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Wang M, Lassers SB, Vakilna YS, Mander BA, Tang WC, Brewer GJ. Spindle oscillations in communicating axons within a reconstituted hippocampal formation are strongest in CA3 without thalamus. Sci Rep 2024; 14:8384. [PMID: 38600114 PMCID: PMC11006914 DOI: 10.1038/s41598-024-58002-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Accepted: 03/25/2024] [Indexed: 04/12/2024] Open
Abstract
Spindle-shaped waves of oscillations emerge in EEG scalp recordings during human and rodent non-REM sleep. The association of these 10-16 Hz oscillations with events during prior wakefulness suggests a role in memory consolidation. Human and rodent depth electrodes in the brain record strong spindles throughout the cortex and hippocampus, with possible origins in the thalamus. However, the source and targets of the spindle oscillations from the hippocampus are unclear. Here, we employed an in vitro reconstruction of four subregions of the hippocampal formation with separate microfluidic tunnels for single axon communication between subregions assembled on top of a microelectrode array. We recorded spontaneous 400-1000 ms long spindle waves at 10-16 Hz in single axons passing between subregions as well as from individual neurons in those subregions. Spindles were nested within slow waves. The highest amplitudes and most frequent occurrence suggest origins in CA3 neurons that send feed-forward axons into CA1 and feedback axons into DG. Spindles had 50-70% slower conduction velocities than spikes and were not phase-locked to spikes suggesting that spindle mechanisms are independent of action potentials. Therefore, consolidation of declarative-cognitive memories in the hippocampus may be separate from the more easily accessible consolidation of memories related to thalamic motor function.
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Affiliation(s)
- Mengke Wang
- Department of Biomedical Engineering, University of California, Irvine, CA, 92697, USA
| | - Samuel B Lassers
- Department of Biomedical Engineering, University of California, Irvine, CA, 92697, USA
| | - Yash S Vakilna
- Texas Institute of Restorative Neurotechnologies (TIRN), The University of Texas Health Science Center (UTHealth), Houston, TX, 77030, USA
| | - Bryce A Mander
- Center for Neurobiology of Learning and Memory and MIND Center, University of California, Irvine, CA, 92697, USA
- Institute for Memory Impairments and Neurological Disorders, University of California, Irvine, CA, 92697, USA
- Department of Psychiatry and Human Behavior, University of California, Irvine, CA, 92868, USA
| | - William C Tang
- Department of Biomedical Engineering, University of California, Irvine, CA, 92697, USA
| | - Gregory J Brewer
- Department of Biomedical Engineering, University of California, Irvine, CA, 92697, USA.
- Center for Neurobiology of Learning and Memory and MIND Center, University of California, Irvine, CA, 92697, USA.
- Institute for Memory Impairments and Neurological Disorders, University of California, Irvine, CA, 92697, USA.
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Bower KL, Noecker AM, Frankemolle-Gilbert AM, McIntyre CC. Model-Based Analysis of Pathway Recruitment During Subthalamic Deep Brain Stimulation. Neuromodulation 2024; 27:455-463. [PMID: 37097269 PMCID: PMC10598236 DOI: 10.1016/j.neurom.2023.02.084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 02/06/2023] [Accepted: 02/27/2023] [Indexed: 04/26/2023]
Abstract
BACKGROUND Subthalamic deep brain stimulation (DBS) is an established clinical therapy, but an anatomically clear definition of the underlying neural target(s) of the stimulation remains elusive. Patient-specific models of DBS are commonly used tools in the search for stimulation targets, and recent iterations of those models are focused on characterizing the brain connections that are activated by DBS. OBJECTIVE The goal of this study was to quantify axonal pathway activation in the subthalamic region from DBS at different electrode locations and stimulation settings. MATERIALS AND METHODS We used an anatomically and electrically detailed computational model of subthalamic DBS to generate recruitment curves for eight different axonal pathways of interest, at three generalized DBS electrode locations in the subthalamic nucleus (STN) (ie, central STN, dorsal STN, posterior STN). These simulations were performed with three levels of DBS electrode localization uncertainty (ie, 0.5 mm, 1.0 mm, 1.5 mm). RESULTS The recruitment curves highlight the diversity of pathways that are theoretically activated with subthalamic DBS, in addition to the dependence of the stimulation location and parameter settings on the pathway activation estimates. The three generalized DBS locations exhibited distinct pathway recruitment curve profiles, suggesting that each stimulation location would have a different effect on network activity patterns. We also found that the use of anodic stimuli could help limit activation of the internal capsule relative to other pathways. However, incorporating realistic levels of DBS electrode localization uncertainty in the models substantially limits their predictive capabilities. CONCLUSIONS Subtle differences in stimulation location and/or parameter settings can impact the collection of pathways that are activated during subthalamic DBS.
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Affiliation(s)
- Kelsey L Bower
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
| | - Angela M Noecker
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA; Department of Biomedical Engineering, Duke University, Durham, NC, USA
| | | | - Cameron C McIntyre
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA; Department of Biomedical Engineering, Duke University, Durham, NC, USA; Department of Neurosurgery, Duke University, Durham, NC, USA.
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Hampl M, Jandova N, Luskova D, Novakova M, Szotkowska T, Cada S, Prochazka J, Kohoutek J, Buchtova M. Early embryogenesis in CHDFIDD mouse model reveals facial clefts and altered cranial neurogenesis. Dis Model Mech 2024:dmm.050261. [PMID: 38511331 DOI: 10.1242/dmm.050261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Accepted: 03/12/2024] [Indexed: 03/22/2024] Open
Abstract
Congenital heart defects, facial dysmorphism and intellectual development disorder (CHDFIDD) is associated with mutations in CDK13 gene, which encodes a transcription regulating Cyclin-dependent kinase 13 (CDK13). Here, we focused on development of craniofacial structures and analyzed early embryonic stages of CHDFIDD mouse models with hypomorphic mutation in Cdk13 gene, which exhibits cleft lip/palate and knockout of Cdk13 with stronger phenotype including midfacial cleft. Cdk13 was found to be physiologically strongly expressed in the mouse embryonic craniofacial structures, namely in the forebrain, nasal epithelium and maxillary mesenchyme. We also uncovered that Cdk13-deficiency leads to development of hypoplastic branches of the trigeminal nerve including maxillary branch and additionally, we detected significant gene expression changes of molecules involved in neurogenesis (Ache, Dcx, Mef2c, Neurog1, Ntn1, Pou4f1) within the developing palatal shelves. These results, together with changes of gene expression of other key face-specific molecules (Fgf8, Foxd1, Msx1, Meis2 and Shh) at early stages in Cdk13 mutant embryos, demonstrate a key role of CDK13 in regulation of craniofacial morphogenesis.
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Affiliation(s)
- Marek Hampl
- Laboratory of Molecular Morphogenesis, Institute of Animal Physiology and Genetics, Czech Academy of Sciences, Brno, Czech Republic
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Nela Jandova
- Laboratory of Molecular Morphogenesis, Institute of Animal Physiology and Genetics, Czech Academy of Sciences, Brno, Czech Republic
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Denisa Luskova
- Laboratory of Molecular Morphogenesis, Institute of Animal Physiology and Genetics, Czech Academy of Sciences, Brno, Czech Republic
| | - Monika Novakova
- Department of Chemistry and Toxicology, Veterinary Research Institute, Brno, Czech Republic
| | - Tereza Szotkowska
- Laboratory of Molecular Morphogenesis, Institute of Animal Physiology and Genetics, Czech Academy of Sciences, Brno, Czech Republic
| | - Stepan Cada
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Jan Prochazka
- Laboratory of Transgenic Models of Diseases, Institute of Molecular Genetics, Czech Academy of Sciences, Prague, Czech Republic
- Czech Centre for Phenogenomics, Institute of Molecular Genetics, Czech Academy of Sciences, Prague, Czech Republic
| | - Jiri Kohoutek
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Marcela Buchtova
- Laboratory of Molecular Morphogenesis, Institute of Animal Physiology and Genetics, Czech Academy of Sciences, Brno, Czech Republic
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
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Burzynska AZ, Anderson C, Arciniegas DB, Calhoun V, Choi IY, Mendez Colmenares A, Kramer AF, Li K, Lee J, Lee P, Thomas ML. Correlates of axonal content in healthy adult span: Age, sex, myelin, and metabolic health. Cereb Circ Cogn Behav 2024; 6:100203. [PMID: 38292016 PMCID: PMC10827486 DOI: 10.1016/j.cccb.2024.100203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 01/10/2024] [Accepted: 01/11/2024] [Indexed: 02/01/2024]
Abstract
As the emerging treatments that target grey matter pathology in Alzheimer's Disease have limited effectiveness, there is a critical need to identify new neural targets for treatments. White matter's (WM) metabolic vulnerability makes it a promising candidate for new interventions. This study examined the age and sex differences in estimates of axonal content, as well the associations of with highly prevalent modifiable health risk factors such as metabolic syndrome and adiposity. We estimated intra-axonal volume fraction (ICVF) using the Neurite Orientation Dispersion and Density Imaging (NODDI) in a sample of 89 cognitively and neurologically healthy adults (20-79 years). We showed that ICVF correlated positively with age and estimates of myelin content. The ICVF was also lower in women than men, across all ages, which difference was accounted for by intracranial volume. Finally, we found no association of metabolic risk or adiposity scores with the current estimates of ICVF. In addition, the previously observed adiposity-myelin associations (Burzynska et al., 2023) were independent of ICVF. Although our findings confirm the vulnerability of axons to aging, they suggest that metabolic dysfunction may selectively affect myelin content, at least in cognitively and neurologically healthy adults with low metabolic risk, and when using the specific MRI techniques. Future studies need to revisit our findings using larger samples and different MRI approaches, and identify modifiable factors that accelerate axonal deterioration as well as mechanisms linking peripheral metabolism with the health of myelin.
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Affiliation(s)
- Agnieszka Z Burzynska
- The BRAiN lab, Department of Human Development and Family Studies/Molecular, Cellular and Integrative Neurosciences, Colorado State University, Fort Collins, CO, USA
| | - Charles Anderson
- Department of Computer Science, Colorado State University, Fort Collins, CO, USA
| | - David B. Arciniegas
- Marcus Institute for Brain Health, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Vince Calhoun
- Tri-institutional Center for Translational Research in Neuroimaging and Data Science (TReNDS), Georgia State, Georgia Tech, Emory, Atlanta, GA, USA
| | - In-Young Choi
- Department of Neurology, Department of Radiology, Hoglund Biomedical Imaging Center, University of Kansas Medical Center, Kansas City, KS, USA
| | - Andrea Mendez Colmenares
- The BRAiN lab, Department of Human Development and Family Studies/Molecular, Cellular and Integrative Neurosciences, Colorado State University, Fort Collins, CO, USA
| | - Arthur F Kramer
- Beckman Institute for Advanced Science and Technology at the University of Illinois, IL, USA
- Center for Cognitive & Brain Health, Northeastern University, Boston, MA, USA
| | - Kaigang Li
- Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA
| | - Jongho Lee
- Department of Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea
| | - Phil Lee
- Department of Radiology, Hoglund Biomedical Imaging Center, University of Kansas Medical Center, Kansas City, KS, USA
| | - Michael L Thomas
- Department of Psychology, Colorado State University, Fort Collins, CO, USA
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Moya-Alvarado G, Aguirre-Soto A, Bronfman FC. Multiple Labeling of Compartmentalized Cortical Neurons in Microfluidic Chambers. Bio Protoc 2024; 14:e4911. [PMID: 38213323 PMCID: PMC10777054 DOI: 10.21769/bioprotoc.4911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 11/13/2023] [Accepted: 11/17/2023] [Indexed: 01/13/2024] Open
Abstract
Neurons are complex cells with two distinct compartments: the somatodendritic and the axonal domains. Because of their polarized morphology, it is challenging to study the differential cellular and molecular mechanisms that occur in axons and impact the soma and dendrites using conventional in vitro culture systems. Compartmentalized cultures offer a solution by physically and chemically separating the axonal from the somatodendritic domain of neurons. The microfluidic chamber model presented in this work is valuable for studying these mechanisms in primary cortical cultures derived from rat and mouse. In addition, this chamber model is compatible with various microscopy methods, such as phase contrast, and fluorescence imaging of living and fixed cells. Key features • Preparation and attachment of PDMS microfluidic chambers to glass coverslips. • Primary culture of cortical neurons and plating cortical neurons in microfluidic chamber. • Confirmation of compartmentalization using the retrograde transport of the fluorescently labeled form of cholera toxin subunit B (f-Ctb). • Immunofluorescence and multilabeling of compartmentalized cortical neurons. • Retrograde transport of fluorescently labeled BDNF.
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Affiliation(s)
- Guillermo Moya-Alvarado
- Department of Physiology, Faculty of Biological Sciences and Center for Aging and Regeneration (CARE), Pontificia Universidad Catolica de Chile, Av. Libertador Bernardo O´Higgins 340, Santiago, 8970117, Chile
| | - Alejandro Aguirre-Soto
- NeuroSignaling Lab (NESLab), Institute of Biomedical Sciences (ICB), Faculty of Medicine, and Faculty of Life Sciences, Universidad Andres Bello, Echaurren 183, 8370146, Santiago, Chile
| | - Francisca C. Bronfman
- NeuroSignaling Lab (NESLab), Institute of Biomedical Sciences (ICB), Faculty of Medicine, and Faculty of Life Sciences, Universidad Andres Bello, Echaurren 183, 8370146, Santiago, Chile
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Tomé D, Dias MS, Correia J, Almeida RD. Fibroblast growth factor signaling in axons: from development to disease. Cell Commun Signal 2023; 21:290. [PMID: 37845690 PMCID: PMC10577959 DOI: 10.1186/s12964-023-01284-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 08/18/2023] [Indexed: 10/18/2023] Open
Abstract
The fibroblast growth factor (FGF) family regulates various and important aspects of nervous system development, ranging from the well-established roles in neuronal patterning to more recent and exciting functions in axonal growth and synaptogenesis. In addition, FGFs play a critical role in axonal regeneration, particularly after spinal cord injury, confirming their versatile nature in the nervous system. Due to their widespread involvement in neural development, the FGF system also underlies several human neurological disorders. While particular attention has been given to FGFs in a whole-cell context, their effects at the axonal level are in most cases undervalued. Here we discuss the endeavor of the FGF system in axons, we delve into this neuronal subcompartment to provide an original view of this multipurpose family of growth factors in nervous system (dys)function. Video Abstract.
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Affiliation(s)
- Diogo Tomé
- Institute of Biomedicine, Department of Medical Sciences - iBiMED, University of Aveiro, Aveiro, Portugal
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
| | - Marta S Dias
- Institute of Biomedicine, Department of Medical Sciences - iBiMED, University of Aveiro, Aveiro, Portugal
| | - Joana Correia
- Institute of Biomedicine, Department of Medical Sciences - iBiMED, University of Aveiro, Aveiro, Portugal
| | - Ramiro D Almeida
- Institute of Biomedicine, Department of Medical Sciences - iBiMED, University of Aveiro, Aveiro, Portugal.
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.
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Ling YTT, Korneva A, Quigley HA, Nguyen TD. Computational study of the mechanical behavior of the astrocyte network and axonal compartments in the mouse optic nerve head. Biomech Model Mechanobiol 2023; 22:1751-1772. [PMID: 37573553 PMCID: PMC10988382 DOI: 10.1007/s10237-023-01752-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Accepted: 07/15/2023] [Indexed: 08/15/2023]
Abstract
Glaucoma is a blinding disease characterized by the degeneration of the retinal ganglion cell (RGC) axons at the optic nerve head (ONH). A major risk factor for glaucoma is the intraocular pressure (IOP). However, it is currently impossible to measure the IOP-induced mechanical response of the axons of the ONH. The objective of this study was to develop a computational modeling method to estimate the IOP-induced strains and stresses in the axonal compartments in the mouse astrocytic lamina (AL) of the ONH, and to investigate the effect of the structural features on the mechanical behavior. We developed experimentally informed finite element (FE) models of six mouse ALs to investigate the effect of structure on the strain responses of the astrocyte network and axonal compartments to pressure elevation. The specimen-specific geometries of the FE models were reconstructed from confocal fluorescent images of cryosections of the mouse AL acquired in a previous study that measured the structural features of the astrocytic processes and axonal compartments. The displacement fields obtained from digital volume correlation in prior inflation tests of the mouse AL were used to determine the displacement boundary conditions of the FE models. We then applied Gaussian process regression to analyze the effects of the structural features on the strain outcomes simulated for the axonal compartments. The axonal compartments experienced, on average, 6 times higher maximum principal strain but 1800 times lower maximum principal stress compared to those experienced by the astrocyte processes. The strains experienced by the axonal compartments were most sensitive to variations in the area of the axonal compartments. Larger axonal compartments that were more vertically aligned, closer to the AL center, and with lower local actin area fraction had higher strains. Understanding the factors affecting the deformation in the axonal compartments will provide insights into mechanisms of glaucomatous axonal damage.
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Affiliation(s)
- Yik Tung Tracy Ling
- Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD, USA
| | - Arina Korneva
- Department of Ophthalmology, Johns Hopkins School of Medicine, Baltimore, MD, USA
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Harry A Quigley
- Department of Ophthalmology, Johns Hopkins School of Medicine, Baltimore, MD, USA
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Thao D Nguyen
- Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD, USA.
- Department of Ophthalmology, Johns Hopkins School of Medicine, Baltimore, MD, USA.
- Department of Materials Science, Johns Hopkins University, Baltimore, MD, USA.
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Davies FCJ, Marshall GF, Pegram E, Gadd D, Abbott CM. Endogenous epitope tagging of eEF1A2 in mice reveals early embryonic expression of eEF1A2 and subcellular compartmentalisation of neuronal eEF1A1 and eEF1A2. Mol Cell Neurosci 2023; 126:103879. [PMID: 37429391 DOI: 10.1016/j.mcn.2023.103879] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 06/29/2023] [Accepted: 07/06/2023] [Indexed: 07/12/2023] Open
Abstract
All vertebrate species express two independently-encoded forms of translation elongation factor eEF1A. In humans and mice eEF1A1 and eEF1A2 are 92 % identical at the amino acid level, but the well conserved developmental switch between the two variants in specific tissues suggests the existence of important functional differences. Heterozygous mutations in eEF1A2 result in neurodevelopmental disorders in humans; the mechanism of pathogenicity is unclear, but one hypothesis is that there is a dominant negative effect on eEF1A1 during development. The high degree of similarity between the eEF1A proteins has complicated expression analysis in the past; here we describe a gene edited mouse line in which we have introduced a V5 tag in the gene encoding eEF1A2. Expression analysis using anti-V5 and anti-eEF1A1 antibodies demonstrates that, in contrast to the prevailing view that eEF1A2 is only expressed postnatally, it is expressed from as early as E11.5 in the developing neural tube. Two colour immunofluorescence also reveals coordinated switching between eEF1A1 and eEF1A2 in different regions of postnatal brain. Completely reciprocal expression of the two variants is seen in post-weaning mouse brain with eEF1A1 expressed in oligodendrocytes and astrocytes and eEF1A2 in neuronal soma. Although eEF1A1 is absent from neuronal cell bodies after development, it is widely expressed in axons. This expression does not appear to coincide with myelin sheaths originating from oligodendrocytes but rather results from localised translation within the axon, suggesting that both variants are transcribed in neurons but show completely distinct subcellular localisation at the protein level. These findings will form an underlying framework for understanding how missense mutations in eEF1A2 result in neurodevelopmental disorders.
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Affiliation(s)
- Faith C J Davies
- Centre for Genomic & Experimental Medicine, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, United Kingdom; Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom
| | - Grant F Marshall
- Centre for Genomic & Experimental Medicine, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, United Kingdom; Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom
| | - Eleanor Pegram
- Centre for Genomic & Experimental Medicine, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, United Kingdom
| | - Danni Gadd
- Centre for Genomic & Experimental Medicine, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, United Kingdom
| | - Catherine M Abbott
- Centre for Genomic & Experimental Medicine, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, United Kingdom; Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom.
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Schlosser-Perrin F, Rossel O, Duffau H, Bonnetblanc F, Mandonnet E. How far does electrical stimulation activate white matter tracts? A computational modeling study. Clin Neurophysiol 2023; 153:68-78. [PMID: 37459667 DOI: 10.1016/j.clinph.2023.06.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2023] [Revised: 06/08/2023] [Accepted: 06/16/2023] [Indexed: 08/21/2023]
Abstract
OBJECTIVE The aim of this study was to model how the different parameters of electrical stimulation (intensity, pulse shape, probe geometry) influence the extent of white matter activation. METHODS The electrical potentials generated by the stimulating electrodes were determined by solving Laplace equation. The temporal evolution of membrane potentials at each nodes of Ranvier of an axon was then computed by solving the coupled system of differential equations describing membrane dynamics and cable propagation. RESULTS Regions of unilateral propagation were observed for monophasic pulses delivered with a bipolar probe aligned along the tract. For biphasic pulses, the largest activation areas and depths were found with a high inter-electrode-distance (IED) bipolar probe, oriented orthogonally to the tract. The smallest activation areas and depths were found for bipolar stimulations with the probe aligned parallel to the tract and low IED. For isotropic white matter regions, the activation area and depth were three times larger than for anisotropic white matter tracts. CONCLUSIONS Bipolar probes with biphasic pulses offer the greatest versatility: an orthogonal orientation acts as two monopolars (increased sensitivity when searching for a tract), whereas a parallel orientation corresponds to a single monopolar (increased specificity). Activation is more superficial when stimulating highly anisotropic tracts. SIGNIFICANCE This knowledge is essential for interpreting the behavorial effects of stimulation and the recordings of axono-cortical evoked potentials.
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Affiliation(s)
| | | | - Hugues Duffau
- Département de Neurochirurgie, Centre Hospitalier Universitaire de Montpellier Gui de Chauliac, Montpellier, France; Team "Neuroplasticity, Stem Cells and Glial Tumors", Institute of Functional Genomics, INSERM U-1191, University of Montpellier, 34090 Montpellier, France; Université de Montpellier, Montpellier, France
| | | | - Emmanuel Mandonnet
- Frontlab, Paris Brain Institute, CNRS UMR 7225, INSERM U1127, Paris, France; Department of Neurosurgery, Lariboisière Hospital, Paris, France; Université de Paris Cité, Paris, France.
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Yang L, Ren Z, Song P, Liu Z, Peng Z, Zhou J, Dong Q. Effects of Curcumin on Axon Growth and Myelin Sheath Formation in an In Vitro Model. Neurochem Res 2023:10.1007/s11064-023-03946-4. [PMID: 37148458 DOI: 10.1007/s11064-023-03946-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 04/20/2023] [Accepted: 05/03/2023] [Indexed: 05/08/2023]
Abstract
Although the beneficial effects of curcumin, extracted from rhizomes of the ginger family genus Curcuma, on the repair and regeneration of nerves have been evaluated in vitro, there are few studies concerning its effects on axon myelination. Here, we used pheochromocytoma cells as an in vitro model of peripheral nerves. Pheochromocytoma cells were cultured alone or cocultured with Schwann cells and treated with increasing concentrations of curcumin. Cell growth was observed, and the expression levels of growth-associated protein 43 (GAP-43), microtubule-associated protein 2 (MAP-2), myelin basic protein (MBP), myelin protein zero (MPZ), Krox-20, and octamer binding factor 6 (Oct-6) were quantified. We found a significant increase in expression of all six proteins following curcumin treatment, with a corresponding increase in the levels of MBP, MPZ, Krox-20, and Oct-6 mRNA. Upregulation was greater with increasing curcumin concentration, showing a concentration-dependent effect. The results suggested that curcumin can promote the growth of axons by upregulating the expression of GAP-43 and MAP-2, stimulate synthesis and secretion of myelin-related proteins, and facilitate formation of the myelin sheath in axons by upregulating the expression of Krox-20 and Oct-6. Therefore, curcumin could be widely applied in future strategies for the treatment of nerve injuries.
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Affiliation(s)
- Luchen Yang
- Department of Urology, Institute of Urology, West China Hospital, Sichuan University, Chengdu, Sichuan, 610041, PR China
| | - Zhengju Ren
- Department of Urology, Institute of Urology, West China Hospital, Sichuan University, Chengdu, Sichuan, 610041, PR China
- Department of Urology, the Second affiliated Hospital of Chongqing Medical University, Chongqing, 400010, PR China
| | - Pan Song
- Department of Urology, Institute of Urology, West China Hospital, Sichuan University, Chengdu, Sichuan, 610041, PR China
| | - Zhenghuan Liu
- Department of Urology, Institute of Urology, West China Hospital, Sichuan University, Chengdu, Sichuan, 610041, PR China
| | - Zhufeng Peng
- Department of Urology, Institute of Urology, West China Hospital, Sichuan University, Chengdu, Sichuan, 610041, PR China
| | - Jing Zhou
- Department of Urology, Institute of Urology, West China Hospital, Sichuan University, Chengdu, Sichuan, 610041, PR China
| | - Qiang Dong
- Department of Urology, Institute of Urology, West China Hospital, Sichuan University, Chengdu, Sichuan, 610041, PR China.
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Chen M, Yan R, Luo J, Ning J, Zhou R, Ding L. The Role of PGC-1α-Mediated Mitochondrial Biogenesis in Neurons. Neurochem Res 2023:10.1007/s11064-023-03934-8. [PMID: 37097395 DOI: 10.1007/s11064-023-03934-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 03/28/2023] [Accepted: 03/31/2023] [Indexed: 04/26/2023]
Abstract
Neurons are highly dependent on mitochondrial ATP production and Ca2+ buffering. Neurons have unique compartmentalized anatomy and energy requirements, and each compartment requires continuously renewed mitochondria to maintain neuronal survival and activity. Peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α) is a key factor in the regulation of mitochondrial biogenesis. It is widely accepted that mitochondria are synthesized in the cell body and transported via axons to the distal end. However, axonal mitochondrial biogenesis is necessary to maintain axonal bioenergy supply and mitochondrial density due to limitations in mitochondrial axonal transport rate and mitochondrial protein lifespan. In addition, impaired mitochondrial biogenesis leading to inadequate energy supply and neuronal damage has been observed in neurological disorders. In this review, we focus on the sites where mitochondrial biogenesis occurs in neurons and the mechanisms by which it maintains axonal mitochondrial density. Finally, we summarize several neurological disorders in which mitochondrial biogenesis is affected.
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Affiliation(s)
- Mengjie Chen
- Beijing Hospital of Traditional Chinese Medicine, Capital Medical University, Beijing, 100010, China
| | - Ruyu Yan
- Beijing Hospital of Traditional Chinese Medicine, Capital Medical University, Beijing, 100010, China
| | - Jiansheng Luo
- Beijing Hospital of Traditional Chinese Medicine, Capital Medical University, Beijing, 100010, China
| | - Jiaqi Ning
- Beijing Hospital of Traditional Chinese Medicine, Capital Medical University, Beijing, 100010, China
| | - Ruiling Zhou
- Beijing Hospital of Traditional Chinese Medicine, Capital Medical University, Beijing, 100010, China
| | - Lingling Ding
- Beijing Hospital of Traditional Chinese Medicine, Capital Medical University, Beijing, 100010, China.
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12
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Abstract
The neuron doctrine laid the foundation for our current thinking about the structural and functional organization of the human brain. With the basic units of the nervous system-neurons-being physically separate, their connectivity relies on the conduction of action potentials in axons and their transmission across the synaptic cleft to the dendrites of other neurons. This study reviews available ex vivo data about the cellular composition of the human cerebral cortex, focusing on axons and dendrites, to conceptualize biological sources of signals detected in vivo with magnetic resonance imaging. To bridge the gap between ex vivo and in vivo observations, I then explain the basic principles of virtual histology, an approach that integrates spatially cell- or process-specific transcriptomic data with magnetic resonance signals to facilitate their neurobiological interpretation. Finally, I provide an overview of the initial insights gained in this manner in studies of brain development and maturation, in both health and disease.
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Affiliation(s)
- Tomáš Paus
- Departments of Psychiatry and Neuroscience, Faculty of Medicine and Centre Hospitalier Universitaire Sainte-Justine, University of Montréal, Montreal, Quebec, Canada.
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13
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Huang MC, Chen CH, Liu TH, Chung AN, Liu YL, Quednow BB, Bavato F. Comorbidity of ketamine dependence with major depressive disorder increases the vulnerability to neuroaxonal pathology. J Psychiatr Res 2023; 158:360-364. [PMID: 36640660 DOI: 10.1016/j.jpsychires.2023.01.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Revised: 01/02/2023] [Accepted: 01/09/2023] [Indexed: 01/11/2023]
Abstract
We recently demonstrated that patients with ketamine dependence (KD) have increased serum levels of neurofilament light chain (NfL), a novel marker of active neuroaxonal pathology, with NfL levels being significantly higher in those KD patients comorbid with major depressive disorder (MDD). However, considering that NfL elevation has been associated with both ketamine-related brain pathology and MDD, we could not determine whether the observed elevation of NfL levels was driven by an interaction of KD with MDD or by MDD itself. Therefore, we compared serum NfL levels between 35 patients with MDD without ketamine use (MDD group), 23 with KD without MDD (KD without MDD group), 30 KD with MDD (KD with MDD group), and 86 healthy controls (HC group). Using a 2*2 (KD*MDD) generalized linear model controlling for age, sex, body mass index, and smoking status, we found that KD and KD*MDD interactions, but not MDD factor, significantly affected NfL levels. Posthoc tests showed that the KD with MDD group had significantly higher NfL levels than all other groups. The KD without MDD group also showed higher NfL levels than the MDD and, as shown before, HC groups. The levels in MDD group were not different from the HC group. These results suggest that the interaction of KD with MDD, but not MDD alone, results in increased vulnerability to neuroaxonal pathology.
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Affiliation(s)
- Ming-Chyi Huang
- Department of Psychiatry, Taipei City Psychiatric Center, Taipei City Hospital, Taipei, Taiwan; Department of Psychiatry, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan; Psychiatric Research Center, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan
| | - Chun-Hsin Chen
- Department of Psychiatry, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan; Psychiatric Research Center, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan; Department of Psychiatry, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan
| | - Tung-Hsia Liu
- Center for Neuropsychiatric Research, National Health Research Institutes, Zhunan, Miaoli County, Taiwan
| | - An-Nie Chung
- Department of Psychiatry, Taipei City Psychiatric Center, Taipei City Hospital, Taipei, Taiwan; Center for Neuropsychiatric Research, National Health Research Institutes, Zhunan, Miaoli County, Taiwan
| | - Yu-Li Liu
- Center for Neuropsychiatric Research, National Health Research Institutes, Zhunan, Miaoli County, Taiwan.
| | - Boris B Quednow
- Experimental and Clinical Pharmacopsychology, Department of Psychiatry, Psychotherapy, and Psychosomatics, Psychiatric Hospital of the University of Zurich, Zurich, Switzerland; Neuroscience Center Zurich, University of Zurich and Swiss Federal Institute of Technology Zurich, Zurich, Switzerland
| | - Francesco Bavato
- Experimental and Clinical Pharmacopsychology, Department of Psychiatry, Psychotherapy, and Psychosomatics, Psychiatric Hospital of the University of Zurich, Zurich, Switzerland
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14
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Pinho-Correia LM, Prokop A. Maintaining essential microtubule bundles in meter-long axons: a role for local tubulin biogenesis? Brain Res Bull 2023; 193:131-145. [PMID: 36535305 DOI: 10.1016/j.brainresbull.2022.12.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Revised: 12/12/2022] [Accepted: 12/14/2022] [Indexed: 12/23/2022]
Abstract
Axons are the narrow, up-to-meter long cellular processes of neurons that form the biological cables wiring our nervous system. Most axons must survive for an organism's lifetime, i.e. up to a century in humans. Axonal maintenance depends on loose bundles of microtubules that run without interruption all along axons. The continued turn-over and the extension of microtubule bundles during developmental, regenerative or plastic growth requires the availability of α/β-tubulin heterodimers up to a meter away from the cell body. The underlying regulation in axons is poorly understood and hardly features in past and contemporary research. Here we discuss potential mechanisms, particularly focussing on the possibility of local tubulin biogenesis in axons. Current knowledge might suggest that local translation of tubulin takes place in axons, but far less is known about the post-translational machinery of tubulin biogenesis involving three chaperone complexes: prefoldin, CCT and TBC. We discuss functional understanding of these chaperones from a range of model organisms including yeast, plants, flies and mice, and explain what is known from human diseases. Microtubules across species depend on these chaperones, and they are clearly required in the nervous system. However, most chaperones display a high degree of functional pleiotropy, partly through independent functions of individual subunits outside their complexes, thus posing a challenge to experimental studies. Notably, we found hardly any studies that investigate their presence and function particularly in axons, thus highlighting an important gap in our understanding of axon biology and pathology.
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Affiliation(s)
- Liliana Maria Pinho-Correia
- The University of Manchester, Manchester Academic Health Science Centre, Faculty of Biology, Medicine and Health, School of Biology, Manchester, UK
| | - Andreas Prokop
- The University of Manchester, Manchester Academic Health Science Centre, Faculty of Biology, Medicine and Health, School of Biology, Manchester, UK.
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15
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Mysona BA, Zhao J, De Greef O, Beisel A, Patel PA, Berman L, Smith SB, Bollinger K. Sigma-1 receptor agonist, (+)-pentazocine, is neuroprotective in a Brown Norway rat microbead model of glaucoma. Exp Eye Res 2023; 226:109308. [PMID: 36400283 PMCID: PMC9839578 DOI: 10.1016/j.exer.2022.109308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 10/23/2022] [Accepted: 11/08/2022] [Indexed: 11/17/2022]
Abstract
PURPOSE Glaucoma is a worldwide leading cause of irreversible blindness. Standard treatments lower intraocular pressure (IOP). Novel treatments to prevent optic nerve (ON) degeneration are needed. Here, we investigate the hypothesis that sigma-1 receptor (S1R) agonist (+)-pentazocine (PTZ) is neuroprotective in a Brown Norway (BN) rat, microbead model of glaucoma. METHODS BN rats (9-11 weeks, male and female) were treated by intraperitoneal injection, 3 times per week with (+)-PTZ (2 mg/kg) or vehicle (VEH) alone. Treatment started 1 week prior to intraocular injection of polystyrene microbeads to elevate IOP. IOP was measured 2-3 times per week. Five weeks post microbead injection, rats were euthanized. ONs were removed, then fixed and processed for 63x oil, light microscope imaging of toluidine blue stained ON cross sections. To facilitate comparison of ON morphology from VEH and (+)-PTZ treated rats with similar ocular hypertensive insults, rats were assigned to low (IOP ≤15.8 mmHg), moderate (15.8 < IOP <28.0 mmHg), and high (IOP ≥28.0 mmHg) groups based on average IOP in the microbead injected eye. Axon numbers, axon density, axonal and glial areas, axon loss, and axon size distributions of naïve, bead, and contralateral ONs were assessed using QuPath program for automated image analysis. RESULTS (+)-PTZ treatment of BN rats protected ONs from damage caused by moderate IOP elevation. Treatment with (+)-PTZ significantly reduced axon loss and glial areas, and increased axon density and axonal areas compared to ONs from VEH treated rats with moderate IOP. (+)-PTZ-mediated neuroprotection was independent of IOP lowering effects. At average IOP ≥28.0 mmHg, (+)-PTZ treatment did not provide measurable neuroprotection. ONs from contralateral eyes exhibited subtle, complex changes in response to conditions in the bead eyes. CONCLUSIONS S1R agonist (+)-PTZ shows promise as a neuroprotective treatment for glaucoma. Future studies to understand the complex molecular mechanisms by which (+)-PTZ provides this neuroprotection are needed.
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Affiliation(s)
- Barbara A Mysona
- Department of Cellular Biology and Anatomy CB-2304, Medical College of Georgia at Augusta University, 1120 15th Street, Augusta, GA, 30912, USA; James and Jean Culver Vision Discovery Institute, Department of Ophthalmology, Medical College of Georgia at Augusta University, 1120 15th Street, Augusta, GA, 30912, USA.
| | - Jing Zhao
- James and Jean Culver Vision Discovery Institute, Department of Ophthalmology, Medical College of Georgia at Augusta University, 1120 15th Street, Augusta, GA, 30912, USA; Department of Ophthalmology, Medical College of Georgia at Augusta University, Augusta, GA, 30912, USA.
| | - Oceane De Greef
- Student Training and Research Program, Graduate School, Augusta University, 1120 15th Street, Augusta, GA, 30912, USA.
| | - August Beisel
- Medical College of Georgia at Augusta University, 1120 15th Street, Augusta, GA, 30912, USA; Department of Ophthalmology, Medical College of Georgia at Augusta University, Augusta, GA, 30912, USA.
| | - Parth A Patel
- Medical College of Georgia at Augusta University, 1120 15th Street, Augusta, GA, 30912, USA.
| | - Lindsay Berman
- Medical College of Georgia at Augusta University, 1120 15th Street, Augusta, GA, 30912, USA.
| | - Sylvia B Smith
- Department of Cellular Biology and Anatomy CB-2304, Medical College of Georgia at Augusta University, 1120 15th Street, Augusta, GA, 30912, USA.
| | - Kathryn Bollinger
- James and Jean Culver Vision Discovery Institute, Department of Ophthalmology, Medical College of Georgia at Augusta University, 1120 15th Street, Augusta, GA, 30912, USA; Department of Ophthalmology, Medical College of Georgia at Augusta University, Augusta, GA, 30912, USA.
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16
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Hu T, Meng S, Zhang Q, Song S, Tan C, Huang J, Chen D. Astrocyte derived TSP2 contributes to synaptic alteration and visual dysfunction in retinal ischemia/reperfusion injury. Cell Biosci 2022; 12:196. [PMID: 36471420 PMCID: PMC9720934 DOI: 10.1186/s13578-022-00932-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Accepted: 11/21/2022] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Despite current intervention measures/therapies are able to ameliorate neuronal death following retinal injuries/diseases, the recovery of visual function remains unsatisfactory. Previous studies revealed that the retinal synapse and neurite changed during the early stage after retinopathy, which was considered to be detrimental to visual signal transmission. However, the specific profiles and the mechanisms underlying retinal neurite and synaptic alteration after retinal pathologies remain poorly understood. METHODS Here, we revealed the spatiotemporal pattern of neurite and synaptic alteration following retinal pathologies using a rat model of acute RI/R induced by high intraocular pressure (HIOP) with Western blotting, Immunofluorescence, and electron microscopy. We further explored the potential role of activated astrocytes and their derived thrombospondin 2 (TSP2) in RI/R induced retinal neurite and synaptic alteration and visual dysfunction through viral transduction and drug injection. RESULTS We found a defasciculation of RGC axons, a compensatory increase of presynaptic proteins (synaptophysin and synapsin 1) and synaptic vesicles between bipolar cells and ganglion cells in the inner plexiform layer (IPL), and the degenerated visual function preceded the neuronal death in rat retinae. These events were accompanied by the activation of astrocytes. Furthermore, we showed that suppressing the activation of astrocytes (intravitreal injection of fluorocitric acid, FC), TSP2 knockdown (TSP2 shRNA-AAV transduction), and competitively inhibiting the binding of TSP2 and α2δ1 (intraperitoneal injection of gabapentin, GBP) effectively alleviated the retinal synaptic and neurite alteration and the visual dysfunction following RI/R injury. CONCLUSIONS (1) At the early stage following RI/R injury, the rat retinae develop a degeneration of ganglion cell axons and the resulting compensatory synaptic remodeling between bipolar cells and ganglion cells in IPL. These changes occur earlier than the massive loss of neurons in the ganglion cell layer (GCL). (2) Activated astrocytes may secret TSP2, which bind to α2δ1, to mediate the degeneration of rat retinal ganglion cell axons, compensatory synaptic remodeling in IPL, and visual dysfunction following RI/R injury.
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Affiliation(s)
- Tu Hu
- grid.216417.70000 0001 0379 7164Eye Center of Xiangya Hospital, Central South University, No. 87 Xiangya Road, Changsha, 410008 Hunan People’s Republic of China ,grid.452223.00000 0004 1757 7615Hunan Key Laboratory of Ophthalmology, Changsha, 410008 Hunan People’s Republic of China ,grid.216417.70000 0001 0379 7164National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, 410008 Hunan People’s Republic of China
| | - Shuhan Meng
- grid.216417.70000 0001 0379 7164Eye Center of Xiangya Hospital, Central South University, No. 87 Xiangya Road, Changsha, 410008 Hunan People’s Republic of China ,grid.452223.00000 0004 1757 7615Hunan Key Laboratory of Ophthalmology, Changsha, 410008 Hunan People’s Republic of China ,grid.216417.70000 0001 0379 7164National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, 410008 Hunan People’s Republic of China
| | - Qianyue Zhang
- grid.216417.70000 0001 0379 7164Eye Center of Xiangya Hospital, Central South University, No. 87 Xiangya Road, Changsha, 410008 Hunan People’s Republic of China ,grid.452223.00000 0004 1757 7615Hunan Key Laboratory of Ophthalmology, Changsha, 410008 Hunan People’s Republic of China ,grid.216417.70000 0001 0379 7164National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, 410008 Hunan People’s Republic of China ,grid.216417.70000 0001 0379 7164Xiangya School of Medicine, Central South University, No. 172 Tongzipo Road, Changsha, 410013 Hunan People’s Republic of China
| | - Shuang Song
- grid.216417.70000 0001 0379 7164XiangYa School of Public Health, Central South University, No.238 Xiangya Road, Changsha, 410078 Hunan People’s Republic of China
| | - Cheng Tan
- grid.216417.70000 0001 0379 7164Department of Anatomy and Neurobiology, School of Basic Medical Science, Central South University, No. 172 Tongzipo Road, Changsha, 410013 Hunan People’s Republic of China
| | - Jufang Huang
- grid.216417.70000 0001 0379 7164Department of Anatomy and Neurobiology, School of Basic Medical Science, Central South University, No. 172 Tongzipo Road, Changsha, 410013 Hunan People’s Republic of China ,grid.452223.00000 0004 1757 7615Hunan Key Laboratory of Ophthalmology, Changsha, 410008 Hunan People’s Republic of China
| | - Dan Chen
- grid.216417.70000 0001 0379 7164Department of Anatomy and Neurobiology, School of Basic Medical Science, Central South University, No. 172 Tongzipo Road, Changsha, 410013 Hunan People’s Republic of China ,grid.452223.00000 0004 1757 7615Hunan Key Laboratory of Ophthalmology, Changsha, 410008 Hunan People’s Republic of China
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Eskandari F, Shafieian M, Aghdam MM, Laksari K. Morphological changes in glial cells arrangement under mechanical loading: A quantitative study. Injury 2022; 53:3617-3623. [PMID: 36089556 DOI: 10.1016/j.injury.2022.08.062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 08/26/2022] [Indexed: 02/02/2023]
Abstract
The mechanical properties and microstructure of brain tissue, as its two main physical parameters, could be affected by mechanical stimuli. In previous studies, microstructural alterations due to mechanical loading have received less attention than the mechanical properties of the tissue. Therefore, the current study aimed to investigate the effect of ex-vivo mechanical forces on the micro-architecture of brain tissue including axons and glial cells. A three-step loading protocol (i.e., loading-recovery-loading) including eight strain levels from 5% to 40% was applied to bovine brain samples with axons aligned in one preferred direction (each sample experienced only one level of strain). After either the first or secondary loading step, the samples were fixed, cut in planes parallel and perpendicular to the loading direction, and stained for histology. The histological images were analyzed to measure the end-to-end length of axons and glial cell-cell distances. The results showed that after both loading steps, as the strain increased, the changes in the cell nuclei arrangement in the direction parallel to axons were more significant compared to the other two perpendicular directions. Based on this evidence, we hypothesized that the spatial pattern of glial cells is highly affected by the orientation of axonal fibers. Moreover, the results revealed that in both loading steps, the maximum cell-cell distance occurred at 15% strain, and this distance decreased for higher strains. Since 15% strain is close to the previously reported brain injury threshold, this evidence could suggest that at higher strains, the axons start to rupture, causing a reduction in the displacement of glial cells. Accordingly, it was concluded that more attention to glial cells' architecture during mechanical loading may lead to introduce a new biomarker for brain injury.
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Affiliation(s)
- Faezeh Eskandari
- Department of Biomedical Engineering, Amirkabir University of Technology, Tehran, Iran
| | - Mehdi Shafieian
- Department of Biomedical Engineering, Amirkabir University of Technology, Tehran, Iran.
| | - Mohammad M Aghdam
- Department of Mechanical Engineering, Amirkabir University of Technology, Tehran, Iran
| | - Kaveh Laksari
- Department of Biomedical Engineering, University of Arizona, Tucson, AZ, USA; Department of Aerospace and Mechanical Engineering, University of Arizona, Tucson, AZ, USA
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18
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Baldacchino K, Peveler WJ, Lemgruber L, Smith RS, Scharler C, Hayden L, Komarek L, Lindsay SL, Barnett SC, Edgar JM, Linington C, Thümmler K. Myelinated axons are the primary target of hemin-mediated oxidative damage in a model of the central nervous system. Exp Neurol 2022; 354:114113. [PMID: 35569511 DOI: 10.1016/j.expneurol.2022.114113] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Revised: 04/29/2022] [Accepted: 05/08/2022] [Indexed: 12/01/2022]
Abstract
Iron released from oligodendrocytes during demyelination or derived from haemoglobin breakdown products is believed to amplify oxidative tissue injury in multiple sclerosis (MS). However, the pathophysiological significance of iron-containing haemoglobin breakdown products themselves is rarely considered in the context of MS and their cellular specificity and mode of action remain unclear. Using myelinating cell cultures, we now report the cytotoxic potential of hemin (ferriprotoporphyrin IX chloride), a major degradation product of haemoglobin, is 25-fold greater than equimolar concentrations of free iron in myelinating cultures; a model that reproduces the complex multicellular environment of the CNS. At low micro molar concentrations (3.3 - 10 μM) we observed hemin preferentially binds to myelin and axons to initiate a complex detrimental response that results in targeted demyelination and axonal loss but spares neuronal cell bodies, astrocytes and the majority of oligodendroglia. Demyelination and axonal loss in this context are executed by a combination of mechanisms that include iron-dependent peroxidation by reactive oxygen species (ROS) and ferroptosis. These effects are microglial-independent, do not require any initiating inflammatory insult and represent a direct effect that compromises the structural integrity of myelinated axons in the CNS. Our data identify hemin-mediated demyelination and axonal loss as a novel mechanism by which intracerebral degradation of haemoglobin may contribute to lesion development in MS.
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Affiliation(s)
- Karl Baldacchino
- Institute of Infection, Immunity and Inflammation, University of Glasgow, G12 8TA Glasgow, United Kingdom
| | - William J Peveler
- WestCHEM, School of Chemistry, University of Glasgow, Joseph Black Building, G12 8QQ Glasgow, UK
| | - Leandro Lemgruber
- Glasgow Imaging Facility, Institute of Infection, Immunity and Inflammation, University of Glasgow, University Avenue, Glasgow G12 8QQ, UK
| | - Rebecca Sherrard Smith
- Institute of Infection, Immunity and Inflammation, University of Glasgow, G12 8TA Glasgow, United Kingdom
| | - Cornelia Scharler
- Institute of Experimental and Clinical Cell Therapy, Paracelsus Medical University, Salzburg, Austria
| | - Lorna Hayden
- Institute of Infection, Immunity and Inflammation, University of Glasgow, G12 8TA Glasgow, United Kingdom
| | - Lina Komarek
- Institute of Infection, Immunity and Inflammation, University of Glasgow, G12 8TA Glasgow, United Kingdom
| | - Susan L Lindsay
- Institute of Infection, Immunity and Inflammation, University of Glasgow, G12 8TA Glasgow, United Kingdom
| | - Susan C Barnett
- Institute of Infection, Immunity and Inflammation, University of Glasgow, G12 8TA Glasgow, United Kingdom
| | - Julia M Edgar
- Institute of Infection, Immunity and Inflammation, University of Glasgow, G12 8TA Glasgow, United Kingdom
| | - Christopher Linington
- Institute of Infection, Immunity and Inflammation, University of Glasgow, G12 8TA Glasgow, United Kingdom
| | - Katja Thümmler
- Institute of Infection, Immunity and Inflammation, University of Glasgow, G12 8TA Glasgow, United Kingdom.
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19
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Navarro-Sempere A, García M, Rodrigues AS, Garcia PV, Camarinho R, Segovia Y. Occurrence of Volcanogenic Inorganic Mercury in Wild Mice Spinal Cord: Potential Health Implications. Biol Trace Elem Res 2022; 200:2838-2847. [PMID: 34415497 PMCID: PMC9132843 DOI: 10.1007/s12011-021-02890-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 08/13/2021] [Indexed: 11/25/2022]
Abstract
Mercury accumulation has been proposed as a toxic factor that causes neurodegenerative diseases. However, the hazardous health effects of gaseous elemental mercury exposure on the spinal cord in volcanic areas have not been reported previously in the literature. To evaluate the presence of volcanogenic inorganic mercury in the spinal cord, a study was carried out in São Miguel island (Azores, Portugal) by comparing the spinal cord of mice exposed chronically to an active volcanic environment (Furnas village) with individuals not exposed (Rabo de Peixe village), through the autometallographic silver enhancement histochemical method. Moreover, a morphometric and quantification analysis of the axons was carried out. Results exhibited mercury deposits at the lumbar level of the spinal cord in the specimens captured at the site with volcanic activity (Furnas village). A decrease in axon calibre and axonal atrophy was also observed in these specimens. Given that these are relevant hallmarks in the neurodegenerative pathologies, our results highlight the importance of the surveillance of the health of populations chronically exposed to active volcanic environments.
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Affiliation(s)
- A Navarro-Sempere
- Department of Biotechnology, Faculty of Science, University of Alicante, Apartado 99, 03080, Alicante, Spain
| | - M García
- Department of Biotechnology, Faculty of Science, University of Alicante, Apartado 99, 03080, Alicante, Spain
| | - A S Rodrigues
- Faculty of Sciences and Technology, University of the Azores, 9501-801, Ponta Delgada, Portugal
- IVAR, Research Institute for Volcanology and Risk Assessment, University of the Azores, 9501-801, Ponta Delgada, Portugal
| | - P V Garcia
- Faculty of Sciences and Technology, University of the Azores, 9501-801, Ponta Delgada, Portugal
- cE3c, Centre for Ecology, Evolution and Environmental Changes, and Azorean Biodiversity Group, University of the Azores, 9501-801, Ponta Delgada, Portugal
| | - R Camarinho
- Faculty of Sciences and Technology, University of the Azores, 9501-801, Ponta Delgada, Portugal
- IVAR, Research Institute for Volcanology and Risk Assessment, University of the Azores, 9501-801, Ponta Delgada, Portugal
| | - Y Segovia
- Department of Biotechnology, Faculty of Science, University of Alicante, Apartado 99, 03080, Alicante, Spain.
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20
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Alagaratnam J, De Francesco D, Zetterberg H, Heslegrave A, Toombs J, Kootstra NA, Underwood J, Gisslen M, Reiss P, Fidler S, Sabin CA, Winston A. Correlation between cerebrospinal fluid and plasma neurofilament light protein in treated HIV infection: results from the COBRA study. J Neurovirol 2022; 28:54-63. [PMID: 34874540 PMCID: PMC9076742 DOI: 10.1007/s13365-021-01026-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 03/24/2021] [Accepted: 10/27/2021] [Indexed: 11/27/2022]
Abstract
Cerebrospinal fluid (CSF) neurofilament light protein (NfL) is a marker of central nervous system neuro-axonal injury. A novel, ultra-sensitive assay can determine plasma NfL. In untreated people-with-HIV (PWH), CSF and plasma NfL are strongly correlated. We aimed to assess this correlation in PWH on suppressive antiretroviral treatment (ART) and lifestyle-similar HIV-negative individuals enrolled into the COmorBidity in Relation to AIDS (COBRA) study. Differences in paired CSF (sandwich ELISA, UmanDiagnostics) and plasma (Simoa digital immunoassay, Quanterix™) NfL between PWH and HIV-negative participants were tested using Wilcoxon's test; associations were assessed using Pearson's correlation. CSF and plasma NfL, standardised to Z-scores, were included as dependent variables in linear regression models to identify factors independently associated with values in PWH and HIV-negative participants. Overall, 132 PWH (all with plasma HIV RNA < 50 copies/mL) and 79 HIV-negative participants were included. Neither CSF (median 570 vs 568 pg/mL, p = 0.37) nor plasma (median 10.7 vs 9.9 pg/mL, p = 0.15) NfL differed significantly between PWH and HIV-negative participants, respectively. CSF and plasma NfL correlated moderately, with no significant difference by HIV status (PWH: rho = 0.52; HIV-negative participants: rho = 0.47, p (interaction) = 0.63). In multivariable regression analysis, higher CSF NfL Z-score was statistically significantly associated with older age and higher CSF protein, and higher plasma NfL Z-score with older age, higher serum creatinine and lower bodyweight. In conclusion, in PWH on ART, the correlation between CSF and plasma NfL is moderate and similar to that observed in lifestyle-similar HIV-negative individuals. Consideration of renal function and bodyweight may be required when utilising plasma NfL.
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Affiliation(s)
- Jasmini Alagaratnam
- Department of Infectious Disease, Faculty of Medicine, Imperial College London, London, UK.
- Department of Genitourinary Medicine &, HIV, St Mary's Hospital, Imperial College Healthcare NHS Trust, London, UK.
| | | | - Henrik Zetterberg
- UK Dementia Research Institute at University College London, London, UK
- Department of Neurodegenerative Disease, UCL Institute of Neurology, Queen Square, University College London, London, UK
- Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, the Sahlgrenska Academy at the University of Gothenburg, Mölndal, Sweden
- Clinical Neurochemistry Laboratory, Sahlgrenska University Hospital, Mölndal, Sweden
| | - Amanda Heslegrave
- UK Dementia Research Institute at University College London, London, UK
| | - Jamie Toombs
- UK Dementia Research Institute at University College London, London, UK
| | - Neeltje A Kootstra
- Department of Experimental Immunology, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Jonathan Underwood
- Department of Infectious Disease, Faculty of Medicine, Imperial College London, London, UK
- Division of Infection and Immunity, Cardiff University, Cardiff, UK
- Department of Infectious Diseases, Cardiff and Vale University Health Board, Cardiff, UK
| | - Magnus Gisslen
- Department of Infectious Diseases, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Department of Infectious Diseases, Region Västra Götaland, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Peter Reiss
- Department of Global Health, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands
- Amsterdam Institute for Global Health and Development, Amsterdam, The Netherlands
- Stichting HIV Monitoring, Amsterdam, The Netherlands
| | - Sarah Fidler
- Department of Infectious Disease, Faculty of Medicine, Imperial College London, London, UK
- Department of Genitourinary Medicine &, HIV, St Mary's Hospital, Imperial College Healthcare NHS Trust, London, UK
| | - Caroline A Sabin
- Institute for Global Health, University College London, London, UK
| | - Alan Winston
- Department of Infectious Disease, Faculty of Medicine, Imperial College London, London, UK
- Department of Genitourinary Medicine &, HIV, St Mary's Hospital, Imperial College Healthcare NHS Trust, London, UK
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21
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Emily MF, Agrawal L, Barzaghi P, Otsuki M, Terenzio M. Use of Microfluidics Chambers to Image Axonal transport in Adult Sensory Neurons. Methods Mol Biol 2022; 2431:271-288. [PMID: 35412282 DOI: 10.1007/978-1-0716-1990-2_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Transport of cargoes along axons is crucial for ensuring effective neuronal function and survival. Lysosomes, which are membrane-bound organelles responsible for the degradation of macromolecules, are among the many cargoes being transported. Compartmentalized systems that allow for the separation of the somatic compartment from the axonal network, are widely used in the field of neurobiology and in the study of axonal transport in particular. Among the various solutions available, microfluidics chambers that take advantage of fluidic separation between different compartments, have seen widespread adoption. Said chambers are made of polydimethylsiloxane (PDMS), a transparent, gas permeable compound, which is compatible with fluorescence microscopy, and have significantly positively impacted cellular neuroscience, drastically increasing our understanding of axonal peripheral signaling. Here we describe a two-layered microfluidics chamber, engineered to allow for the culture of adult sensory neurons. This device was designed to promote the proper placement of adult sensory neurons in the somatic chamber in proximity of the microgrooves. We detail the production of the master mold, how to fabricate and assemble the device and how to disaggregate and load the cells in it. In addition, we provide details on how to conduct and analyze an axonal transport experiment using a custom made script in MATLAB designed by our laboratory.
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Affiliation(s)
- Maria Fransiska Emily
- Molecular Neuroscience Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Lokesh Agrawal
- Molecular Neuroscience Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Paolo Barzaghi
- Imaging Section, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Miki Otsuki
- Molecular Neuroscience Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Marco Terenzio
- Molecular Neuroscience Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan.
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22
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Li C, Sun R, Chen J, Hong J, Sun J, Zeng Y, Zhang X, Dou Z, Wen H. Different training patterns at recovery stage improve cognitive function in ischemic stroke rats through regulation of the axonal growth inhibitor pathway. Behav Brain Res 2021; 421:113730. [PMID: 34971645 DOI: 10.1016/j.bbr.2021.113730] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 12/23/2021] [Accepted: 12/23/2021] [Indexed: 02/07/2023]
Abstract
Running wheel exercise training (RWE) and skilled reaching training (SRT) are physical training approaches with positive effects on cognitive function. However, few studies have compared the different effects of these exercises on long-term memory, and their mechanism remains unknown. This study investigated the effects of SRT and RWE, at the recovery stage, on the cognitive function of transient middle cerebral artery occlusion (tMCAO) rats and explored their association with NgR1/Rho-A/ROCK/LOTUS/LGI1 signaling. Adult Sprague-Dawley rats (n = 55) were divided into four groups after pretraining: SRT, RWE, tMCAO, and Sham. Rats were subjected to modified neurological severity score (mNSS) measurements and forelimb grip strength and the Morris water maze tests. Using immunofluorescence and western blotting, we evaluated axonal growth inhibitor expression in the peri-infarct cortex on days 28 and 56 after tMCAO. Results showed the mNSS reduced, whereas the grip strengths improved in RWE and SRT groups. The escape latency in the Morris water maze test was shorter, whereas the number of times of crossing the platform was higher in both the SRT and RWE groups than in the tMCAO group on day 56; furthermore, the parameters in the SRT group improved compared to those in the RWE group. Physical exercise training could improve cognitive functions by reducing the expression of the NgR1/RhoA/ROCK axon growth inhibitors and increasing the expression of the endogenous antagonists LOTUS/LGI1. Exercise training beginning at the recovery stage could improve the cognitive function in tMCAO rats through a mechanism probably associated with the axonal growth inhibitor pathway.
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Affiliation(s)
- Chao Li
- Department of Rehabilitation Medicine, The Third Affiliated Hospital, Sun Yat-sen University, 600 Tianhe Road, Guangzhou 510630, Guangdong Province, China
| | - Ruifang Sun
- Department of Rehabilitation Medicine, Huazhong University of Science and Technology Union Shenzhen Hospital, 89 Taoyuan Road, Nanshan District, Shenzhen 518000, Guangdong Province, China
| | - Jiemei Chen
- Department of Rehabilitation Medicine, The Third Affiliated Hospital, Sun Yat-sen University, 600 Tianhe Road, Guangzhou 510630, Guangdong Province, China
| | - Jiena Hong
- Department of Rehabilitation Medicine, The Third Affiliated Hospital, Sun Yat-sen University, 600 Tianhe Road, Guangzhou 510630, Guangdong Province, China
| | - Ju Sun
- Department of Rehabilitation Medicine, The Third Affiliated Hospital, Sun Yat-sen University, 600 Tianhe Road, Guangzhou 510630, Guangdong Province, China; Department of Rehabilitation Medicine, Guangzhou Panyu Central Hospital, No.8 Fuyu east Road, Guangzhou 511400, Guangdong Province, China
| | - Yan Zeng
- Department of Rehabilitation Medicine, The Third Affiliated Hospital, Sun Yat-sen University, 600 Tianhe Road, Guangzhou 510630, Guangdong Province, China
| | - Xue Zhang
- Department of Rehabilitation Medicine, The Third Affiliated Hospital, Sun Yat-sen University, 600 Tianhe Road, Guangzhou 510630, Guangdong Province, China
| | - Zulin Dou
- Department of Rehabilitation Medicine, The Third Affiliated Hospital, Sun Yat-sen University, 600 Tianhe Road, Guangzhou 510630, Guangdong Province, China
| | - Hongmei Wen
- Department of Rehabilitation Medicine, The Third Affiliated Hospital, Sun Yat-sen University, 600 Tianhe Road, Guangzhou 510630, Guangdong Province, China.
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23
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Sun J, Sun R, Li C, Luo X, Chen J, Hong J, Zeng Y, Wang QM, Wen H. NgR1 pathway expression in cerebral ischemic Sprague-Dawley rats with cognitive impairment. Iran J Basic Med Sci 2021; 24:767-775. [PMID: 34630954 PMCID: PMC8487595 DOI: 10.22038/ijbms.2021.53316.12011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/08/2020] [Accepted: 04/27/2021] [Indexed: 11/29/2022]
Abstract
Objective(s): This study aimed to determine the effect of ischemic occlusion duration and recovery time course on motor and cognitive function, identify optimal conditions for assessing cognitive function with minimal interference from motor deficits, and elucidate the underlying mechanism of axonal inhibitors. Materials and Methods: Sprague-Dawley (SD) rats were randomly allocated to the transient middle cerebral artery occlusion (tMCAO) 60-min (tMCAO60min), tMCAO90min, tMCAO120min, and sham groups. We conducted forelimb grip strength, two-way shuttle avoidance task, and novel object recognition task (NORT)tests at three time points (14, 21, and 28 days). Expression of Nogo receptor-1 (NgR1), the endogenous antagonist lateral olfactory tract usher substance, ras homolog family member A (Rho-A), and RhoA-activated Rho kinase (ROCK) was examined in the ipsilateral thalamus. Results: There was no difference in grip strength between sham and tMCAO90min rats at 28 days. tMCAO90min and tMCAO120min rats showed lower discrimination indices in the NORT than sham rats on day 28. Compared with that in sham rats, the active avoidance response rate was lower in tMCAO90min rats on days 14, 21, and 28 and in tMCAO120min rats on days 14 and 21. Furthermore, 50-54% of rats in the tMCAO90min group developed significant cognitive impairment on day 28, and thalamic NgR1, RhoA, and ROCK expression were greater in tMCAO90min rats than in sham rats. Conclusion: Employing 90-min tMCAO in SD rats and assessing cognitive function 28 days post-stroke could minimize motor dysfunction effects in cognitive function assessments. Axonal inhibitor deregulation could be involved in poststroke cognitive impairment.
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Affiliation(s)
- Ju Sun
- Department of Rehabilitation Medicine, The Third Affiliated Hospital, Sun Yat-sen University, 600 Tianhe Road, Guangzhou 510630, Guangdong Province, China.,Department of Rehabilitation Medicine, Guangzhou Panyu Central Hospital, No.8 Fuyu east Road, Guangzhou 511400, Guangdong Province, China
| | - Ruifang Sun
- Department of Rehabilitation Medicine, The Third Affiliated Hospital, Sun Yat-sen University, 600 Tianhe Road, Guangzhou 510630, Guangdong Province, China
| | - Chao Li
- Department of Rehabilitation Medicine, The Third Affiliated Hospital, Sun Yat-sen University, 600 Tianhe Road, Guangzhou 510630, Guangdong Province, China
| | - Xun Luo
- Kerry Rehabilitation Medicine Research Institute, Shenzhen 518048, Guangdong Province, China.,Shenzhen Dapeng New District Nan'ao People's Hospital Shenzhen 518048, Guangdong Province, China
| | - Jiemei Chen
- Department of Rehabilitation Medicine, The Third Affiliated Hospital, Sun Yat-sen University, 600 Tianhe Road, Guangzhou 510630, Guangdong Province, China
| | - Jiena Hong
- Department of Rehabilitation Medicine, The Third Affiliated Hospital, Sun Yat-sen University, 600 Tianhe Road, Guangzhou 510630, Guangdong Province, China
| | - Yan Zeng
- Department of Rehabilitation Medicine, The Third Affiliated Hospital, Sun Yat-sen University, 600 Tianhe Road, Guangzhou 510630, Guangdong Province, China
| | - Qing Mei Wang
- Stroke Biological Recovery Laboratory, Spaulding Rehabilitation Hospital, The Teaching Affiliate of Harvard Medical School,96 13 Street, Charlestown, MA 02129, USA
| | - Hongmei Wen
- Department of Rehabilitation Medicine, The Third Affiliated Hospital, Sun Yat-sen University, 600 Tianhe Road, Guangzhou 510630, Guangdong Province, China
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24
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Broussard GJ, Petreanu L. Eavesdropping wires: Recording activity in axons using genetically encoded calcium indicators. J Neurosci Methods 2021; 360:109251. [PMID: 34119572 PMCID: PMC8363211 DOI: 10.1016/j.jneumeth.2021.109251] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 05/31/2021] [Accepted: 06/05/2021] [Indexed: 12/23/2022]
Abstract
Neurons broadcast electrical signals to distal brain regions through extensive axonal arbors. Genetically encoded calcium sensors permit the direct observation of action potential activity at axonal terminals, providing unique insights on the organization and function of neural projections. Here, we consider what information can be gleaned from axonal recordings made at scales ranging from the summed activity extracted from multi-cell axon projections to single boutons. In particular, we discuss the application of different recently developed multi photon and fiber photometry methods for recording neural activity in axons of rodents. We define experimental difficulties associated with imaging approaches in the axonal compartment and highlight the latest methodological advances for addressing these issues. Finally, we reflect on ways in which new technologies can be used in conjunction with axon calcium imaging to address current questions in neurobiology.
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Affiliation(s)
| | - Leopoldo Petreanu
- Champalimaud Research, Champalimaud Center for the Unknown, Lisbon, Portugal.
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25
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Hu R, Xu HP, He KL, Chen Y, Wu L, Ma RJ. [Advances about perineuronal nets in the repair of nerve function after spinal cord injury]. Zhongguo Gu Shang 2021; 34:91-6. [PMID: 33666027 DOI: 10.12200/j.issn.1003-0034.2021.01.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Perineuronal nets (PNNs) is a complex network composed of highly condensed extracellular matrix molecules surrounding neurons. It plays an important role in maintaining the performance of neurons and protecting them from harmful substances. However, after spinal cord injury, PNNs forms a physical barrier that surrounds the neuron and limits neuroplasticity, impedes axonal regeneration and myelin formation, and promotes local neuroinflammatory uptake. This paper mainly describes the composition and function of PNNs of neurons and its regulatory effects on axonal regeneration, myelin formation and neuroinflammation after spinal cord injury.
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Affiliation(s)
- Rong Hu
- The Third Clinical Medical College of Zhejiang Chinese Medical University, Hangzhou 310053, Zhejiang, China
| | - Hai-Peng Xu
- The Third Clinical Medical College of Zhejiang Chinese Medical University, Hangzhou 310053, Zhejiang, China
| | - Ke-Lin He
- The Third Clinical Medical College of Zhejiang Chinese Medical University, Hangzhou 310053, Zhejiang, China
| | - Yi Chen
- The Third Clinical Medical College of Zhejiang Chinese Medical University, Hangzhou 310053, Zhejiang, China
| | - Lei Wu
- The Third Clinical Medical College of Zhejiang Chinese Medical University, Hangzhou 310053, Zhejiang, China
| | - Rui-Jie Ma
- The Third Clinical Medical College of Zhejiang Chinese Medical University, Hangzhou 310053, Zhejiang, China
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26
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Abstract
Aging is characterized by a decline in neuronal function in all animal species investigated so far. Functional changes are accompanied by and may be in part caused by, structurally visible degenerative changes in neurons. In the mammalian brain, normal aging shows abnormalities in dendrites and axons, as well as ultrastructural changes in synapses, rather than global neuron loss. The analysis of the structural features of aging neurons, as well as their causal link to molecular mechanisms on the one hand, and the functional decline on the other hand is crucial in order to understand the aging process in the brain. Invertebrate model organisms like Drosophila and C. elegans offer the opportunity to apply a forward genetic approach to the analysis of aging. In the present review, we aim to summarize findings concerning abnormalities in morphology and ultrastructure in invertebrate brains during normal aging and compare them to what is known for the mammalian brain. It becomes clear that despite of their considerably shorter life span, invertebrates display several age-related changes very similar to the mammalian condition, including the retraction of dendritic and axonal branches at specific locations, changes in synaptic density and increased accumulation of presynaptic protein complexes. We anticipate that continued research efforts in invertebrate systems will significantly contribute to reveal (and possibly manipulate) the molecular/cellular pathways leading to neuronal aging in the mammalian brain.
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Affiliation(s)
- Sandra C Koch
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles (UCLA), Los Angeles, California, USA
| | - Annie Nelson
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles (UCLA), Los Angeles, California, USA
| | - Volker Hartenstein
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles (UCLA), Los Angeles, California, USA.
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27
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Bagnato F, Gauthier SA, Laule C, Moore GRW, Bove R, Cai Z, Cohen-Adad J, Harrison DM, Klawiter EC, Morrow SA, Öz G, Rooney WD, Smith SA, Calabresi PA, Henry RG, Oh J, Ontaneda D, Pelletier D, Reich DS, Shinohara RT, Sicotte NL. Imaging Mechanisms of Disease Progression in Multiple Sclerosis: Beyond Brain Atrophy. J Neuroimaging 2021; 30:251-266. [PMID: 32418324 DOI: 10.1111/jon.12700] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 02/04/2020] [Accepted: 02/18/2020] [Indexed: 12/11/2022] Open
Abstract
Clinicians involved with different aspects of the care of persons with multiple sclerosis (MS) and scientists with expertise on clinical and imaging techniques convened in Dallas, TX, USA on February 27, 2019 at a North American Imaging in Multiple Sclerosis Cooperative workshop meeting. The aim of the workshop was to discuss cardinal pathobiological mechanisms implicated in the progression of MS and novel imaging techniques, beyond brain atrophy, to unravel these pathologies. Indeed, although brain volume assessment demonstrates changes linked to disease progression, identifying the biological mechanisms leading up to that volume loss are key for understanding disease mechanisms. To this end, the workshop focused on the application of advanced magnetic resonance imaging (MRI) and positron emission tomography (PET) imaging techniques to assess and measure disease progression in both the brain and the spinal cord. Clinical translation of quantitative MRI was recognized as of vital importance, although the need to maintain a relatively short acquisition time mandated by most radiology departments remains the major obstacle toward this effort. Regarding PET, the panel agreed upon its utility to identify ongoing pathological processes. However, due to costs, required expertise, and the use of ionizing radiation, PET was not considered to be a viable option for ongoing care of persons with MS. Collaborative efforts fostering robust study designs and imaging technique standardization across scanners and centers are needed to unravel disease mechanisms leading to progression and discovering medications halting neurodegeneration and/or promoting repair.
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Affiliation(s)
- Francesca Bagnato
- Neuroimaging Unit, Neuroimmunology Division, Department of Neurology, Vanderbilt University Medical Center, Nashville, TN
| | - Susan A Gauthier
- Judith Jaffe Multiple Sclerosis Center, Department of Neurology, Feil Family Brain and Mind Institute, and Department of Radiology, Weill Cornell Medicine, New York, NY
| | - Cornelia Laule
- Department of Radiology, Pathology, and Laboratory Medicine, Department of Physics and Astronomy, and International Collaboration on Repair Discoveries (ICORD), University of British Columbia, Vancouver, British Columbia, Canada
| | - George R Wayne Moore
- Department of Pathology and Laboratory Medicine, and International Collaboration on Repair Discoveries (ICORD), University of British Columbia, Vancouver, British Columbia, Canada
| | - Riley Bove
- Department of Neurology, Weill Institute for Neurosciences, University of California, San Francisco, CA
| | - Zhengxin Cai
- Department of Radiology and Biomedical Imaging, PET Center, Yale University, New Haven, CT
| | - Julien Cohen-Adad
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal and Functional Neuroimaging Unit, CRIUGM, University of Montreal, Montreal, Quebec, Canada
| | - Daniel M Harrison
- Department of Neurology, University of Maryland School of Medicine, Baltimore, MD
| | - Eric C Klawiter
- Massachusetts General Hospital, Harvard Medical School, Boston, MA
| | - Sarah A Morrow
- Department of Clinical Neurological Sciences, University of Western Ontario, London, Ontario, Canada
| | - Gülin Öz
- Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN
| | - William D Rooney
- Advanced Imaging Research Center, Departments of Biomedical Engineering, Neurology, and Behavioral Neuroscience, Oregon Health & Science University, Portland, OR
| | - Seth A Smith
- Radiology and Radiological Sciences and Vanderbilt University Imaging Institute, Vanderbilt University Medical Center, and Biomedical Engineering, Vanderbilt University, Nashville, TN
| | - Peter A Calabresi
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD
| | - Roland G Henry
- Departments of Neurology, Radiology and Biomedical Imaging, and the UC San Francisco & Berkeley Bioengineering Graduate Group, University of California San Francisco, San Francisco, CA
| | - Jiwon Oh
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD.,Division of Neurology, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada
| | - Daniel Ontaneda
- Mellen Center for Multiple Sclerosis, Neurological Institute, Cleveland Clinic, Cleveland, OH
| | - Daniel Pelletier
- Department of Neurology, University of Southern California Keck School of Medicine, Los Angeles, CA
| | - Daniel S Reich
- Translational Neuroradiology Section, National Institute of Neurological Disorders and Stroke, Bethesda, MD
| | - Russell T Shinohara
- Department of Biostatistics, Epidemiology, and Informatics, Penn Statistics in Imaging and Visualization Center, University of Pennsylvania, Philadelphia, PA
| | - Nancy L Sicotte
- Department of Neurology, Cedars-Sinai Medical Center, Los Angeles, CA
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- Neuroimaging Unit, Neuroimmunology Division, Department of Neurology, Vanderbilt University Medical Center, Nashville, TN
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28
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Miranda-Saksena M, Boadle RA, Cunningham AL. Preparation of Herpes Simplex Virus-Infected Primary Neurons for Transmission Electron Microscopy. Methods Mol Biol 2020; 2060:343-54. [PMID: 31617189 DOI: 10.1007/978-1-4939-9814-2_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Transmission electron microscopy (TEM) provides the resolution necessary to identify both viruses and subcellular components of cells infected with many types of viruses, including herpes simplex virus. Recognized as a powerful tool in both diagnostic and research-based virology laboratories, TEM has made possible the identification of new viruses and has contributed to the elucidation of virus life cycle and virus-host cell interaction.While there are many sample preparation techniques for TEM, conventional processing using chemical fixation and resin embedding remains a useful technique, available in virtually all EM laboratories, for studying virus/cell ultrastructure. In this chapter, we describe the preparation of herpes simplex virus infected primary neurons, grown on plastic coverslips, to allow for sectioning of neurons and axons in their growth plane. This technique allows for TEM examination of cell bodies, axons, growth cones and varicosities, providing powerful insights into virus-cell interaction.
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29
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Stavrou M, Sargiannidou I, Christofi T, Kleopa KA. Genetic mechanisms of peripheral nerve disease. Neurosci Lett 2021; 742:135357. [PMID: 33249104 DOI: 10.1016/j.neulet.2020.135357] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 08/24/2020] [Accepted: 09/02/2020] [Indexed: 12/17/2022]
Abstract
Peripheral neuropathies of genetic etiology are a very diverse group of disorders manifesting either as non-syndromic inherited neuropathies without significant manifestations outside the peripheral nervous system, or as part of a systemic or syndromic genetic disorder. The former and most frequent group is collectively known as Charcot-Marie-Tooth disease (CMT), with prevalence as high as 1:2,500 world-wide, and has proven to be genetically highly heterogeneous. More than 100 different genes have been identified so far to cause various CMT forms, following all possible inheritance patterns. CMT causative genes belong to several common functional pathways that are essential for the integrity of the peripheral nerve. Their discovery has provided insights into the normal biology of axons and myelinating cells, and has highlighted the molecular mechanisms including both loss of function and gain of function effects, leading to peripheral nerve degeneration. Demyelinating neuropathies result from dysfunction of genes primarily affecting myelinating Schwann cells, while axonal neuropathies are caused by genes affecting mostly neurons and their long axons. Furthermore, mutation in genes expressed outside the nervous system, as in the case of inherited amyloid neuropathies, may cause peripheral neuropathy resulting from accumulation of β-structured amyloid fibrils in peripheral nerves in addition to various organs. Increasing insights into the molecular-genetic mechanisms have revealed potential therapeutic targets. These will enable the development of novel therapeutics for genetic neuropathies that remain, in their majority, without effective treatment.
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30
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Jirawatnotai S, Kaewpichai K, Tirakotai W, Mothong W, Kaewsema A, Sriswadpong P. Nerve to the Zygomaticus Major Muscle for Facial Reanimation Surgery: A Cadaveric Study for Branching Patterns and Axonal Count. Asian J Neurosurg 2020; 15:516-520. [PMID: 33145200 PMCID: PMC7591169 DOI: 10.4103/ajns.ajns_90_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Revised: 07/19/2020] [Accepted: 05/12/2020] [Indexed: 11/04/2022] Open
Abstract
Background In facial reanimation surgery, higher donor facial nerve axonal load yields a superior outcome. Nerves supplying the zygomaticus major muscle are primary donors for the grafting procedure; however, their topography has not been studied in detail. This study identified potential donor nerves by quantifying axon loads of the zygomaticus major muscle through histological analysis of cadaveric specimens. Materials and Methods Forty-three hemifaces from 26 fresh human cadavers were studied. Branching patterns of nerves were classified according to their shapes. All branches of interest were sectioned and stained for an axon count. The potential donors were mapped into each tributary of nerves supplying the zygomaticus major. Results Branching patterns were categorized into five types: Y-type (28%), X-type (28%), H-type (19%), E-type (14%), and F-type (11%). The mean number of axons in the most superiorly and proximally located main branches was 1387.33 ± 406.59 in Y-type, 1021.42 ± 187.79 in X-type, 1222.75 ± 193.82 in H-type, 1496.17 ± 364.567 in E-type, and 1353.40 ± 256.07 in F-type (P > 0.05). A topographic relation between facial nerves supplying the zygomaticus major muscle and their mean axonal load was illustrated. The zygomatic/buccal branches were found within 5 mm from Zuker's point in 100% of X-, Y-, H-, and E-type and 75% of F-type specimens. Conclusions Most proximal facial nerve branches supplying the zygomaticus major, arising at the anterior border of a parotid gland, contained over 900 axons in all five branching types. The primary subbranches may be used in selected cases if donor weakness is a concern. Further, our study provides evidence that demonstrates the precision of Zuker's point.
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Affiliation(s)
- Supasid Jirawatnotai
- Department of Surgery, Plastic and Reconstructive Surgery Unit, Lerdsin Hospital, Bangkok, Thailand
| | - Kitipong Kaewpichai
- Department of Surgery, Plastic and Reconstructive Surgery Unit, Lerdsin Hospital, Bangkok, Thailand
| | - Wuttipong Tirakotai
- Department of Neurosurgery, Prasat Neurological Institute, Bangkok, Thailand
| | - Wilaiwan Mothong
- Department of Anatomy, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
| | - Atitaya Kaewsema
- Department of Anatomy, Peripheral Nerve Research Unit, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Papat Sriswadpong
- Department of Surgery, Plastic and Reconstructive Surgery Unit, Lerdsin Hospital, Bangkok, Thailand
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31
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Kandula T, Park SB, Carey KA, Lin CSY, Farrar MA. Peripheral nerve maturation and excitability properties from early childhood: Comparison of motor and sensory nerves. Clin Neurophysiol 2020; 131:2452-2459. [PMID: 32829292 DOI: 10.1016/j.clinph.2020.06.035] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 06/11/2020] [Accepted: 06/28/2020] [Indexed: 10/23/2022]
Abstract
OBJECTIVE Understanding of maturational properties of sensory and motor axons is of central importance for determining the impact of nerve changes in health and in disease in children and young adults. METHODS This study investigated maturation of sensory axons using axonal excitability parameters of the median nerve in 47 children, adolescents and young adults (25 males, 22 females; age range 1-25 years) and compared them to concurrent motor studies. RESULTS The overall pattern of sensory maturation was similar to motor maturation demonstrating prolongation of the strength duration time constant (P < 0.001), reduction of hyperpolarising threshold electrotonus (P = 0.002), prolongation of accommodation half-time (P = 0.005), reduction in hyperpolarising current-threshold slope (P = 0.03), and a shift to the right of the refractory cycle curve (P < 0.001), reflecting changes in passive membrane properties and fast potassium channel conductances. Sensory axons, however, had a greater increase in strength duration time constant and more attenuated changes in depolarising threshold electrotonus and current-threshold parameters, attributable to a more depolarised resting membrane potential evident from early childhood and maintained in adults. Peak amplitude was established early in sensory axons whereas motor amplitude increased with age (P < 0.001), reflecting non-axonal motor unit changes. CONCLUSIONS Maturational trajectories of sensory and motor axons were broadly parallel in children and young adults, but sensory-motor differences were initiated early in maturation. SIGNIFICANCE Identifying the evolution of biophysical changes within and between sensory and motor axons through childhood and adolescence is fundamental to understanding developmental physiology and interpreting disease-related changes in immature nerves.
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Affiliation(s)
- Tejaswi Kandula
- School of Women's and Children's Health, UNSW Medicine, UNSW Sydney, High Street, Randwick, NSW 2031, Australia; Department of Neurology, Sydney Children's Hospital, High Street, Randwick, NSW 2031, Australia
| | - Susanna B Park
- Brain and Mind Centre, Faculty of Medicine and Health, University of Sydney, 94 Mallett Street, Camperdown, NSW 2051, Australia
| | - Kate A Carey
- School of Women's and Children's Health, UNSW Medicine, UNSW Sydney, High Street, Randwick, NSW 2031, Australia
| | - Cindy S-Y Lin
- Brain and Mind Centre, Faculty of Medicine and Health, University of Sydney, 94 Mallett Street, Camperdown, NSW 2051, Australia
| | - Michelle A Farrar
- School of Women's and Children's Health, UNSW Medicine, UNSW Sydney, High Street, Randwick, NSW 2031, Australia; Department of Neurology, Sydney Children's Hospital, High Street, Randwick, NSW 2031, Australia.
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32
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Bautista J, Chandrasekhar A, Komirishetty PK, Duraikannu A, Zochodne DW. Regenerative plasticity of intact human skin axons. J Neurol Sci 2020; 417:117058. [PMID: 32755738 DOI: 10.1016/j.jns.2020.117058] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 07/01/2020] [Accepted: 07/22/2020] [Indexed: 01/29/2023]
Abstract
The evaluation of human epidermal innervation and its impact by disease has largely focused on rigorous immunohistochemical counts of PGP 9.5 labelled axons. In this brief and preliminary report, we expand the repertoire of epidermal axon markers to include those with an influence on their regenerative plasticity. We studied human lower limb punch skin samples with tandem analyses of their mRNA content using qRT-PCR. Normal human subjects (n = 11) and two patients with newly diagnosed CIDP were sampled with the latter undergoing serial tandem biopsies before and after 3 months of immunotherapy. Controls expressed regeneration proteins within dermal and epidermal axons: GAP43 (growth associated protein 43), Shh (sonic hedgehog) and SCG (superior cervical ganglion-10; stathmin 2). Moreover, this expression accompanied intraepidermal nerve fiber density (IENF) within normal established values. CIDP patients had lower IENF but also expressed GAP43, Shh, and SCG. Tandem qRT-PCR identified confirmed the presence not only of these plasticity markers but of additional regeneration related mRNAs. CIDP patients had marked elevation of several mRNAs, with improvement following treatment. The findings support the concept of dynamic skin axon plasticity in humans is relevant toward consideration of newer therapeutic approaches.
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Affiliation(s)
- J Bautista
- Division of Neurology, Department of Medicine, Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| | - A Chandrasekhar
- Division of Neurology, Department of Medicine, Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| | - P K Komirishetty
- Division of Neurology, Department of Medicine, Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| | - A Duraikannu
- Division of Neurology, Department of Medicine, Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| | - D W Zochodne
- Division of Neurology, Department of Medicine, Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada.
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Radler MR, Suber A, Spiliotis ET. Spatial control of membrane traffic in neuronal dendrites. Mol Cell Neurosci 2020; 105:103492. [PMID: 32294508 DOI: 10.1016/j.mcn.2020.103492] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 03/24/2020] [Accepted: 04/01/2020] [Indexed: 02/06/2023] Open
Abstract
Neuronal dendrites are highly branched and specialized compartments with distinct structures and secretory organelles (e.g., spines, Golgi outposts), and a unique cytoskeletal organization that includes microtubules of mixed polarity. Dendritic membranes are enriched with proteins, which specialize in the formation and function of the post-synaptic membrane of the neuronal synapse. How these proteins partition preferentially in dendrites, and how they traffic in a manner that is spatiotemporally accurate and regulated by synaptic activity are long-standing questions of neuronal cell biology. Recent studies have shed new insights into the spatial control of dendritic membrane traffic, revealing new classes of proteins (e.g., septins) and cytoskeleton-based mechanisms with dendrite-specific functions. Here, we review these advances by revisiting the fundamental mechanisms that control membrane traffic at the levels of protein sorting and motor-driven transport on microtubules and actin filaments. Overall, dendrites possess unique mechanisms for the spatial control of membrane traffic, which might have specialized and co-evolved with their highly arborized morphology.
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Affiliation(s)
- Megan R Radler
- Department of Biology, Drexel University, 3245 Chestnut St, Philadelphia, PA 19104, USA
| | - Ayana Suber
- Department of Biology, Drexel University, 3245 Chestnut St, Philadelphia, PA 19104, USA
| | - Elias T Spiliotis
- Department of Biology, Drexel University, 3245 Chestnut St, Philadelphia, PA 19104, USA.
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Sargiannidou I, Kagiava A, Kleopa KA. Gene therapy approaches targeting Schwann cells for demyelinating neuropathies. Brain Res 2020; 1728:146572. [PMID: 31790684 DOI: 10.1016/j.brainres.2019.146572] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 11/12/2019] [Accepted: 11/26/2019] [Indexed: 11/27/2022]
Abstract
Charcot-Marie-Tooth disease (CMT) encompasses numerous genetically heterogeneous inherited neuropathies, which together are one of the commonest neurogenetic disorders. Axonal CMT types result from mutations in neuronally expressed genes, whereas demyelinating CMT forms mostly result from mutations in genes expressed by myelinating Schwann cells. The demyelinating forms are the most common, and may be caused by dominant mutations and gene dosage effects (as in CMT1), as well as by recessive mutations and loss of function mechanisms (as in CMT4). The discovery of causative genes and increasing insights into molecular mechanisms through the study of experimental disease models has provided the basis for the development of gene therapy approaches. For demyelinating CMT, gene silencing or gene replacement strategies need to be targeted to Schwann cells. Progress in gene replacement for two different CMT forms, including CMT1X caused by GJB1 gene mutations, and CMT4C, caused by SH3TC2 gene mutations, has been made through the use of a myelin-specific promoter to restrict expression in Schwann cells, and by lumbar intrathecal delivery of lentiviral viral vectors to achieve more widespread biodistribution in the peripheral nervous system. This review summarizes the molecular-genetic mechanisms of selected demyelinating CMT neuropathies and the progress made so far, as well as the remaining challenges in the path towards a gene therapy to treat these disorders through the use of optimal gene therapy tools including clinically translatable delivery methods and adeno-associated viral (AAV) vectors.
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Affiliation(s)
- Irene Sargiannidou
- Neuroscience Laboratory, The Cyprus Institute of Neurology and Genetics and Cyprus School of Molecular Medicine, Nicosia, Cyprus
| | - Alexia Kagiava
- Neuroscience Laboratory, The Cyprus Institute of Neurology and Genetics and Cyprus School of Molecular Medicine, Nicosia, Cyprus
| | - Kleopas A Kleopa
- Neuroscience Laboratory, The Cyprus Institute of Neurology and Genetics and Cyprus School of Molecular Medicine, Nicosia, Cyprus; Neurology Clinics, The Cyprus Institute of Neurology and Genetics and Cyprus School of Molecular Medicine, Nicosia, Cyprus.
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35
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Singh AK, Abdullahi A, Soller M, David A, Brogna S. Visualisation of ribosomes in Drosophila axons using Ribo-BiFC. Biol Open 2020; 8:bio047233. [PMID: 31822474 PMCID: PMC6955225 DOI: 10.1242/bio.047233] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Accepted: 12/02/2019] [Indexed: 11/20/2022] Open
Abstract
The distribution of assembled, and potentially translating, ribosomes within cells can be visualised in Drosophila by using Bimolecular Fluorescence Complementation (BiFC) to monitor the interaction between tagged pairs of 40S and 60S ribosomal proteins (RPs) that are close neighbours across inter-subunit junctions in the assembled 80S ribosome. Here we describe transgenes expressing two novel RP pairs tagged with Venus-based BiFC fragments that considerably increase the sensitivity of this technique we termed Ribo-BiFC. This improved method should provide a convenient way of monitoring the local distribution of ribosomes in most Drosophila cells and we suggest that it could be implemented in other organisms. We visualised 80S ribosomes in different neurons, particularly photoreceptors in the larva, pupa and adult brain. Assembled ribosomes are most abundant in the various neuronal cell bodies, but they are also present along the full length of axons. They are concentrated in growth cones of developing photoreceptors and are apparent at the terminals of mature larval photoreceptors targeting the larval optical neuropil. Surprisingly, there is relatively less puromycin incorporation in the distal portion of axons in the larval optic stalk, suggesting that some of the ribosomes that have initiated translation may not be engaged in elongation in growing axons.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Anand K Singh
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Akilu Abdullahi
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Matthias Soller
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Alexandre David
- Oncology Department, Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094 Montpellier cedex 5, France
| | - Saverio Brogna
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
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36
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Danastas K, Cunningham AL, Miranda-Saksena M. The Use of Microfluidic Neuronal Devices to Study the Anterograde Axonal Transport of Herpes Simplex Virus-1. Methods Mol Biol 2020; 2060:409-418. [PMID: 31617194 DOI: 10.1007/978-1-4939-9814-2_25] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Understanding how herpes simplex virus-1 (HSV-1) interacts with different parts of the neuron is fundamental in understanding the mechanisms behind HSV-1 transport during primary and recurrent infections. In this chapter, we describe a unique neuronal culture system that is capable of compartmentalizing neuronal cell bodies from their axons to study the transport of HSV-1 along axons. The ability to separate neuronal cell bodies and axons provides a unique model to investigate the mechanisms used by HSV-1 for viral transport, assembly, and exit from different parts of the neuron.
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Affiliation(s)
- Kevin Danastas
- Centre for Virus Research, The Westmead Institute for Medical Research, Westmead, NSW, Australia
- The University of Sydney, Westmead, NSW, Australia
| | - Anthony L Cunningham
- Centre for Virus Research, The Westmead Institute for Medical Research, Westmead, NSW, Australia
- Sydney Medical School, The University of Sydney, Westmead, NSW, Australia
| | - Monica Miranda-Saksena
- Centre for Virus Research, The Westmead Institute for Medical Research, Westmead, NSW, Australia.
- The University of Sydney, Westmead, NSW, Australia.
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37
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Alves CB, Almeida AS, Marques DM, Faé AHL, Machado ACL, Oliveira DL, Portela LVC, Porciúncula LO. Caffeine and adenosine A 2A receptors rescue neuronal development in vitro of frontal cortical neurons in a rat model of attention deficit and hyperactivity disorder. Neuropharmacology 2019; 166:107782. [PMID: 31756336 DOI: 10.1016/j.neuropharm.2019.107782] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 08/24/2019] [Accepted: 09/16/2019] [Indexed: 01/23/2023]
Abstract
Although some studies have supported the effects of caffeine for treatment of Attention deficit and hyperactivity disorder (ADHD), there were no evidences about its effects at the neuronal level. In this study, we sought to find morphological alterations during in vitro development of frontal cortical neurons from Spontaneoulsy hypertensive rats (SHR, an ADHD rat model) and Wistar-Kyoto rats (WKY, control strain). Further, we investigated the effects of caffeine and adenosine A1 and A2A receptors (A1R and A2AR) signaling. Cultured cortical neurons from WKY and SHR were analyzed by immunostaining of microtubule-associated protein 2 (MAP-2) and tau protein after treatment with either caffeine, or A1R and A2AR agonists or antagonists. Besides, the involvement of PI3K and not PKA signaling was also assessed. Neurons from ADHD model displayed less neurite branching, shorter maximal neurite length and decreased axonal outgrowth. While caffeine recovered neurite branching and elongation from ADHD neurons via both PKA and PI3K signaling, A2AR agonist (CGS 21680) promoted more neurite branching via PKA signaling. The selective A2AR antagonist (SCH 58261) was efficient in recovering axonal outgrowth from ADHD neurons through PI3K and not PKA signaling. For the first time, frontal cortical neurons were isolated from ADHD model and they presented disturbances in the differentiation and outgrowth. By showing that caffeine and A2AR may act at neuronal level rescuing ADHD neurons outgrowth, our findings strengthen the potential of caffeine and A2AR receptors as an adjuvant for ADHD treatment.
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Affiliation(s)
- Catiane B Alves
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600, Anexo, Santana, Porto Alegre, RS, Brazil, 90035-003
| | - Amanda S Almeida
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600, Anexo, Santana, Porto Alegre, RS, Brazil, 90035-003
| | - Daniela M Marques
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600, Anexo, Santana, Porto Alegre, RS, Brazil, 90035-003
| | - Ana Helena L Faé
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600, Anexo, Santana, Porto Alegre, RS, Brazil, 90035-003
| | - Ana Carolina L Machado
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600, Anexo, Santana, Porto Alegre, RS, Brazil, 90035-003
| | - Diogo L Oliveira
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600, Anexo, Santana, Porto Alegre, RS, Brazil, 90035-003
| | - Luis Valmor C Portela
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600, Anexo, Santana, Porto Alegre, RS, Brazil, 90035-003
| | - Lisiane O Porciúncula
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600, Anexo, Santana, Porto Alegre, RS, Brazil, 90035-003.
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Abstract
During the development of the peripheral nervous system, axons and myelinating Schwann cells form a unique symbiotic unit, which is realized by a finely tuned network of molecular signals and reciprocal interactions. The importance of this complex interplay becomes evident after injury or in diseases in which aspects of axo-glial interaction are perturbed. This Review focuses on the specific interdependence of axons and Schwann cells in peripheral nerve development that enables axonal outgrowth, Schwann cell lineage progression, radial sorting and, finally, formation and maintenance of the myelin sheath.
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Affiliation(s)
- Robert Fledrich
- Institute of Anatomy, Leipzig University, 04103 Leipzig, Germany .,Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Theresa Kungl
- Institute of Anatomy, Leipzig University, 04103 Leipzig, Germany.,Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Klaus-Armin Nave
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Ruth M Stassart
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany .,Department of Neuropathology, University Clinic Leipzig, 04103 Leipzig, Germany
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Drakesmith M, Harms R, Rudrapatna SU, Parker GD, Evans CJ, Jones DK. Estimating axon conduction velocity in vivo from microstructural MRI. Neuroimage 2019; 203:116186. [PMID: 31542512 PMCID: PMC6854468 DOI: 10.1016/j.neuroimage.2019.116186] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 09/09/2019] [Accepted: 09/10/2019] [Indexed: 11/19/2022] Open
Abstract
The conduction velocity (CV) of action potentials along axons is a key neurophysiological property central to neural communication. The ability to estimate CV in humans in vivo from non-invasive MRI methods would therefore represent a significant advance in neuroscience. However, there are two major challenges that this paper aims to address: (1) Much of the complexity of the neurophysiology of action potentials cannot be captured with currently available MRI techniques. Therefore, we seek to establish the variability in CV that can be captured when predicting CV purely from parameters that have been reported to be estimatable from MRI: inner axon diameter (AD) and g-ratio. (2) errors inherent in existing MRI-based biophysical models of tissue will propagate through to estimates of CV, the extent to which is currently unknown. Issue (1) is investigated by performing a sensitivity analysis on a comprehensive model of axon electrophysiology and determining the relative sensitivity to various morphological and electrical parameters. The investigations suggest that 85% of the variance in CV is accounted for by variation in AD and g-ratio. The observed dependency of CV on AD and g-ratio is well characterised by the previously reported model by Rushton. Issue (2) is investigated through simulation of diffusion and relaxometry MRI data for a range of axon morphologies, applying models of restricted diffusion and relaxation processes to derive estimates of axon volume fraction (AVF), AD and g-ratio and estimating CV from the derived parameters. The results show that errors in the AVF have the biggest detrimental impact on estimates of CV, particularly for sparse fibre populations (AVF<0.3). For our equipment set-up and acquisition protocol, CV estimates are most accurate (below 5% error) where AVF is above 0.3, g-ratio is between 0.6 and 0.85 and AD is high (above 4μm). CV estimates are robust to errors in g-ratio estimation but are highly sensitive to errors in AD estimation, particularly where ADs are small. We additionally show CV estimates in human corpus callosum in a small number of subjects. In conclusion, we demonstrate accurate CV estimates are possible in regions of the brain where AD is sufficiently large. Problems with estimating ADs for smaller axons presents a problem for estimating CV across the whole CNS and should be the focus of further study.
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Affiliation(s)
- Mark Drakesmith
- Cardiff University Brain Research Imaging Centre, Cardiff University, Cardiff, United Kingdom; Neuroscience and Mental Health Research Institute, Cardiff University, Cardiff, United Kingdom.
| | - Robbert Harms
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, the Netherlands
| | - Suryanarayana Umesh Rudrapatna
- Cardiff University Brain Research Imaging Centre, Cardiff University, Cardiff, United Kingdom; Phillips Inovation Campus, Bangalore, India
| | - Greg D Parker
- Cardiff University Brain Research Imaging Centre, Cardiff University, Cardiff, United Kingdom; Experimental MRI Centre (EMRIC), School of Biosciences, Cardiff University, Cardiff, United Kingdom
| | - C John Evans
- Cardiff University Brain Research Imaging Centre, Cardiff University, Cardiff, United Kingdom; Neuroscience and Mental Health Research Institute, Cardiff University, Cardiff, United Kingdom
| | - Derek K Jones
- Cardiff University Brain Research Imaging Centre, Cardiff University, Cardiff, United Kingdom; Neuroscience and Mental Health Research Institute, Cardiff University, Cardiff, United Kingdom; Mary McKillop Institute for Health Research, Faculty of Health Sciences, Australian Catholic University, Melbourne, Victoria, 3065, Australia
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Nijssen J, Aguila J, Hedlund E. Axon-seq for in Depth Analysis of the RNA Content of Neuronal Processes. Bio Protoc 2019; 9:e3312. [PMID: 33654821 DOI: 10.21769/bioprotoc.3312] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 06/24/2019] [Accepted: 07/22/2019] [Indexed: 11/02/2022] Open
Abstract
Neuronal processes have an RNA composition that is distinct from the cell body. Therefore, to fully understand neuronal biology in health and disease we need to study both somas, dendrites and axons. Here we describe a detailed protocol of a newly refined method, Axon-seq, for RNA sequencing of axons (and dendrites) grown in isolation using single microfluidic devices. We also detail how to generate motor neurons from mouse and human pluripotent stem cells for sequencing, but Axon-seq is applicable to any neuronal cell. In Axon-seq, the axons are recruited through a growth factor gradient, lysed and directly processed to cDNA without RNA isolation. A careful bioinformatic step ensures that any soma-contaminated samples are easily identified and removed.
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Affiliation(s)
- Jik Nijssen
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Julio Aguila
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Eva Hedlund
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
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Choi S, Sadra A, Kang J, Ryu JR, Kim JH, Sun W, Huh SO. Farnesylation-defective Rheb Increases Axonal Length Independently of mTORC1 Activity in Embryonic Primary Neurons. Exp Neurobiol 2019; 28:172-182. [PMID: 31138988 PMCID: PMC6526111 DOI: 10.5607/en.2019.28.2.172] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 03/27/2019] [Accepted: 03/28/2019] [Indexed: 02/01/2023] Open
Abstract
Rheb (Ras homolog enriched in the brain) is a small GTPase protein that plays an important role in cell signaling for development of the neocortex through modulation of mTORC1 (mammalian-target-of-rapamycin-complex-1) activity. mTORC1 is known to control various biological processes including axonal growth in forming complexes at the lysosomal membrane compartment. As such, anchoring of Rheb on the lysosomal membrane via the farnesylation of Rheb at its cysteine residue (C180) is required for its promotion of mTOR activity. To test the significance of Rheb farnesylation, we overexpressed a farnesylation mutant form of Rheb, Rheb C180S, in primary rat hippocampal neurons and also in mouse embryonic neurons using in utero electroporation. Interestingly, we found that Rheb C180S maintained promotional effect of axonal elongation similar to the wild-type Rheb in both test systems. On the other hand, Rheb C180S failed to exhibit the multiple axon-promoting effect which is found in wild-type Rheb. The levels of phospho-4EBP1, a downstream target of mTORC1, were surprisingly increased in Rheb C180S transfected neurons, despite the levels of phosphorylated mTOR being significantly decreased compared to control vector transfectants. A specific mTORC1 inhibitor, rapamycin, also could not completely abolish axon elongation characteristics of Rheb C180S in transfected cells. Our data suggests that Rheb in a non-membrane compartment can promote the axonal elongation via phosphorylation of 4EBP1 and through an mTORC1-independent pathway.
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Affiliation(s)
- Seunghyuk Choi
- Department of Pharmacology, College of Medicine, Institute of Natural Medicine, Hallym University, Chuncheon 24252, Korea
| | - Ali Sadra
- Department of Pharmacology, College of Medicine, Institute of Natural Medicine, Hallym University, Chuncheon 24252, Korea
| | - Jieun Kang
- Department of Pharmacology, College of Medicine, Institute of Natural Medicine, Hallym University, Chuncheon 24252, Korea
| | - Jae Ryun Ryu
- Department of Anatomy, Korea University College of Medicine, Brain Korea 21 Plus, Seoul 02841, Korea
| | - June Hoan Kim
- Department of Anatomy, Korea University College of Medicine, Brain Korea 21 Plus, Seoul 02841, Korea
| | - Woong Sun
- Department of Anatomy, Korea University College of Medicine, Brain Korea 21 Plus, Seoul 02841, Korea
| | - Sung-Oh Huh
- Department of Pharmacology, College of Medicine, Institute of Natural Medicine, Hallym University, Chuncheon 24252, Korea
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Pervolaraki E, Tyson AL, Pibiri F, Poulter SL, Reichelt AC, Rodgers RJ, Clapcote SJ, Lever C, Andreae LC, Dachtler J. The within-subject application of diffusion tensor MRI and CLARITY reveals brain structural changes in Nrxn2 deletion mice. Mol Autism 2019; 10:8. [PMID: 30858964 PMCID: PMC6394023 DOI: 10.1186/s13229-019-0261-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Accepted: 02/18/2019] [Indexed: 01/08/2023] Open
Abstract
Background Of the many genetic mutations known to increase the risk of autism spectrum disorder, a large proportion cluster upon synaptic proteins. One such family of presynaptic proteins are the neurexins (NRXN), and recent genetic and mouse evidence has suggested a causative role for NRXN2 in generating altered social behaviours. Autism has been conceptualised as a disorder of atypical connectivity, yet how single-gene mutations affect such connectivity remains under-explored. To attempt to address this, we have developed a quantitative analysis of microstructure and structural connectivity leveraging diffusion tensor MRI (DTI) with high-resolution 3D imaging in optically cleared (CLARITY) brain tissue in the same mouse, applied here to the Nrxn2α knockout (KO) model. Methods Fixed brains of Nrxn2α KO mice underwent DTI using 9.4 T MRI, and diffusion properties of socially relevant brain regions were quantified. The same tissue was then subjected to CLARITY to immunolabel axons and cell bodies, which were also quantified. Results DTI revealed increases in fractional anisotropy in the amygdala (including the basolateral nuclei), the anterior cingulate cortex, the orbitofrontal cortex and the hippocampus. Axial diffusivity of the anterior cingulate cortex and orbitofrontal cortex was significantly increased in Nrxn2α KO mice, as were tracts between the amygdala and the orbitofrontal cortex. Using CLARITY, we find significantly altered axonal orientation in the amygdala, orbitofrontal cortex and the anterior cingulate cortex, which was unrelated to cell density. Conclusions Our findings demonstrate that deleting a single neurexin gene (Nrxn2α) induces atypical structural connectivity within socially relevant brain regions. More generally, our combined within-subject DTI and CLARITY approach presents a new, more sensitive method of revealing hitherto undetectable differences in the autistic brain. Electronic supplementary material The online version of this article (10.1186/s13229-019-0261-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | - Adam L Tyson
- 2Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, SE1 1UL UK.,3MRC Centre for Neurodevelopmental Disorders, King's College London, London, SE1 1UL UK.,4Department of Forensic and Neurodevelopmental Sciences, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, SE5 8AF UK
| | - Francesca Pibiri
- 5Department of Psychology, Durham University, South Road, Durham, DH1 3LE UK
| | - Steven L Poulter
- 5Department of Psychology, Durham University, South Road, Durham, DH1 3LE UK
| | - Amy C Reichelt
- 6Robarts Research Institute, Western University, London, ON N6A 5B7 Canada
| | - R John Rodgers
- 7School of Psychology, University of Leeds, Leeds, LS2 9JT UK
| | - Steven J Clapcote
- 1School of Biomedical Sciences, University of Leeds, Leeds, LS2 9JT UK
| | - Colin Lever
- 5Department of Psychology, Durham University, South Road, Durham, DH1 3LE UK
| | - Laura C Andreae
- 2Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, SE1 1UL UK.,3MRC Centre for Neurodevelopmental Disorders, King's College London, London, SE1 1UL UK
| | - James Dachtler
- 1School of Biomedical Sciences, University of Leeds, Leeds, LS2 9JT UK.,5Department of Psychology, Durham University, South Road, Durham, DH1 3LE UK
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Abstract
Tau is a microtubule-associated protein that is involved in both normal and pathological processes in neurons. Since the discovery and characterization of tau over 40 years ago, our understanding of tau's normal functions and toxic roles in neurodegenerative tauopathies has continued to expand. Fast axonal transport is a critical process for maintaining axons and functioning synapses, critical subcellular compartments underlying neuronal connectivity. Signs of fast axonal transport disruption are pervasive in Alzheimer's disease and other tauopathies and various mechanisms have been proposed for regulation of fast axonal transport by tau. Post-translational modifications of tau including phosphorylation at specific sites, FTDP-17 point mutations, and oligomerization, confer upon tau a toxic effect on fast axonal transport. Consistent with the well-established dependence of axons on fast axonal transport, these disease-related modifications are closely associated temporally and spatially with axonal degeneration in the early disease stages. These factors position tau as a potentially critical factor mediating the disruption of fast axonal transport that precedes synaptic dysfunction and axonal degeneration at later disease stages. In this chapter, we review the evidence that tau affects fast axonal transport and examine several potential mechanisms proposed to underlie this toxicity.
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Affiliation(s)
- Benjamin Combs
- Department of Translational Neuroscience, College of Human Medicine, Michigan State University, Grand Rapids, MI, USA
| | - Rebecca L Mueller
- Department of Translational Neuroscience, College of Human Medicine, Michigan State University, Grand Rapids, MI, USA.,Neuroscience Program, Michigan State University, East Lansing, MI, USA
| | - Gerardo Morfini
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL, USA.,Marine Biological Laboratory, Woods Hole, MA, USA
| | - Scott T Brady
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL, USA.,Marine Biological Laboratory, Woods Hole, MA, USA
| | - Nicholas M Kanaan
- Department of Translational Neuroscience, College of Human Medicine, Michigan State University, Grand Rapids, MI, USA. .,Neuroscience Program, Michigan State University, East Lansing, MI, USA. .,Hauenstein Neuroscience Center, Mercy Health Saint Mary's, Grand Rapids, MI, USA.
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Sharma S, Laule C, Moore GRW, Li DKB, Zhang Y. Correlating new directional measures of myelin and axonal integrity in T2-weighted MRI with quantitative histology in multiple sclerosis. J Neurosci Methods 2019; 311:369-376. [PMID: 30240805 DOI: 10.1016/j.jneumeth.2018.09.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 09/17/2018] [Accepted: 09/17/2018] [Indexed: 10/28/2022]
Abstract
BACKGROUND Imaging measurement of structure alignment has shown increasing importance in determining tissue properties. It is not known if a similar ability for characterizing neuropathology exists. NEW METHODS This study aimed to validate a new alignment-assessing method for measuring myelin and axonal properties using quantitative histological metrics. The new method involved analysis of the Fourier transform (FT) power spectrum in standard magnetic resonance imaging (MRI). T2-weighted MRI were collected from 10 post-mortem multiple sclerosis (MS) brain samples. Three tissue types were examined: lesions, diffusely abnormal white matter, and normal appearing white matter. MRI analysis included computing the FT power spectrum; extracting alignment histograms; and calculating dominant orientation and alignment complexity (angular entropy). Post MRI, the brain samples were processed for myelin and axonal staining, and the stained images were used to derive quantitative orientation measures using structure tensor analysis for MRI comparison. RESULTS There were significant differences in orientation metrics between tissue types in both MRI and histology, and MRI measurements correlated strongly with histological indices. Moreover, the joint effect of myelin and axonal entropy explained over 95% of the variance of MRI angular entropy. COMPARISON WITH EXISTING METHOD There is no established method for characterizing myelin and axonal pathology using standard MRI. Advanced MRI methods have the potential to do this but are still in research development and are not yet routinely acquired in clinical practice. CONCLUSIONS Alignment measurement using clinical MRI scans may become a valuable new method for characterizing myelin and axonal properties in MS patients.
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Affiliation(s)
- Shrushrita Sharma
- Department of Radiology, University of Calgary, Alberta, Canada; Department of Clinical Neurosciences, University of Calgary, Alberta, Canada; Hotchkiss Brain Institute, University of Calgary, Alberta, Canada
| | - Cornelia Laule
- Department of Radiology, University of British Columbia, British Columbia, Canada; Department of Pathology and Laboratory Medicine, University of British Columbia, British Columbia, Canada; International Collaboration on Repair Discoveries (ICORD), University of British Columbia, British Columbia, Canada; Department of Physics & Astronomy, University of British Columbia, British Columbia, Canada
| | - G R Wayne Moore
- Department of Pathology and Laboratory Medicine, University of British Columbia, British Columbia, Canada; International Collaboration on Repair Discoveries (ICORD), University of British Columbia, British Columbia, Canada
| | - David K B Li
- Department of Radiology, University of British Columbia, British Columbia, Canada
| | - Yunyan Zhang
- Department of Radiology, University of Calgary, Alberta, Canada; Department of Clinical Neurosciences, University of Calgary, Alberta, Canada; Hotchkiss Brain Institute, University of Calgary, Alberta, Canada.
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45
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Williams MR, Sharma P, Macdonald C, Pearce RKB, Hirsch SR, Maier M. Axonal myelin decrease in the splenium in major depressive disorder. Eur Arch Psychiatry Clin Neurosci 2019; 269:387-395. [PMID: 29980921 PMCID: PMC6525661 DOI: 10.1007/s00406-018-0904-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2017] [Accepted: 04/17/2018] [Indexed: 12/13/2022]
Abstract
The corpus callosum has become a key area of interest for researchers in severe mental illness. Disruptions in fractional anisotropy in the callosum have been reported in schizophrenia and major depressive disorder. No change has been reported in oligodendrocyte density and overall size of the callosum in either illness, suggesting that gross morphology is unchanged, but subtler organisational disruption may exist within this structure. Using high-resolution oil immersion microscopy, we examined the cross-sectional area of the nerve fibre and the axonal myelin sheath; and using standard high-resolution light microscopy, we measured the density of myelinated axons. These measurements were made in the splenium of the corpus callosum. Measures were taken in the sagittal plane in the callosal splenium to contrast with the previous similar examination of the callosal genu. Cases of major depressive disorder had significantly decreased mean myelin cross-sectional area (p = 0.014) per axon in the splenium than in controls or schizophrenia groups. There was no significant change in the density of myelinated axons. The results suggest a clear decrease of myelin in the axons of the callosal splenium in MDD, although this type of neuropathological study is unable to clarify whether this is caused by changes during life or has a developmental origin. In contrast with increased myelin in the callosal genu, this result suggests a longitudinal change in callosal myelination in major depressive disorder not present in normal or schizophrenic brains.
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Affiliation(s)
- Matthew R Williams
- Robert Steiner Unit, Hammersmith Hospital, London, W12 0NN, UK.
- Neuropathology Unit, Division of Experimental Medicine, Imperial College London, Charing Cross Campus, St Dunstan's Road, London, W6 8RP, UK.
| | - P Sharma
- Neuropathology Unit, Division of Experimental Medicine, Imperial College London, Charing Cross Campus, St Dunstan's Road, London, W6 8RP, UK
- Ophthalmology Department, East and North Hertfordshire NHS Trust, Lister Hospital, Coreys Mill Lane, Stevenage, SG1 4AB, UK
| | - C Macdonald
- Neuropathology Unit, Division of Experimental Medicine, Imperial College London, Charing Cross Campus, St Dunstan's Road, London, W6 8RP, UK
- KHPC Biobank, Innovation Hub, Guy's Cancer Centre, Great Maze Pond, London, SE1 9RT, UK
| | - R K B Pearce
- Neuropathology Unit, Division of Experimental Medicine, Imperial College London, Charing Cross Campus, St Dunstan's Road, London, W6 8RP, UK
| | - S R Hirsch
- Claybrook Centre, West London Mental Health NHS Trust, Claybrook Road, London, W6 8LN, UK
| | - M Maier
- Trust HQ, West London Mental Health NHS Trust, Uxbridge Road, Southall, UB1 3EU, UK
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Innocenti GM, Dyrby TB, Girard G, St-Onge E, Thiran JP, Daducci A, Descoteaux M. Topological principles and developmental algorithms might refine diffusion tractography. Brain Struct Funct 2018; 224:1-8. [PMID: 30264235 PMCID: PMC6373358 DOI: 10.1007/s00429-018-1759-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 09/20/2018] [Indexed: 01/09/2023]
Abstract
The identification and reconstruction of axonal pathways in the living brain or "ex-vivo" is promising a revolution in connectivity studies bridging the gap from animal to human neuroanatomy with extensions to brain structural-functional correlates. Unfortunately, the methods suffer from juvenile drawbacks. In this perspective paper we mention several computational and developmental principles, which might stimulate a new generation of algorithms and a discussion bridging the neuroimaging and neuroanatomy communities.
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Affiliation(s)
- Giorgio M Innocenti
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden. .,Brain and Mind Institute, Ecole Polytechnique Féderale de Lausanne EPFL, Lausanne, Switzerland. .,Signal Processing Laboratory (LT55) Ecole Polytechnique Féderale de Lausanne (EPFL-STI-IEL-LT55), Station 11, 1015, Lausanne, Switzerland.
| | - Tim B Dyrby
- Danish Research Centre for Magnetic Resonance, Center for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark.,Department of Applied Mathematics and Computer Science, Technical University of Denmark, Kongens, Lyngby, Denmark
| | - Gabriel Girard
- Signal Processing Laboratory (LT55) Ecole Polytechnique Féderale de Lausanne (EPFL-STI-IEL-LT55), Station 11, 1015, Lausanne, Switzerland
| | - Etienne St-Onge
- Sherbrooke Connectivity Imaging Laboratory (SCIL), Computer Science Department, Faculty of Science, Université de Sherbrooke, Quebec, Canada
| | - Jean-Philippe Thiran
- Signal Processing Laboratory (LT55) Ecole Polytechnique Féderale de Lausanne (EPFL-STI-IEL-LT55), Station 11, 1015, Lausanne, Switzerland.,Department of Radiology, University Hospital Center (CHUV), University of Lausanne (UNIL), Lausanne, Switzerland
| | | | - Maxime Descoteaux
- Sherbrooke Connectivity Imaging Laboratory (SCIL), Computer Science Department, Faculty of Science, Université de Sherbrooke, Quebec, Canada.,Department of Nuclear Medicine and Radiobiology, Sherbrooke Molecular Imaging Center, Faculty of Medicine and Health Science, Université de Sherbrooke, Sherbrook, Canada
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Walker CK, Roche JK, Sinha V, Roberts RC. Substantia nigra ultrastructural pathology in schizophrenia. Schizophr Res 2018; 197:209-218. [PMID: 29274737 PMCID: PMC6013319 DOI: 10.1016/j.schres.2017.12.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 11/30/2017] [Accepted: 12/11/2017] [Indexed: 12/12/2022]
Abstract
Schizophrenia is a severe mental illness affecting approximately 1% of the population worldwide. Despite its prevalence, the cause remains unknown, and treatment is not effective in all patients. Dopamine is thought to play a role in schizophrenia pathology, yet the substantia nigra (SN), the origin of dopaminergic pathways, has not been studied extensively in schizophrenia. In this study, electron microscopy was used to examine neurons, oligodendrocytes, and myelinated axons in the SN of normal controls (NCs, n=9) and schizophrenia subjects with varying response to antipsychotic drugs [SZ, n=14; treatment resistant (TR)=6, treatment responsive (RESP)=6, unknown=2]. Postmortem tissue was analyzed for qualitative and quantitative markers of ultrastuctural integrity. A significantly higher percentage of axons in the schizophrenia group had inclusions in the myelin sheath compared to NCs (SZ: 3.9±1.7, NC: 2.6±2.0). When considering treatment response, a significantly higher percentage of axons lacked cytoplasm (TR: 9.7±5.5, NC: 3.5±2.3), contained cellular debris (TR: 7.5±3.2, NC: 2.3±1.3) or had protrusions in the myelin sheath (TR: 0.4±0.5, NC: 0.2±0.3). The G-ratio, a measure of myelin thickness, was significantly different between treatment response groups and was greater in TR (0.72±0.02) as compared to NCs (0.68±0.03), indicating decreased myelination in TR. These findings, which suggest myelin pathology in the SN in schizophrenia, are consistent with findings elsewhere in the brain. In addition, our results suggest cytoskeletal abnormalities, which may or may not be associated with myelin pathology.
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Affiliation(s)
| | - Joy K. Roche
- Department of Psychology, University of Alabama at Birmingham
| | - Vidushi Sinha
- Department of Psychology, University of Alabama at Birmingham
| | - Rosalinda C. Roberts
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham
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Miller GW, Chandrasekaran V, Yaghoobi B, Lein PJ. Opportunities and challenges for using the zebrafish to study neuronal connectivity as an endpoint of developmental neurotoxicity. Neurotoxicology 2018; 67:102-111. [PMID: 29704525 PMCID: PMC6177215 DOI: 10.1016/j.neuro.2018.04.016] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 04/23/2018] [Accepted: 04/24/2018] [Indexed: 01/28/2023]
Abstract
Chemical exposures have been implicated as environmental risk factors that interact with genetic susceptibilities to influence individual risk for complex neurodevelopmental disorders, including autism spectrum disorder, schizophrenia, attention deficit hyperactivity disorder and intellectual disabilities. Altered patterns of neuronal connectivity represent a convergent mechanism of pathogenesis for these and other neurodevelopmental disorders, and growing evidence suggests that chemicals can interfere with specific signaling pathways that regulate the development of neuronal connections. There is, therefore, a growing interest in developing screening platforms to identify chemicals that alter neuronal connectivity. Cell-cell, cell-matrix interactions and systemic influences are known to be important in defining neuronal connectivity in the developing brain, thus, a systems-based model offers significant advantages over cell-based models for screening chemicals for effects on neuronal connectivity. The embryonic zebrafish represents a vertebrate model amenable to higher throughput chemical screening that has proven useful in characterizing conserved mechanisms of neurodevelopment. Moreover, the zebrafish is readily amenable to gene editing to integrate genetic susceptibilities. Although use of the zebrafish model in toxicity testing has increased in recent years, the diverse tools available for imaging structural differences in the developing zebrafish brain have not been widely applied to studies of the influence of gene by environment interactions on neuronal connectivity in the developing zebrafish brain. Here, we discuss tools available for imaging of neuronal connectivity in the developing zebrafish, review what has been published in this regard, and suggest a path forward for applying this information to developmental neurotoxicity testing.
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Affiliation(s)
- Galen W. Miller
- Department of Molecular Biosciences, University of California, Davis, Davis, CA 95616, USA
| | - Vidya Chandrasekaran
- Department of Biology, Saint Mary’s College of California, Moraga, CA 94575, USA
| | - Bianca Yaghoobi
- Department of Molecular Biosciences, University of California, Davis, Davis, CA 95616, USA
| | - Pamela J. Lein
- Department of Molecular Biosciences, University of California, Davis, Davis, CA 95616, USA
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49
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Kimball EC, Jefferys JL, Pease ME, Oglesby EN, Nguyen C, Schaub J, Pitha I, Quigley HA. The effects of age on mitochondria, axonal transport, and axonal degeneration after chronic IOP elevation using a murine ocular explant model. Exp Eye Res 2018; 172:78-85. [PMID: 29625080 PMCID: PMC5994189 DOI: 10.1016/j.exer.2018.04.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 03/07/2018] [Accepted: 04/02/2018] [Indexed: 01/03/2023]
Abstract
The purpose of this study was to compare younger and older mice after chronic intraocular pressure (IOP) elevation lasting up to 4 days with respect to mitochondrial density, structure, and movement, as well as axonal integrity, in an ex vivo explant model. We studied 2 transgenic mouse strains, both on a C57BL/6J background, one expressing yellow fluorescent protein (YFP) in selected axons and one expressing cyan fluorescent protein (CFP) in all mitochondria. Mice of 4 months or 14 months of age were exposed to chronic IOP by anterior chamber microbead injection for 14 h, 1, 3, or 4 days. The optic nerve head of globe--optic nerve explants were examined by laser scanning microscopy. Mitochondrial density, structure, and movement were quantified in the CFP explants, and axonal integrity was quantified in YFP explants. In control mice, there was a trend towards decreased mitochondrial density (# per mm2) with age when comparing younger to older, control mice, but this was not significant (1947 ± 653 vs 1412 ± 356; p = 0.19). Mitochondrial density decreased after IOP elevation, significantly, by 31%, in younger mice (p = 0.04) but trending towards a decrease, by 22%, in older mice (p = 0.82) compared to age matched controls. Mitochondrial mean size was not altered after chronic IOP elevation for 14 h or more (p ≥ 0.16). When assessing mitochondrial movement, in younger mice, 5% were mobile at any given time; 4% in the anterograde direction and 1% retrograde. In younger untreated tissue, only 75% of explants had moving mitochondria (mean = 15.8 moving/explant), while after glaucoma induction only 24% of explants had moving mitochondria (mean = 4.2 moving/explant; difference from control, p = 0.03). The distance mitochondria traveled in younger mice was unchanged after glaucoma exposure, but in older glaucoma explants the distance traveled was less than half of older controls (p < 0.0003). In younger mice, mitochondrial speed increased after 14 h of elevated IOP (p = 0.006); however, in older glaucoma explants, movement was actually slower than controls (p = 0.02). In RGC-YFP explants, axonal integrity declined significantly after 4 days of IOP elevation to a similar degree in both younger and older mice. Older mice underwent greater loss of mitochondrial movement with chronic IOP elevation than younger mice, but suffered similar short-term axonal fragmentation in C57BL/6J mice. These transgenic strains, studied in explants, permit observations of alterations in intracellular structure and organelle activity in experimental glaucoma.
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Affiliation(s)
- Elizabeth C Kimball
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USA.
| | - Joan L Jefferys
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USA
| | - Mary E Pease
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USA
| | - Ericka N Oglesby
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USA
| | - Cathy Nguyen
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USA
| | - Julie Schaub
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USA
| | - Ian Pitha
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USA; The Center for Nanomedicine, Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USA
| | - Harry A Quigley
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USA
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50
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Liu L, Yuan H, Yi Y, Koellhoffer EC, Munshi Y, Bu F, Zhang Y, Zhang Z, McCullough LD, Li J. Ras-Related C3 Botulinum Toxin Substrate 1 Promotes Axonal Regeneration after Stroke in Mice. Transl Stroke Res 2018; 9:506-14. [PMID: 29476448 DOI: 10.1007/s12975-018-0611-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 01/09/2018] [Accepted: 01/10/2018] [Indexed: 12/18/2022]
Abstract
Neurite plasticity is a critical aspect of brain functional recovery after stroke. Emerging data suggest that Ras-related C3 botulinum toxin substrate 1 (Rac1) plays a central role in axonal regeneration in the injured brain, specifically by stimulating neuronal intrinsic growth and counteracting the growth inhibitory signaling that leads to growth cone collapse. Therefore, we investigated the functional role of Rac1 in axonal regeneration after stroke.Delayed treatment with a specific Rac1 inhibitor, NSC 23766, worsened functional recovery, which was assessed by the pellet reaching test from day 14 to day 28 after stroke. It additionally reduced axonal density in the peri-infarct zone, assessed 28 days after stroke, with no effect on brain cavity size or on the number of newly formed cells. Accordingly, Rac1 overexpression using lentivirus promoted axonal regeneration and functional recovery after stroke from day 14 to day 28. Rac1 inhibition led to inactivation of pro-regenerative molecules, including mitogen-activated protein kinase kinase (p-MEK)1/2, LIM domain kinase (LIMK)1, and extracellular signal-regulated kinase (p-ERK)1/2 at 14 days after stroke. Inhibition of Rac1 reduced axonal length and number in cultured primary mouse cortical neurons using microfluidic chambers after oxygen-glucose deprivation (OGD) without affecting cell viability. In contrast, inhibition of Rac1 increased levels of glial fibrillary acidic protein, an extrinsic inhibitory signal for axonal growth, after stroke in vivo and in primary astrocytes after OGD.In conclusion, Rac1 signaling enhances axonal regeneration and improve post-stroke functional recovery in experimental models of stroke.
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