RESUMO
Early pathological upregulation of adenosine A2A receptors (A2ARs), one of the caffeine targets, by neurons is thought to be involved in the development of synaptic and memory deficits in Alzheimer's disease (AD) but mechanisms remain ill-defined. To tackle this question, we promoted a neuronal upregulation of A2AR in the hippocampus of APP/PS1 mice developing AD-like amyloidogenesis. Our findings revealed that the early upregulation of A2AR in the presence of an ongoing amyloid pathology exacerbates memory impairments of APP/PS1 mice. These behavioural changes were not linked to major change in the development of amyloid pathology but rather associated with increased phosphorylated tau at neuritic plaques. Moreover, proteomic and transcriptomic analyses coupled with quantitative immunofluorescence studies indicated that neuronal upregulation of the receptor promoted both neuronal and non-neuronal autonomous alterations, i.e. enhanced neuroinflammatory response but also loss of excitatory synapses and impaired neuronal mitochondrial function, presumably accounting for the detrimental effect on memory. Overall, our results provide compelling evidence that neuronal A2AR dysfunction, as seen in the brain of patients, contributes to amyloid-related pathogenesis and underscores the potential of A2AR as a relevant therapeutic target for mitigating cognitive impairments in this neurodegenerative disorder.
Assuntos
Doença de Alzheimer , Precursor de Proteína beta-Amiloide , Transtornos da Memória , Camundongos Transgênicos , Neurônios , Receptor A2A de Adenosina , Sinapses , Animais , Transtornos da Memória/metabolismo , Transtornos da Memória/genética , Transtornos da Memória/patologia , Camundongos , Receptor A2A de Adenosina/metabolismo , Receptor A2A de Adenosina/genética , Sinapses/metabolismo , Sinapses/patologia , Precursor de Proteína beta-Amiloide/genética , Precursor de Proteína beta-Amiloide/metabolismo , Neurônios/metabolismo , Neurônios/patologia , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Doença de Alzheimer/genética , Hipocampo/metabolismo , Hipocampo/patologia , Presenilina-1/genética , Modelos Animais de Doenças , Placa Amiloide/patologia , Placa Amiloide/metabolismo , Masculino , Camundongos Endogâmicos C57BLRESUMO
Aging is the main risk factor of cognitive neurodegenerative diseases such as Alzheimer's disease, with epigenome alterations as a contributing factor. Here, we compared transcriptomic/epigenomic changes in the hippocampus, modified by aging and by tauopathy, an AD-related feature. We show that the cholesterol biosynthesis pathway is severely impaired in hippocampal neurons of tauopathic but not of aged mice pointing to vulnerability of these neurons in the disease. At the epigenomic level, histone hyperacetylation was observed at neuronal enhancers associated with glutamatergic regulations only in the tauopathy. Lastly, a treatment of tau mice with the CSP-TTK21 epi-drug that restored expression of key cholesterol biosynthesis genes counteracted hyperacetylation at neuronal enhancers and restored object memory. As acetyl-CoA is the primary substrate of both pathways, these data suggest that the rate of the cholesterol biosynthesis in hippocampal neurons may trigger epigenetic-driven changes, that may compromise the functions of hippocampal neurons in pathological conditions.
Assuntos
Doença de Alzheimer , Colesterol , Hipocampo , Camundongos Transgênicos , Neurônios , Animais , Doença de Alzheimer/metabolismo , Doença de Alzheimer/genética , Hipocampo/metabolismo , Colesterol/biossíntese , Colesterol/metabolismo , Neurônios/metabolismo , Camundongos , Epigenômica , Epigênese Genética , Camundongos Endogâmicos C57BL , Envelhecimento/metabolismo , Envelhecimento/genética , Masculino , Proteínas tau/metabolismo , Proteínas tau/genéticaRESUMO
α-synucleinopathies, encompassing Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy, are devastating neurodegenerative diseases for which available therapeutic options are scarce, mostly because of our limited understanding of their pathophysiology. Although these pathologies are attributed to an intracellular accumulation of the α-synuclein protein in the nervous system with subsequent neuronal loss, the trigger(s) of this accumulation is/are not clearly identified. Among the existing hypotheses, interest in the hypothesis advocating the involvement of infectious agents in the onset of these diseases is renewed. In this article, we aimed to review the ongoing relevant factors favoring and opposing this hypothesis, focusing on (1) the potential antimicrobial role of α-synuclein, (2) potential entry points of pathogens in regard to early symptoms of diverse α-synucleinopathies, (3) pre-existing literature reviews assessing potential associations between infectious agents and Parkinson's disease, (4) original studies assessing these associations for dementia with Lewy bodies and multiple system atrophy (identified through a systematic literature review), and finally (5) potential susceptibility factors modulating the effects of infectious agents on the nervous system. © 2022 International Parkinson and Movement Disorder Society.
Assuntos
Doença por Corpos de Lewy , Atrofia de Múltiplos Sistemas , Doença de Parkinson , Sinucleinopatias , Humanos , Doença por Corpos de Lewy/patologia , Atrofia de Múltiplos Sistemas/patologia , Doença de Parkinson/diagnóstico , alfa-Sinucleína/metabolismoRESUMO
Microglia play a critical role in maintaining neural function. While microglial activity follows a circadian rhythm, it is not clear how this intrinsic clock relates to their function, especially in stimulated conditions such as in the control of systemic energy homeostasis or memory formation. In this study, we found that microglia-specific knock-down of the core clock gene, Bmal1, resulted in increased microglial phagocytosis in mice subjected to high-fat diet (HFD)-induced metabolic stress and likewise among mice engaged in critical cognitive processes. Enhanced microglial phagocytosis was associated with significant retention of pro-opiomelanocortin (POMC)-immunoreactivity in the mediobasal hypothalamus in mice on a HFD as well as the formation of mature spines in the hippocampus during the learning process. This response ultimately protected mice from HFD-induced obesity and resulted in improved performance on memory tests. We conclude that loss of the rigorous control implemented by the intrinsic clock machinery increases the extent to which microglial phagocytosis can be triggered by neighboring neurons under metabolic stress or during memory formation. Taken together, microglial responses associated with loss of Bmal1 serve to ensure a healthier microenvironment for neighboring neurons in the setting of an adaptive response. Thus, microglial Bmal1 may be an important therapeutic target for metabolic and cognitive disorders with relevance to psychiatric disease.
Assuntos
Fatores de Transcrição ARNTL , Dieta Hiperlipídica , Memória , Microglia , Obesidade , Fatores de Transcrição ARNTL/genética , Fatores de Transcrição ARNTL/metabolismo , Animais , Ritmo Circadiano/fisiologia , Dieta Hiperlipídica/efeitos adversos , Técnicas de Silenciamento de Genes , Hipocampo/metabolismo , Hipocampo/fisiologia , Aprendizagem/fisiologia , Memória/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Microglia/metabolismo , Obesidade/etiologia , Obesidade/genética , Obesidade/metabolismo , Obesidade/prevenção & controle , Fagocitose/fisiologia , Pró-Opiomelanocortina/metabolismo , Estresse Fisiológico/fisiologiaRESUMO
Neurodegenerative diseases, including Huntington's disease (HD) and Alzheimer's disease (AD), are progressive conditions characterized by selective, disease-dependent loss of neuronal regions and/or subpopulations. Neuronal loss is preceded by a long period of neuronal dysfunction, during which glial cells also undergo major changes, including neuroinflammatory response. Those dramatic changes affecting both neuronal and glial cells associate with epigenetic and transcriptional dysregulations, characterized by defined cell-type-specific signatures. Notably, increasing studies support the view that altered regulation of transcriptional enhancers, which are distal regulatory regions of the genome capable of modulating the activity of promoters through chromatin looping, play a critical role in transcriptional dysregulation in HD and AD. We review current knowledge on enhancers in HD and AD, and highlight challenging issues to better decipher the epigenetic code of neurodegenerative diseases.
Assuntos
Doença de Alzheimer/genética , Elementos Facilitadores Genéticos/genética , Epigênese Genética/genética , Doença de Huntington/genética , Degeneração Neural/genética , Doença de Alzheimer/patologia , Animais , Regulação da Expressão Gênica/fisiologia , Humanos , Doença de Huntington/patologia , Degeneração Neural/patologia , Neuroglia/patologia , Neurônios/patologiaRESUMO
In Alzheimer's disease, the tauopathy is known as a major mechanism responsible for the development of cognitive deficits. Early biomarkers of such affectations for diagnosis/stratification are crucial in Alzheimer's disease research, and brain connectome studies increasingly show their potential establishing pathology fingerprints at the network level. In this context, we conducted an in vivo multimodal MRI study on young Thy-Tau22 transgenic mice expressing tauopathy, performing resting state functional MRI and structural brain imaging to identify early connectome signatures of the pathology, relating with histological and behavioural investigations. In the prodromal phase of tauopathy, before the emergence of cognitive impairments, Thy-Tau22 mice displayed selective modifications of brain functional connectivity involving three main centres: hippocampus (HIP), amygdala (AMG) and the isocortical areas, notably the somatosensory (SS) cortex. Each of these regions showed differential histopathological profiles. Disrupted ventral HIP-AMG functional pathway and altered dynamic functional connectivity were consistent with high pathological tau deposition and astrogliosis in both hippocampus and amygdala, and significant microglial reactivity in amygdalar nuclei. These patterns were concurrent with widespread functional hyperconnectivity of memory-related circuits of dorsal hippocampus-encompassing dorsal HIP-SS communication-in the absence of significant cortical histopathological markers. These findings suggest the coexistence of two intermingled mechanisms of response at the functional connectome level in the early phases of pathology: a maladaptive and a likely compensatory response. Captured in the connectivity patterns, such first responses to pathology could further be used in translational investigations as a lead towards an early biomarker of tauopathy as well as new targets for future treatments.
Assuntos
Transtornos da Memória/patologia , Transtornos da Memória/psicologia , Rede Nervosa/patologia , Tauopatias/patologia , Tauopatias/psicologia , Animais , Astrócitos/patologia , Encéfalo/diagnóstico por imagem , Encéfalo/patologia , Disfunção Cognitiva/genética , Disfunção Cognitiva/psicologia , Conectoma , Progressão da Doença , Gliose/patologia , Humanos , Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Transtornos da Memória/etiologia , Camundongos , Camundongos Transgênicos , Rede Nervosa/diagnóstico por imagem , Tauopatias/complicações , Tauopatias/diagnóstico por imagem , Proteínas tau/metabolismoRESUMO
BACKGROUND: CREB-dependent transcription necessary for long-term memory is driven by interactions with CREB-binding protein (CBP), a multi-domain protein that binds numerous transcription factors potentially affecting expression of thousands of genes. Identifying specific domain functions for multi-domain proteins is essential to understand processes such as cognitive function and circadian clocks. We investigated the function of the CBP KIX domain in hippocampal memory and gene expression using CBPKIX/KIX mice with mutations that prevent phospho-CREB (Ser133) binding. RESULTS: We found that CBPKIX/KIX mice were impaired in long-term memory, but not learning acquisition or short-term memory for the Morris water maze. Using an unbiased analysis of gene expression in the dorsal hippocampus after training in the Morris water maze or contextual fear conditioning, we discovered dysregulation of CREB, CLOCK, and BMAL1 target genes and downregulation of circadian genes in CBPKIX/KIX mice. Given our finding that the CBP KIX domain was important for transcription of circadian genes, we profiled circadian activity and phase resetting in CBPKIX/KIX mice. CBPKIX/KIX mice exhibited delayed activity peaks after light offset and longer free-running periods in constant dark. Interestingly, CBPKIX/KIX mice displayed phase delays and advances in response to photic stimulation comparable to wildtype littermates. Thus, this work delineates site-specific regulation of the circadian clock by a multi-domain protein. CONCLUSIONS: These studies provide insight into the significance of the CBP KIX domain by defining targets of CBP transcriptional co-activation in memory and the role of the CBP KIX domain in vivo on circadian rhythms.
Assuntos
Proteína de Ligação a CREB/genética , Ritmo Circadiano/genética , Memória de Longo Prazo , Domínios Proteicos , Animais , Proteína de Ligação a CREB/química , Proteína de Ligação a CREB/metabolismo , Feminino , Masculino , CamundongosRESUMO
Response and place memory systems have long been considered independent, encoding information in parallel, and involving the striatum and hippocampus, respectively. Most experimental studies supporting this view used simple, repetitive tasks, with unrestrained access to spatial cues. They did not give animals an opportunity to correct a response strategy by shifting to a place one, which would demonstrate dynamic, adaptive interactions between both memory systems in the navigation correction process. In a first experiment, rats were trained in the double-H maze for different durations (1, 6, or 14 days; 4 trials/day) to acquire a repetitive task in darkness (forcing a response memory-based strategy) or normal light (placing response and place memory systems in balance), or to acquire a place memory. All rats were given a misleading shifted-start probe trial 24-h post-training to test both their strategy and their ability to correct their navigation directly or in response to negative feedback. Additional analyses focused on the dorsal striatum and the dorsal hippocampus using c-Fos gene expression imaging and, in a second experiment, reversible muscimol inactivation. The results indicate that, depending on training protocol and duration, the striatum, which was unexpectedly the first to come into play in the dual strategy task, and the hippocampus are both required when rats have to correct their navigation after having acquired a repetitive task in a cued environment. Partly contradicting the model established by Packard and McGaugh (1996, Neurobiology of Learning and Memory, vol. 65), these data point to memory systems that interact in more complex ways than considered so far. To some extent, they also challenge the notion of hippocampus-independent response memory and striatum-independent place memory systems.
Assuntos
Hipocampo/fisiologia , Aprendizagem em Labirinto/fisiologia , Neostriado/fisiologia , Neurônios/fisiologia , Memória Espacial/fisiologia , Navegação Espacial/fisiologia , Animais , Sinais (Psicologia) , Masculino , Proteínas Proto-Oncogênicas c-fos/análise , Ratos Long-EvansRESUMO
Accumulating data support the role of tau pathology in cognitive decline in ageing and Alzheimer's disease, but underlying mechanisms remain ill-defined. Interestingly, ageing and Alzheimer's disease have been associated with an abnormal upregulation of adenosine A2A receptor (A2AR), a fine tuner of synaptic plasticity. However, the link between A2AR signalling and tau pathology has remained largely unexplored. In the present study, we report for the first time a significant upregulation of A2AR in patients suffering from frontotemporal lobar degeneration with the MAPT P301L mutation. To model these alterations, we induced neuronal A2AR upregulation in a tauopathy mouse model (THY-Tau22) using a new conditional strain allowing forebrain overexpression of the receptor. We found that neuronal A2AR upregulation increases tau hyperphosphorylation, potentiating the onset of tau-induced memory deficits. This detrimental effect was linked to a singular microglial signature as revealed by RNA sequencing analysis. In particular, we found that A2AR overexpression in THY-Tau22 mice led to the hippocampal upregulation of C1q complement protein-also observed in patients with frontotemporal lobar degeneration-and correlated with the loss of glutamatergic synapses, likely underlying the observed memory deficits. These data reveal a key impact of overactive neuronal A2AR in the onset of synaptic loss in tauopathies, paving the way for new therapeutic approaches.
Assuntos
Complemento C1q/metabolismo , Neurônios/metabolismo , Receptor A2A de Adenosina/genética , Receptor A2A de Adenosina/metabolismo , Sinapses/patologia , Tauopatias/genética , Tauopatias/patologia , Animais , Autopsia , Degeneração Lobar Frontotemporal/genética , Degeneração Lobar Frontotemporal/metabolismo , Hipocampo/metabolismo , Hipocampo/patologia , Humanos , Transtornos da Memória/etiologia , Transtornos da Memória/psicologia , Camundongos , Camundongos Transgênicos , Mutação , Aprendizagem Espacial , Tauopatias/psicologia , Proteínas tau/genéticaRESUMO
Aging weakens memory functions. Exposing healthy rodents or pathological rodent models to environmental enrichment (EE) housing improves their cognitive functions by changing neuronal levels of excitation, cellular signaling, and plasticity, notably in the hippocampus. At the molecular level, brain derived-neurotrophic factor (BDNF) represents an important player that supports EE-associated changes. EE facilitation of learning was also shown to correlate with chromatin acetylation in the hippocampus. It is not known, however, whether such mechanisms are still into play during aging. In this study, we exposed a cohort of aged rats (18-month-old) to either a 6 month period of EE or standard housing conditions and investigated chromatin acetylation-associated events [histone acetyltranferase activity, gene expression, and histone 3 (H3) acetylation] and epigenetic modulation of the Bdnf gene under rest conditions and during learning. We show that EE leads to upregulation of acetylation-dependent mechanisms in aged rats, whether at rest or following a learning challenge. We found an increased expression of Bdnf through Exon-I-dependent transcription, associated with an enrichment of acetylated H3 at several sites of Bdnf promoter I, more particularly on a proximal nuclear factor κB (NF-κB) site under learning conditions. We further evidenced p65/NF-κB binding to chromatin at promoters of genes important for plasticity and hippocampus-dependent learning (e.g., Bdnf, CamK2D). Altogether, our findings demonstrate that aged rats respond to a belated period of EE by increasing hippocampal plasticity, together with activating sustained acetylation-associated mechanisms recruiting NF-κB and promoting related gene transcription. These responses are likely to trigger beneficial effects associated with EE during aging. SIGNIFICANCE STATEMENT: Aging weakens memory functions. Optimizing the neuronal circuitry required for normal brain function can be achieved by increasing sensory, motor, and cognitive stimuli resulting from interactions with the environment (behavioral therapy). This can be experimentally modeled by exposing rodents to environmental enrichment (EE), as with large cages, numerous and varied toys, and interaction with other rodents. However, EE effects in aged rodents has been poorly studied, and it is not known whether beneficial mechanisms evidenced in the young adults can still be recruited during aging. Our study shows that aged rats respond to a belated period of EE by activating specific epigenetic and transcriptional signaling that promotes gene expression likely to facilitate plasticity and learning behaviors.
Assuntos
Envelhecimento/fisiologia , Envelhecimento/psicologia , Meio Ambiente , Hipocampo/crescimento & desenvolvimento , Hipocampo/fisiologia , Aprendizagem/fisiologia , NF-kappa B/metabolismo , Plasticidade Neuronal/fisiologia , Acetilação , Animais , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Cromatina/metabolismo , Epigênese Genética , Feminino , Expressão Gênica/genética , Aprendizagem em Labirinto/fisiologia , Neurogênese/fisiologia , Ratos , Ratos Long-Evans , Memória Espacial/fisiologia , Sinapses/fisiologia , Fator de Transcrição RelA/genética , Fator de Transcrição RelA/metabolismoRESUMO
Although the elaborate combination of histone and non-histone protein complexes defines chromatin organization and hence regulates numerous nuclear processes, the role of chromatin organizing proteins remains unexplored at the organismal level. The highly abundant, multifunctional, chromatin-associated protein and transcriptional coactivator positive coactivator 4 (PC4/Sub1) is absolutely critical for life, because its absence leads to embryonic lethality. Here, we report results obtained with conditional PC4 knock-out (PC4(f/f) Nestin-Cre) mice where PC4 is knocked out specifically in the brain. Compared with the control (PC4(+/+) Nestin-Cre) mice, PC4(f/f) Nestin-Cre mice are smaller with decreased nocturnal activity but are fertile and show no motor dysfunction. Neurons in different areas of the brains of these mice show sensitivity to hypoxia/anoxia, and decreased adult neurogenesis was observed in the dentate gyrus. Interestingly, PC4(f/f) Nestin-Cre mice exhibit a severe deficit in spatial memory extinction, whereas acquisition and long term retention were unaffected. Gene expression analysis of the dorsal hippocampus of PC4(f/f) Nestin-Cre mice revealed dysregulated expression of several neural function-associated genes, and PC4 was consistently found to localize on the promoters of these genes, indicating that PC4 regulates their expression. These observations indicate that non-histone chromatin-associated proteins like PC4 play a significant role in neuronal plasticity.
Assuntos
Proteínas de Ligação a DNA/metabolismo , Giro Denteado/metabolismo , Regulação da Expressão Gênica/fisiologia , Neurogênese/fisiologia , Plasticidade Neuronal/fisiologia , Memória Espacial/fisiologia , Animais , Proteínas de Ligação a DNA/genética , Hipóxia/metabolismo , Hipóxia/patologia , Camundongos , Camundongos KnockoutRESUMO
Huntington's disease (HD) is a neurodegenerative disease associated with extensive down-regulation of genes controlling neuronal function, particularly in the striatum. Whether altered epigenetic regulation underlies transcriptional defects in HD is unclear. Integrating RNA-sequencing (RNA-seq) and chromatin-immunoprecipitation followed by massively parallel sequencing (ChIP-seq), we show that down-regulated genes in HD mouse striatum associate with selective decrease in H3K27ac, a mark of active enhancers, and RNA Polymerase II (RNAPII). In addition, we reveal that decreased genes in HD mouse striatum display a specific epigenetic signature, characterized by high levels and broad patterns of H3K27ac and RNAPII. Our results indicate that this signature is that of super-enhancers, a category of broad enhancers regulating genes defining tissue identity and function. Specifically, we reveal that striatal super-enhancers display extensive H3K27 acetylation within gene bodies, drive transcription characterized by low levels of paused RNAPII, regulate neuronal function genes and are enriched in binding motifs for Gata transcription factors, such as Gata2 regulating striatal identity genes. Together, our results provide evidence for preferential down-regulation of genes controlled by super-enhancers in HD striatum and indicate that enhancer topography is a major parameter determining the propensity of a gene to be deregulated in a neurodegenerative disease.
Assuntos
Corpo Estriado/metabolismo , Elementos Facilitadores Genéticos , Regulação da Expressão Gênica , Doença de Huntington/genética , Animais , Modelos Animais de Doenças , Regulação para Baixo , Epigênese Genética , Perfilação da Expressão Gênica , Histonas/metabolismo , Doença de Huntington/metabolismo , Camundongos , Camundongos Transgênicos , Modelos Biológicos , Neurônios/metabolismo , Ligação Proteica , RNA Polimerase II/metabolismo , Fatores de Transcrição/metabolismo , Transcrição Gênica , TranscriptomaRESUMO
Although the brain functions of specific acetyltransferases such as the CREB-binding protein (CBP) and p300 have been well documented using mutant transgenic mice models, studies based on their direct pharmacological activation are still missing due to the lack of cell-permeable activators. Here we present a small-molecule (TTK21) activator of the histone acetyltransferases CBP/p300, which, when conjugated to glucose-based carbon nanosphere (CSP), passed the blood-brain barrier, induced no toxicity, and reached different parts of the brain. After intraperitoneal administration in mice, CSP-TTK21 significantly acetylated histones in the hippocampus and frontal cortex. Remarkably, CSP-TTK21 treatment promoted the formation of long and highly branched doublecortin-positive neurons in the subgranular zone of the dentate gyrus and reduced BrdU incorporation, suggesting that CBP/p300 activation favors maturation and differentiation of adult neuronal progenitors. In addition, mRNA levels of the neuroD1 differentiation marker and BDNF, a neurotrophin required for the terminal differentiation of newly generated neurons, were both increased in the hippocampus concomitantly with an enrichment of acetylated-histone on their proximal promoter. Finally, we found that CBP/p300 activation during a spatial training, while not improving retention of a recent memory, resulted in a significant extension of memory duration. This report is the first evidence for CBP/p300-mediated histone acetylation in the brain by an activator molecule, which has beneficial implications for the brain functions of adult neurogenesis and long-term memory. We propose that direct stimulation of acetyltransferase function could be useful in terms of therapeutic options for brain diseases.
Assuntos
Proteína de Ligação a CREB/metabolismo , Ativadores de Enzimas/farmacologia , Memória/efeitos dos fármacos , Neurogênese/efeitos dos fármacos , Fatores de Transcrição de p300-CBP/metabolismo , Acetiltransferases/metabolismo , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Encéfalo/crescimento & desenvolvimento , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Contagem de Células , Núcleo Celular/metabolismo , Imunoprecipitação da Cromatina , Dendritos/metabolismo , Dendritos/ultraestrutura , Imunofluorescência , Hipocampo/citologia , Hipocampo/metabolismo , Histona Acetiltransferases/metabolismo , Histonas/isolamento & purificação , Imuno-Histoquímica , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Nanosferas , Neurônios/metabolismo , Neurônios/ultraestrutura , Reação em Cadeia da Polimerase em Tempo RealRESUMO
BACKGROUND: The thalamic reuniens (Re) and rhomboid (Rh) nuclei are bidirectionally connected with the medial prefrontal cortex (mPFC) and the hippocampus (Hip). Fiber-sparing N-methyl-D-aspartate lesions of the ReRh disrupt cognitive functions, including persistence of certain memories. Because such lesions irremediably damage neurons interconnecting the ReRh with the mPFC and the Hip, it is impossible to know if one or both pathways contribute to memory persistence. Addressing such an issue requires selective, pathway-restricted and direction-specific disconnections. NEW METHOD: A recent method associates a retrograde adeno-associated virus (AAV) expressing Cre recombinase with an anterograde AAV expressing a Cre-dependent caspase, making such disconnection feasible by caspase-triggered apoptosis when both constructs meet intracellularly. We injected an AAVrg-Cre-GFP into the ReRh and an AAV5-taCasp into the mPFC. As expected, part of mPFC neurons died, but massive neurotoxicity of the AAVrg-Cre-GFP was found in ReRh, contrasting with normal density of DAPI staining. Other stainings demonstrated increasing density of reactive astrocytes and microglia in the neurodegeneration site. COMPARISON WITH EXISTING METHODS: Reducing the viral titer (by a 4-fold dilution) and injection volume (to half) attenuated toxicity substantially, still with evidence for partial disconnection between mPFC and ReRh. CONCLUSIONS: There is an imperative need to verify potential collateral damage inherent in this type of approach, which is likely to distort interpretation of experimental data. Therefore, controls allowing to distinguish collateral phenotypic effects from those linked to the desired disconnection is essential. It is also crucial to know for how long neurons expressing the Cre-GFP protein remain operational post-infection.
Assuntos
Dependovirus , Tálamo , Ratos , Animais , Dependovirus/genética , Tálamo/fisiologia , Núcleos da Linha Média do Tálamo/fisiologia , Hipocampo/fisiologia , Córtex Pré-Frontal/fisiologia , Neurônios , Caspases/farmacologia , Vias Neurais/fisiologiaRESUMO
The noradrenergic Locus CÅruleus is one of the major arousal structures involved in inducing wakefulness. While brain noradrenaline (NA) amounts display 24-h variations, the origin of NA rhythm is currently unknown. In this study, we tested the hypothesis that NA rhythm could result from its rhythmic synthesis. Therefore, we investigated the 24-h expression profile of NA rate-limiting enzyme, tyrosine hydroxylase (th), in the Locus CÅruleus (LC) of the nocturnal rat and the diurnal rodent Arvicanthis, under 12â¯h:12â¯h light/dark (LD) and constant darkness (DD) conditions. In both species, th mRNA levels vary significantly over 24-h. In nocturnal rats, th mRNA profiles show a unimodal rhythm, with peak values in late day in LD, and in the middle of the subjective day in DD. In contrast, th mRNA rhythm in Arvicanthis is characterized by a bimodal profile, with higher levels at the beginning of the day and of the night in LD, and in the middle of the subjective day and night in DD. The rhythmic pattern of th expression may be dependent on a LC clock machinery. Therefore, we investigated the expression of three clock genes, namely bmal1, per1, and per2, and found that their mRNAs display significant variations between day and nighttime points in both species, but in opposite directions. These data show that NA rhythm may be related to circadian expression of th gene in both species, but differs between nocturnal and diurnal rodents. Furthermore, the phase opposition of clock gene expression in the rat compared to Arvicanthis suggests that the clock machinery might be one of the mechanisms involved in th rhythmic expression.
Assuntos
Ritmo Circadiano , Murinae , Animais , Murinae/genética , Murinae/metabolismo , Núcleo Supraquiasmático/metabolismo , Luz , Locus Cerúleo/metabolismo , RNA Mensageiro/metabolismoRESUMO
Cytoplasmic mislocalization of the nuclear Fused in Sarcoma (FUS) protein is associated to amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Cytoplasmic FUS accumulation is recapitulated in the frontal cortex and spinal cord of heterozygous Fus∆NLS/+ mice. Yet, the mechanisms linking FUS mislocalization to hippocampal function and memory formation are still not characterized. Herein, we show that in these mice, the hippocampus paradoxically displays nuclear FUS accumulation. Multi-omic analyses showed that FUS binds to a set of genes characterized by the presence of an ETS/ELK-binding motifs, and involved in RNA metabolism, transcription, ribosome/mitochondria and chromatin organization. Importantly, hippocampal nuclei showed a decompaction of the neuronal chromatin at highly expressed genes and an inappropriate transcriptomic response was observed after spatial training of Fus∆NLS/+ mice. Furthermore, these mice lacked precision in a hippocampal-dependent spatial memory task and displayed decreased dendritic spine density. These studies shows that mutated FUS affects epigenetic regulation of the chromatin landscape in hippocampal neurons, which could participate in FTD/ALS pathogenic events. These data call for further investigation in the neurological phenotype of FUS-related diseases and open therapeutic strategies towards epigenetic drugs.
Assuntos
Esclerose Lateral Amiotrófica , Demência Frontotemporal , Animais , Camundongos , Esclerose Lateral Amiotrófica/genética , Cromatina/metabolismo , Epigênese Genética , Demência Frontotemporal/genética , Hipocampo/metabolismo , Mutação , Proteína FUS de Ligação a RNA/genética , Proteína FUS de Ligação a RNA/metabolismoRESUMO
Molecular mechanisms underlying cognitive deficits in Huntington's disease (HD), a striatal neurodegenerative disorder, are unknown. Here, we generated ChIPseq, 4Cseq and RNAseq data on striatal tissue of HD and control mice during striatum-dependent egocentric memory process. Multi-omics analyses showed altered activity-dependent epigenetic gene reprogramming of neuronal and glial genes regulating striatal plasticity in HD mice, which correlated with memory deficit. First, our data reveal that spatial chromatin re-organization and transcriptional induction of BDNF-related markers, regulating neuronal plasticity, were reduced since memory acquisition in the striatum of HD mice. Second, our data show that epigenetic memory implicating H3K9 acetylation, which established during late phase of memory process (e.g. during consolidation/recall) and contributed to glia-mediated, TGFß-dependent plasticity, was compromised in HD mouse striatum. Specifically, memory-dependent regulation of H3K9 acetylation was impaired at genes controlling extracellular matrix and myelination. Our study investigating the interplay between epigenetics and memory identifies H3K9 acetylation and TGFß signaling as new targets of striatal plasticity, which might offer innovative leads to improve HD.
Assuntos
Doença de Huntington , Camundongos , Animais , Doença de Huntington/genética , Acetilação , Modelos Animais de Doenças , Corpo Estriado , Fator de Crescimento Transformador betaRESUMO
At the present time, no viable treatment exists for cognitive and olfactory deficits in Down syndrome (DS). We show in a DS model (Ts65Dn mice) that these progressive nonreproductive neurological symptoms closely parallel a postpubertal decrease in hypothalamic as well as extrahypothalamic expression of a master molecule that controls reproduction-gonadotropin-releasing hormone (GnRH)-and appear related to an imbalance in a microRNA-gene network known to regulate GnRH neuron maturation together with altered hippocampal synaptic transmission. Epigenetic, cellular, chemogenetic, and pharmacological interventions that restore physiological GnRH levels abolish olfactory and cognitive defects in Ts65Dn mice, whereas pulsatile GnRH therapy improves cognition and brain connectivity in adult DS patients. GnRH thus plays a crucial role in olfaction and cognition, and pulsatile GnRH therapy holds promise to improve cognitive deficits in DS.
Assuntos
Cognição , Disfunção Cognitiva , Síndrome de Down , Hormônio Liberador de Gonadotropina , Transtornos do Olfato , Adulto , Animais , Cognição/efeitos dos fármacos , Cognição/fisiologia , Disfunção Cognitiva/tratamento farmacológico , Disfunção Cognitiva/etiologia , Modelos Animais de Doenças , Síndrome de Down/complicações , Síndrome de Down/tratamento farmacológico , Síndrome de Down/psicologia , Feminino , Hormônio Liberador de Gonadotropina/farmacologia , Hormônio Liberador de Gonadotropina/fisiologia , Hormônio Liberador de Gonadotropina/uso terapêutico , Humanos , Hipotálamo/efeitos dos fármacos , Hipotálamo/metabolismo , Masculino , Camundongos , Pessoa de Meia-Idade , Transtornos do Olfato/tratamento farmacológico , Transtornos do Olfato/etiologia , Transmissão Sináptica/efeitos dos fármacos , Adulto JovemRESUMO
Caffeine is the most widely consumed psychoactive substance in the world. Strikingly, the molecular pathways engaged by its regular consumption remain unclear. We herein addressed the mechanisms associated with habitual (chronic) caffeine consumption in the mouse hippocampus using untargeted orthogonal omics techniques. Our results revealed that chronic caffeine exerts concerted pleiotropic effects in the hippocampus at the epigenomic, proteomic, and metabolomic levels. Caffeine lowered metabolism-related processes (e.g., at the level of metabolomics and gene expression) in bulk tissue, while it induced neuron-specific epigenetic changes at synaptic transmission/plasticity-related genes and increased experience-driven transcriptional activity. Altogether, these findings suggest that regular caffeine intake improves the signal-to-noise ratio during information encoding, in part through fine-tuning of metabolic genes, while boosting the salience of information processing during learning in neuronal circuits.
Assuntos
Cafeína , Proteômica , Animais , Cafeína/metabolismo , Cafeína/farmacologia , Hipocampo/metabolismo , Aprendizagem , Camundongos , Plasticidade Neuronal/fisiologiaRESUMO
Neurodegenerative diseases, such as polyglutamine-related diseases, amyotrophic lateral sclerosis, and Alzheimer's disease are accompanied by transcriptional dysfunctions, leading to neuronal death. It is becoming more evident that the chromatin acetylation status is impaired during the lifetime of neurons, by a common mechanism related to the loss of function of histone acetyltransferase (HAT) activity. Notably, the HAT termed cAMP response element binding protein (CREB)-binding protein (CBP) was shown to display neuroprotective functions. Several other HATs have now been shown to participate in basic but vital neuronal functions. In addition, there is increasing evidence of several HATs (including CBP), as essential regulators of neuronal plasticity and memory formation processes. In order to counteract neuronal loss and/or memory deficits in neurodegenerative diseases, the current therapeutic strategies involve the use of small molecules antagonizing histone deacetylase (HDAC) activity (i.e. HDAC inhibitors). Although this strategy lacks specificity, some of these molecules display promising therapeutic properties. With the rapidly evolving literature on HATs and their respective functions in neuronal survival and memory formation, it seems essential to envisage direct stimulation of the acetyltransferase function as a new therapeutic tool in neurodegenerative diseases. In this review, we will highlight the present understanding and the future prospects of such therapeutic approach.