scholarly journals Tau-mediated Disruption of the Spliceosome Triggers Cryptic RNA-splicing and Neurodegeneration in Alzheimer’s Disease

2019 ◽  
Author(s):  
Yi-Chen Hsieh ◽  
Caiwei Guo ◽  
Hari K. Yalamanchili ◽  
Measho Abreha ◽  
Rami Al-Ouran ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Rna Splicing ◽  
Intron Retention ◽  
Neurofibrillary Tangle ◽  
Neuronal Loss ◽  
Mrna Splicing ◽  
Postmortem Brain ◽  
Loss Of Function ◽  
Human Postmortem Brain

SUMMARYIn Alzheimer’s disease (AD), spliceosomal proteins with critical roles in RNA processing aberrantly aggregate and mislocalize to Tau neurofibrillary tangles. We test the hypothesis that Tau-spliceosome interactions disrupt pre-mRNA splicing in AD. In human postmortem brain with AD pathology, Tau coimmunoprecipitates with spliceosomal core components. In Drosophila models, pan-neuronal Tau expression triggers reductions in core and U1-specific spliceosomal proteins, and genetic disruption of these factors, including SmB, U1-70K, and U1A, enhances Tau-mediated neurodegeneration. We further show that loss-of-function in SmB, encoding a core spliceosomal protein, causes decreased survival, progressive locomotor impairment, and neuronal loss, independent of Tau toxicity. Lastly, RNA-sequencing reveals a similar profile of mRNA splicing errors in SmB mutant and Tau transgenic flies, including intron retention and non-annotated cryptic splice junctions. In human brains, we confirm cryptic splicing errors in association with neurofibrillary tangle pathologic burden. Our results implicate spliceosome disruption and perturbations of the neuronal transcriptome in Tau-mediated neurodegeneration in AD.

Modulation of ϐ-amyloid production and fibrillization

2001 ◽  
Vol 67 ◽  
pp. 1-14 ◽  
Author(s):  
David Allsop ◽  
Lance J. Twyman ◽  
Yvonne Davies ◽  
Susan Moore ◽  
Amber York ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Amyloid Fibrils ◽  
Senile Plaques ◽  
Neurofibrillary Tangle ◽  
Neuronal Loss ◽  
Brain Parenchyma ◽  
Amino Acid Peptide ◽  
Close Relatives ◽  
The Brain

Alzheimer's disease (AD) is the most common cause of dementia in old age and presently affects an estimated 4 million people in the U.S.A. and 0.75 million people in the U.K. It is a relentless, degenerative brain disease, characterized by progressive cognitive impairment. In the final stages of the disease, patients are often bedridden, doubly incontinent and unable to speak or to recognize close relatives. Pathological changes of Alzheimer's disease include extensive neuronal loss and the presence of numerous neurofibrillary tangles and senile plaques in the brain. The senile plaques contain amyloid fibrils derived from a 39-43-amino-acid peptide referred to as ϐ-amyloid or Aϐ. The basic theory of the so-called 'amyloid hypothesis' is that the deposition of aggregated forms of Aϐ in the brain parenchyma triggers a pathological cascade of events that leads to neurofibrillary tangle formation, neuronal loss and the associated dementia [1]. Here we discuss progress towards the identification of inhibitors of Aϐ production and fibrillization.

scholarly journals Phosphorylated tau fluid biomarker sites recognize earlier neurofibrillary tangle maturity levels in the postmortem Alzheimer’s disease brain

2021 ◽  
Author(s):  
Christina M. Moloney ◽  
Sydney A. Labuzan ◽  
Julia E. Crook ◽  
Habeeba Siddiqui ◽  
Monica Castanedes-Casey ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Neurofibrillary Tangle ◽  
Global Scale ◽  
Postmortem Brain ◽  
Braak Stage ◽  
Phosphorylated Tau ◽  
Regional Vulnerability ◽  
Early Fluid ◽  
Fluid Biomarker

AbstractAlzheimer’s disease (AD) biomarkers have become increasingly more reliable in predicting AD pathology. While phosphorylated tau fluid biomarkers have been studied for over 20 years, there is a lack of deep characterization of these sites in the postmortem brain. Neurofibrillary tangle-bearing neurons, one of the major neuropathologic hallmarks of AD, undergo morphologic changes that mature along a continuum as hyperphosphorylated tau aggregates. To facilitate interpretation of phosphorylated tau sites as an early fluid biomarker, our goal was to characterize which neurofibrillary tangle maturity levels (pretangle, intermediary 1, mature tangle, intermediary 2, and ghost tangle) they recognize. We queried the Florida Autopsied Multi-Ethnic (FLAME) cohort for cases from Braak stages I-VI. We excluded non-AD pathologies and tauopathies. A total of 24 cases, 2 males and 2 females for each Braak stage, were selected. We performed immunohistochemistry on the posterior hippocampus using antibodies directed towards phospho (p) threonine (T) 181, pT205, pT217, and pT231. Slides were digitized to enable quantification of tau burden. To examine differences in regional vulnerability between CA1 and subiculum, we developed a semi-quantitative system to rank the frequency of each neurofibrillary tangle maturity level. We identified all neurofibrillary tangle maturity levels at least once for each phosphorylated tau site. Primarily earlier neurofibrillary tangle maturity levels (pretangle, intermediary 1, mature tangle) were recognized for all phosphorylated tau sites. There was an increase in tau burden in the subiculum compared to CA1; however, this was attenuated compared to thioflavin-S positive tangle counts. On a global scale, tau burden generally increased with each Braak stage. These results provide neurobiologic evidence that these phosphorylated tau fluid biomarker sites are present during earlier neurofibrillary tangle maturity levels. This may help explain why these phosphorylated tau biomarker sites are observed before symptom onset in fluids.

scholarly journals Microglia Activation in the Brain as Inflammatory Biomarker of Alzheimer’s Disease Neuropathology and Clinical Dementia

2006 ◽  
Vol 22 (1-2) ◽  
pp. 95-102 ◽  
Author(s):  
Zhongmin Xiang ◽  
Vahram Haroutunian ◽  
Lap Ho ◽  
Dushant Purohit ◽  
Giulio Maria Pasinetti
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Molecular Layer ◽  
Neurofibrillary Tangle ◽  
Microglia Activation ◽  
Postmortem Brain ◽  
Neuritic Plaque ◽  
Clinical Dementia Rating ◽  
Inflammatory Biomarker ◽  
Hla Dr

The role of microglia-mediated inflammation in the progression of Alzheimer’s disease (AD) neuropathology remains unclear. In this study, postmortem brain sections from AD and control cases were subjected to Human Leukocyte Antigen (HLA)-DR immunohistochemistry to examine microglia activation in the progression of AD assessed by pre-mortem clinical dementia rating (CDR) and postmortem pathological manifestations of neuritic plaque (NP) and neurofibrillary tangle (NT) according to the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD). In both gray and white matter of the entorhinal cortex (EC) and HLA-DR immunostaining increased with the progression of CDR or CERAD NP, and to a lesser degree with CERAD NT. Between CDR stages HLA-DR significance was found in moderate (CDR 2) to severe dementia (CDR 5) where as between CERAD NP stages staining increased significantly from NP 0 (no plaque) to NP 1 (sparse plaques), suggesting increased microglia activation begins with amyloid NP deposition. In the hippocampus, a significant increase in microglia immunostaining was found in the pyramidal cell layer of CA1 as early as CDR 1, and in the upper molecular layer of the dentate gyrus in CDR 0.5. This increase continues with the progression of CDR and reaches maximum in CDR 5. When assessed by CERAD NP stages however, a significant increase in microglia immunostaining was found only in mid-to-late stages (NP 3) and reduced staining was seen in NP 5. These results suggest that microglia activation increases with the progression of AD, with the increase varying depending on the involved brain region.

scholarly journals TOMM40 RNA Transcription in Alzheimer’s Disease Brain and Its Implication in Mitochondrial Dysfunction

Genes ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 871
Author(s):  
Eun-Gyung Lee ◽  
Sunny Chen ◽  
Lesley Leong ◽  
Jessica Tulloch ◽  
Chang-En Yu
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Mitochondrial Dysfunction ◽  
Postmortem Brain ◽  
Human Postmortem Brain ◽  
Mitochondrial Dna Copy Number ◽  
Mitochondrial Functions ◽  
Differential Transcription ◽  
And Control ◽  
Rna Levels

Increasing evidence suggests that the Translocase of Outer Mitochondria Membrane 40 (TOMM40) gene may contribute to the risk of Alzheimer’s disease (AD). Currently, there is no consensus as to whether TOMM40 expression is up- or down-regulated in AD brains, hindering a clear interpretation of TOMM40’s role in this disease. The aim of this study was to determine if TOMM40 RNA levels differ between AD and control brains. We applied RT-qPCR to study TOMM40 transcription in human postmortem brain (PMB) and assessed associations of these RNA levels with genetic variants in APOE and TOMM40. We also compared TOMM40 RNA levels with mitochondrial functions in human cell lines. Initially, we found that the human genome carries multiple TOMM40 pseudogenes capable of producing highly homologous RNAs that can obscure precise TOMM40 RNA measurements. To circumvent this obstacle, we developed a novel RNA expression assay targeting the primary transcript of TOMM40. Using this assay, we showed that TOMM40 RNA was upregulated in AD PMB. Additionally, elevated TOMM40 RNA levels were associated with decreases in mitochondrial DNA copy number and mitochondrial membrane potential in oxidative stress-challenged cells. Overall, differential transcription of TOMM40 RNA in the brain is associated with AD and could be an indicator of mitochondrial dysfunction.

Entorhinal verrucae correlate with surface geometry

2012 ◽  
Vol 3 (2) ◽  
Author(s):  
Jean Augustinack ◽  
Kristen Huber ◽  
Gheorghe Postelnicu ◽  
Matthew Frosch ◽  
Rudolph Pienaar ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Entorhinal Cortex ◽  
Ex Vivo ◽  
Neurofibrillary Tangle ◽  
Neuronal Loss ◽  
Surface Geometry ◽  
Curvature Analysis ◽  
Significant Difference ◽  
Large Neurons

AbstractEntorhinal verrucae are unique, small elevations on the surface of entorhinal cortex, formed due to distinctive clustering of large neurons in entorhinal layer II. In Alzheimer’s disease, the verrucae atrophy as a result of neurofibrillary tangle formation and concomitant neuronal loss. Previously, we found significant decreases in verrucae height, width, surface area, and volume even in the mildest stage of Alzheimer’s disease. In this report, we introduce a new method for analyzing verrucae prominence using measures of their curvature. Smoothed surfaces and curvatures were generated using FreeSurfer (http://surfer.nmr.mgh.harvard.edu) from 100 μm3 ex vivo MRI isosurfaces. We examined the positive and negative components of mean curvature AreaNorm(H+/-) and Gaussian curvature AreaNorm(K +/−) in entorhinal cortex. A significant difference was found between entorhinal (n=10) and non-entorhinal cortices (n=9) for both AreaNorm(H+/-) and AreaNorm(K +/−). We also validated our curvature analysis through a comparison with previously published verrucae measures derived from manual labels of individual verrucae. A significant positive correlation was found between mean verrucae height and AreaNorm(H+/-). Both mean verrucae height and volume were significantly positively correlated with AreaNorm(K +/−). These results demonstrate that K and H are accurate metrics for detecting the presence or absence of entorhinal verrucae. Curvature analysis may be a useful and sensitive technique for detecting local surface changes in entorhinal cortex.

scholarly journals A novel missense variant in ACAA1 contributes to early-onset Alzheimer’s disease, impairs lysosomal function, and facilitates amyloid-β pathology and cognitive decline

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Rongcan Luo ◽  
Yu Fan ◽  
Jing Yang ◽  
Maosen Ye ◽  
Deng-Feng Zhang ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Early Onset ◽  
Neurofibrillary Tangle ◽  
Amyloid Β ◽  
Neuronal Loss ◽  
Missense Variant ◽  
Lysosomal Function

AbstractAlzheimer’s disease (AD) is characterized by progressive synaptic dysfunction, neuronal death, and brain atrophy, with amyloid-β (Aβ) plaque deposits and hyperphosphorylated tau neurofibrillary tangle accumulation in the brain tissue, which all lead to loss of cognitive function. Pathogenic mutations in the well-known AD causal genes including APP, PSEN1, and PSEN2 impair a variety of pathways, including protein processing, axonal transport, and metabolic homeostasis. Here we identified a missense variant rs117916664 (c.896T>C, p.Asn299Ser [p.N299S]) of the acetyl-CoA acyltransferase 1 (ACAA1) gene in a Han Chinese AD family by whole-genome sequencing and validated its association with early-onset familial AD in an independent cohort. Further in vitro and in vivo evidence showed that ACAA1 p.N299S contributes to AD by disturbing its enzymatic activity, impairing lysosomal function, and aggravating the Aβ pathology and neuronal loss, which finally caused cognitive impairment in a murine model. Our findings reveal a fundamental role of peroxisome-mediated lysosomal dysfunction in AD pathogenesis.

scholarly journals Altered synaptic ingestion by human microglia in Alzheimer’s disease

2019 ◽  
Author(s):  
Makis Tzioras ◽  
Michael J.D. Daniels ◽  
Declan King ◽  
Karla Popovic ◽  
Rebecca K. Holloway ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Human Brain ◽  
Mouse Models ◽  
Disease Risk ◽  
Synaptic Proteins ◽  
Postmortem Brain ◽  
Human Microglia ◽  
Human Postmortem Brain ◽  
Synapse Loss

AbstractSynapse loss correlates strongly with cognitive decline in Alzheimer’s disease, but the mechanisms underpinning this phenomenon remain unclear. Recent evidence from mouse models points to microglial cells as mediators of synapse removal, and human genetic evidence implicates microglia in disease risk. Here we demonstrate that microglia from human postmortem brain contain synaptic proteins and that greater amounts are observed in microglia from Alzheimer’s compared to non-diseased brain tissue. Further, we observe that primary human adult microglia phagocytose synapses isolated from human brain, and that AD brain-derived synapses are phagocytosed more rapidly and abundantly than controls. Together, these data show that synapses in the human AD brain are more prone to ingestion by microglia. Our findings provide evidence from human tissue implicating altered microglial-mediated synaptic uptake in AD pathobiology.One Sentence SummaryAD alters synapse ingestion by microglia

scholarly journals Defining early changes in Alzheimer’s disease from RNA sequencing of brain regions differentially affected by pathology

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Boris Guennewig ◽  
Julia Lim ◽  
Lee Marshall ◽  
Andrew N. McCorkindale ◽  
Patrick J. Paasila ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Rna Sequencing ◽  
Neuronal Loss ◽  
Brain Regions ◽  
Post Mortem ◽  
Tau Pathology ◽  
Membrane Spanning ◽  
Immune Related Genes ◽  
Vesicle Secretion

AbstractTau pathology in Alzheimer’s disease (AD) spreads in a predictable pattern that corresponds with disease symptoms and severity. At post-mortem there are cortical regions that range from mildly to severely affected by tau pathology and neuronal loss. A comparison of the molecular signatures of these differentially affected areas within cases and between cases and controls may allow the temporal modelling of disease progression. Here we used RNA sequencing to explore differential gene expression in the mildly affected primary visual cortex and moderately affected precuneus of ten age-, gender- and RNA quality-matched post-mortem brains from AD patients and healthy controls. The two regions in AD cases had similar transcriptomic signatures but there were broader abnormalities in the precuneus consistent with the greater tau load. Both regions were characterised by upregulation of immune-related genes such as those encoding triggering receptor expressed on myeloid cells 2 and membrane spanning 4-domains A6A and milder changes in insulin/IGF1 signalling. The precuneus in AD was also characterised by changes in vesicle secretion and downregulation of the interneuronal subtype marker, somatostatin. The ‘early’ AD transcriptome is characterised by perturbations in synaptic vesicle secretion on a background of neuroimmune dysfunction. In particular, the synaptic deficits that characterise AD may begin with the somatostatin division of inhibitory neurotransmission.

scholarly journals Disruption of a RAC1-centred network is associated with Alzheimer’s disease pathology and causes age-dependent neurodegeneration

2020 ◽  
Vol 29 (5) ◽  
pp. 817-833 ◽  
Author(s):  
Masataka Kikuchi ◽  
Michiko Sekiya ◽  
Norikazu Hara ◽  
Akinori Miyashita ◽  
Ryozo Kuwano ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Genetic Model ◽  
Neurofibrillary Tangle ◽  
Neuronal Cell ◽  
Brain Regions ◽  
Protein Domain ◽  
Expression Data ◽  
Integrated Network ◽  
Age Dependent

Abstract The molecular biological mechanisms of Alzheimer’s disease (AD) involve disease-associated crosstalk through many genes and include a loss of normal as well as a gain of abnormal interactions among genes. A protein domain network (PDN) is a collection of physical bindings that occur between protein domains, and the states of the PDNs in patients with AD are likely to be perturbed compared to those in normal healthy individuals. To identify PDN changes that cause neurodegeneration, we analysed the PDNs that occur among genes co-expressed in each of three brain regions at each stage of AD. Our analysis revealed that the PDNs collapsed with the progression of AD stage and identified five hub genes, including Rac1, as key players in PDN collapse. Using publicly available as well as our own gene expression data, we confirmed that the mRNA expression level of the RAC1 gene was downregulated in the entorhinal cortex (EC) of AD brains. To test the causality of these changes in neurodegeneration, we utilized Drosophila as a genetic model and found that modest knockdown of Rac1 in neurons was sufficient to cause age-dependent behavioural deficits and neurodegeneration. Finally, we identified a microRNA, hsa-miR-101-3p, as a potential regulator of RAC1 in AD brains. As the Braak neurofibrillary tangle (NFT) stage progressed, the expression levels of hsa-miR-101-3p were increased specifically in the EC. Furthermore, overexpression of hsa-miR-101-3p in the human neuronal cell line SH-SY5Y caused RAC1 downregulation. These results highlight the utility of our integrated network approach for identifying causal changes leading to neurodegeneration in AD.

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