RESUMO
The accumulation of α-synuclein induces neuronal loss in midbrain nuclei and leads to the disruption of motor circuits, while the pathology of α-synuclein in cortical regions remains elusive. To better characterize cortical synucleinopathy, here we generate a mouse model with the overexpression of human α-synuclein in the primary motor cortex (M1) of mice. A combination of molecular, in vivo recording, and behavioral approaches reveal that cortical expression of human α-synuclein results in the overexcitation of cortical pyramidal neurons (PNs), which are regulated by the decreased inhibitory inputs from parvalbumin-interneurons (PV-INs) to impair complex motor skill learning. Further mechanistic dissections reveal that human α-synuclein aggregation activates ferroptosis, contributing to PV-IN degeneration and motor circuit dysfunction. Taken together, the current study adds more knowledge to the emerging role and pathogenic mechanism of ferroptosis in neurodegenerative diseases.
Assuntos
Ferroptose , Interneurônios , Parvalbuminas , alfa-Sinucleína , Animais , Parvalbuminas/metabolismo , Humanos , Interneurônios/metabolismo , Interneurônios/patologia , alfa-Sinucleína/metabolismo , Camundongos , Córtex Motor/metabolismo , Córtex Motor/patologia , Camundongos Transgênicos , Masculino , Modelos Animais de Doenças , Células Piramidais/metabolismo , Células Piramidais/patologia , AprendizagemRESUMO
We elucidated the molecular fingerprint of vulnerable excitatory neurons within select cortical lamina of individuals with Down syndrome (DS) for mechanistic understanding and therapeutic potential that also informs Alzheimer's disease (AD) pathophysiology. Frontal cortex (BA9) layer III (L3) and layer V (L5) pyramidal neurons were microisolated from postmortem human DS and age- and sex-matched controls (CTR) to interrogate differentially expressed genes (DEGs) and key biological pathways relevant to neurodegenerative programs. We identified > 2300 DEGs exhibiting convergent dysregulation of gene expression in both L3 and L5 pyramidal neurons in individuals with DS versus CTR subjects. DEGs included over 100 triplicated human chromosome 21 genes in L3 and L5 neurons, demonstrating a trisomic neuronal karyotype in both laminae. In addition, thousands of other DEGs were identified, indicating gene dysregulation is not limited to trisomic genes in the aged DS brain, which we postulate is relevant to AD pathobiology. Convergent L3 and L5 DEGs highlighted pertinent biological pathways and identified key pathway-associated targets likely underlying corticocortical neurodegeneration and related cognitive decline in individuals with DS. Select key DEGs were interrogated as potential hub genes driving dysregulation, namely the triplicated DEGs amyloid precursor protein (APP) and superoxide dismutase 1 (SOD1), along with key signaling DEGs including mitogen activated protein kinase 1 and 3 (MAPK1, MAPK3) and calcium calmodulin dependent protein kinase II alpha (CAMK2A), among others. Hub DEGs determined from multiple pathway analyses identified potential therapeutic candidates for amelioration of cortical neuron dysfunction and cognitive decline in DS with translational relevance to AD.
Assuntos
Síndrome de Down , Lobo Frontal , Células Piramidais , Síndrome de Down/patologia , Síndrome de Down/genética , Síndrome de Down/metabolismo , Humanos , Células Piramidais/patologia , Células Piramidais/metabolismo , Masculino , Feminino , Lobo Frontal/patologia , Lobo Frontal/metabolismo , Pessoa de Meia-Idade , Idoso , Fenótipo , Adulto , Idoso de 80 Anos ou maisRESUMO
Neuroinflammation, aging, and neurodegenerative disorders are associated with excessive accumulation of neutral lipids in lipid droplets (LDs) in microglia. Type 2 diabetes mellitus (T2DM) may cause neuroinflammation and is a risk factor for neurodegenerative disorders. Here, we show that hippocampal pyramidal neurons contain smaller, more abundant LDs than their neighboring microglia. The density of LDs varied between pyramidal cells in adjacent subregions, with CA3 neurons containing more LDs than CA1 neurons. Within the CA3 region, a gradual increase in the LD content along the pyramidal layer from the hilus toward CA2 was observed. Interestingly, the high neuronal LD content correlated with less ramified microglial morphotypes. Using the db/db model of T2DM, we demonstrated that diabetes increased the number of LDs per microglial cell without affecting the neuronal LD density. High-intensity interval exercise induced smaller changes in the number of LDs in microglia but was not sufficient to counteract the diabetes-induced changes in LD accumulation. The changes observed in response to T2DM may contribute to the cerebral effects of T2DM and provide a mechanistic link between T2DM and neurodegenerative disorders.
Assuntos
Diabetes Mellitus Tipo 2 , Hipocampo , Gotículas Lipídicas , Microglia , Neurônios , Microglia/metabolismo , Animais , Gotículas Lipídicas/metabolismo , Hipocampo/metabolismo , Hipocampo/patologia , Diabetes Mellitus Tipo 2/metabolismo , Diabetes Mellitus Tipo 2/patologia , Neurônios/metabolismo , Neurônios/patologia , Masculino , Camundongos , Condicionamento Físico Animal , Células Piramidais/metabolismo , Células Piramidais/patologia , Camundongos Endogâmicos C57BL , Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Experimental/patologia , Metabolismo dos Lipídeos , Doenças Neuroinflamatórias/metabolismo , Doenças Neuroinflamatórias/patologiaRESUMO
Alzheimer's disease (AD) remains of unknown etiology and lacks a cure. This study aimed to evaluate the therapeutic potential of a novel bithiophene derivative at two doses against AlCl3-induced AD in a rat model. Adult male rats (Rattus norvegicus) were divided into six groups (n=6): Group one consisted of naïve animals, group two received bithiophene (1â¯mg/kg) every other day for 30 days, and groups 3-6 were subjected to AlCl3 (100â¯mg/kg, equivalent to 20.23â¯mg Al3+) for 45 consecutive days. Groups four and five received low (0.5â¯mg/kg) or high (1â¯mg/kg) doses of bithiophene, respectively. Group six received memantine (20â¯mg/kg) daily for 30 days. All treatments were administered orally. Aluminum exposure resulted in severe degeneration of both histological and ultrastructural aspects of cells. Administration of the low dose of bithiophene significantly restored the number of CA1 pyramidal cells and the thickness of the stratum granulosum of the dentate gyrus. However, the high dose of bithiophene increased viable CA1 pyramidal cell numbers significantly without restoring the thickness of the stratum granulosum or reducing vacuolization or pyknotic changes. The low dose of bithiophene restored the normal histological and cytological structure of both cortical and hippocampal neurons affected by dementia. Further investigation is required to explore the molecular mechanisms underlying the ameliorative effects on Alzheimer's disease-induced deteriorations in the cortex and hippocampus.
Assuntos
Alumínio , Doença de Alzheimer , Modelos Animais de Doenças , Tiofenos , Animais , Doença de Alzheimer/tratamento farmacológico , Doença de Alzheimer/patologia , Doença de Alzheimer/induzido quimicamente , Tiofenos/farmacologia , Ratos , Masculino , Alumínio/toxicidade , Cloreto de Alumínio , Células Piramidais/efeitos dos fármacos , Células Piramidais/patologia , Células Piramidais/ultraestrutura , Células Piramidais/metabolismoRESUMO
Traumatic brain injury (TBI) is an established risk factor for developing neurodegenerative disease. However, how TBI leads from acute injury to chronic neurodegeneration is limited to postmortem models. There is a lack of connections between in vitro and in vivo TBI models that can relate injury forces to both macroscale tissue damage and brain function at the cellular level. Needle-induced cavitation (NIC) is a technique that can produce small cavitation bubbles in soft tissues, which allows us to relate small strains and strain rates in living tissue to ensuing acute cell death, tissue damage, and tissue remodeling. Here, we applied NIC to mouse brain slices to create a new model of TBI with high spatial and temporal resolution. We specifically targeted the hippocampus, which is a brain region critical for learning and memory and an area in which injury causes cognitive pathologies in humans and rodent models. By combining NIC with patch-clamp electrophysiology, we demonstrate that NIC in the cornu ammonis 3 region of the hippocampus dynamically alters synaptic release onto cornu ammonis 1 pyramidal neurons in a cannabinoid 1 receptor-dependent manner. Further, we show that NIC induces an increase in extracellular matrix protein GFAP associated with neural repair that is mitigated by cannabinoid 1 receptor antagonism. Together, these data lay the groundwork for advanced approaches in understanding how TBI impacts neural function at the cellular level and the development of treatments that promote neural repair in response to brain injury.
Assuntos
Hipocampo , Camundongos Endogâmicos C57BL , Animais , Camundongos , Hipocampo/patologia , Hipocampo/metabolismo , Masculino , Neuroglia/metabolismo , Neuroglia/patologia , Lesões Encefálicas Traumáticas/patologia , Lesões Encefálicas Traumáticas/metabolismo , Lesões Encefálicas Traumáticas/fisiopatologia , Proteína Glial Fibrilar Ácida/metabolismo , Células Piramidais/metabolismo , Células Piramidais/patologia , Concussão Encefálica/patologia , Concussão Encefálica/metabolismo , Concussão Encefálica/fisiopatologiaRESUMO
It is well established that hearing loss can lead to widespread plasticity within the central auditory pathway, which is thought to contribute to the pathophysiology of audiological conditions such as tinnitus and hyperacusis. Emerging evidence suggests that hearing loss can also result in plasticity within brain regions involved in higher-level cognitive functioning like the prefrontal cortex; findings which may underlie the association between hearing loss and cognitive impairment documented in epidemiological studies. Using the 40-Hz auditory steady state response to assess sound-evoked gamma oscillations, we previously showed that noise-induced hearing loss results in impaired gamma phase coherence within the prefrontal but not the auditory cortex. To determine whether region-specific structural or molecular changes accompany this differential plasticity following hearing loss, in the present study we utilized Golgi-Cox staining to assess dendritic organization and synaptic density, as well as Western blotting to measure changes in synaptic signaling proteins in these cortical regions. We show that following noise exposure, impaired gamma phase coherence within the prefrontal cortex is accompanied by alterations in pyramidal cell dendritic morphology and decreased expression of proteins involved in GABAergic (GAD65) and glutamatergic (NR2B) neurotransmission; findings that were not observed in the auditory cortex, where gamma phase coherence remained unchanged post-noise exposure. In contrast to the noise-induced effects we observed in the prefrontal cortex, plasticity in the auditory cortex was characterized by an increase in NR2B suggesting increased excitability, as well as increases in the synaptic proteins PSD95 and synaptophysin within the auditory cortex. Overall, our results highlight the disparate effect of noise-induced hearing loss on auditory and higher-level brain regions as well as potential structural and molecular mechanisms by which hearing loss may contribute to impaired cognitive and sensory functions mediated by the prefrontal and auditory cortices.
Assuntos
Córtex Auditivo , Perda Auditiva Provocada por Ruído , Córtex Pré-Frontal , Perda Auditiva Provocada por Ruído/fisiopatologia , Perda Auditiva Provocada por Ruído/patologia , Perda Auditiva Provocada por Ruído/metabolismo , Córtex Auditivo/metabolismo , Córtex Auditivo/fisiopatologia , Córtex Auditivo/patologia , Córtex Pré-Frontal/metabolismo , Córtex Pré-Frontal/patologia , Animais , Masculino , Plasticidade Neuronal/fisiologia , Glutamato Descarboxilase/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Proteína 4 Homóloga a Disks-Large/metabolismo , Dendritos/patologia , Dendritos/metabolismo , Ritmo Gama/fisiologia , Células Piramidais/metabolismo , Células Piramidais/patologia , RatosRESUMO
BACKGROUND: We have previously identified auto-antibody (Ab) to collapsin response mediator protein 2 (CRMP2) in patients with encephalitis. The present study aims to evaluate the pathogenic effects of anti-CRMP2 Ab. METHODS: Recombinant CRMP2 protein was injected subcutaneously into mice to establish an active immune mouse model with anti-CRMP2 Ab. Behavioral assessments, histopathological staining, and electrophysiological testing were performed to identify any pathogenic changes. RESULTS: The mice exhibited signs of impaired motor coordination four weeks post-immunization of CRMP2 protein. Moreover, CRMP2 immunized mice for eight weeks showed anxiety-like behaviors indicating by tests of open field and the elevated plus maze. After incubating the CA1 region of hippocampal brain section with the sera from CRMP2 immunized mice, the whole-cell path-clamp recordings showed increased excitability of pyramidal neurons. However, no obvious inflammation and infiltration of immune cells were observed by histopathological analysis. Western blot showed that the phosphorylation levels of CRMP2-Thr514 and -Ser522 were not affected. CONCLUSION: In an active immunization model with CRMP2 protein, impaired coordination and anxiety-like behaviors were observed. Also, anti-CRMP2 Abs containing sera heightened the excitability of hippocampal pyramidal neurons in vitro, which imply the pathogenic effects of anti-CRMP2 Ab.
Assuntos
Ansiedade , Peptídeos e Proteínas de Sinalização Intercelular , Proteínas do Tecido Nervoso , Células Piramidais , Animais , Células Piramidais/patologia , Células Piramidais/metabolismo , Células Piramidais/imunologia , Ansiedade/imunologia , Ansiedade/patologia , Camundongos , Proteínas do Tecido Nervoso/imunologia , Peptídeos e Proteínas de Sinalização Intercelular/imunologia , Masculino , Autoanticorpos/imunologia , Comportamento Animal/efeitos dos fármacos , Modelos Animais de Doenças , Fosforilação , Hipocampo/patologia , Hipocampo/imunologia , Hipocampo/metabolismoRESUMO
Cognitive disorders, including Down syndrome (DS), present significant morphological alterations in neuron architectural complexity. However, the relationship between neuromorphological alterations and impaired brain function is not fully understood. To address this gap, we propose a novel computational model that accounts for the observed cell deformations in DS. The model consists of a cross-sectional layer of the mouse motor cortex, composed of 3000 neurons. The network connectivity is obtained by accounting explicitly for two single-neuron morphological parameters: the mean dendritic tree radius and the spine density in excitatory pyramidal cells. We obtained these values by fitting reconstructed neuron data corresponding to three mouse models: wild-type (WT), transgenic (TgDyrk1A), and trisomic (Ts65Dn). Our findings reveal a dynamic interplay between pyramidal and fast-spiking interneurons leading to the emergence of gamma activity (â¼40 Hz). In the DS models this gamma activity is diminished, corroborating experimental observations and validating our computational methodology. We further explore the impact of disrupted excitation-inhibition balance by mimicking the reduction recurrent inhibition present in DS. In this case, gamma power exhibits variable responses as a function of the external input to the network. Finally, we perform a numerical exploration of the morphological parameter space, unveiling the direct influence of each structural parameter on gamma frequency and power. Our research demonstrates a clear link between changes in morphology and the disruption of gamma oscillations in DS. This work underscores the potential of computational modeling to elucidate the relationship between neuron architecture and brain function, and ultimately improve our understanding of cognitive disorders.
Assuntos
Biologia Computacional , Síndrome de Down , Modelos Neurológicos , Síndrome de Down/fisiopatologia , Síndrome de Down/patologia , Animais , Camundongos , Células Piramidais/patologia , Células Piramidais/fisiologia , Neurônios/fisiologia , Neurônios/patologia , Interneurônios/fisiologia , Interneurônios/patologia , Simulação por Computador , Córtex Motor/fisiopatologia , Córtex Motor/patologia , Modelos Animais de Doenças , Humanos , Camundongos Transgênicos , Rede Nervosa/fisiopatologia , Rede Nervosa/patologiaRESUMO
Epilepsy is known to cause alterations in neural networks. However, many details of these changes remain poorly understood. The objective of this study was to investigate changes in the properties of hippocampal CA1 pyramidal neurons and their synaptic inputs in a rat lithium-pilocarpine model of epilepsy. In the chronic phase of the model, we found a marked loss of pyramidal neurons in the CA1 area. However, the membrane properties of the neurons remained essentially unaltered. The results of the electrophysiological and morphological studies indicate that the direct pathway from the entorhinal cortex to CA1 neurons is reinforced in epileptic animals, whereas the inputs to them from CA3 are either unaltered or even diminished. In particular, the dendritic spine density in the str. lacunosum moleculare, where the direct pathway from the entorhinal cortex terminates, was found to be 2.5 times higher in epileptic rats than in control rats. Furthermore, the summation of responses upon stimulation of the temporoammonic pathway was enhanced by approximately twofold in epileptic rats. This enhancement is believed to be a significant contributing factor to the heightened epileptic activity observed in the entorhinal cortex of epileptic rats using an ex vivo 4-aminopyridine model.
Assuntos
Região CA1 Hipocampal , Modelos Animais de Doenças , Epilepsia , Lítio , Pilocarpina , Células Piramidais , Animais , Células Piramidais/patologia , Células Piramidais/metabolismo , Ratos , Epilepsia/induzido quimicamente , Epilepsia/patologia , Epilepsia/fisiopatologia , Masculino , Região CA1 Hipocampal/patologia , Lítio/toxicidade , Lítio/farmacologia , Córtex Entorrinal/patologia , Ratos WistarRESUMO
Nerve regeneration and circuit reconstruction remain a challenge following spinal cord injury (SCI). Corticospinal pyramidal neurons possess strong axon projection ability. In this study, human induced pluripotent stem cells (iPSCs) were differentiated into pyramidal neuronal precursors (PNPs) by addition of small molecule dorsomorphin into the culture. iPSC-derived PNPs were transplanted acutely into a rat contusion SCI model on the same day of injury. Following engraftment, the SCI rats showed significantly improved motor functions compared with vehicle control group as revealed by behavioral tests. Eight weeks following engraftment, the PNPs matured into corticospinal pyramidal neurons and extended axons into distant host spinal cord tissues, mostly in a caudal direction. Host neurons rostral to the lesion site also grew axons into the graft. Possible synaptic connections as a bridging relay may have been formed between host and graft-derived neurons, as indicated by pre- and post-synaptic marker staining and the regulation of chemogenetic regulatory systems. PNP graft showed an anti-inflammatory effect at the injury site and could bias microglia/macrophages towards a M2 phenotype. In addition, PNP graft was safe and no tumor formation was detected after transplantation into immunodeficient mice and SCI rats. The potential to reconstruct a neuronal relay circuitry across the lesion site and to modulate the microenvironment in SCI makes PNPs a promising cellular candidate for treatment of SCI.
Assuntos
Diferenciação Celular , Modelos Animais de Doenças , Células-Tronco Pluripotentes Induzidas , Traumatismos da Medula Espinal , Animais , Traumatismos da Medula Espinal/terapia , Traumatismos da Medula Espinal/patologia , Humanos , Células-Tronco Pluripotentes Induzidas/citologia , Células-Tronco Pluripotentes Induzidas/transplante , Células-Tronco Pluripotentes Induzidas/metabolismo , Ratos , Ratos Sprague-Dawley , Células Piramidais/metabolismo , Células Piramidais/patologia , Camundongos , Células-Tronco Neurais/transplante , Células-Tronco Neurais/citologia , Células-Tronco Neurais/metabolismo , Células-Tronco Embrionárias/citologia , Células-Tronco Embrionárias/metabolismo , Feminino , Regeneração Nervosa , Axônios/metabolismoRESUMO
The prevalence of pyramidal cells (PCs) in the mammalian cerebral cortex underscore their value as they play a crucial role in various brain functions, ranging from cognition, sensory processing, to motor output. PC morphology significantly influences brain connectivity and plays a critical role in maintaining normal brain function. Pathological alterations to PC morphology are thought to contribute to the aetiology of neurodevelopmental disorders such as autism spectrum disorder (ASD) and schizophrenia. This review explores the relationship between abnormalities in PC morphology in key cortical areas and the clinical manifestations in schizophrenia and ASD. We focus largely on human postmortem studies and provide evidence that dendritic segment length, complexity and spine density are differentially affected in these disorders. These morphological alterations can lead to disruptions in cortical connectivity, potentially contributing to the cognitive and behavioural deficits observed in these disorders. Furthermore, we highlight the importance of investigating the functional and structural characteristics of PCs in these disorders to illuminate the underlying pathogenesis and stimulate further research in this area.
Assuntos
Transtornos do Neurodesenvolvimento , Células Piramidais , Humanos , Células Piramidais/patologia , Animais , Transtornos do Neurodesenvolvimento/patologia , Transtornos do Neurodesenvolvimento/fisiopatologia , Transtorno do Espectro Autista/patologia , Transtorno do Espectro Autista/fisiopatologia , Esquizofrenia/patologia , Esquizofrenia/fisiopatologia , Córtex Cerebral/patologiaRESUMO
Diabetes mellitus (DM) is a metabolic disorder impacting cerebral function. The administration of Streptozotocin (STZ) is a well-known animal model of insulinopenic type 1 DM in rats. STZ-induced DM results in a myriad of alteration in the periphery and central nervous system (CNS). Cerebrolysin (CBL) is a neuropeptide preparation that promotes synaptic and neuronal plasticity in various animal models. In all cases, CBL was administered when the model was established. This research aims to investigate the neuroprotective and neurorepair effect of CBL on the cytoarchitecture of neurons and spine density in pyramidal neurons of the prefrontal (PFC) and the CA1 region of the dorsal hippocampus, as well as spheroidal neurons of the dentate gyrus (DG), in STZ-induced DM. In the first experimental condition, STZ and CBL are administered at the same time to evaluate the potential preventive effect of CBL. In the second experimental condition, CBL was administered two months after establishing the DM model to measure the potential neurorepair effect of CBL. STZ-induced hyperglycemia remained unaltered by the administration of CBL in both experimental conditions. In the first experimental condition, CBL treatment preserved the neuronal morphology in PFC layer 3, PFC layer 5 and the DG of the hippocampus, while also maintaining spine density in the PFC-3, DG and CA1 hippocampus. Furthermore, CBL induced neurorepair in neurons within the PFC-3, PFC-5 and CA1 regions of the hippocampus, along with an increase in spine density in the PFC-3, DG and CA1 hippocampus. These findings suggest that CBL´s effects on neuroplasticity could be observed before or after the damage was evident.
Assuntos
Aminoácidos , Diabetes Mellitus Experimental , Diabetes Mellitus Tipo 1 , Fármacos Neuroprotetores , Animais , Fármacos Neuroprotetores/farmacologia , Fármacos Neuroprotetores/administração & dosagem , Diabetes Mellitus Tipo 1/tratamento farmacológico , Aminoácidos/farmacologia , Aminoácidos/administração & dosagem , Masculino , Diabetes Mellitus Experimental/tratamento farmacológico , Estreptozocina/farmacologia , Modelos Animais de Doenças , Ratos Wistar , Ratos , Células Piramidais/efeitos dos fármacos , Células Piramidais/patologia , Córtex Pré-Frontal/efeitos dos fármacos , Hipocampo/efeitos dos fármacos , Espinhas Dendríticas/efeitos dos fármacos , Plasticidade Neuronal/efeitos dos fármacos , Neurônios/efeitos dos fármacosRESUMO
Canonical transient receptor potential channel 3 (TRPC3) is the most abundant TRPC channel in the brain and is highly expressed in all subfields of the hippocampus. Previous studies have suggested that TRPC3 channels may be involved in the hyperexcitability of hippocampal pyramidal neurons and seizures. Genetic ablation of TRPC3 channel expression reduced the intensity of pilocarpine-induced status epilepticus (SE). However, the underlying cellular mechanisms remain unexplored and the contribution of TRPC3 channels to SE-induced neurodegeneration is not determined. In this study, we investigated the contribution of TRPC3 channels to the electrophysiological properties of hippocampal pyramidal neurons and hippocampal synaptic plasticity, and the contribution of TRPC3 channels to seizure-induced neuronal cell death. We found that genetic ablation of TRPC3 expression did not alter basic electrophysiological properties of hippocampal pyramidal neurons and had a complex impact on epileptiform bursting in CA3. However, TRPC3 channels contribute significantly to long-term potentiation in CA1 and SE-induced neurodegeneration. Our results provided further support for therapeutic potential of TRPC3 inhibitors and raised new questions that need to be answered by future studies.
Assuntos
Morte Celular , Hipocampo , Células Piramidais , Convulsões , Canais de Cátion TRPC , Animais , Canais de Cátion TRPC/metabolismo , Canais de Cátion TRPC/genética , Camundongos , Células Piramidais/metabolismo , Células Piramidais/patologia , Hipocampo/metabolismo , Hipocampo/patologia , Convulsões/metabolismo , Convulsões/patologia , Estado Epiléptico/metabolismo , Estado Epiléptico/patologia , Estado Epiléptico/induzido quimicamente , Masculino , Neurônios/metabolismo , Pilocarpina , Potenciação de Longa Duração , Camundongos Knockout , Camundongos Endogâmicos C57BL , Plasticidade NeuronalRESUMO
BACKGROUND: Mutations in the X-linked gene cyclin-dependent kinase-like 5 (CDKL5) cause a severe neurological disorder characterised by early-onset epileptic seizures, autism and intellectual disability (ID). Impaired hippocampal function has been implicated in other models of monogenic forms of autism spectrum disorders and ID and is often linked to epilepsy and behavioural abnormalities. Many individuals with CDKL5 deficiency disorder (CDD) have null mutations and complete loss of CDKL5 protein, therefore in the current study we used a Cdkl5-/y rat model to elucidate the impact of CDKL5 loss on cellular excitability and synaptic function of CA1 pyramidal cells (PCs). We hypothesised abnormal pre and/or post synaptic function and plasticity would be observed in the hippocampus of Cdkl5-/y rats. METHODS: To allow cross-species comparisons of phenotypes associated with the loss of CDKL5, we generated a loss of function mutation in exon 8 of the rat Cdkl5 gene and assessed the impact of the loss of CDLK5 using a combination of extracellular and whole-cell electrophysiological recordings, biochemistry, and histology. RESULTS: Our results indicate that CA1 hippocampal long-term potentiation (LTP) is enhanced in slices prepared from juvenile, but not adult, Cdkl5-/y rats. Enhanced LTP does not result from changes in NMDA receptor function or subunit expression as these remain unaltered throughout development. Furthermore, Ca2+ permeable AMPA receptor mediated currents are unchanged in Cdkl5-/y rats. We observe reduced mEPSC frequency accompanied by increased spine density in basal dendrites of CA1 PCs, however we find no evidence supporting an increase in silent synapses when assessed using a minimal stimulation protocol in slices. Additionally, we found no change in paired-pulse ratio, consistent with normal release probability at Schaffer collateral to CA1 PC synapses. CONCLUSIONS: Our data indicate a role for CDKL5 in hippocampal synaptic function and raise the possibility that altered intracellular signalling rather than synaptic deficits contribute to the altered plasticity. LIMITATIONS: This study has focussed on the electrophysiological and anatomical properties of hippocampal CA1 PCs across early postnatal development. Studies involving other brain regions, older animals and behavioural phenotypes associated with the loss of CDKL5 are needed to understand the pathophysiology of CDD.
Assuntos
Modelos Animais de Doenças , Potenciação de Longa Duração , Proteínas Serina-Treonina Quinases , Receptores de AMPA , Receptores de N-Metil-D-Aspartato , Espasmos Infantis , Animais , Masculino , Ratos , Região CA1 Hipocampal/metabolismo , Região CA1 Hipocampal/patologia , Região CA1 Hipocampal/fisiopatologia , Síndromes Epilépticas/genética , Síndromes Epilépticas/metabolismo , Potenciais Pós-Sinápticos Excitadores , Doenças Genéticas Ligadas ao Cromossomo X/genética , Doenças Genéticas Ligadas ao Cromossomo X/metabolismo , Doenças Genéticas Ligadas ao Cromossomo X/fisiopatologia , Hipocampo/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Serina-Treonina Quinases/genética , Células Piramidais/metabolismo , Células Piramidais/patologia , Receptores de AMPA/metabolismo , Receptores de AMPA/genética , Receptores de N-Metil-D-Aspartato/metabolismo , Receptores de N-Metil-D-Aspartato/genética , Espasmos Infantis/genética , Espasmos Infantis/metabolismo , Sinapses/metabolismoRESUMO
Loss-of-function mutations in the progranulin (GRN) gene are an autosomal dominant cause of Frontotemporal Dementia (FTD). These mutations typically result in haploinsufficiency of the progranulin protein. Grn+/- mice provide a model for progranulin haploinsufficiency and develop FTD-like behavioral abnormalities by 9-10 months of age. In previous work, we demonstrated that Grn+/- mice develop a low dominance phenotype in the tube test that is associated with reduced dendritic arborization of layer II/III pyramidal neurons in the prelimbic region of the medial prefrontal cortex (mPFC), a region key for social dominance behavior in the tube test assay. In this study, we investigated whether progranulin haploinsufficiency induced changes in dendritic spine density and morphology. Individual layer II/III pyramidal neurons in the prelimbic mPFC of 9-10 month old wild-type or Grn+/- mice were targeted for iontophoretic microinjection of fluorescent dye, followed by high-resolution confocal microscopy and 3D reconstruction for morphometry analysis. Dendritic spine density in Grn+/- mice was comparable to wild-type littermates, but the apical dendrites in Grn+/- mice had a shift in the proportion of spine types, with fewer stubby spines and more thin spines. Additionally, apical dendrites of Grn+/- mice had longer spines and smaller thin spine head diameter in comparison to wild-type littermates. These changes in spine morphology may contribute to altered circuit-level activity and social dominance deficits in Grn+/- mice.
Assuntos
Espinhas Dendríticas , Haploinsuficiência , Córtex Pré-Frontal , Progranulinas , Animais , Espinhas Dendríticas/metabolismo , Córtex Pré-Frontal/patologia , Córtex Pré-Frontal/metabolismo , Progranulinas/deficiência , Progranulinas/genética , Camundongos , Células Piramidais/metabolismo , Células Piramidais/patologia , Masculino , Camundongos Endogâmicos C57BLRESUMO
Enlargement of the cerebrospinal fluid (CSF)-filled brain ventricles (cerebral ventriculomegaly), the cardinal feature of congenital hydrocephalus (CH), is increasingly recognized among patients with autism spectrum disorders (ASD). KATNAL2, a member of Katanin family microtubule-severing ATPases, is a known ASD risk gene, but its roles in human brain development remain unclear. Here, we show that nonsense truncation of Katnal2 (Katnal2Δ17) in mice results in classic ciliopathy phenotypes, including impaired spermatogenesis and cerebral ventriculomegaly. In both humans and mice, KATNAL2 is highly expressed in ciliated radial glia of the fetal ventricular-subventricular zone as well as in their postnatal ependymal and neuronal progeny. The ventriculomegaly observed in Katnal2Δ17 mice is associated with disrupted primary cilia and ependymal planar cell polarity that results in impaired cilia-generated CSF flow. Further, prefrontal pyramidal neurons in ventriculomegalic Katnal2Δ17 mice exhibit decreased excitatory drive and reduced high-frequency firing. Consistent with these findings in mice, we identified rare, damaging heterozygous germline variants in KATNAL2 in five unrelated patients with neurosurgically treated CH and comorbid ASD or other neurodevelopmental disorders. Mice engineered with the orthologous ASD-associated KATNAL2 F244L missense variant recapitulated the ventriculomegaly found in human patients. Together, these data suggest KATNAL2 pathogenic variants alter intraventricular CSF homeostasis and parenchymal neuronal connectivity by disrupting microtubule dynamics in fetal radial glia and their postnatal ependymal and neuronal descendants. The results identify a molecular mechanism underlying the development of ventriculomegaly in a genetic subset of patients with ASD and may explain persistence of neurodevelopmental phenotypes in some patients with CH despite neurosurgical CSF shunting.
Assuntos
Cílios , Hidrocefalia , Microtúbulos , Animais , Feminino , Humanos , Masculino , Camundongos , ATPases Associadas a Diversas Atividades Celulares/genética , ATPases Associadas a Diversas Atividades Celulares/metabolismo , Transtorno do Espectro Autista/genética , Transtorno do Espectro Autista/patologia , Transtorno do Espectro Autista/metabolismo , Cílios/metabolismo , Cílios/patologia , Epêndima/metabolismo , Epêndima/patologia , Hidrocefalia/genética , Hidrocefalia/patologia , Hidrocefalia/metabolismo , Katanina/metabolismo , Katanina/genética , Microtúbulos/metabolismo , Neurônios/metabolismo , Células Piramidais/metabolismo , Células Piramidais/patologiaRESUMO
Rett syndrome (RTT) is a neurodevelopmental disorder caused by mutations in MECP2, which encodes methyl-CpG-binding protein 2, a transcriptional regulator of many genes, including brain-derived neurotrophic factor (BDNF). BDNF levels are lower in multiple brain regions of Mecp2-deficient mice, and experimentally increasing BDNF levels improve atypical phenotypes in Mecp2 mutant mice. Due to the low blood-brain barrier permeability of BDNF itself, we tested the effects of LM22A-4, a brain-penetrant, small-molecule ligand of the BDNF receptor TrkB (encoded by Ntrk2), on dendritic spine density and form in hippocampal pyramidal neurons and on behavioral phenotypes in female Mecp2 heterozygous (HET) mice. A 4-week systemic treatment of Mecp2 HET mice with LM22A-4 restored spine volume in MeCP2-expressing neurons to wild-type (WT) levels, whereas spine volume in MeCP2-lacking neurons remained comparable to that in neurons from female WT mice. Female Mecp2 HET mice engaged in aggressive behaviors more than WT mice, the levels of which were reduced to WT levels by the 4-week LM22A-4 treatment. These data provide additional support to the potential usefulness of novel therapies not only for RTT but also to other BDNF-related disorders.
Assuntos
Comportamento Animal , Benzamidas , Espinhas Dendríticas , Proteína 2 de Ligação a Metil-CpG , Fenótipo , Receptor trkB , Síndrome de Rett , Animais , Feminino , Camundongos , Comportamento Animal/efeitos dos fármacos , Benzamidas/farmacologia , Benzamidas/uso terapêutico , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Espinhas Dendríticas/efeitos dos fármacos , Espinhas Dendríticas/metabolismo , Espinhas Dendríticas/patologia , Modelos Animais de Doenças , Heterozigoto , Hipocampo/patologia , Hipocampo/metabolismo , Hipocampo/efeitos dos fármacos , Ligantes , Proteína 2 de Ligação a Metil-CpG/metabolismo , Proteína 2 de Ligação a Metil-CpG/genética , Camundongos Endogâmicos C57BL , Células Piramidais/efeitos dos fármacos , Células Piramidais/metabolismo , Células Piramidais/patologia , Receptor trkB/metabolismo , Síndrome de Rett/patologia , Síndrome de Rett/tratamento farmacológicoRESUMO
Social hierarchy is a fundamental feature of social organization that can influence brain and emotional processing regarding social ranks. Several areas, including the medial prefrontal cortex (mPFC), the hippocampus, and the basolateral nucleus of the amygdala (BLA), are recognized to be involved in the regulation of emotional processing. However, its delicate structural correlates in brain regions are poorly understood. To address this issue, social hierarchy in home-caged sibling Wistar rats (three male rats/cage) was determined by employing a social confrontation tube test (postnatal weeks 9-12). Then, locomotor activity and anxiety-like behaviors were evaluated using an open-field test (OFT) and elevated plus-maze (EPM) at 13 weeks of age. The rapid Golgi impregnation method was conducted to quantify the spine density of the first secondary branch of the primary dendrite in 20⯵m length. The results indicated that dominant rats had significantly higher anxiety-like behaviors compared to subordinates, as was evident by lower open-arm entries and time spent in the EPM and lower entries and time spent in the center of OFT. The spine density analysis revealed a significantly higher number of spines in subordinates compared to the dominant rats in dmPFC pyramidal neurons and the apical and basal dendrites of hippocampal CA1 pyramidal neurons. However, the spine density of pyramidal-like neurons in the BLA was higher in dominant rats. Our findings suggest that dominant social rank is associated with higher anxiety and differential density of the dendritic spine in the prefrontal cortex and limbic regions of the brain in male rats.
Assuntos
Ansiedade , Espinhas Dendríticas , Hierarquia Social , Córtex Pré-Frontal , Ratos Wistar , Animais , Córtex Pré-Frontal/patologia , Masculino , Espinhas Dendríticas/fisiologia , Ansiedade/patologia , Ansiedade/fisiopatologia , Ratos , Células Piramidais/patologia , Células Piramidais/fisiologia , Comportamento Animal/fisiologia , Sistema Límbico/patologia , Complexo Nuclear Basolateral da Amígdala/patologia , Hipocampo/patologiaRESUMO
ß-Thalassaemia is one of the most common genetic diseases worldwide. During the past few decades, life expectancy of patients has increased significantly owing to advance in medical treatments. Cognitive impairment, once has been neglected, has gradually become more documented. Cognitive impairment in ß-thalassaemia patients is associated with natural history of the disease and socioeconomic factors. Herein, to determined effect of ß-thalassaemia intrinsic factors, 22-month-old ß-thalassaemia mouse was used as a model to assess cognitive impairment and to investigate any aberrant brain pathology in ß-thalassaemia. Open field test showed that ß-thalassaemia mice had decreased motor function. However, no difference of neuronal degeneration in primary motor cortex, layer 2/3 area was found. Interestingly, impaired learning and memory function accessed by a Morris water maze test was observed and correlated with a reduced number of living pyramidal neurons in hippocampus at the CA3 region in ß-thalassaemia mice. Cognitive impairment in ß-thalassaemia mice was significantly correlated with several intrinsic ß-thalassaemic factors including iron overload, anaemia, damaged red blood cells (RBCs), phosphatidylserine (PS)-exposed RBC large extracellular vesicles (EVs) and PS-exposed medium EVs. This highlights the importance of blood transfusion and iron chelation in ß-thalassaemia patients. In addition, to improve patients' quality of life, assessment of cognitive functions should become part of routine follow-up.
Assuntos
Disfunção Cognitiva , Modelos Animais de Doenças , Hipocampo , Talassemia beta , Animais , Talassemia beta/patologia , Talassemia beta/complicações , Talassemia beta/genética , Disfunção Cognitiva/etiologia , Disfunção Cognitiva/patologia , Camundongos , Hipocampo/patologia , Hipocampo/metabolismo , Masculino , Neurônios/metabolismo , Neurônios/patologia , Sobrecarga de Ferro/patologia , Sobrecarga de Ferro/metabolismo , Sobrecarga de Ferro/complicações , Vesículas Extracelulares/metabolismo , Eritrócitos/metabolismo , Eritrócitos/patologia , Células Piramidais/metabolismo , Células Piramidais/patologia , Aprendizagem em LabirintoRESUMO
Alterations in the experience-dependent and autonomous elaboration of neural circuits are assumed to underlie autism spectrum disorder (ASD), though it is unclear what synaptic traits are responsible. Here, utilizing a valproic acid-induced ASD marmoset model, which shares common molecular features with idiopathic ASD, we investigate changes in the structural dynamics of tuft dendrites of upper-layer pyramidal neurons and adjacent axons in the dorsomedial prefrontal cortex through two-photon microscopy. In model marmosets, dendritic spine turnover is upregulated, and spines are generated in clusters and survived more often than in control marmosets. Presynaptic boutons in local axons, but not in commissural long-range axons, demonstrate hyperdynamic turnover in model marmosets, suggesting alterations in projection-specific plasticity. Intriguingly, nasal oxytocin administration attenuates clustered spine emergence in model marmosets. Enhanced clustered spine generation, possibly unique to certain presynaptic partners, may be associated with ASD and be a potential therapeutic target.