RESUMO
Reduction of amyloid beta (Aß) has been shown to be effective in treating Alzheimer's disease (AD), but the underlying assumption that neurons are the main source of pathogenic Aß is untested. Here, we challenge this prevailing belief by demonstrating that oligodendrocytes are an important source of Aß in the human brain and play a key role in promoting abnormal neuronal hyperactivity in an AD knock-in mouse model. We show that selectively suppressing oligodendrocyte Aß production improves AD brain pathology and restores neuronal function in the mouse model in vivo. Our findings suggest that targeting oligodendrocyte Aß production could be a promising therapeutic strategy for treating AD.
Assuntos
Doença de Alzheimer , Peptídeos beta-Amiloides , Modelos Animais de Doenças , Camundongos Transgênicos , Neurônios , Oligodendroglia , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Doença de Alzheimer/genética , Animais , Oligodendroglia/metabolismo , Peptídeos beta-Amiloides/metabolismo , Humanos , Neurônios/metabolismo , Camundongos , Encéfalo/metabolismo , Encéfalo/patologia , Masculino , Feminino , Técnicas de Introdução de GenesRESUMO
The human genome expresses thousands of natural antisense transcripts (NAT) that can regulate epigenetic state, transcription, RNA stability or translation of their overlapping genes1,2. Here we describe MAPT-AS1, a brain-enriched NAT that is conserved in primates and contains an embedded mammalian-wide interspersed repeat (MIR), which represses tau translation by competing for ribosomal RNA pairing with the MAPT mRNA internal ribosome entry site3. MAPT encodes tau, a neuronal intrinsically disordered protein (IDP) that stabilizes axonal microtubules. Hyperphosphorylated, aggregation-prone tau forms the hallmark inclusions of tauopathies4. Mutations in MAPT cause familial frontotemporal dementia, and common variations forming the MAPT H1 haplotype are a significant risk factor in many tauopathies5 and Parkinson's disease. Notably, expression of MAPT-AS1 or minimal essential sequences from MAPT-AS1 (including MIR) reduces-whereas silencing MAPT-AS1 expression increases-neuronal tau levels, and correlate with tau pathology in human brain. Moreover, we identified many additional NATs with embedded MIRs (MIR-NATs), which are overrepresented at coding genes linked to neurodegeneration and/or encoding IDPs, and confirmed MIR-NAT-mediated translational control of one such gene, PLCG1. These results demonstrate a key role for MAPT-AS1 in tauopathies and reveal a potentially broad contribution of MIR-NATs to the tightly controlled translation of IDPs6, with particular relevance for proteostasis in neurodegeneration.
Assuntos
Biossíntese de Proteínas/genética , Proteostase/genética , RNA Antissenso/genética , Tauopatias/genética , Tauopatias/metabolismo , Proteínas tau/genética , Proteínas tau/metabolismo , Idoso , Animais , Sítios de Ligação , Encéfalo/metabolismo , Encéfalo/patologia , Estudos de Casos e Controles , Diferenciação Celular , Progressão da Doença , Feminino , Humanos , Sítios Internos de Entrada Ribossomal/genética , Masculino , Camundongos , Camundongos Transgênicos , Pessoa de Meia-Idade , Neurônios/metabolismo , Neurônios/patologia , Ribossomos/metabolismo , Proteínas tau/biossínteseRESUMO
BACKGROUND: Although age is the biggest known risk factor for dementia, there remains uncertainty about other factors over the life course that contribute to a person's risk for cognitive decline later in life. Furthermore, the pathological processes leading to dementia are not fully understood. The main goals of Insight 46-a multi-phase longitudinal observational study-are to collect detailed cognitive, neurological, physical, cardiovascular, and sensory data; to combine those data with genetic and life-course information collected from the MRC National Survey of Health and Development (NSHD; 1946 British birth cohort); and thereby contribute to a better understanding of healthy ageing and dementia. METHODS/DESIGN: Phase 1 of Insight 46 (2015-2018) involved the recruitment of 502 members of the NSHD (median age = 70.7 years; 49% female) and has been described in detail by Lane and Parker et al. 2017. The present paper describes phase 2 (2018-2021) and phase 3 (2021-ongoing). Of the 502 phase 1 study members who were invited to a phase 2 research visit, 413 were willing to return for a clinic visit in London and 29 participated in a remote research assessment due to COVID-19 restrictions. Phase 3 aims to recruit 250 study members who previously participated in both phases 1 and 2 of Insight 46 (providing a third data time point) and 500 additional members of the NSHD who have not previously participated in Insight 46. DISCUSSION: The NSHD is the oldest and longest continuously running British birth cohort. Members of the NSHD are now at a critical point in their lives for us to investigate successful ageing and key age-related brain morbidities. Data collected from Insight 46 have the potential to greatly contribute to and impact the field of healthy ageing and dementia by combining unique life course data with longitudinal multiparametric clinical, imaging, and biomarker measurements. Further protocol enhancements are planned, including in-home sleep measurements and the engagement of participants through remote online cognitive testing. Data collected are and will continue to be made available to the scientific community.
Assuntos
Demência , Idoso , Feminino , Humanos , Masculino , Envelhecimento , Assistência Ambulatorial , Encéfalo , Estudos Observacionais como AssuntoRESUMO
INTRODUCTION: Familial Alzheimer's disease (fAD) is heterogeneous in terms of age at onset and clinical presentation. A greater understanding of the pathogenicity of fAD variants and how these contribute to heterogeneity will enhance our understanding of the mechanisms of AD more widely. METHODS: To determine the pathogenicity of the unclassified PSEN1 P436S mutation, we studied an expanded kindred of eight affected individuals, with magnetic resonance imaging (MRI) (two individuals), patient-derived induced pluripotent stem cell (iPSC) models (two donors), and post-mortem histology (one donor). RESULTS: An autosomal dominant pattern of inheritance of fAD was seen, with an average age at symptom onset of 46 years and atypical features. iPSC models and post-mortem tissue supported high production of amyloid beta 43 (Aß43). PSEN1 peptide maturation was unimpaired. DISCUSSION: We confirm that the P436S mutation in PSEN1 causes atypical fAD. The location of the mutation in the critical PSEN1 proline-alanine-leucine-proline (PALP) motif may explain the early age at onset despite appropriate protein maturation. HIGHLIGHTS: PSEN1 P436S mutations cause familial Alzheimer's disease. This mutation is associated with atypical clinical presentation. Induced pluripotent stem cells (iPSCs) and post-mortem studies support increased amyloid beta (Aß43) production. Early age at onset highlights the importance of the PALP motif in PSEN1 function.
Assuntos
Doença de Alzheimer , Peptídeos beta-Amiloides , Células-Tronco Pluripotentes Induzidas , Mutação , Presenilina-1 , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Idade de Início , Doença de Alzheimer/genética , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/metabolismo , Encéfalo/patologia , Imageamento por Ressonância Magnética , Linhagem , Presenilina-1/genéticaRESUMO
Neurodegenerative Diseases such as Alzheimer's Disease represent a major public health challenge, with no disease modifying therapies available. The availability of induced pluripotent stem cells from patients with phenotypes and genotypes of interest, that can be subsequently differentiated in vitro into disease-affected cell types, has revolutionised our ability to generate physiologically relevant disease models. The recent availability of brain organoids - self-organising in vitro tissue models - as enabled the generation of complex, multicellular systems to study brain development and disease. Although widely used for modelling neurodevelopment, early studies have demonstrated great promise in the use of organoids as models of neurodegenerative disease. Here, I will review recent progress to model neurodegenerative diseases using organoids and comment on future directions and challenges.
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Doença de Alzheimer/genética , Encéfalo/metabolismo , Síndrome de Creutzfeldt-Jakob/genética , Doença de Huntington/genética , Modelos Biológicos , Organoides/metabolismo , Doença de Parkinson/genética , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Doença de Alzheimer/fisiopatologia , Encéfalo/patologia , Diferenciação Celular , Síndrome de Creutzfeldt-Jakob/metabolismo , Síndrome de Creutzfeldt-Jakob/patologia , Síndrome de Creutzfeldt-Jakob/fisiopatologia , Humanos , Doença de Huntington/metabolismo , Doença de Huntington/patologia , Doença de Huntington/fisiopatologia , Células-Tronco Pluripotentes Induzidas/citologia , Células-Tronco Pluripotentes Induzidas/metabolismo , Mutação , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Células-Tronco Neurais/citologia , Células-Tronco Neurais/metabolismo , Neuroglia/citologia , Neuroglia/metabolismo , Neurônios/citologia , Neurônios/metabolismo , Especificidade de Órgãos , Organoides/citologia , Doença de Parkinson/metabolismo , Doença de Parkinson/patologia , Doença de Parkinson/fisiopatologia , Técnicas de Cultura de TecidosRESUMO
One form of early life stress, prenatal exposure to glucocorticoids (GCs), confers a higher risk of psychiatric and neurodevelopmental disorders in later life. Increasingly, the importance of microglia in these disorders is recognized. Studies on GCs exposure during microglial development have been limited, and there are few, if any, human studies. We established an in vitro model of ELS by continuous pre-exposure of human iPS-microglia to GCs during primitive hematopoiesis (the critical stage of iPS-microglial differentiation) and then examined how this exposure affected the microglial phenotype as they differentiated and matured to microglia, using RNA-seq analyses and functional assays. The iPS-microglia predominantly expressed glucocorticoid receptors over mineralocorticoid receptors, and in particular, the GR-α splice variant. Chronic GCs exposure during primitive hematopoiesis was able to recapitulate in vivo ELS effects. Thus, pre-exposure to prolonged GCs resulted in increased type I interferon signaling, the presence of Cyclic GMP-AMP synthase-positive (cGAS) micronuclei, cellular senescence and reduced proliferation in the matured iPS-microglia. The findings from this in vitro ELS model have ramifications for the responses of microglia in the pathogenesis of GC- mediated ELS-associated disorders such as schizophrenia, attention-deficit hyperactivity disorder and autism spectrum disorder.
Assuntos
Experiências Adversas da Infância , Glucocorticoides , Microglia , Receptores de Glucocorticoides , Humanos , Transtorno do Espectro Autista/etiologia , Instabilidade Genômica , Glucocorticoides/efeitos adversos , Glucocorticoides/metabolismo , Microglia/efeitos dos fármacos , Microglia/fisiologia , Células Progenitoras Mieloides/metabolismo , Receptores de Glucocorticoides/genética , Receptores de Glucocorticoides/metabolismo , Células-Tronco Pluripotentes Induzidas/efeitos dos fármacos , Células-Tronco Pluripotentes Induzidas/metabolismo , Interferon Tipo I/metabolismoRESUMO
The microtubule-associated protein tau gene (MAPT) 10+16 intronic mutation causes frontotemporal lobar degeneration (FTLD) by increasing expression of four-repeat (4R)-tau isoforms. We investigated the potential role for astrocytes in the pathogenesis of FTLD by studying the expression of 4R-tau. We derived astrocytes and neurons from induced pluripotent stem cells from two asymptomatic 10+16 carriers which, compared to controls, showed persistently increased 4R:3R-tau transcript and protein ratios in both cell types. However, beyond 300 days culture, 10+16 neurons showed less marked increase of this 4R:3R-tau transcript ratio compared to astrocytes. Interestingly, throughout maturation, both 10+16 carriers consistently displayed different 4R:3R-tau transcript and protein ratios. These elevated levels of 4R-tau in astrocytes implicate glial cells in the pathogenic process and also suggests a cell-type-specific regulation and may inform and help on treatment of pre-clinical tauopathies.
Assuntos
Degeneração Lobar Frontotemporal , Tauopatias , Proteínas tau , Astrócitos/metabolismo , Humanos , Mutação/genética , Isoformas de Proteínas/genética , Tauopatias/genética , Tauopatias/metabolismo , Proteínas tau/genética , Proteínas tau/metabolismoRESUMO
Frontotemporal dementia and parkinsonism (FTDP-17) caused by the 10+16 splice-site mutation in the gene encoding microtubule-associated protein tau (MAPT) provides an established platform to model tau-related dementia in vitro Neurons derived from human induced pluripotent stem cells (iPSCs) have been shown to recapitulate the neurodevelopmental profile of tau pathology during in vitro corticogenesis, as in the adult human brain. However, the neurophysiological phenotype of these cells has remained unknown, leaving unanswered questions regarding the functional relevance and the gnostic power of this disease model. In this study, we used electrophysiology to explore the membrane properties and intrinsic excitability of the generated neurons and found that human cells mature by â¼150â days of neurogenesis to become compatible with matured cortical neurons. In earlier FTDP-17, however, neurons exhibited a depolarized resting membrane potential associated with increased resistance and reduced voltage-gated Na+- and K+-channel-mediated conductance. Expression of the Nav1.6 protein was reduced in FTDP-17. These effects led to reduced cell capability of induced firing and changed the action potential waveform in FTDP-17. The revealed neuropathology might thus contribute to the clinicopathological profile of the disease. This sheds new light on the significance of human in vitro models of dementia.
Assuntos
Demência Frontotemporal , Células-Tronco Pluripotentes Induzidas , Adulto , Demência Frontotemporal/genética , Humanos , Mutação , Neurônios , Fenótipo , Proteínas tau/genéticaRESUMO
In vitro studies of autosomal dominant Alzheimer's disease implicate longer amyloid-ß peptides in disease pathogenesis; however, less is known about the behaviour of these mutations in vivo. In this cross-sectional cohort study, we used liquid chromatography-tandem mass spectrometry to analyse 66 plasma samples from individuals who were at risk of inheriting a mutation or were symptomatic. We tested for differences in amyloid-ß (Aß)42:38, Aß42:40 and Aß38:40 ratios between presenilin 1 (PSEN1) and amyloid precursor protein (APP) carriers. We examined the relationship between plasma and in vitro models of amyloid-ß processing and tested for associations with parental age at onset. Thirty-nine participants were mutation carriers (28 PSEN1 and 11 APP). Age- and sex-adjusted models showed marked differences in plasma amyloid-ß between genotypes: higher Aß42:38 in PSEN1 versus APP (P < 0.001) and non-carriers (P < 0.001); higher Aß38:40 in APP versus PSEN1 (P < 0.001) and non-carriers (P < 0.001); while Aß42:40 was higher in both mutation groups compared to non-carriers (both P < 0.001). Amyloid-ß profiles were reasonably consistent in plasma and cell lines. Within the PSEN1 group, models demonstrated associations between Aß42:38, Aß42:40 and Aß38:40 ratios and parental age at onset. In vivo differences in amyloid-ß processing between PSEN1 and APP carriers provide insights into disease pathophysiology, which can inform therapy development.
Assuntos
Doença de Alzheimer/sangue , Doença de Alzheimer/genética , Peptídeos beta-Amiloides/sangue , Peptídeos beta-Amiloides/genética , Presenilina-1/sangue , Presenilina-1/genética , Adulto , Doença de Alzheimer/diagnóstico , Biomarcadores/sangue , Estudos de Coortes , Estudos Transversais , Feminino , Genótipo , Humanos , Células-Tronco Pluripotentes Induzidas/metabolismo , Estudos Longitudinais , Masculino , Pessoa de Meia-IdadeRESUMO
INTRODUCTION: The second most common form of early-onset dementia-frontotemporal dementia (FTD)-is often characterized by the aggregation of the microtubule-associated protein tau. Here we studied the mechanism of tau-induced neuronal dysfunction in neurons with the FTD-related 10+16 MAPT mutation. METHODS: Live imaging, electrophysiology, and redox proteomics were used in 10+16 induced pluripotent stem cell-derived neurons and a model of tau spreading in primary cultures. RESULTS: Overproduction of mitochondrial reactive oxygen species (ROS) in 10+16 neurons alters the trafficking of specific glutamate receptor subunits via redox regulation. Increased surface expression of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N-methyl-D-aspartate (NMDA) receptors containing GluA1 and NR2B subunits leads to impaired glutamatergic signaling, calcium overload, and excitotoxicity. Mitochondrial antioxidants restore the altered response and prevent neuronal death. Importantly, extracellular 4R tau induces the same pathological response in healthy neurons, thus proposing a mechanism for disease propagation. DISCUSSION: These results demonstrate mitochondrial ROS modulate glutamatergic signaling in FTD, and suggest a new therapeutic strategy.
Assuntos
Demência Frontotemporal , Células-Tronco Pluripotentes Induzidas , Demência Frontotemporal/genética , Humanos , Células-Tronco Pluripotentes Induzidas/metabolismo , Mitocôndrias , Neurônios/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Proteínas tau/metabolismoRESUMO
Induced pluripotent stem cell (iPSC) technology enables the generation of human neurons in vitro, which contain the precise genome of the cell donor, therefore permitting the generation of disease models from individuals with a disease-associated genotype of interest. This approach has been extensively used to model inherited forms of Alzheimer's disease and frontotemporal dementia. The combination of iPSC-derived neuronal models with targeted mass spectrometry analysis has provided unprecedented insights into the regulation of specific proteins in human neuronal physiology and pathology. For example enabling investigations into tau and APP/Aß, specifically: protein isoform expression, relative levels of cleavage fragments, aggregated species and functionally critical post-translational modifications. The use of mass spectrometry has enabled a determination of how closely iPSC-derived models recapitulate disease profiles observed in the human brain. This review will highlight the progress to date in studies using iPSCs and mass spectrometry to model Alzheimer's disease and dementia. We go on to convey our optimism, as studies in the near future will make use of this precedent, together with novel techniques such as genome editing and stable isotope labelling, to provide real progress towards an in depth understanding of early neurodegenerative processes and development of novel therapeutic agents.
Assuntos
Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/análise , Demência/metabolismo , Células-Tronco Pluripotentes Induzidas/química , Espectrometria de Massas/métodos , Proteínas tau/análise , Animais , Modelos Animais de Doenças , HumanosRESUMO
Familial Alzheimer's disease (fAD) mutations alter amyloid precursor protein (APP) cleavage by γ-secretase, increasing the proportion of longer amyloidogenic amyloid-ß (Aß) peptides. Using five control induced pluripotent stem cell (iPSC) lines and seven iPSC lines generated from fAD patients, we investigated the effects of mutations on the Aß secretome in human neurons generated in 2D and 3D. We also analysed matched CSF, post-mortem brain tissue, and iPSCs from the same participant with the APP V717I mutation. All fAD mutation lines demonstrated an increased Aß42:40 ratio relative to controls, yet displayed varied signatures for Aß43, Aß38, and short Aß fragments. We propose four qualitatively distinct mechanisms behind raised Aß42:40. (1) APP V717I mutations alter γ-secretase cleavage site preference. Whereas, distinct presenilin 1 (PSEN1) mutations lead to either (2) reduced γ-secretase activity, (3) altered protein stability or (4) reduced PSEN1 maturation, all culminating in reduced γ-secretase carboxypeptidase-like activity. These data support Aß mechanistic tenets in a human physiological model and substantiate iPSC-neurons for modelling fAD.
Assuntos
Doença de Alzheimer/genética , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/genética , Mutação , Neurônios/metabolismo , Neurônios/patologia , Adulto , Idoso , Doença de Alzheimer/metabolismo , Secretases da Proteína Precursora do Amiloide/metabolismo , Peptídeos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/genética , Precursor de Proteína beta-Amiloide/metabolismo , Células Cultivadas , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Fragmentos de Peptídeos/genética , Fragmentos de Peptídeos/metabolismo , Presenilina-1/genética , Presenilina-1/metabolismo , Adulto JovemRESUMO
Frontotemporal dementia (FTD) describes a group of clinically heterogeneous conditions that frequently affect people under the age of 65 (Le Ber et al., 2013). There are multiple genetic causes of FTD, including coding or splice-site mutations in MAPT, GRN mutations that lead to haploinsufficiency of progranulin protein, and a hexanucleotide GGGGCC repeat expansion in C9ORF72. Pathologically, FTD is characterised by abnormal protein accumulations in neurons and glia. These aggregates can be composed of the microtubule-associated protein tau (observed in FTD with MAPT mutations), the DNA/RNA-binding protein TDP-43 (seen in FTD with mutations in GRN or C9ORF72 repeat expansions) or dipeptide proteins generated by repeat associated non-ATG translation of the C9ORF72 repeat expansion. There are currently no disease-modifying therapies for FTD and the availability of in vitro models that recapitulate pathologies in a disease-relevant cell type would accelerate the development of novel therapeutics. It is now possible to generate patient-specific stem cells through the reprogramming of somatic cells from a patient with a genotype/phenotype of interest into induced pluripotent stem cells (iPSCs). iPSCs can subsequently be differentiated into a plethora of cell types including neurons, astrocytes and microglia. Using this approach has allowed researchers to generate in vitro models of genetic FTD in human cell types that are largely inaccessible during life. In this review we explore the recent progress in the use of iPSCs to model FTD, and consider the merits, limitations and future prospects of this approach.
Assuntos
Demência Frontotemporal/genética , Células-Tronco Pluripotentes Induzidas/metabolismo , Proteínas tau/genética , Axônios/metabolismo , Transporte Biológico , Proteína C9orf72/genética , Proteína C9orf72/fisiologia , Diferenciação Celular , Técnicas de Reprogramação Celular , Expansão das Repetições de DNA , Proteínas de Ligação a DNA/fisiologia , Regulação da Expressão Gênica no Desenvolvimento , Humanos , Íntrons/genética , Microtúbulos/fisiologia , Mitocôndrias/fisiologia , Modelos Genéticos , Mutação de Sentido Incorreto , Degeneração Neural , Neuroglia/metabolismo , Neuroglia/patologia , Neurônios/metabolismo , Neurônios/patologia , Organoides , Progranulinas/genética , Progranulinas/fisiologia , Agregação Patológica de Proteínas , Isoformas de Proteínas , Processamento de Proteína , Espécies Reativas de Oxigênio , Proteínas tau/química , Proteínas tau/metabolismoRESUMO
The joint modeling of brain imaging information and genetic data is a promising research avenue to highlight the functional role of genes in determining the pathophysiological mechanisms of Alzheimer's disease (AD). However, since genome-wide association (GWA) studies are essentially limited to the exploration of statistical correlations between genetic variants and phenotype, the validation and interpretation of the findings are usually nontrivial and prone to false positives. To address this issue, in this work, we investigate the functional genetic mechanisms underlying brain atrophy in AD by studying the involvement of candidate variants in known genetic regulatory functions. This approach, here termed functional prioritization, aims at testing the sets of gene variants identified by high-dimensional multivariate statistical modeling with respect to known biological processes to introduce a biology-driven validation scheme. When applied to the Alzheimer's Disease Neuroimaging Initiative (ADNI) cohort, the functional prioritization allowed for identifying a link between tribbles pseudokinase 3 (TRIB3) and the stereotypical pattern of gray matter loss in AD, which was confirmed in an independent validation sample, and that provides evidence about the relation between this gene and known mechanisms of neurodegeneration.
Assuntos
Doença de Alzheimer/genética , Encéfalo/patologia , Proteínas de Ciclo Celular/genética , Proteínas Serina-Treonina Quinases/antagonistas & inibidores , Proteínas Repressoras/genética , Idoso , Doença de Alzheimer/diagnóstico por imagem , Doença de Alzheimer/patologia , Atrofia/diagnóstico por imagem , Atrofia/genética , Atrofia/metabolismo , Encéfalo/diagnóstico por imagem , Disfunção Cognitiva/diagnóstico por imagem , Disfunção Cognitiva/genética , Disfunção Cognitiva/patologia , Estudos de Coortes , Feminino , Predisposição Genética para Doença , Humanos , Imageamento por Ressonância Magnética , Masculino , Análise Multivariada , Polimorfismo de Nucleotídeo Único , Proteínas Serina-Treonina Quinases/genéticaRESUMO
Corticobasal degeneration typically progresses gradually over 5-7 years from onset till death. Fulminant corticobasal degeneration cases with a rapidly progressive course were rarely reported (RP-CBD). This study aimed to investigate their neuropathological characteristics. Of the 124 autopsy-confirmed corticobasal degeneration cases collected from 14 centres, we identified 6 RP-CBD cases (4.8%) who died of advanced disease within 3 years of onset. These RP-CBD cases had different clinical phenotypes including rapid global cognitive decline (N = 2), corticobasal syndrome (N = 2) and Richardson's syndrome (N = 2). We also studied four corticobasal degeneration cases with an average disease duration of 3 years or less, who died of another unrelated illness (Intermediate-CBD). Finally, we selected 12 age-matched corticobasal degeneration cases out of a cohort of 110, who had a typical gradually progressive course and reached advanced clinical stage (End-stage-CBD). Quantitative analysis showed high overall tau burden (p = 0.2) and severe nigral cell loss (p = 0.47) in both the RP-CBD and End-stage-CBD groups consistent with advanced pathological changes, while the Intermediate-CBD group (mean disease duration = 3 years) had milder changes than End-stage-CBD (p < 0.05). These findings indicated that RP-CBD cases had already developed advanced pathological changes as those observed in End-stage-CBD cases (mean disease duration = 6.7 years), but within a significantly shorter duration (2.5 years; p < 0.001). Subgroup analysis was performed to investigate the cellular patterns of tau aggregates in the anterior frontal cortex and caudate by comparing neuronal-to-astrocytic plaque ratios between six RP-CBD cases, four Intermediate-CBD and 12 age-matched End-stage-CBD. Neuronal-to-astrocytic plaque ratios of Intermediate-CBD and End-stage-CBD, but not RP-CBD, positively correlated with disease duration in both the anterior frontal cortex and caudate (p = 0.02). In contrast to the predominance of astrocytic plaques we previously reported in preclinical asymptomatic corticobasal degeneration cases, neuronal tau aggregates predominated in RP-CBD exceeding those in Intermediate-CBD (anterior frontal cortex: p < 0.001, caudate: p = 0.001) and End-stage-CBD (anterior frontal cortex: p = 0.03, caudate: p = 0.01) as demonstrated by its higher neuronal-to-astrocytic plaque ratios in both anterior frontal cortex and caudate. We did not identify any difference in age at onset, any pathogenic tau mutation or concomitant pathologies that could have contributed to the rapid progression of these RP-CBD cases. Mild TDP-43 pathology was observed in three RP-CBD cases. All RP-CBD cases were men. The MAPT H2 haplotype, known to be protective, was identified in one RP-CBD case (17%) and 8 of the matched End-stage-CBD cases (67%). We conclude that RP-CBD is a distinct aggressive variant of corticobasal degeneration with characteristic neuropathological substrates resulting in a fulminant disease process as evident both clinically and pathologically. Biological factors such as genetic modifiers likely play a pivotal role in the RP-CBD variant and should be the subject of future research.
Assuntos
Doenças dos Gânglios da Base/patologia , Doenças Neurodegenerativas/patologia , Proteínas tau/metabolismo , Idoso , Idoso de 80 Anos ou mais , Doenças dos Gânglios da Base/metabolismo , Córtex Cerebral/patologia , Progressão da Doença , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Doenças Neurodegenerativas/metabolismoRESUMO
Mutations in the gene encoding valosin-containing protein (VCP) lead to multisystem proteinopathies including frontotemporal dementia. We have previously shown that patient-derived VCP mutant fibroblasts exhibit lower mitochondrial membrane potential, uncoupled respiration, and reduced ATP levels. This study addresses the underlying basis for mitochondrial uncoupling using VCP knockdown neuroblastoma cell lines, induced pluripotent stem cells (iPSCs), and iPSC-derived cortical neurons from patients with pathogenic mutations in VCP Using fluorescent live cell imaging and respiration analysis we demonstrate a VCP mutation/knockdown-induced dysregulation in the adenine nucleotide translocase, which results in a slower rate of ADP or ATP translocation across the mitochondrial membranes. This deregulation can explain the mitochondrial uncoupling and lower ATP levels in VCP mutation-bearing neurons via reduced ADP availability for ATP synthesis. This study provides evidence for a role of adenine nucleotide translocase in the mechanism underlying altered mitochondrial function in VCP-related degeneration, and this new insight may inform efforts to better understand and manage neurodegenerative disease and other proteinopathies.
Assuntos
Difosfato de Adenosina/metabolismo , Adenosina Trifosfatases , Trifosfato de Adenosina/metabolismo , Proteínas de Ciclo Celular , Membranas Mitocondriais/metabolismo , Mutação , Neurônios/metabolismo , Difosfato de Adenosina/genética , Adenosina Trifosfatases/genética , Adenosina Trifosfatases/metabolismo , Trifosfato de Adenosina/genética , Transporte Biológico Ativo/fisiologia , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Linhagem Celular Tumoral , Humanos , Células-Tronco Pluripotentes Induzidas/metabolismo , Células-Tronco Pluripotentes Induzidas/patologia , Translocases Mitocondriais de ADP e ATP/genética , Translocases Mitocondriais de ADP e ATP/metabolismo , Doenças Neurodegenerativas/genética , Doenças Neurodegenerativas/metabolismo , Neurônios/patologia , Deficiências na Proteostase/genética , Deficiências na Proteostase/metabolismo , Proteína com ValosinaRESUMO
The alternative splicing of the tau gene, MAPT, generates six protein isoforms in the adult human central nervous system (CNS). Tau splicing is developmentally regulated and dysregulated in disease. Mutations in MAPT that alter tau splicing cause frontotemporal dementia (FTD) with tau pathology, providing evidence for a causal link between altered tau splicing and disease. The use of induced pluripotent stem cell (iPSC)-derived neurons has revolutionized the way we model neurological disease in vitro. However, as most tau mutations are located within or around the alternatively spliced exon 10, it is important that iPSC-neurons splice tau appropriately in order to be used as disease models. To address this issue, we analyzed the expression and splicing of tau in iPSC-derived cortical neurons from control patients and FTD patients with the 10 + 16 intronic mutation in MAPT. We show that control neurons only express the fetal tau isoform (0N3R), even at extended time points of 100 days in vitro. Neurons from FTD patients with the 10 + 16 mutation in MAPT express both 0N3R and 0N4R tau isoforms, demonstrating that this mutation overrides the developmental regulation of exon 10 inclusion in our in vitro model. Further, at extended time points of 365 days in vitro, we observe a switch in tau splicing to include six tau isoforms as seen in the adult human CNS. Our results demonstrate the importance of neuronal maturity for use in in vitro modeling and provide a system that will be important for understanding the functional consequences of altered tau splicing.
Assuntos
Processamento Alternativo , Demência Frontotemporal/genética , Mutação , Neurônios/metabolismo , Células-Tronco/metabolismo , Proteínas tau/genética , Biomarcadores , Diferenciação Celular , Linhagem Celular , Córtex Cerebral/citologia , Córtex Cerebral/metabolismo , Fibroblastos/citologia , Fibroblastos/metabolismo , Demência Frontotemporal/metabolismo , Haplótipos , Humanos , Células-Tronco Pluripotentes Induzidas/citologia , Células-Tronco Pluripotentes Induzidas/metabolismo , Lactente , Recém-Nascido , Íntrons , Neurônios/citologia , Fosforilação , Sítios de Splice de RNA , Células-Tronco/citologiaRESUMO
The cerebellum forms a highly ordered and indispensible component of motor function within the adult neuraxis, consisting of several distinct cellular subtypes. Cerebellar disease, through a variety of genetic and acquired causes, results in the loss of function of defined subclasses of neurons, and remains a significant and untreatable health care burden. The scarcity of therapies in this arena can partially be explained by unresolved disease mechanisms due to inaccessibility of human cerebellar neurons in a relevant experimental context where initiating disease mechanisms could be functionally elucidated, or drug screens conducted. In this review we discuss the potential promise of human induced pluripotent stem cells (hiPSCs) for regenerative neurology, with a particular emphasis on in vitro modelling of cerebellar degeneration. We discuss progress made thus far using hiPSC-based models of neurodegeneration, noting the relatively slower pace of discovery made in modelling cerebellar dysfunction. We conclude by speculating how strategies attempting cerebellar differentiation from hiPSCs can be refined to allow the generation of accurate disease models. This in turn will permit a greater understanding of cerebellar pathophysiology to inform mechanistically rationalised therapies, which are desperately needed in this field.
Assuntos
Diferenciação Celular , Doenças Cerebelares/patologia , Células-Tronco Pluripotentes Induzidas , HumanosRESUMO
The MAPT (microtubule-associated protein tau) locus is one of the most remarkable in neurogenetics due not only to its involvement in multiple neurodegenerative disorders, including progressive supranuclear palsy, corticobasal degeneration, Parksinson's disease and possibly Alzheimer's disease, but also due its genetic evolution and complex alternative splicing features which are, to some extent, linked and so all the more intriguing. Therefore, obtaining robust information regarding the expression, splicing and genetic regulation of this gene within the human brain is of immense importance. In this study, we used 2011 brain samples originating from 439 individuals to provide the most reliable and coherent information on the regional expression, splicing and regulation of MAPT available to date. We found significant regional variation in mRNA expression and splicing of MAPT within the human brain. Furthermore, at the gene level, the regional distribution of mRNA expression and total tau protein expression levels were largely in agreement, appearing to be highly correlated. Finally and most importantly, we show that while the reported H1/H2 association with gene level expression is likely to be due to a technical artefact, this polymorphism is associated with the expression of exon 3-containing isoforms in human brain. These findings would suggest that contrary to the prevailing view, genetic risk factors for neurodegenerative diseases at the MAPT locus are likely to operate by changing mRNA splicing in different brain regions, as opposed to the overall expression of the MAPT gene.
Assuntos
Lobo Frontal/metabolismo , Regulação da Expressão Gênica , Tauopatias/genética , Proteínas tau/genética , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Encéfalo/metabolismo , Estudos de Casos e Controles , Feminino , Estudos de Associação Genética , Predisposição Genética para Doença , Haplótipos , Humanos , Mutação INDEL , Masculino , Pessoa de Meia-Idade , Especificidade de Órgãos , Polimorfismo de Nucleotídeo Único , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Locos de Características Quantitativas , Sítios de Splice de RNA , Tauopatias/metabolismo , Transcrição Gênica , Adulto Jovem , Proteínas tau/metabolismoRESUMO
Genetic backgrounds influence cellular phenotypes, drug responses, and health outcomes, yet most human iPSC lines are derived from individuals of European descent, with lines from indigenous Africans particularly scarce. Addressing this gap, we generated iPSCs from dermal fibroblasts of a healthy 60-year-old indigenous Nigerian male of the Babur ethnic group using Sendai virus. The iPSC line displayed a normal karyotype, was characterized for pluripotency markers and differentiated into neural progenitor cells and astrocytes. To enhance African representation in research, this iPSC line will be available to the scientific community, with ongoing efforts focused on creating an open-access African iPSC biobank. Resource Table.