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Dan L, Zhang Z. Alzheimer's disease: an axonal injury disease? Front Aging Neurosci 2023; 15:1264448. [PMID: 37927337 PMCID: PMC10620718 DOI: 10.3389/fnagi.2023.1264448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Accepted: 09/14/2023] [Indexed: 11/07/2023] Open
Abstract
Alzheimer's disease (AD) is the primary cause of dementia and is anticipated to impose a substantial economic burden in the future. Over a significant period, the widely accepted amyloid cascade hypothesis has guided research efforts, and the recent FDA approval of an anti- amyloid-beta (Aβ) protofibrils antibody, believed to decelerate AD progression, has further solidified its significance. However, the excessive emphasis placed on the amyloid cascade hypothesis has overshadowed the physiological nature of Aβ and tau proteins within axons. Axons, specialized neuronal structures, sustain damage during the early stages of AD, exerting a pivotal influence on disease progression. In this review, we present a comprehensive summary of the relationship between axonal damage and AD pathology, amalgamating the physiological roles of Aβ and tau proteins, along with the impact of AD risk genes such as APOE and TREM2. Furthermore, we underscore the exceptional significance of axonal damage in the context of AD.
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Affiliation(s)
| | - Zhaohui Zhang
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan, Hubei, China
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Salvadores N, Gerónimo-Olvera C, Court FA. Axonal Degeneration in AD: The Contribution of Aβ and Tau. Front Aging Neurosci 2020; 12:581767. [PMID: 33192476 PMCID: PMC7593241 DOI: 10.3389/fnagi.2020.581767] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Accepted: 09/09/2020] [Indexed: 12/25/2022] Open
Abstract
Alzheimer's disease (AD) represents the most common age-related neurodegenerative disorder, affecting around 35 million people worldwide. Despite enormous efforts dedicated to AD research over decades, there is still no cure for the disease. Misfolding and accumulation of Aβ and tau proteins in the brain constitute a defining signature of AD neuropathology, and mounting evidence has documented a link between aggregation of these proteins and neuronal dysfunction. In this context, progressive axonal degeneration has been associated with early stages of AD and linked to Aβ and tau accumulation. As the axonal degeneration mechanism has been starting to be unveiled, it constitutes a promising target for neuroprotection in AD. A comprehensive understanding of the mechanism of axonal destruction in neurodegenerative conditions is therefore critical for the development of new therapies aimed to prevent axonal loss before irreversible neuronal death occurs in AD. Here, we review current evidence of the involvement of Aβ and tau pathologies in the activation of signaling cascades that can promote axonal demise.
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Affiliation(s)
- Natalia Salvadores
- Center for Integrative Biology, Faculty of Sciences, Universidad Mayor, Santiago, Chile.,Fondap Geroscience Center for Brain Health and Metabolism, Santiago, Chile
| | - Cristian Gerónimo-Olvera
- Center for Integrative Biology, Faculty of Sciences, Universidad Mayor, Santiago, Chile.,Fondap Geroscience Center for Brain Health and Metabolism, Santiago, Chile
| | - Felipe A Court
- Center for Integrative Biology, Faculty of Sciences, Universidad Mayor, Santiago, Chile.,Fondap Geroscience Center for Brain Health and Metabolism, Santiago, Chile.,Buck Institute for Research on Aging, Novato, CA, United States
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Lee JG, Sung YH, Baek IJ. Generation of genetically-engineered animals using engineered endonucleases. Arch Pharm Res 2018; 41:885-897. [PMID: 29777358 PMCID: PMC6153862 DOI: 10.1007/s12272-018-1037-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2018] [Accepted: 05/01/2018] [Indexed: 02/06/2023]
Abstract
The key to successful drug discovery and development is to find the most suitable animal model of human diseases for the preclinical studies. The recent emergence of engineered endonucleases is allowing for efficient and precise genome editing, which can be used to develop potentially useful animal models for human diseases. In particular, zinc finger nucleases, transcription activator-like effector nucleases, and the clustered regularly interspaced short palindromic repeat systems are revolutionizing the generation of diverse genetically-engineered experimental animals including mice, rats, rabbits, dogs, pigs, and even non-human primates that are commonly used for preclinical studies of the drug discovery. Here, we describe recent advances in engineered endonucleases and their application in various laboratory animals. We also discuss the importance of genome editing in animal models for more closely mimicking human diseases.
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Affiliation(s)
- Jong Geol Lee
- ConveRgence mEDIcine research cenTer (CREDIT), Asan Institute for Life Sciences, Asan Medical Center, Seoul, Republic of Korea
- College of Veterinary Medicine, Chungbuk National University, Cheongju, Republic of Korea
| | - Young Hoon Sung
- ConveRgence mEDIcine research cenTer (CREDIT), Asan Institute for Life Sciences, Asan Medical Center, Seoul, Republic of Korea.
- Department of Convergence Medicine, ConveRgence mEDIcine research cenTer (CREDIT), Asan Institute for Life Sciences, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
| | - In-Jeoung Baek
- ConveRgence mEDIcine research cenTer (CREDIT), Asan Institute for Life Sciences, Asan Medical Center, Seoul, Republic of Korea.
- Department of Convergence Medicine, ConveRgence mEDIcine research cenTer (CREDIT), Asan Institute for Life Sciences, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
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4
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Live-Cell Imaging Reveals Tau Isoforms Imbalance Disrupts Traffic of APP Vesicles in Human Neurons. J Neurosci 2018; 37:1968-1970. [PMID: 28228519 DOI: 10.1523/jneurosci.3688-16.2017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 01/14/2017] [Accepted: 01/19/2017] [Indexed: 11/21/2022] Open
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Xu L, Zheng J, Margittai M, Nussinov R, Ma B. How Does Hyperphopsphorylation Promote Tau Aggregation and Modulate Filament Structure and Stability? ACS Chem Neurosci 2016; 7:565-75. [PMID: 26854860 PMCID: PMC7831686 DOI: 10.1021/acschemneuro.5b00294] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Tau proteins are hyperphosphorylated at common sites in their N- and C-terminal domains in at least three neurodegenerative diseases, Parkinson, dementia with Lewy bodies, and Alzheimer's, suggesting specific pathology but general mechanism. Full-length human tau filament comprises a rigid core and a two-layered fuzzy coat. Tau is categorized into two groups of isoforms, with either four repeats (R1-R4) or three repeats (R1, R3, and R4); their truncated constructs are respectively called K18 and K19. Using multiscale molecular dynamics simulations, we explored the conformational consequences of hyperhposphorylation on tau's repeats. Our lower conformational energy filament models suggest a rigid filament core with a radius of ∼30 to 40 Å and an outer layer with a thickness of ∼140 Å consisting of a double-layered polyelectrolyte. The presence of the phosphorylated terminal domains alters the relative stabilities in the K18 ensemble, thus shifting the populations of the full-length filaments. However, the structure with the straight repeats in the core region is still the most stable, similar to the truncated K18 peptide species without the N- and C-terminus. Our simulations across different scales of resolution consistently reveal that hyperphosphorylation of the two terminal domains decreases the attractive interactions among the N- and C-terminus and repeat domain. To date, the relationship on the conformational level between phosphorylation and aggregation has not been understood. Our results suggest that the exposure of the repeat domain upon hyperphosphorylation could enhance tau filament aggregation. Thus, we discovered that even though these neurodegenerative diseases vary and their associated tau filaments are phosphorylated to different extents, remarkably, the three pathologies appear to share a common tau aggregation mechanism.
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Affiliation(s)
- Liang Xu
- School of Chemistry, Dalian University of Technology, Dalian 116024, China
| | - Jie Zheng
- Department of Chemical & Biomolecular Engineering, The University of Akron, Akron, Ohio 44325, United States
| | - Martin Margittai
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80208, United States
| | - Ruth Nussinov
- Sackler Institute of Molecular Medicine, Department of Human Genetics and Molecular Medicine, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
- Basic Research Program, Leidos Biomedical Research, Inc., Cancer and Inflammation Program, Frederick National Laboratory for Cancer Research, NCI, Frederick, Maryland 21702, United States
| | - Buyong Ma
- Basic Research Program, Leidos Biomedical Research, Inc., Cancer and Inflammation Program, Frederick National Laboratory for Cancer Research, NCI, Frederick, Maryland 21702, United States
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Gilley J, Ando K, Seereeram A, Rodríguez-Martín T, Pooler AM, Sturdee L, Anderton BH, Brion JP, Hanger DP, Coleman MP. Mislocalization of neuronal tau in the absence of tangle pathology in phosphomutant tau knockin mice. Neurobiol Aging 2015; 39:1-18. [PMID: 26923397 DOI: 10.1016/j.neurobiolaging.2015.11.028] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Revised: 11/25/2015] [Accepted: 11/28/2015] [Indexed: 01/22/2023]
Abstract
Hyperphosphorylation and fibrillar aggregation of the microtubule-associated protein tau are key features of Alzheimer's disease and other tauopathies. To investigate the involvement of tau phosphorylation in the pathological process, we generated a pair of complementary phosphomutant tau knockin mouse lines. One exclusively expresses phosphomimetic tau with 18 glutamate substitutions at serine and/or threonine residues in the proline-rich and first microtubule-binding domains to model hyperphosphorylation, whereas its phosphodefective counterpart has matched alanine substitutions. Consistent with expected effects of genuine phosphorylation, association of the phosphomimetic tau with microtubules and neuronal membranes is severely disrupted in vivo, whereas the phosphodefective mutations have more limited or no effect. Surprisingly, however, age-related mislocalization of tau is evident in both lines, although redistribution appears more widespread and more pronounced in the phosphomimetic tau knockin. Despite these changes, we found no biochemical or immunohistological evidence of pathological tau aggregation in mice of either line up to at least 2 years of age. These findings raise important questions about the role of tau phosphorylation in driving pathology in human tauopathies.
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Affiliation(s)
- Jonathan Gilley
- Signalling Programme, The Babraham Institute, Cambridge, UK.
| | - Kunie Ando
- Laboratory of Histology, Neuroanatomy and Neuropathology, Faculty of Medicine, ULB Neuroscience Institute, Université Libre de Bruxelles, Brussells, Belgium
| | - Anjan Seereeram
- Department of Basic and Clinical Neuroscience (PO37), Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK
| | - Teresa Rodríguez-Martín
- Department of Basic and Clinical Neuroscience (PO37), Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK
| | - Amy M Pooler
- Department of Basic and Clinical Neuroscience (PO37), Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK
| | - Laura Sturdee
- Signalling Programme, The Babraham Institute, Cambridge, UK
| | - Brian H Anderton
- Department of Basic and Clinical Neuroscience (PO37), Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK
| | - Jean-Pierre Brion
- Laboratory of Histology, Neuroanatomy and Neuropathology, Faculty of Medicine, ULB Neuroscience Institute, Université Libre de Bruxelles, Brussells, Belgium
| | - Diane P Hanger
- Department of Basic and Clinical Neuroscience (PO37), Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK
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7
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Chan AWS. Progress and prospects for genetic modification of nonhuman primate models in biomedical research. ILAR J 2014; 54:211-23. [PMID: 24174443 DOI: 10.1093/ilar/ilt035] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The growing interest of modeling human diseases using genetically modified (transgenic) nonhuman primates (NHPs) is a direct result of NHPs (rhesus macaque, etc.) close relation to humans. NHPs share similar developmental paths with humans in their anatomy, physiology, genetics, and neural functions; and in their cognition, emotion, and social behavior. The NHP model within biomedical research has played an important role in the development of vaccines, assisted reproductive technologies, and new therapies for many diseases. Biomedical research has not been the primary role of NHPs. They have mainly been used for safety evaluation and pharmacokinetics studies, rather than determining therapeutic efficacy. The development of the first transgenic rhesus macaque (2001) revolutionized the role of NHP models in biomedicine. Development of the transgenic NHP model of Huntington's disease (2008), with distinctive clinical features, further suggested the uniqueness of the model system; and the potential role of the NHP model for human genetic disorders. Modeling human genetic diseases using NHPs will continue to thrive because of the latest advances in molecular, genetic, and embryo technologies. NHPs rising role in biomedical research, specifically pre-clinical studies, is foreseeable. The path toward the development of transgenic NHPs and the prospect of transgenic NHPs in their new role in future biomedicine needs to be reviewed. This article will focus on the advancement of transgenic NHPs in the past decade, including transgenic technologies and disease modeling. It will outline new technologies that may have significant impact in future NHP modeling and will conclude with a discussion of the future prospects of the transgenic NHP model.
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Piccardo P, Cervenak J, Bu M, Miller L, Asher DM. Complex proteinopathy with accumulations of prion protein, hyperphosphorylated tau, α-synuclein and ubiquitin in experimental bovine spongiform encephalopathy of monkeys. J Gen Virol 2014; 95:1612-1618. [PMID: 24769839 DOI: 10.1099/vir.0.062083-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Proteins aggregate in several slowly progressive neurodegenerative diseases called 'proteinopathies'. Studies with cell cultures and transgenic mice overexpressing mutated proteins suggested that aggregates of one protein induced misfolding and aggregation of other proteins as well - a possible common mechanism for some neurodegenerative diseases. However, most proteinopathies are 'sporadic', without gene mutation or overexpression. Thus, proteinopathies in WT animals genetically close to humans might be informative. Squirrel monkeys infected with the classical bovine spongiform encephalopathy agent developed an encephalopathy resembling variant Creutzfeldt-Jakob disease with accumulations not only of abnormal prion protein (PrP(TSE)), but also three other proteins: hyperphosphorylated tau (p-tau), α-synuclein and ubiquitin; β-amyloid protein (Aβ) did not accumulate. Severity of brain lesions correlated with spongiform degeneration. No amyloid was detected. These results suggested that PrP(TSE) enhanced formation of p-tau and aggregation of α-synuclein and ubiquitin, but not Aβ, providing a new experimental model for neurodegenerative diseases associated with complex proteinopathies.
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Affiliation(s)
- Pedro Piccardo
- Laboratory of Bacterial and TSE Agents, Division of Emerging Transfusion Transmitted Diseases, Office of Blood Research and Review, Center for Biologics Evaluation and Research, Food and Drug Administration, 1401 Rockville Pike, HFM-313, Rockville, MD 20852, USA
| | - Juraj Cervenak
- Laboratory of Bacterial and TSE Agents, Division of Emerging Transfusion Transmitted Diseases, Office of Blood Research and Review, Center for Biologics Evaluation and Research, Food and Drug Administration, 1401 Rockville Pike, HFM-313, Rockville, MD 20852, USA
| | - Ming Bu
- Laboratory of Bacterial and TSE Agents, Division of Emerging Transfusion Transmitted Diseases, Office of Blood Research and Review, Center for Biologics Evaluation and Research, Food and Drug Administration, 1401 Rockville Pike, HFM-313, Rockville, MD 20852, USA
| | - Lindsay Miller
- Laboratory of Bacterial and TSE Agents, Division of Emerging Transfusion Transmitted Diseases, Office of Blood Research and Review, Center for Biologics Evaluation and Research, Food and Drug Administration, 1401 Rockville Pike, HFM-313, Rockville, MD 20852, USA
| | - David M Asher
- Laboratory of Bacterial and TSE Agents, Division of Emerging Transfusion Transmitted Diseases, Office of Blood Research and Review, Center for Biologics Evaluation and Research, Food and Drug Administration, 1401 Rockville Pike, HFM-313, Rockville, MD 20852, USA
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Jackson HM, Soto I, Graham LC, Carter GW, Howell GR. Clustering of transcriptional profiles identifies changes to insulin signaling as an early event in a mouse model of Alzheimer's disease. BMC Genomics 2013; 14:831. [PMID: 24274089 PMCID: PMC3907022 DOI: 10.1186/1471-2164-14-831] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Accepted: 11/14/2013] [Indexed: 11/23/2022] Open
Abstract
Background Alzheimer’s disease affects more than 35 million people worldwide but there is no known cure. Age is the strongest risk factor for Alzheimer’s disease but it is not clear how age-related changes impact the disease. Here, we used a mouse model of Alzheimer’s disease to identify age-specific changes that occur prior to and at the onset of traditional Alzheimer-related phenotypes including amyloid plaque formation. To identify these early events we used transcriptional profiling of mouse brains combined with computational approaches including singular value decomposition and hierarchical clustering. Results Our study identifies three key events in early stages of Alzheimer’s disease. First, the most important drivers of Alzheimer’s disease onset in these mice are age-specific changes. These include perturbations of the ribosome and oxidative phosphorylation pathways. Second, the earliest detectable disease-specific changes occur to genes commonly associated with the hypothalamic-adrenal-pituitary (HPA) axis. These include the down-regulation of genes relating to metabolism, depression and appetite. Finally, insulin signaling, in particular the down-regulation of the insulin receptor substrate 4 (Irs4) gene, may be an important event in the transition from age-related changes to Alzheimer’s disease specific-changes. Conclusion A combination of transcriptional profiling combined with computational analyses has uncovered novel features relevant to Alzheimer’s disease in a widely used mouse model and offers avenues for further exploration into early stages of AD.
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Affiliation(s)
- Harriet M Jackson
- The Jackson Laboratory, 600 Main Street, Bar Harbor, Maine 04609, USA.
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Duka V, Lee JH, Credle J, Wills J, Oaks A, Smolinsky C, Shah K, Mash DC, Masliah E, Sidhu A. Identification of the sites of tau hyperphosphorylation and activation of tau kinases in synucleinopathies and Alzheimer's diseases. PLoS One 2013; 8:e75025. [PMID: 24073234 PMCID: PMC3779212 DOI: 10.1371/journal.pone.0075025] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Accepted: 08/08/2013] [Indexed: 12/03/2022] Open
Abstract
OBJECTIVE Most neurodegenerative diseases contain hyperphosphorylated Tau [p-Tau]. We examined for the first time epitopes at which Tau is hyperphosphorylated in Parkinson's disease, dementia with Lewy bodies and Alzheimer's disease, and also select Tau kinases. METHODS Postmortem frontal cortex from Parkinson's disease, dementia with Lewy bodies, Alzheimer's disease and striata from Parkinson's disease, were analyzed by immunoblots using commercially available antibodies against 20 different phospho-epitopes of Tau. Major Tau kinases were also screened. Results in diseased tissues were compared to nondiseased controls. RESULTS In Alzheimer's disease, Tau was hyperphosphorylated at all the 20 epitopes of p-Tau. In dementia with Lewy bodies, p-Tau formation occurred at 6 sites sharing 30% overlap with Alzheimer's disease, while in Parkinson's frontal cortex, an area which does not degenerate, Tau hyperphosphorylation was seen at just 3 epitopes, indicating 15% overlap with Alzheimer's disease. In Parkinson's disease striatum, an area which undergoes considerable neurodegeneration, Tau was hyperphosphorylated at 10 epitopes, sharing 50% overlap with Alzheimer's disease. Between frontal cortex of Parkinson's disease and dementia with Lewy bodies, there were only two p-Tau epitopes in common. In striata of Parkinson's disease, there were 3 clusters of Tau hyperphosphorylated at 3 contiguous sites, while two such clusters were detected in dementia with Lewy bodies; such clusters disrupt axonal transport of mitochondria, cause microtubule remodeling and result in cell death. p-GSK-3β, a major Tau kinase, was activated in all brain regions examined, except in dementia with Lewy bodies. Activation of other Tau kinases was seen in all brain regions, with no clear pattern of activation. INTERPRETATION Our studies suggest that the three neurodegenerative diseases each have a signature-specific profile of p-Tau formation which may be useful in understanding the genesis of the diseases and for the development of a panel of specific biomarkers.
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Affiliation(s)
- Valeriy Duka
- Department of Biochemistry and Molecular & Cellular Biology, Georgetown University Medical Center, Washington, District of Columbia, United States of America
| | - Jae-Hoon Lee
- Department of Biochemistry and Molecular & Cellular Biology, Georgetown University Medical Center, Washington, District of Columbia, United States of America
| | - Joel Credle
- Department of Biochemistry and Molecular & Cellular Biology, Georgetown University Medical Center, Washington, District of Columbia, United States of America
| | - Jonathan Wills
- Department of Biochemistry and Molecular & Cellular Biology, Georgetown University Medical Center, Washington, District of Columbia, United States of America
| | - Adam Oaks
- Department of Biochemistry and Molecular & Cellular Biology, Georgetown University Medical Center, Washington, District of Columbia, United States of America
| | - Ciaran Smolinsky
- Department of Biochemistry and Molecular & Cellular Biology, Georgetown University Medical Center, Washington, District of Columbia, United States of America
| | - Ketul Shah
- Department of Biochemistry and Molecular & Cellular Biology, Georgetown University Medical Center, Washington, District of Columbia, United States of America
| | - Deborah C. Mash
- Department of Neurology and Molecular and Cellular Pharmacology, Miller School of Medicine, University of Miami, Miami, Florida, United States of America
| | - Eliezer Masliah
- Department of Neuroscience, University of California San Diego, La Jolla, California, United States of America
| | - Anita Sidhu
- Department of Biochemistry and Molecular & Cellular Biology, Georgetown University Medical Center, Washington, District of Columbia, United States of America
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Welch A, Mingarelli M, Riedel G, Platt B. Mapping changes in mouse brain metabolism with PET/CT. J Nucl Med 2013; 54:1946-53. [PMID: 24009277 DOI: 10.2967/jnumed.113.121509] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED Because preclinical imaging offers challenges and opportunities, we set out to investigate and optimize image processing techniques to measure changes in mouse brain metabolism with preclinical (18)F-FDG PET/CT. In particular, we considered the effects of scan length, image registration methods, image quantification methods, and smoothing during statistical parametric mapping (SPM). METHODS A cohort of 12 wild-type mice was scanned on 3 occasions at an average age of 6, 10, and 14 mo. The impact of the scan length (10, 20, 30, or 40 min) was determined, and images were registered to a template based on either the PET or the CT image. Analysis was performed using SPM or predefined regions of interest (ROIs). Data were expressed in units of standardized uptake value or percentage injected dose per gram of tissue for absolute values; images were also normalized to whole-brain activity. RESULTS Significant variability was observed in global brain (18)F-FDG uptake between animals. Normalizing images to the whole-brain activity significantly improved detection of regional changes in metabolism. Registration based on CT images provided greater power for detecting changes in metabolism than did registration based on PET images only. In line with an age-dependent decline in brain metabolism, both ROI and SPM-based methods revealed significant changes; SPM, however, was generally more sensitive and region-specific. For example, small clusters of voxels within an ROI differed significantly between ages even in the absence of significant changes in average uptake over the whole region. Finally, and contrary to expectation, we found little benefit from longer scan times yet a marked reduction in uptake from 45 to 85 min after injection and regional variations in the rate of washout. CONCLUSION With appropriate processing, preclinical PET/CT provides a highly sensitive method for reliable identification of metabolic changes in the mouse brain.
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Affiliation(s)
- Andy Welch
- School of Medicine and Dentistry, University of Aberdeen, Aberdeen, United Kingdom; and
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Kanaan NM, Pigino GF, Brady ST, Lazarov O, Binder LI, Morfini GA. Axonal degeneration in Alzheimer's disease: when signaling abnormalities meet the axonal transport system. Exp Neurol 2013; 246:44-53. [PMID: 22721767 PMCID: PMC3465504 DOI: 10.1016/j.expneurol.2012.06.003] [Citation(s) in RCA: 146] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Revised: 04/17/2012] [Accepted: 06/09/2012] [Indexed: 12/17/2022]
Abstract
Alzheimer's disease (AD) is characterized by progressive, age-dependent degeneration of neurons in the central nervous system. A large body of evidence indicates that neurons affected in AD follow a dying-back pattern of degeneration, where abnormalities in synaptic function and axonal connectivity long precede somatic cell death. Mechanisms underlying dying-back degeneration of neurons in AD remain elusive but several have been proposed, including deficits in fast axonal transport (FAT). Accordingly, genetic evidence linked alterations in FAT to dying-back degeneration of neurons, and FAT defects have been widely documented in various AD models. In light of these findings, we discuss experimental evidence linking several AD-related pathogenic polypeptides to aberrant activation of signaling pathways involved in the phosphoregulation of microtubule-based motor proteins. While each pathway appears to affect FAT in a unique manner, in the context of AD, many of these pathways might work synergistically to compromise the delivery of molecular components critical for the maintenance and function of synapses and axons. Therapeutic approaches aimed at preventing FAT deficits by normalizing the activity of specific protein kinases may help prevent degeneration of vulnerable neurons in AD.
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Affiliation(s)
- Nicholas M Kanaan
- Department of Translational Science and Molecular Medicine, College of Human Medicine, Michigan State University, Grand Rapids, MI, USA
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Tarragon E, Lopez D, Estrada C, Ana GC, Schenker E, Pifferi F, Bordet R, Richardson JC, Herrero MT. Octodon degus: a model for the cognitive impairment associated with Alzheimer's disease. CNS Neurosci Ther 2013; 19:643-8. [PMID: 23710760 DOI: 10.1111/cns.12125] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Revised: 04/18/2013] [Accepted: 04/19/2013] [Indexed: 12/12/2022] Open
Abstract
Octodon degus (O. degus) is a diurnal rodent that spontaneously develops several physiopathological conditions, analogous in many cases to those experienced by humans. In light of this, O. degus has recently been identified as a very valuable animal model for research in several medical fields, especially those concerned with neurodegenerative diseases in which risk is associated with aging. Octodon degus spontaneously develops β-amyloid deposits analogous to those observed in some cases of Alzheimer's disease (AD). Moreover, these deposits are thought to be the key feature for AD diagnosis, and one of the suggested causes of cell loss and cognitive deficit. This review aims to bring together information to support O. degus as a valuable model for the study of AD.
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Affiliation(s)
- Ernesto Tarragon
- Clinical & Experimental Neuroscience (NiCE) and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), School of Health Sciences (Medicine), University Jaume I of Castellon, Castellon de la Plana, Spain
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