , Ratos , Canais Iônicos/fisiologia , Canais Iônicos/metabolismo , Masculino , Potenciais de Ação/fisiologia , Ratos Sprague-DawleyRESUMO
Adult neural stem cells (NSCs) in the hippocampal dentate gyrus continuously proliferate and generate new neurons throughout life. Although various functions of organelles are closely related to the regulation of adult neurogenesis, the role of endoplasmic reticulum (ER)-related molecules in this process remains largely unexplored. Here we show that Derlin-1, an ER-associated degradation component, spatiotemporally maintains adult hippocampal neurogenesis through a mechanism distinct from its established role as an ER quality controller. Derlin-1 deficiency in the mouse central nervous system leads to the ectopic localization of newborn neurons and impairs NSC transition from active to quiescent states, resulting in early depletion of hippocampal NSCs. As a result, Derlin-1-deficient mice exhibit phenotypes of increased seizure susceptibility and cognitive dysfunction. Reduced Stat5b expression is responsible for adult neurogenesis defects in Derlin-1-deficient NSCs. Inhibition of histone deacetylase activity effectively induces Stat5b expression and restores abnormal adult neurogenesis, resulting in improved seizure susceptibility and cognitive dysfunction in Derlin-1-deficient mice. Our findings indicate that the Derlin-1-Stat5b axis is indispensable for the homeostasis of adult hippocampal neurogenesis.
Assuntos
Hipocampo , Proteínas de Membrana , Células-Tronco Neurais , Neurogênese , Fator de Transcrição STAT5 , Animais , Camundongos , Proliferação de Células , Giro Denteado/metabolismo , Giro Denteado/citologia , Hipocampo/metabolismo , Hipocampo/citologia , Homeostase , Proteínas de Membrana/metabolismo , Proteínas de Membrana/genética , Camundongos Knockout , Células-Tronco Neurais/metabolismo , Células-Tronco Neurais/citologia , Convulsões/metabolismo , Convulsões/genética , Transdução de Sinais , Fator de Transcrição STAT5/metabolismo , Fator de Transcrição STAT5/genéticaRESUMO
Quiescence, a hallmark of adult neural stem cells (NSCs), is required for maintaining the NSC pool to support life-long continuous neurogenesis in the adult dentate gyrus (DG). Whether long-lasting epigenetic modifications maintain NSC quiescence over the long term in the adult DG is not well-understood. Here we show that mice with haploinsufficiency of Setd1a, a schizophrenia risk gene encoding a histone H3K4 methyltransferase, develop an enlarged DG with more dentate granule cells after young adulthood. Deletion of Setd1a specifically in quiescent NSCs in the adult DG promotes their activation and neurogenesis, which is countered by inhibition of the histone demethylase LSD1. Mechanistically, RNA-sequencing and CUT & RUN analyses of cultured quiescent adult NSCs reveal Setd1a deletion-induced transcriptional changes and many Setd1a targets, among which down-regulation of Bhlhe40 promotes quiescent NSC activation in the adult DG in vivo. Together, our study reveals a Setd1a-dependent epigenetic mechanism that sustains NSC quiescence in the adult DG.
Assuntos
Giro Denteado , Epigênese Genética , Hipocampo , Histona-Lisina N-Metiltransferase , Células-Tronco Neurais , Neurogênese , Animais , Feminino , Masculino , Camundongos , Células-Tronco Adultas/metabolismo , Células-Tronco Adultas/citologia , Giro Denteado/citologia , Giro Denteado/metabolismo , Hipocampo/metabolismo , Hipocampo/citologia , Histona Desmetilases/metabolismo , Histona Desmetilases/genética , Histona-Lisina N-Metiltransferase/metabolismo , Histona-Lisina N-Metiltransferase/genética , Camundongos Endogâmicos C57BL , Camundongos Knockout , Células-Tronco Neurais/metabolismo , Células-Tronco Neurais/citologia , Neurogênese/genéticaRESUMO
Adult neurogenesis is a unique form of neuronal plasticity in which newly generated neurons are integrated into the adult dentate gyrus in a process that is modulated by environmental stimuli. Adult-born neurons can contribute to spatial memory, but it is unknown whether they alter neural representations of space in the hippocampus. Using in vivo two-photon calcium imaging, we find that male and female mice previously housed in an enriched environment, which triggers an increase in neurogenesis, have increased spatial information encoding in the dentate gyrus. Ablating adult neurogenesis blocks the effect of enrichment and lowers spatial information, as does the chemogenetic silencing of adult-born neurons. Both ablating neurogenesis and silencing adult-born neurons decreases the calcium activity of dentate gyrus neurons, resulting in a decreased amplitude of place-specific responses. These findings are in contrast with previous studies that suggested a predominantly inhibitory action for adult-born neurons. We propose that adult neurogenesis improves representations of space by increasing the gain of dentate gyrus neurons and thereby improving their ability to tune to spatial features. This mechanism may mediate the beneficial effects of environmental enrichment on spatial learning and memory.
Assuntos
Giro Denteado , Hipocampo , Neurogênese , Neurônios , Memória Espacial , Animais , Neurogênese/fisiologia , Masculino , Feminino , Giro Denteado/fisiologia , Giro Denteado/citologia , Camundongos , Neurônios/fisiologia , Neurônios/metabolismo , Hipocampo/fisiologia , Hipocampo/citologia , Hipocampo/metabolismo , Memória Espacial/fisiologia , Camundongos Endogâmicos C57BL , Plasticidade Neuronal/fisiologia , Cálcio/metabolismo , Aprendizagem Espacial/fisiologiaRESUMO
The hippocampus receives sequences of sensory inputs from the cortex during exploration and encodes the sequences with millisecond precision. We developed a predictive autoencoder model of the hippocampus including the trisynaptic and monosynaptic circuits from the entorhinal cortex (EC). CA3 was trained as a self-supervised recurrent neural network to predict its next input. We confirmed that CA3 is predicting ahead by analyzing the spike coupling between simultaneously recorded neurons in the dentate gyrus, CA3, and CA1 of the mouse hippocampus. In the model, CA1 neurons signal prediction errors by comparing CA3 predictions to the next direct EC input. The model exhibits the rapid appearance and slow fading of CA1 place cells and displays replay and phase precession from CA3. The model could be learned in a biologically plausible way with error-encoding neurons. Similarities between the hippocampal and thalamocortical circuits suggest that such computation motif could also underlie self-supervised sequence learning in the cortex.
Assuntos
Hipocampo , Aprendizagem , Animais , Camundongos , Hipocampo/fisiologia , Hipocampo/citologia , Aprendizagem/fisiologia , Modelos Neurológicos , Córtex Entorrinal/fisiologia , Córtex Entorrinal/citologia , Neurônios/fisiologia , Região CA1 Hipocampal/fisiologia , Região CA1 Hipocampal/citologia , Região CA3 Hipocampal/fisiologia , Região CA3 Hipocampal/citologia , Camundongos Endogâmicos C57BL , Redes Neurais de Computação , Masculino , Potenciais de Ação/fisiologia , Giro Denteado/fisiologia , Giro Denteado/citologiaRESUMO
Dendritic spines are sites of synaptic plasticity and their head size correlates with the strength of the corresponding synapse. We recently showed that the distribution of spine head sizes follows a lognormal-like distribution even after blockage of activity or plasticity induction. As the cytokine tumor necrosis factor (TNF) influences synaptic transmission and constitutive TNF and receptor (TNF-R)-deficiencies cause changes in spine head size distributions, we tested whether these genetic alterations disrupt the lognormality of spine head sizes. Furthermore, we distinguished between spines containing the actin-modulating protein synaptopodin (SP-positive), which is present in large, strong and stable spines and those lacking it (SP-negative). Our analysis revealed that neither TNF-deficiency nor the absence of TNF-R1, TNF-R2 or TNF-R 1 and 2 (TNF-R1/R2) degrades the general lognormal-like, skewed distribution of spine head sizes (all spines, SP-positive spines, SP-negative spines). However, TNF, TNF-R1 and TNF-R2-deficiency affected the width of the lognormal distribution, and TNF-R1/2-deficiency shifted the distribution to the left. Our findings demonstrate the robustness of the lognormal-like, skewed distribution, which is maintained even in the face of genetic manipulations that alter the distribution of spine head sizes. Our observations are in line with homeostatic adaptation mechanisms of neurons regulating the distribution of spines and their head sizes.
Assuntos
Espinhas Dendríticas , Giro Denteado , Camundongos Endogâmicos C57BL , Camundongos Knockout , Receptores Tipo II do Fator de Necrose Tumoral , Receptores Tipo I de Fatores de Necrose Tumoral , Fator de Necrose Tumoral alfa , Animais , Espinhas Dendríticas/metabolismo , Camundongos , Receptores Tipo I de Fatores de Necrose Tumoral/deficiência , Receptores Tipo I de Fatores de Necrose Tumoral/metabolismo , Receptores Tipo I de Fatores de Necrose Tumoral/genética , Giro Denteado/metabolismo , Giro Denteado/citologia , Fator de Necrose Tumoral alfa/metabolismo , Receptores Tipo II do Fator de Necrose Tumoral/deficiência , Receptores Tipo II do Fator de Necrose Tumoral/metabolismo , Receptores Tipo II do Fator de Necrose Tumoral/genética , Neurônios/metabolismo , Masculino , Proteínas dos Microfilamentos/metabolismo , Proteínas dos Microfilamentos/genética , Proteínas dos Microfilamentos/deficiênciaRESUMO
The dentate gyrus plays a key role in the discrimination of memories by segregating and storing similar episodes. Whether hilar mossy cells, which constitute a major excitatory principal cell type in the mammalian hippocampus, contribute to this decorrelation function has remained largely unclear. Using two-photon calcium imaging of head-fixed mice performing a spatial virtual reality task, we show that mossy cell populations robustly discriminate between familiar and novel environments. The degree of discrimination depends on the extent of visual cue differences between contexts. A context decoder revealed that successful environmental classification is explained mainly by activity difference scores of mossy cells. By decoding mouse position, we reveal that in addition to place cells, the coordinated activity among active mossy cells markedly contributes to the encoding of space. Thus, by decorrelating context information according to the degree of environmental differences, mossy cell populations support pattern separation processes within the dentate gyrus.
Assuntos
Giro Denteado , Animais , Camundongos , Giro Denteado/fisiologia , Giro Denteado/citologia , Masculino , Camundongos Endogâmicos C57BL , Fibras Musgosas Hipocampais/fisiologia , Fibras Musgosas Hipocampais/metabolismoRESUMO
Quiescent adult neural stem cells (NSCs) in the mammalian brain arise from proliferating NSCs during development. Beyond acquisition of quiescence, an adult NSC hallmark, little is known about the process, milestones, and mechanisms underlying the transition of developmental NSCs to an adult NSC state. Here, we performed targeted single-cell RNA-seq analysis to reveal the molecular cascade underlying NSC development in the early postnatal mouse dentate gyrus. We identified two sequential steps, first a transition to quiescence followed by further maturation, each of which involved distinct changes in metabolic gene expression. Direct metabolic analysis uncovered distinct milestones, including an autophagy burst before NSC quiescence acquisition and cellular reactive oxygen species level elevation along NSC maturation. Functionally, autophagy is important for the NSC transition to quiescence during early postnatal development. Together, our study reveals a multi-step process with defined milestones underlying establishment of the adult NSC pool in the mammalian brain.
Assuntos
Autofagia , Hipocampo , Células-Tronco Neurais , Células-Tronco Neurais/metabolismo , Células-Tronco Neurais/citologia , Animais , Camundongos , Hipocampo/metabolismo , Hipocampo/citologia , Neurogênese , Giro Denteado/metabolismo , Giro Denteado/citologia , Giro Denteado/crescimento & desenvolvimento , Diferenciação Celular , Camundongos Endogâmicos C57BL , Espécies Reativas de Oxigênio/metabolismo , Células-Tronco Adultas/metabolismo , Células-Tronco Adultas/citologia , Análise de Célula Única , Proliferação de CélulasRESUMO
Human hippocampal organoids (hHOs) derived from human induced pluripotent stem cells (hiPSCs) have emerged as promising models for investigating neurodegenerative disorders, such as schizophrenia and Alzheimer's disease. However, obtaining the electrical information of these free-floating organoids in a noninvasive manner remains a challenge using commercial multi-electrode arrays (MEAs). The three-dimensional (3D) MEAs developed recently acquired only a few neural signals due to limited channel numbers. Here, we report a hippocampal cyborg organoid (cyb-organoid) platform coupling a liquid metal-polymer conductor (MPC)-based mesh neuro-interface with hHOs. The mesh MPC (mMPC) integrates 128-channel multielectrode arrays distributed on a small surface area (~2*2 mm). Stretchability (up to 500%) and flexibility of the mMPC enable its attachment to hHOs. Furthermore, we show that under Wnt3a and SHH activator induction, hHOs produce HOPX+ and PAX6+ progenitors and ZBTB20+PROX1+ dentate gyrus (DG) granule neurons. The transcriptomic signatures of hHOs reveal high similarity to the developing human hippocampus. We successfully detect neural activities from hHOs via the mMPC from this cyb-organoid. Compared with traditional planar devices, our non-invasive coupling offers an adaptor for recording neural signals from 3D models.
Assuntos
Hipocampo , Células-Tronco Pluripotentes Induzidas , Organoides , Humanos , Organoides/metabolismo , Organoides/citologia , Hipocampo/citologia , Hipocampo/metabolismo , Células-Tronco Pluripotentes Induzidas/citologia , Células-Tronco Pluripotentes Induzidas/metabolismo , Neurônios/metabolismo , Neurônios/citologia , Metais/química , Transcriptoma , Giro Denteado/citologia , Giro Denteado/metabolismoRESUMO
Glutamatergic mossy cells (MCs) mediate associational and commissural connectivity, exhibiting significant heterogeneity along the septotemporal axis of the mouse dentate gyrus (DG). However, it remains unclear whether the neuronal features of MCs are conserved across mammals. This study compares the neuroanatomy of MCs in the DG of mice and monkeys. The MC marker, calretinin, distinguishes two subpopulations: septal and temporal. Dual-colored fluorescence labeling is utilized to compare the axonal projection patterns of these subpopulations. In both mice and monkeys, septal and temporal MCs project axons across the longitudinal axis of the ipsilateral DG, indicating conserved associational projections. However, unlike in mice, no MC subpopulations in monkeys make commissural projections to the contralateral DG. In monkeys, temporal MCs send associational fibers exclusively to the inner molecular layer, while septal MCs give rise to wide axonal projections spanning multiple molecular layers, akin to equivalent MC subpopulations in mice. Despite conserved septotemporal heterogeneity, interspecies differences are observed in the topological organization of septal MCs, particularly in the relative axonal density in each molecular layer along the septotemporal axis of the DG. In summary, this comparative analysis sheds light on both conserved and divergent features of MCs in the DG of mice and monkeys. These findings have implications for understanding functional differentiation along the septotemporal axis of the DG and contribute to our knowledge of the anatomical evolution of the DG circuit in mammals.
Assuntos
Axônios , Calbindina 2 , Giro Denteado , Camundongos Endogâmicos C57BL , Animais , Masculino , Giro Denteado/citologia , Giro Denteado/anatomia & histologia , Calbindina 2/metabolismo , Fibras Musgosas Hipocampais/fisiologia , Camundongos , Especificidade da Espécie , FemininoRESUMO
Repetitive firing of granule cells (GCs) in the dentate gyrus (DG) facilitates synaptic transmission to the CA3 region. This facilitation can gate and amplify the flow of information through the hippocampus. High-frequency bursts in the DG are linked to behavior and plasticity, but GCs do not readily burst. Under normal conditions, a single shock to the perforant path in a hippocampal slice typically drives a GC to fire a single spike, and only occasionally more than one spike is seen. Repetitive spiking in GCs is not robust, and the mechanisms are poorly understood. Here, we used a hybrid genetically encoded voltage sensor to image voltage changes evoked by cortical inputs in many mature GCs simultaneously in hippocampal slices from male and female mice. This enabled us to study relatively infrequent double and triple spikes. We found GCs are relatively homogeneous and their double spiking behavior is cell autonomous. Blockade of GABA type A receptors increased multiple spikes and prolonged the interspike interval, indicating inhibitory interneurons limit repetitive spiking and set the time window for successive spikes. Inhibiting synaptic glutamate release showed that recurrent excitation mediated by hilar mossy cells contributes to, but is not necessary for, multiple spiking. Blockade of T-type Ca2+ channels did not reduce multiple spiking but prolonged interspike intervals. Imaging voltage changes in different GC compartments revealed that second spikes can be initiated in either dendrites or somata. Thus, pharmacological and biophysical experiments reveal roles for both synaptic circuitry and intrinsic excitability in GC repetitive spiking.
Assuntos
Potenciais de Ação , Giro Denteado , Animais , Giro Denteado/fisiologia , Giro Denteado/citologia , Masculino , Camundongos , Feminino , Potenciais de Ação/fisiologia , Sinapses/fisiologia , Neurônios/fisiologia , Camundongos Endogâmicos C57BL , Transmissão Sináptica/fisiologia , Camundongos TransgênicosRESUMO
Light exposure can profoundly affect neurological functions and behaviors. Here, we show that short-term exposure to moderate (400 lux) white light during Y-maze test promoted spatial memory retrieval and induced only mild anxiety in mice. This beneficial effect involves the activation of a circuit including neurons in the central amygdala (CeA), locus coeruleus (LC), and dentate gyrus (DG). Specifically, moderate light activated corticotropin-releasing hormone (CRH) positive (+) CeA neurons and induced the release of corticotropin-releasing factor (CRF) from their axon terminals ending in the LC. CRF then activated tyrosine hydroxylase-expressing LC neurons, which send projections to DG and release norepinephrine (NE). NE activated ß-adrenergic receptors on CaMKIIα-expressing DG neurons, ultimately promoting spatial memory retrieval. Our study thus demonstrated a specific light scheme that can promote spatial memory without excessive stress, and unraveled the underlying CeA-LC-DG circuit and associated neurochemical mechanisms.
Assuntos
Tonsila do Cerebelo , Luz , Memória Espacial , Tonsila do Cerebelo/citologia , Tonsila do Cerebelo/metabolismo , Animais , Camundongos , Ansiedade , Giro Denteado/citologia , Giro Denteado/metabolismo , Neurônios , Locus Cerúleo/citologia , Locus Cerúleo/metabolismo , Hormônio Liberador da Corticotropina/metabolismo , Norepinefrina/metabolismo , Vias Neurais , Aprendizagem em Labirinto , Camundongos Endogâmicos C57BLRESUMO
The dentate gyrus (DG) plays critical roles in cognitive functions, such as learning, memory, and spatial coding, and its dysfunction is implicated in various neuropsychiatric disorders. However, it remains largely unknown how information is represented in this region. Here, we recorded neuronal activity in the DG using Ca2+ imaging in freely moving mice and analyzed this activity using machine learning. The activity patterns of populations of DG neurons enabled us to successfully decode position, speed, and motion direction in an open field, as well as current and future location in a T-maze, and each individual neuron was diversely and independently tuned to these multiple information types. Our data also showed that each type of information is unevenly distributed in groups of DG neurons, and different types of information are independently encoded in overlapping, but different, populations of neurons. In alpha-calcium/calmodulin-dependent kinase II (αCaMKII) heterozygous knockout mice, which present deficits in spatial remote and working memory, the decoding accuracy of position in the open field and future location in the T-maze were selectively reduced. These results suggest that multiple types of information are independently distributed in DG neurons.
Assuntos
Cognição , Giro Denteado , Neurônios , Animais , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/genética , Cognição/fisiologia , Giro Denteado/citologia , Giro Denteado/fisiologia , Memória de Curto Prazo/fisiologia , Camundongos , Camundongos Knockout , Neurônios/fisiologiaRESUMO
Immature dentate granule cells (imGCs) arising from adult hippocampal neurogenesis contribute to plasticity and unique brain functions in rodents1,2 and are dysregulated in multiple human neurological disorders3-5. Little is known about the molecular characteristics of adult human hippocampal imGCs, and even their existence is under debate1,6-8. Here we performed single-nucleus RNA sequencing aided by a validated machine learning-based analytic approach to identify imGCs and quantify their abundance in the human hippocampus at different stages across the lifespan. We identified common molecular hallmarks of human imGCs across the lifespan and observed age-dependent transcriptional dynamics in human imGCs that suggest changes in cellular functionality, niche interactions and disease relevance, that differ from those in mice9. We also found a decreased number of imGCs with altered gene expression in Alzheimer's disease. Finally, we demonstrated the capacity for neurogenesis in the adult human hippocampus with the presence of rare dentate granule cell fate-specific proliferating neural progenitors and with cultured surgical specimens. Together, our findings suggest the presence of a substantial number of imGCs in the adult human hippocampus via low-frequency de novo generation and protracted maturation, and our study reveals their molecular properties across the lifespan and in Alzheimer's disease.
Assuntos
Envelhecimento , Hipocampo , Longevidade , Neurogênese , Neurônios , Adulto , Envelhecimento/genética , Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Animais , Proliferação de Células , Giro Denteado/citologia , Giro Denteado/patologia , Perfilação da Expressão Gênica , Hipocampo/citologia , Hipocampo/patologia , Humanos , Longevidade/genética , Aprendizado de Máquina , Camundongos , Células-Tronco Neurais/citologia , Células-Tronco Neurais/metabolismo , Células-Tronco Neurais/patologia , Neurogênese/genética , Neurônios/citologia , Neurônios/metabolismo , Neurônios/patologia , Reprodutibilidade dos Testes , Análise de Sequência de RNA , Análise de Célula Única , Transcrição GênicaRESUMO
Long-term memory formation relies on synaptic plasticity, neuronal activity-dependent gene transcription, and epigenetic modifications. Multiple studies have shown that HDAC inhibitor (HDACi) treatments can enhance individual aspects of these processes and thereby act as putative cognitive enhancers. However, their mode of action is not fully understood. In particular, it is unclear how systemic application of HDACis, which are devoid of substrate specificity, can target pathways that promote memory formation. In this study, we explore the electrophysiological, transcriptional, and epigenetic responses that are induced by CI-994, a class I HDACi, combined with contextual fear conditioning (CFC) in mice. We show that CI-994mediated improvement of memory formation is accompanied by enhanced long-term potentiation in the hippocampus, a brain region recruited by CFC, but not in the striatum, a brain region not primarily implicated in fear learning. Furthermore, using a combination of bulk and single-cell RNA-sequencing, we find that, when paired with CFC, HDACi treatment engages synaptic plasticity-promoting gene expression more strongly in the hippocampus, specifically in the dentate gyrus (DG). Finally, using chromatin immunoprecipitation-sequencing (ChIP-seq) of DG neurons, we show that the combined action of HDACi application and conditioning is required to elicit enhancer histone acetylation in pathways that underlie improved memory performance. Together, these results indicate that systemic HDACi administration amplifies brain region-specific processes that are naturally induced by learning.
Assuntos
Benzamidas , Giro Denteado , Inibidores de Histona Desacetilases , Memória de Longo Prazo , Fenilenodiaminas , Animais , Benzamidas/farmacologia , Comunicação Celular/efeitos dos fármacos , Giro Denteado/citologia , Giro Denteado/efeitos dos fármacos , Giro Denteado/fisiologia , Inibidores de Histona Desacetilases/farmacologia , Memória de Longo Prazo/efeitos dos fármacos , Camundongos , Plasticidade Neuronal , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Fenilenodiaminas/farmacologia , RNA-Seq , Análise de Célula ÚnicaRESUMO
Genetic studies of hippocampal granule neuron development have been used to elucidate cellular functions of Pten and Fmr1. While mutations in each gene cause neurodevelopmental disorders such as autism and fragile X syndrome, how Pten and Fmr1 function alone or together during normal development is not known. Moreover, Pten mRNA is bound by the fragile X mental retardation protein (FMRP) RNA binding protein, but how this physical interaction impinges on phosphatase and tensin homolog protein (PTEN) expression is not known. To understand the interaction of PTEN and FMRP, we investigated the dentate gyrus granule neuron development in Pten and Fmr1 knockout (KO) mice. Interestingly, heterozygosity of Pten restored Fmr1 KO cellular phenotypes, including dendritic arborization, and spine density, while PTEN protein expression was significantly increased in Fmr1 KO animals. However, complete deletion of both Pten and Fmr1 resulted in a dramatic increase in dendritic length, spine density, and spine length. In addition, overexpression of PTEN in Fmr1 KO Pten heterozygous background reduced dendritic length, arborization, spine density, and spine length including pS6 levels. Our findings suggest that PTEN levels are negatively regulated by FMRP, and some Fmr1 KO phenotypes are caused by dysregulation of PTEN protein. These observations provide evidence for the genetic interaction of PTEN and FMRP and a possible mechanistic basis for the pathogenesis of Fmr1-related fragile X neurodevelopmental disorders.