1
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Veldmann M, Edwards LJ, Pine KJ, Ehses P, Ferreira M, Weiskopf N, Stoecker T. Improving MR axon radius estimation in human white matter using spiral acquisition and field monitoring. Magn Reson Med 2024; 92:1898-1912. [PMID: 38817204 DOI: 10.1002/mrm.30180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Revised: 04/08/2024] [Accepted: 05/15/2024] [Indexed: 06/01/2024]
Abstract
PURPOSE To compare MR axon radius estimation in human white matter using a multiband spiral sequence combined with field monitoring to the current state-of-the-art echo-planar imaging (EPI)-based approach. METHODS A custom multiband spiral sequence was used for diffusion-weighted imaging at ultra-highb $$ b $$ -values. Field monitoring and higher order image reconstruction were employed to greatly reduce artifacts in spiral images. Diffusion weighting parameters were chosen to match a state-of-the art EPI-based axon radius mapping protocol. The spiral approach was compared to the EPI approach by comparing the image signal-to-noise ratio (SNR) and performing a test-retest study to assess the respective variability and repeatability of axon radius mapping. Effective axon radius estimates were compared over white matter voxels and along the left corticospinal tract. RESULTS Increased SNR and reduced artifacts in spiral images led to reduced variability in resulting axon radius maps, especially in low-SNR regions. Test-retest variability was reduced by a factor of approximately 1.5 using the spiral approach. Reduced repeatability due to significant bias was found for some subjects in both spiral and EPI approaches, and attributed to scanner instability, pointing to a previously unknown limitation of the state-of-the-art approach. CONCLUSION Combining spiral readouts with field monitoring improved mapping of the effective axon radius compared to the conventional EPI approach.
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Affiliation(s)
- Marten Veldmann
- MR Physics, German Center for Neurodegenerative Diseases (DZNE) e.V, Bonn, Germany
| | - Luke J Edwards
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Kerrin J Pine
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Philipp Ehses
- MR Physics, German Center for Neurodegenerative Diseases (DZNE) e.V, Bonn, Germany
| | - Mónica Ferreira
- Clinical Research, German Center for Neurodegenerative Diseases (DZNE) e.V, Bonn, Germany
- University of Bonn, Bonn, Germany
| | - Nikolaus Weiskopf
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
- Felix Bloch Institute for Solid State Physics, Faculty of Physics and Earth System Sciences, Leipzig University, Leipzig, Germany
- Wellcome Centre for Human Neuroimaging, Institute of Neurology, University College London, London, UK
| | - Tony Stoecker
- MR Physics, German Center for Neurodegenerative Diseases (DZNE) e.V, Bonn, Germany
- Department of Physics & Astronomy, University of Bonn, Bonn, Germany
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Davids M, Vendramini L, Klein V, Ferris N, Guerin B, Wald LL. Experimental validation of a PNS-optimized whole-body gradient coil. Magn Reson Med 2024; 92:1788-1803. [PMID: 38767407 PMCID: PMC11262990 DOI: 10.1002/mrm.30157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2023] [Revised: 03/19/2024] [Accepted: 04/28/2024] [Indexed: 05/22/2024]
Abstract
PURPOSE Peripheral nerve stimulation (PNS) limits the usability of state-of-the-art whole-body and head-only MRI gradient coils. We used detailed electromagnetic and neurodynamic modeling to set an explicit PNS constraint during the design of a whole-body gradient coil and constructed it to compare the predicted and experimentally measured PNS thresholds to those of a matched design without PNS constraints. METHODS We designed, constructed, and tested two actively shielded whole-body Y-axis gradient coil winding patterns: YG1 is a conventional symmetric design without PNS-optimization, whereas YG2's design used an additional constraint on the allowable PNS threshold in the head-imaging landmark, yielding an asymmetric winding pattern. We measured PNS thresholds in 18 healthy subjects at five landmark positions (head, cardiac, abdominal, pelvic, and knee). RESULTS The PNS-optimized design YG2 achieved 46% higher average experimental thresholds for a head-imaging landmark than YG1 while incurring a 15% inductance penalty. For cardiac, pelvic, and knee imaging landmarks, the PNS thresholds increased between +22% and +35%. For abdominal imaging, PNS thresholds did not change significantly between YG1 and YG2 (-3.6%). The agreement between predicted and experimental PNS thresholds was within 11.4% normalized root mean square error for both coils and all landmarks. The PNS model also produced plausible predictions of the stimulation sites when compared to the sites of perception reported by the subjects. CONCLUSION The PNS-optimization improved the PNS thresholds for the target scan landmark as well as most other studied landmarks, potentially yielding a significant improvement in image encoding performance that can be safely used in humans.
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Affiliation(s)
- Mathias Davids
- Martinos Center for Biomedical Imaging, Charlestown, MA, United States
- Harvard Medical School, Boston, MA, United States
| | - Livia Vendramini
- Martinos Center for Biomedical Imaging, Charlestown, MA, United States
| | - Valerie Klein
- Martinos Center for Biomedical Imaging, Charlestown, MA, United States
- Harvard Medical School, Boston, MA, United States
| | - Natalie Ferris
- Harvard Graduate Program in Biophysics, Harvard University, Cambridge, MA, United States
- Harvard-MIT Division of Health Sciences and Technology, Boston, MA, United States
| | - Bastien Guerin
- Martinos Center for Biomedical Imaging, Charlestown, MA, United States
- Harvard Medical School, Boston, MA, United States
| | - Lawrence L. Wald
- Martinos Center for Biomedical Imaging, Charlestown, MA, United States
- Harvard Medical School, Boston, MA, United States
- Harvard-MIT Division of Health Sciences and Technology, Boston, MA, United States
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3
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Almuklass AM, Alassaf AM, Alanazi RF, Alnafisah TR, Alrehaily TA, Al Malik Y. Nerve conduction, latency, and its association with hand function in young men. PLoS One 2024; 19:e0310813. [PMID: 39348363 PMCID: PMC11441660 DOI: 10.1371/journal.pone.0310813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Accepted: 09/07/2024] [Indexed: 10/02/2024] Open
Abstract
INTRODUCTION The median and ulnar nerves have been suggested to play a significant role in hand function; however, there are insufficient data to determine the strength of this association. This study aimed to investigate the correlation between hand function as measured with the Grooved pegboard test (GPT) and conduction velocity and latency of the median and ulnar nerves. METHODS We collected convenience samples in the College of Medicine, KSAU-HS. We used GPT to characterize hand function and performed measured nerve conduction velocity (NCV) and latency of the ulnar and median nerves of both hands. We used the Edinburgh handedness inventory (EHI) to determine hand dominance. RESULTS We recruited 28 healthy medical students aged 20-29 years (mean: 21.46 ± 1.62 years). Most were right-handed (n = 25, 89.3%), with a mean EHI score of 302 ± 210. The mean GPT time was significantly faster in the dominant (65.5 ± 6.4 s) than in the non-dominant (75.0 ± 9.6 s) hand. The NCV for the ulnar nerve of the dominant hand was significantly correlated with GPT (r = -0.52, p = 0.005) while median nerve was not correlated (0.24, p = 0.21). Regression analysis and collinearity test showed that the ulnar NCV explained 20% of the variance in GPT of the dominant hand (R2 = 0.203, p = 0.016). CONCLUSION The ulnar nerve conduction velocity, explained 20% of the variance in GPT times of the young men. Performance on this biomarker of neurological health seems to be more influenced by other factors in healthy young individuals.
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Affiliation(s)
- Awad M Almuklass
- Basic Medical Science Department, College of Medicine, King Saud Bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia
- King Abdullah International Medical Research Center, Riyadh, Saudi Arabia
| | - Abdulmajeed Mansour Alassaf
- Basic Medical Science Department, College of Medicine, King Saud Bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia
| | - Rakan F Alanazi
- Basic Medical Science Department, College of Medicine, King Saud Bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia
| | - Turki Rashed Alnafisah
- Basic Medical Science Department, College of Medicine, King Saud Bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia
| | - Thamir Ali Alrehaily
- Basic Medical Science Department, College of Medicine, King Saud Bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia
| | - Yaser Al Malik
- Basic Medical Science Department, College of Medicine, King Saud Bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia
- King Abdullah International Medical Research Center, Riyadh, Saudi Arabia
- Division of Neurology, King Abdulaziz Medical City, National Guard Health Affairs, Riyadh, Saudi Arabia
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4
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Marshall-Phelps KLH, Almeida RG. Axonal neurotransmitter release in the regulation of myelination. Biosci Rep 2024; 44:BSR20231616. [PMID: 39230890 PMCID: PMC11427734 DOI: 10.1042/bsr20231616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2024] [Revised: 08/30/2024] [Accepted: 09/04/2024] [Indexed: 09/05/2024] Open
Abstract
Myelination of axons is a key determinant of fast action potential propagation, axonal health and circuit function. Previously considered a static structure, it is now clear that myelin is dynamically regulated in response to neuronal activity in the central nervous system (CNS). However, how activity-dependent signals are conveyed to oligodendrocytes remains unclear. Here, we review the potential mechanisms by which neurons could communicate changing activity levels to myelin, with a focus on the accumulating body of evidence to support activity-dependent vesicular signalling directly onto myelin sheaths. We discuss recent in vivo findings of activity-dependent fusion of neurotransmitter vesicles from non-synaptic axonal sites, and how modulation of this vesicular fusion regulates the stability and growth of myelin sheaths. We also consider the potential mechanisms by which myelin could sense and respond to axon-derived signals to initiate remodelling, and the relevance of these adaptations for circuit function. We propose that axonal vesicular signalling represents an important and underappreciated mode of communication by which neurons can transmit activity-regulated signals to myelinating oligodendrocytes and, potentially, more broadly to other cell types in the CNS.
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Affiliation(s)
- Katy L H Marshall-Phelps
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, U.K
- MS Society Edinburgh Centre for MS Research, University of Edinburgh, Edinburgh, U.K
| | - Rafael G Almeida
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, U.K
- MS Society Edinburgh Centre for MS Research, University of Edinburgh, Edinburgh, U.K
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Manesh SB, Kondiles BR, Wheeler S, Liu J, Zhang L, Chernoff C, Duncan GJ, Ramer MS, Tetzlaff W. Compensatory changes after spinal cord injury in a remyelination deficient mouse model. J Neurochem 2024. [PMID: 39268880 DOI: 10.1111/jnc.16220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2024] [Revised: 08/22/2024] [Accepted: 08/23/2024] [Indexed: 09/15/2024]
Abstract
The development of therapeutic strategies to reduce impairments following spinal cord injury (SCI) motivates an active area of research, because there are no effective therapies. One strategy is to address injury-induced demyelination of spared axons by promoting endogenous or exogenous remyelination. However, previously, we showed that new myelin was not necessary to regain hindlimb stepping following moderate thoracic spinal cord contusion in 3-month-old mice. The present analysis investigated two potential mechanisms by which animals can re-establish locomotion in the absence of remyelination: compensation through intact white matter and conduction through spared axons. We induced a severe contusion injury to reduce the spared white matter rim in the remyelination deficient model, with no differences in recovery between remyelination deficient animals and injured littermate controls. We investigated the nodal properties of the axons at the lesion and found that in the remyelination deficient model, axons express the Nav1.2 voltage-gated sodium channel, a sub-type not typically expressed at mature nodes of Ranvier. In a moderate contusion injury, conduction velocities through the lesions of remyelination deficient animals were similar to those in animals with the capacity to remyelinate after injury. Detailed gait analysis and kinematics reveal subtle differences between remyelination deficient animals and remyelination competent controls, but no worse deficits. It is possible that upregulation of Nav1.2 channels may contribute to establishing conduction through the lesion. This conduction could contribute to compensation and regained motor function in mouse models of SCI. Such compensatory mechanism may have implications for interpreting efficacy results for remyelinating interventions in mice and the development of therapies for improving recovery following SCI.
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Affiliation(s)
- S B Manesh
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, British Columbia, Canada
| | - B R Kondiles
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - S Wheeler
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, British Columbia, Canada
| | - J Liu
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, British Columbia, Canada
| | - L Zhang
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, British Columbia, Canada
| | - C Chernoff
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, British Columbia, Canada
| | - G J Duncan
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, British Columbia, Canada
| | - M S Ramer
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - W Tetzlaff
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
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Calabro FJ, Parr AC, Sydnor VJ, Hetherington H, Prasad KM, Ibrahim TS, Sarpal DK, Famalette A, Verma P, Luna B. Leveraging ultra-high field (7T) MRI in psychiatric research. Neuropsychopharmacology 2024:10.1038/s41386-024-01980-6. [PMID: 39251774 DOI: 10.1038/s41386-024-01980-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2024] [Revised: 06/21/2024] [Accepted: 07/23/2024] [Indexed: 09/11/2024]
Abstract
Non-invasive brain imaging has played a critical role in establishing our understanding of the neural properties that contribute to the emergence of psychiatric disorders. However, characterizing core neurobiological mechanisms of psychiatric symptomatology requires greater structural, functional, and neurochemical specificity than is typically obtainable with standard field strength MRI acquisitions (e.g., 3T). Ultra-high field (UHF) imaging at 7 Tesla (7T) provides the opportunity to identify neurobiological systems that confer risk, determine etiology, and characterize disease progression and treatment outcomes of major mental illnesses. Increases in scanner availability, regulatory approval, and sequence availability have made the application of UHF to clinical cohorts more feasible than ever before, yet the application of UHF approaches to the study of mental health remains nascent. In this technical review, we describe core neuroimaging methodologies which benefit from UHF acquisition, including high resolution structural and functional imaging, single (1H) and multi-nuclear (e.g., 31P) MR spectroscopy, and quantitative MR techniques for assessing brain tissue iron and myelin. We discuss advantages provided by 7T MRI, including higher signal- and contrast-to-noise ratio, enhanced spatial resolution, increased test-retest reliability, and molecular and neurochemical specificity, and how these have begun to uncover mechanisms of psychiatric disorders. Finally, we consider current limitations of UHF in its application to clinical cohorts, and point to ongoing work that aims to overcome technical hurdles through the continued development of UHF hardware, software, and protocols.
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Affiliation(s)
- Finnegan J Calabro
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, USA.
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.
| | - Ashley C Parr
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, USA
| | - Valerie J Sydnor
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, USA
| | | | - Konasale M Prasad
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
- Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, PA, USA
| | - Tamer S Ibrahim
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
| | - Deepak K Sarpal
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, USA
| | - Alyssa Famalette
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, USA
| | - Piya Verma
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, USA
| | - Beatriz Luna
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Psychology, University of Pittsburgh, Pittsburgh, PA, USA
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7
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Salzer J, Feltri ML, Jacob C. Schwann Cell Development and Myelination. Cold Spring Harb Perspect Biol 2024; 16:a041360. [PMID: 38503507 PMCID: PMC11368196 DOI: 10.1101/cshperspect.a041360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/21/2024]
Abstract
Glial cells in the peripheral nervous system (PNS), which arise from the neural crest, include axon-associated Schwann cells (SCs) in nerves, synapse-associated SCs at the neuromuscular junction, enteric glia, perikaryon-associated satellite cells in ganglia, and boundary cap cells at the border between the central nervous system (CNS) and the PNS. Here, we focus on axon-associated SCs. These SCs progress through a series of formative stages, which culminate in the generation of myelinating SCs that wrap large-caliber axons and of nonmyelinating (Remak) SCs that enclose multiple, small-caliber axons. In this work, we describe SC development, extrinsic signals from the axon and extracellular matrix (ECM) and the intracellular signaling pathways they activate that regulate SC development, and the morphogenesis and organization of myelinating SCs and the myelin sheath. We review the impact of SCs on the biology and integrity of axons and their emerging role in regulating peripheral nerve architecture. Finally, we explain how transcription and epigenetic factors control and fine-tune SC development and myelination.
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Affiliation(s)
- James Salzer
- Neuroscience Institute, New York University Grossman School of Medicine, New York, New York 10016, USA
| | - M Laura Feltri
- Institute for Myelin and Glia Exploration, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, New York 14203, USA
- IRCCS Neurological Institute Carlo Besta, Milano 20133, Italy
- Department of Biotechnology and Translational Sciences, Universita' Degli Studi di Milano, Milano 20133, Italy
| | - Claire Jacob
- Faculty of Biology, Institute of Developmental Biology and Neurobiology, Johannes Gutenberg University Mainz, Mainz 55128, Germany
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Nguyen PT, Makowiecki K, Lewis TS, Fortune AJ, Clutterbuck M, Reale LA, Taylor BV, Rodger J, Cullen CL, Young KM. Low intensity repetitive transcranial magnetic stimulation enhances remyelination by newborn and surviving oligodendrocytes in the cuprizone model of toxic demyelination. Cell Mol Life Sci 2024; 81:346. [PMID: 39134808 PMCID: PMC11335270 DOI: 10.1007/s00018-024-05391-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2023] [Revised: 07/30/2024] [Accepted: 08/01/2024] [Indexed: 08/22/2024]
Abstract
In people with multiple sclerosis (MS), newborn and surviving oligodendrocytes (OLs) can contribute to remyelination, however, current therapies are unable to enhance or sustain endogenous repair. Low intensity repetitive transcranial magnetic stimulation (LI-rTMS), delivered as an intermittent theta burst stimulation (iTBS), increases the survival and maturation of newborn OLs in the healthy adult mouse cortex, but it is unclear whether LI-rTMS can promote remyelination. To examine this possibility, we fluorescently labelled oligodendrocyte progenitor cells (OPCs; Pdgfrα-CreER transgenic mice) or mature OLs (Plp-CreER transgenic mice) in the adult mouse brain and traced the fate of each cell population over time. Daily sessions of iTBS (600 pulses; 120 mT), delivered during cuprizone (CPZ) feeding, did not alter new or pre-existing OL survival but increased the number of myelin internodes elaborated by new OLs in the primary motor cortex (M1). This resulted in each new M1 OL producing ~ 471 µm more myelin. When LI-rTMS was delivered after CPZ withdrawal (during remyelination), it significantly increased the length of the internodes elaborated by new M1 and callosal OLs, increased the number of surviving OLs that supported internodes in the corpus callosum (CC), and increased the proportion of axons that were myelinated. The ability of LI-rTMS to modify cortical neuronal activity and the behaviour of new and surviving OLs, suggests that it may be a suitable adjunct intervention to enhance remyelination in people with MS.
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Affiliation(s)
- Phuong Tram Nguyen
- Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia
| | - Kalina Makowiecki
- Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia
| | - Thomas S Lewis
- Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia
| | - Alastair J Fortune
- Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia
| | - Mackenzie Clutterbuck
- Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia
| | - Laura A Reale
- Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia
| | - Bruce V Taylor
- Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia
| | - Jennifer Rodger
- School of Biological Sciences, The University of Western Australia, Crawley, WA, Australia
- Perron Institute for Neurological and Translational Science, Nedlands, WA, Australia
| | - Carlie L Cullen
- Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia
- Mater Research Institute, The University of Queensland, Woolloongabba, QLD, Australia
| | - Kaylene M Young
- Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia.
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Huang J, Pan X, Yan N. Structural biology and molecular pharmacology of voltage-gated ion channels. Nat Rev Mol Cell Biol 2024:10.1038/s41580-024-00763-7. [PMID: 39103479 DOI: 10.1038/s41580-024-00763-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/26/2024] [Indexed: 08/07/2024]
Abstract
Voltage-gated ion channels (VGICs), including those for Na+, Ca2+ and K+, selectively permeate ions across the cell membrane in response to changes in membrane potential, thus participating in physiological processes involving electrical signalling, such as neurotransmission, muscle contraction and hormone secretion. Aberrant function or dysregulation of VGICs is associated with a diversity of neurological, psychiatric, cardiovascular and muscular disorders, and approximately 10% of FDA-approved drugs directly target VGICs. Understanding the structure-function relationship of VGICs is crucial for our comprehension of their working mechanisms and role in diseases. In this Review, we discuss how advances in single-particle cryo-electron microscopy have afforded unprecedented structural insights into VGICs, especially on their interactions with clinical and investigational drugs. We present a comprehensive overview of the recent advances in the structural biology of VGICs, with a focus on how prototypical drugs and toxins modulate VGIC activities. We explore how these structures elucidate the molecular basis for drug actions, reveal novel pharmacological sites, and provide critical clues to future drug discovery.
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Affiliation(s)
- Jian Huang
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Xiaojing Pan
- Institute of Bio-Architecture and Bio-Interactions (IBABI), Shenzhen Medical Academy of Research and Translation (SMART), Shenzhen, Guangdong, China.
| | - Nieng Yan
- Institute of Bio-Architecture and Bio-Interactions (IBABI), Shenzhen Medical Academy of Research and Translation (SMART), Shenzhen, Guangdong, China.
- Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, State Key Laboratory of Membrane Biology, Tsinghua University, Beijing, China.
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10
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Ibañez S, Sengupta N, Luebke JI, Wimmer K, Weaver CM. Myelin dystrophy impairs signal transmission and working memory in a multiscale model of the aging prefrontal cortex. eLife 2024; 12:RP90964. [PMID: 39028036 PMCID: PMC11259433 DOI: 10.7554/elife.90964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2024] Open
Abstract
Normal aging leads to myelin alterations in the rhesus monkey dorsolateral prefrontal cortex (dlPFC), which are positively correlated with degree of cognitive impairment. It is hypothesized that remyelination with shorter and thinner myelin sheaths partially compensates for myelin degradation, but computational modeling has not yet explored these two phenomena together systematically. Here, we used a two-pronged modeling approach to determine how age-related myelin changes affect a core cognitive function: spatial working memory. First, we built a multicompartment pyramidal neuron model fit to monkey dlPFC empirical data, with an axon including myelinated segments having paranodes, juxtaparanodes, internodes, and tight junctions. This model was used to quantify conduction velocity (CV) changes and action potential (AP) failures after demyelination and subsequent remyelination. Next, we incorporated the single neuron results into a spiking neural network model of working memory. While complete remyelination nearly recovered axonal transmission and network function to unperturbed levels, our models predict that biologically plausible levels of myelin dystrophy, if uncompensated by other factors, can account for substantial working memory impairment with aging. The present computational study unites empirical data from ultrastructure up to behavior during normal aging, and has broader implications for many demyelinating conditions, such as multiple sclerosis or schizophrenia.
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Affiliation(s)
- Sara Ibañez
- Department of Anatomy & Neurobiology, Boston University Chobanian & Avedisian School of MedicineBostonUnited States
- Centre de Recerca Matemàtica, Edifici C, Campus BellaterraBellaterraSpain
- Departament de Matemàtiques, Universitat Autònoma de Barcelona, Edifici CBellaterraSpain
| | - Nilapratim Sengupta
- Department of Anatomy & Neurobiology, Boston University Chobanian & Avedisian School of MedicineBostonUnited States
- Department of Mathematics, Franklin and Marshall CollegeLancasterUnited States
| | - Jennifer I Luebke
- Department of Anatomy & Neurobiology, Boston University Chobanian & Avedisian School of MedicineBostonUnited States
| | - Klaus Wimmer
- Centre de Recerca Matemàtica, Edifici C, Campus BellaterraBellaterraSpain
- Departament de Matemàtiques, Universitat Autònoma de Barcelona, Edifici CBellaterraSpain
| | - Christina M Weaver
- Department of Mathematics, Franklin and Marshall CollegeLancasterUnited States
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11
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Radulescu CI, Ferrari Bardile C, Garcia-Miralles M, Sidik H, Yusof NABM, Pouladi MA. Environmental Deprivation Effects on Myelin Ultrastructure in Huntington Disease and Wildtype Mice. Mol Neurobiol 2024; 61:4278-4288. [PMID: 38079108 DOI: 10.1007/s12035-023-03799-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Accepted: 11/12/2023] [Indexed: 07/11/2024]
Abstract
Environmental deprivation can have deleterious effects on adaptive myelination and oligodendroglia function. Early stage Huntington disease (HD) is characterised by white-matter myelin abnormalities in both humans and animal models. However, whether deprived environments exacerbate myelin-related pathological features of HD is not clearly understood. Here, we investigated the impact of deprivation and social isolation on ultrastructural features of myelin in the corpus callosum of the YAC128 mouse model of HD and wildtype (WT) mice using transmission electron microscopy. HD pathology on its own leads to increased representation of altered myelin features, such as thinner sheaths and compromised morphology. Interestingly, deprivation mirrors these effects in WT mice but does not greatly exacerbate the already aberrant myelin in HD mice, indicating a disease-related floor effect in the latter animals. These novel findings indicate that environmental deprivation causes abnormalities in myelin ultrastructure in the otherwise healthy corpus callosum of wild-type mice but has distinct effects on HD mice, where compromised myelin integrity is manifest from early stages of the disease.
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Affiliation(s)
- Carola I Radulescu
- Agency for Science, Technology and Research (A*STAR), Translational Laboratory in Genetic Medicine (TLGM), Singapore, 138648, Singapore
- UK Dementia Research Institute (DRI), Department of Brain Sciences, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London, W12 0NN, UK
| | - Costanza Ferrari Bardile
- Agency for Science, Technology and Research (A*STAR), Translational Laboratory in Genetic Medicine (TLGM), Singapore, 138648, Singapore
- Department of Medical Genetics, Centre for Molecular Medicine and Therapeutics, Djavad Mowafaghian Centre for Brain Health, British Columbia Children's Hospital Research Institute, University of British Columbia, 950 West 28th Avenue, Vancouver, V5Z 4H4, Canada
| | - Marta Garcia-Miralles
- Agency for Science, Technology and Research (A*STAR), Translational Laboratory in Genetic Medicine (TLGM), Singapore, 138648, Singapore
| | - Harwin Sidik
- Agency for Science, Technology and Research (A*STAR), Translational Laboratory in Genetic Medicine (TLGM), Singapore, 138648, Singapore
| | - Nur Amirah Binte Mohammad Yusof
- Agency for Science, Technology and Research (A*STAR), Translational Laboratory in Genetic Medicine (TLGM), Singapore, 138648, Singapore
| | - Mahmoud A Pouladi
- Agency for Science, Technology and Research (A*STAR), Translational Laboratory in Genetic Medicine (TLGM), Singapore, 138648, Singapore.
- Department of Medical Genetics, Centre for Molecular Medicine and Therapeutics, Djavad Mowafaghian Centre for Brain Health, British Columbia Children's Hospital Research Institute, University of British Columbia, 950 West 28th Avenue, Vancouver, V5Z 4H4, Canada.
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12
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Ribeiro M, Andreis FR, Jabban L, Nielsen TGNDS, Smirnov SV, Lutteroth C, Proulx MJ, Rocha PRF, Metcalfe B. Ex-vivo systems for neuromodulation: A comparison of ex-vivo and in-vivo large animal nerve electrophysiology. J Neurosci Methods 2024; 406:110116. [PMID: 38548122 DOI: 10.1016/j.jneumeth.2024.110116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 03/05/2024] [Accepted: 03/21/2024] [Indexed: 04/04/2024]
Abstract
BACKGROUND Little research exists on extending ex-vivo systems to large animal nerves, and to the best of our knowledge, there has yet to be a study comparing these against in-vivo data. This paper details the first ex-vivo system for large animal peripheral nerves to be compared with in-vivo results. NEW METHOD Detailed ex-vivo and in-vivo closed-loop neuromodulation experiments were conducted on pig ulnar nerves. Temperatures from 20 °C to 37 °C were evaluated for the ex-vivo system. The data were analysed in the time and velocity domains, and a regression analysis established how evoked compound action potential amplitude and modal conduction velocity (CV) varied with temperature and time after explantation. MAIN RESULTS Pig ulnar nerves were sustained ex-vivo up to 5 h post-explantation. CV distributions of ex-vivo and in-vivo data were compared, showing closer correspondence at 37 °C. Regression analysis results also demonstrated that modal CV and time since explantation were negatively correlated, whereas modal CV and temperature were positively correlated. COMPARISON WITH EXISTING METHODS Previous ex-vivo systems were primarily aimed at small animal nerves, and we are not aware of an ex-vivo system to be directly compared with in-vivo data. This new approach provides a route to understand how ex-vivo systems for large animal nerves can be developed and compared with in-vivo data. CONCLUSION The proposed ex-vivo system results were compared with those seen in-vivo, providing new insights into large animal nerve activity post-explantation. Such a system is crucial for complementing in-vivo experiments, maximising collected experimental data, and accelerating neural interface development.
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Affiliation(s)
- Mafalda Ribeiro
- Centre for Accountable, Responsible, and Transparent AI (ART-AI), Department of Computer Science, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom; Department of Electronic & Electrical Engineering, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom.
| | - Felipe R Andreis
- Centre for Neuroplasticity and Pain (CNAP), Department of Health Science and Technology, Aalborg University, Selma Lagerløfs Vej 249, 9260, Gistrup, Denmark
| | - Leen Jabban
- Department of Electronic & Electrical Engineering, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom
| | - Thomas G N dS Nielsen
- Centre for Neuroplasticity and Pain (CNAP), Department of Health Science and Technology, Aalborg University, Selma Lagerløfs Vej 249, 9260, Gistrup, Denmark
| | - Sergey V Smirnov
- Department of Life Sciences, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom
| | - Christof Lutteroth
- Centre for Accountable, Responsible, and Transparent AI (ART-AI), Department of Computer Science, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom; Department of Computer Science, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom
| | - Michael J Proulx
- Centre for Accountable, Responsible, and Transparent AI (ART-AI), Department of Computer Science, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom; Department of Psychology, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom
| | - Paulo R F Rocha
- Centre for Functional Ecology - Science for People & the Planet (CFE), TERRA Associate Laboratory, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456, Coimbra, Portugal
| | - Benjamin Metcalfe
- Centre for Accountable, Responsible, and Transparent AI (ART-AI), Department of Computer Science, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom; The Bath Institute for the Augmented Human, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom.
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13
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Gast H, Assaf Y. Weighting the structural connectome: Exploring its impact on network properties and predicting cognitive performance in the human brain. Netw Neurosci 2024; 8:119-137. [PMID: 38562285 PMCID: PMC10861171 DOI: 10.1162/netn_a_00342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2023] [Accepted: 10/11/2023] [Indexed: 04/04/2024] Open
Abstract
Brain function does not emerge from isolated activity, but rather from the interactions and exchanges between neural elements that form a network known as the connectome. The human connectome consists of structural and functional aspects. The structural connectome (SC) represents the anatomical connections, and the functional connectome represents the resulting dynamics that emerge from this arrangement of structures. As there are different ways of weighting these connections, it is important to consider how such different approaches impact study conclusions. Here, we propose that different weighted connectomes result in varied network properties, and while neither superior the other, selection might affect interpretation and conclusions in different study cases. We present three different weighting models, namely, number of streamlines (NOS), fractional anisotropy (FA), and axon diameter distribution (ADD), to demonstrate these differences. The later, is extracted using recently published AxSI method and is first compared to commonly used weighting methods. Moreover, we explore the functional relevance of each weighted SC, using the Human Connectome Project (HCP) database. By analyzing intelligence-related data, we develop a predictive model for cognitive performance based on graph properties and the National Institutes of Health (NIH) toolbox. Results demonstrate that the ADD SC, combined with a functional subnetwork model, outperforms other models in estimating cognitive performance.
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Affiliation(s)
- Hila Gast
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Yaniv Assaf
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
- The Strauss Center for Neuroimaging, Tel Aviv University, Tel Aviv, Israel
- School of Neurobiology, Biochemistry and Biophysics, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
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14
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Huang WQ, Sheng H, Wang H, Qi Y, Wang F, Hua Y. Volume electron microscopy reveals age-related ultrastructural differences of globular bush cell axons in mouse central auditory system. Neurobiol Aging 2024; 136:111-124. [PMID: 38342072 DOI: 10.1016/j.neurobiolaging.2024.01.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 01/30/2024] [Accepted: 01/31/2024] [Indexed: 02/13/2024]
Abstract
In mammals, thick axonal calibers wrapped with heavy myelin sheaths are prevalent in the auditory nervous system. These features are crucial for fast traveling of nerve impulses with minimal attenuation required for sound signal transmission. In particular, the long-range projections from the cochlear nucleus - the axons of globular bush cells (GBCs) - to the medial nucleus of the trapezoid body (MNTB) are tonotopically organized. However, it remains controversial in gerbils and mice whether structural and functional adaptations are present among the GBC axons targeting different MNTB frequency regions. By means of high-throughput volume electron microscopy, we compared the GBC axons in full-tonotopy-ranged MNTB slices from the C57BL/6 mice at different ages. Our quantification reveals distinct caliber diameter and myelin profile of the GBC axons with endings at lateral and medial MNTB, arguing for modulation of functionally heterogeneous axon subgroups. In addition, we reported axon-specific differences in axon caliber, node of Ranvier, and myelin sheath among juvenile, adult, and old mice, indicating the age-related changes of GBC axon morphology over time. These findings provide structural insight into the maturation and degeneration of GBC axons with frequency tuning across the lifespan of mice.
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Affiliation(s)
- Wen-Qing Huang
- Department of Otolaryngology-Head and Neck Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China; Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Department of Central Laboratory, Shanghai Children's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
| | - Haibin Sheng
- Department of Otolaryngology-Head and Neck Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Haoyu Wang
- Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yumeng Qi
- Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Fangfang Wang
- Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
| | - Yunfeng Hua
- Department of Otolaryngology-Head and Neck Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China; Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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15
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Nabel AL, Teich L, Wohlfrom H, Alexandrova O, Heß M, Pecka M, Grothe B. Development of myelination and axon diameter for fast and precise action potential conductance. Glia 2024; 72:794-808. [PMID: 38174817 DOI: 10.1002/glia.24504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 12/19/2023] [Accepted: 12/22/2023] [Indexed: 01/05/2024]
Abstract
Axons of globular bushy cells in the cochlear nucleus convey hyper-accurate signals to the superior olivary complex, the initial site of binaural processing via comparably thick axons and the calyx of the Held synapse. Bushy cell fibers involved in hyper-accurate binaural processing of low-frequency sounds are known to have an unusual internode length-to-axon caliber ratio (L/d) correlating with higher conduction velocity and superior temporal precision of action potentials. How the L/d-ratio develops and what determines this unusual myelination pattern is unclear. Here we describe a gradual developmental transition from very simple to complex, mature nodes of Ranvier on globular bushy cell axons during a 2-week period starting at postnatal day P6/7. The molecular composition of nodes matured successively along the axons from somata to synaptic terminals with morphologically and molecularly mature nodes appearing almost exclusively after hearing onset. Internodal distances are initially coherent with the canonical L/d-ratio of ~100. Several days after hearing onset, however, an over-proportional increase in axon caliber occurs in cells signaling low-frequency sounds which alters their L/d ratio to ~60. Hence, oligodendrocytes initially myelinating axons according to their transient axon caliber but a subsequent differential axon thickening after hearing onset results in the unusual myelination pattern.
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Affiliation(s)
- Alisha L Nabel
- Division of Neurobiology, Faculty of Biology, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
- Graduate School of Systemic Neurosciences, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
| | - Laurin Teich
- Division of Neurobiology, Faculty of Biology, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
- Graduate School of Systemic Neurosciences, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
- Division of Neurobiology, Faculty of Biology, Munich Cluster for Systems Neurology (SyNergy), Martinsried, Germany
| | - Hilde Wohlfrom
- Division of Neurobiology, Faculty of Biology, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
| | - Olga Alexandrova
- Division of Neurobiology, Faculty of Biology, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
| | - Martin Heß
- Division of Systematic Zoology, Faculty of Biology, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
| | - Michael Pecka
- Division of Neurobiology, Faculty of Biology, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
| | - Benedikt Grothe
- Division of Neurobiology, Faculty of Biology, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
- Division of Neurobiology, Faculty of Biology, Munich Cluster for Systems Neurology (SyNergy), Martinsried, Germany
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16
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Bartmeyer PM, Biscola NP, Havton LA. Nonbinary 2D Distribution Tool Maps Autonomic Nerve Fiber Clustering in Lumbosacral Ventral Roots of Rhesus Macaques. eNeuro 2024; 11:ENEURO.0009-23.2024. [PMID: 38548331 PMCID: PMC11015947 DOI: 10.1523/eneuro.0009-23.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 12/13/2023] [Accepted: 02/05/2024] [Indexed: 04/14/2024] Open
Abstract
Neuromodulation of the peripheral nervous system (PNS) by electrical stimulation may augment autonomic function after injury or in neurodegenerative disorders. Nerve fiber size, myelination, and distance between individual fibers and the stimulation electrode may influence response thresholds to electrical stimulation. However, information on the spatial distribution of nerve fibers within the PNS is sparse. We developed a new two-dimensional (2D) morphological mapping tool to assess spatial heterogeneity and clustering of nerve fibers. The L6-S3 ventral roots (VRs) in rhesus macaques were used as a model system to map preganglionic parasympathetic, γ-motor, and α-motor fibers. Random and ground truth distributions of nerve fiber centroids were determined for each VR by light microscopy. The proposed tool allows for nonbinary determinations of fiber heterogeneity by defining the minimum distance between nerve fibers for cluster inclusion and comparisons with random fiber distributions for each VR. There was extensive variability in the relative composition of nerve fiber types and degree of 2D fiber heterogeneity between different L6-S3 VR levels within and across different animals. There was a positive correlation between the proportion of autonomic fibers and the degree of nerve fiber clustering. Nerve fiber cluster heterogeneity between VRs may contribute to varied functional outcomes from neuromodulation.
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Affiliation(s)
- Petra M Bartmeyer
- Departments of Neurology, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Natalia P Biscola
- Departments of Neurology, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Leif A Havton
- Departments of Neurology, Icahn School of Medicine at Mount Sinai, New York, New York 10029
- Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York 10029
- James J. Peters Veterans Affairs Medical Center, Bronx, New York 10468
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17
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Bin JM, Suminaite D, Benito-Kwiecinski SK, Kegel L, Rubio-Brotons M, Early JJ, Soong D, Livesey MR, Poole RJ, Lyons DA. Importin 13-dependent axon diameter growth regulates conduction speeds along myelinated CNS axons. Nat Commun 2024; 15:1790. [PMID: 38413580 PMCID: PMC10899189 DOI: 10.1038/s41467-024-45908-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Accepted: 02/06/2024] [Indexed: 02/29/2024] Open
Abstract
Axon diameter influences the conduction properties of myelinated axons, both directly, and indirectly through effects on myelin. However, we have limited understanding of mechanisms controlling axon diameter growth in the central nervous system, preventing systematic dissection of how manipulating diameter affects myelination and conduction along individual axons. Here we establish zebrafish to study axon diameter. We find that importin 13b is required for axon diameter growth, but does not affect cell body size or axon length. Using neuron-specific ipo13b mutants, we assess how reduced axon diameter affects myelination and conduction, and find no changes to myelin thickness, precision of action potential propagation, or ability to sustain high frequency firing. However, increases in conduction speed that occur along single myelinated axons with development are tightly linked to their growth in diameter. This suggests that axon diameter growth is a major driver of increases in conduction speeds along myelinated axons over time.
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Affiliation(s)
- Jenea M Bin
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK.
| | - Daumante Suminaite
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | | | - Linde Kegel
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Maria Rubio-Brotons
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Jason J Early
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Daniel Soong
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Matthew R Livesey
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
- Sheffield Institute for Translational Neuroscience, University of Sheffield, Sheffield, S10 2HQ, UK
- Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
| | - Richard J Poole
- Department of Cell and Developmental Biology, University College London, London, WC1E 6BT, UK
| | - David A Lyons
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK.
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18
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Zhang Z, Wang W, Huang X, Liu G. Distributed loss-amplification modeling for the mid-infrared signal propagating in the myelinated and demyelinated nerve. APPLIED OPTICS 2023; 62:8606-8613. [PMID: 38037977 DOI: 10.1364/ao.503485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Accepted: 10/20/2023] [Indexed: 12/02/2023]
Abstract
The terahertz (THz) to infrared (IR) neural signal model is a potential mechanism for explaining neural communication. Myelinated neurons could be a lossy dielectric waveguide that can propagate these THz-IR neural signals. We propose an electromagnetic loss-amplification model to describe the propagation characteristics of mid-IR signals on myelinated neurons. During transmission with loss and amplification, neural signal intensity can be consistently maintained at 15.9 pW in bands 55 to 75 THz. This phenomenon becomes more pronounced as the number of myelin sheaths increases. However, escalated degrees of demyelination result in a reduction of signal intensity from 15.9 to 10 pW. This phenomenon eventually disrupts the process of loss amplification, consequently impeding the transmission of the signal. These results may contribute to a deeper understanding of mid-IR signal propagation mechanisms in myelinated nerves and studies of diseases associated with demyelination.
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19
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Carrillo-Barberà P, Rondelli AM, Morante-Redolat JM, Vernay B, Williams A, Bankhead P. AimSeg: A machine-learning-aided tool for axon, inner tongue and myelin segmentation. PLoS Comput Biol 2023; 19:e1010845. [PMID: 37976310 PMCID: PMC10691719 DOI: 10.1371/journal.pcbi.1010845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Revised: 12/01/2023] [Accepted: 11/05/2023] [Indexed: 11/19/2023] Open
Abstract
Electron microscopy (EM) images of axons and their ensheathing myelin from both the central and peripheral nervous system are used for assessing myelin formation, degeneration (demyelination) and regeneration (remyelination). The g-ratio is the gold standard measure of assessing myelin thickness and quality, and traditionally is determined from measurements made manually from EM images-a time-consuming endeavour with limited reproducibility. These measurements have also historically neglected the innermost uncompacted myelin sheath, known as the inner tongue. Nonetheless, the inner tongue has been shown to be important for myelin growth and some studies have reported that certain conditions can elicit its enlargement. Ignoring this fact may bias the standard g-ratio analysis, whereas quantifying the uncompacted myelin has the potential to provide novel insights in the myelin field. In this regard, we have developed AimSeg, a bioimage analysis tool for axon, inner tongue and myelin segmentation. Aided by machine learning classifiers trained on transmission EM (TEM) images of tissue undergoing remyelination, AimSeg can be used either as an automated workflow or as a user-assisted segmentation tool. Validation results on TEM data from both healthy and remyelinating samples show good performance in segmenting all three fibre components, with the assisted segmentation showing the potential for further improvement with minimal user intervention. This results in a considerable reduction in time for analysis compared with manual annotation. AimSeg could also be used to build larger, high quality ground truth datasets to train novel deep learning models. Implemented in Fiji, AimSeg can use machine learning classifiers trained in ilastik. This, combined with a user-friendly interface and the ability to quantify uncompacted myelin, makes AimSeg a unique tool to assess myelin growth.
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Affiliation(s)
- Pau Carrillo-Barberà
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Universitat de València, Valencia, Spain
- Departamento de Biología Celular, Biología Funcional y Antropología Física, Universitat de València, Valencia, Spain
- Instituto de Biotecnología y Biomedicina (BioTecMed), Universitat de València, Valencia, Spain
- Centre for Genomic & Experimental Medicine, Institute of Genetics and Cancer, University of Edinburgh, Edinburgh, United Kingdom
| | - Ana Maria Rondelli
- Centre for Regenerative Medicine, Institute for Regeneration and Repair, University of Edinburgh, Edinburgh BioQuarter, Edinburgh, United Kingdom
- MS Society Edinburgh Centre for MS Research, Edinburgh BioQuarter, Edinburgh, United Kingdom
| | - Jose Manuel Morante-Redolat
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Universitat de València, Valencia, Spain
- Departamento de Biología Celular, Biología Funcional y Antropología Física, Universitat de València, Valencia, Spain
- Instituto de Biotecnología y Biomedicina (BioTecMed), Universitat de València, Valencia, Spain
| | - Bertrand Vernay
- Centre for Regenerative Medicine, Institute for Regeneration and Repair, University of Edinburgh, Edinburgh BioQuarter, Edinburgh, United Kingdom
- Centre d’imagerie, Institut de Génétique et de Biologie Moléculaire et Cellulaire CNRS UMR 7104—Inserm U 1258, Illkirch, France
| | - Anna Williams
- Centre for Regenerative Medicine, Institute for Regeneration and Repair, University of Edinburgh, Edinburgh BioQuarter, Edinburgh, United Kingdom
- MS Society Edinburgh Centre for MS Research, Edinburgh BioQuarter, Edinburgh, United Kingdom
| | - Peter Bankhead
- Centre for Genomic & Experimental Medicine, Institute of Genetics and Cancer, University of Edinburgh, Edinburgh, United Kingdom
- Edinburgh Pathology and CRUK Scotland Centre, Institute of Genetics and Cancer, University of Edinburgh, Edinburgh, United Kingdom
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Escelsior A, Inuggi A, Amadeo MB, Engel-Yeger B, Trabucco A, Esposito D, Campus C, Bovio A, Comparini S, Pereira da Silva B, Serafini G, Gori M, Amore M. Sensation seeking correlates with increased white matter integrity of structures associated with visuospatial processing in healthy adults. Front Neurosci 2023; 17:1267700. [PMID: 37954876 PMCID: PMC10637364 DOI: 10.3389/fnins.2023.1267700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 10/03/2023] [Indexed: 11/14/2023] Open
Abstract
Introduction The ability to process sensory information is an essential adaptive function, and hyper- or hypo-sensitive maladaptive profiles of responses to environmental stimuli generate sensory processing disorders linked to cognitive, affective, and behavioral alterations. Consequently, assessing sensory processing profiles might help research the vulnerability and resilience to mental disorders. The research on neuroradiological correlates of the sensory processing profiles is mainly limited to the young-age population or neurodevelopmental disorders. So, this study aims to examine the structural MRI correlates of sensory profiles in a sample of typically developed adults. Methods We investigated structural cortical thickness (CT) and white matter integrity, through Diffusion Tensor Imaging (DTI), correlates of Adolescent/Adult Sensory Profile (AASP) questionnaire subscales in 57 typical developing subjects (34F; mean age: 32.7 ± 9.3). Results We found significant results only for the sensation seeking (STS) subscale. Positive and negative correlations emerged with fractional anisotropy (FA) and radial diffusivity (RD) in anterior thalamic radiation, optic radiation, superior longitudinal fasciculus, corpus callosum, and the cingulum bundle. No correlation between sensation seeking and whole brain cortical thickness was found. Discussion Overall, our results suggest a positive correlation between sensation seeking and higher white matter structural integrity in those tracts mainly involved in visuospatial processing but no correlation with gray matter structure. The enhanced structural integrity associated with sensation seeking may reflect a neurobiological substrate linked to active research of sensory stimuli and resilience to major psychiatric disorders like schizophrenia, bipolar disorder, and depression.
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Affiliation(s)
- Andrea Escelsior
- Section of Psychiatry, Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), University of Genoa, Genoa, Italy
- IRCCS Ospedale Policlinico San Martino, Genoa, Italy
| | - Alberto Inuggi
- Section of Psychiatry, Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), University of Genoa, Genoa, Italy
| | - Maria Bianca Amadeo
- U-VIP Unit for Visually Impaired People, Fondazione Istituto Italiano di Tecnologia, Genoa, Italy
| | - Batya Engel-Yeger
- Faculty of Social Welfare and Health Sciences, Department of Occupational Therapy, University of Haifa, Haifa, Israel
| | - Alice Trabucco
- Section of Psychiatry, Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), University of Genoa, Genoa, Italy
- IRCCS Ospedale Policlinico San Martino, Genoa, Italy
| | - Davide Esposito
- U-VIP Unit for Visually Impaired People, Fondazione Istituto Italiano di Tecnologia, Genoa, Italy
| | - Claudio Campus
- U-VIP Unit for Visually Impaired People, Fondazione Istituto Italiano di Tecnologia, Genoa, Italy
| | - Anna Bovio
- Section of Psychiatry, Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), University of Genoa, Genoa, Italy
| | - Sara Comparini
- Section of Psychiatry, Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), University of Genoa, Genoa, Italy
| | - Beatriz Pereira da Silva
- Section of Psychiatry, Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), University of Genoa, Genoa, Italy
| | - Gianluca Serafini
- Section of Psychiatry, Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), University of Genoa, Genoa, Italy
- IRCCS Ospedale Policlinico San Martino, Genoa, Italy
| | - Monica Gori
- U-VIP Unit for Visually Impaired People, Fondazione Istituto Italiano di Tecnologia, Genoa, Italy
| | - Mario Amore
- Section of Psychiatry, Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), University of Genoa, Genoa, Italy
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Wu L, Wang F, Moncman CL, Pandey M, Clarke HA, Frazier HN, Young LE, Gentry MS, Cai W, Thibault O, Sun RC, Andres DA. RIT1 regulation of CNS lipids RIT1 deficiency Alters cerebral lipid metabolism and reduces white matter tract oligodendrocytes and conduction velocities. Heliyon 2023; 9:e20384. [PMID: 37780758 PMCID: PMC10539968 DOI: 10.1016/j.heliyon.2023.e20384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 07/21/2023] [Accepted: 09/20/2023] [Indexed: 10/03/2023] Open
Abstract
Oligodendrocytes (OLs) generate lipid-rich myelin membranes that wrap axons to enable efficient transmission of electrical impulses. Using a RIT1 knockout mouse model and in situ high-resolution matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) coupled with MS-based lipidomic analysis to determine the contribution of RIT1 to lipid homeostasis. Here, we report that RIT1 loss is associated with altered lipid levels in the central nervous system (CNS), including myelin-associated lipids within the corpus callosum (CC). Perturbed lipid metabolism was correlated with reduced numbers of OLs, but increased numbers of GFAP+ glia, in the CC, but not in grey matter. This was accompanied by reduced myelin protein expression and axonal conduction deficits. Behavioral analyses revealed significant changes in voluntary locomotor activity and anxiety-like behavior in RIT1KO mice. Together, these data reveal an unexpected role for RIT1 in the regulation of cerebral lipid metabolism, which coincide with altered white matter tract oligodendrocyte levels, reduced axonal conduction velocity, and behavioral abnormalities in the CNS.
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Affiliation(s)
- Lei Wu
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, KY 40536, USA
| | - Fang Wang
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, KY 40536, USA
| | - Carole L. Moncman
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, KY 40536, USA
| | - Mritunjay Pandey
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, KY 40536, USA
| | - Harrison A. Clarke
- Department of Neuroscience, College of Medicine, University of Kentucky, KY 40536, USA
| | - Hilaree N. Frazier
- Department of Pharmacological and Nutritional Sciences, College of Medicine, University of Kentucky, KY 40536, USA
| | - Lyndsay E.A. Young
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, KY 40536, USA
- Markey Cancer Center, Lexington, KY 40536, USA
| | - Matthew S. Gentry
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, KY 40536, USA
- Markey Cancer Center, Lexington, KY 40536, USA
- Department of Biochemistry and Molecular Biology, University of Florida, College of Medicine, Gainesville, FL 32611, USA
- Center for Advanced Spatial Biomolecule Research, University of Florida, College of Medicine, Gainesville, FL 32611, USA
| | - Weikang Cai
- Department of Biomedical Sciences, New York Institute of Technology College of Osteopathic Medicine, NY 11568, USA
| | - Olivier Thibault
- Department of Pharmacological and Nutritional Sciences, College of Medicine, University of Kentucky, KY 40536, USA
| | - Ramon C. Sun
- Department of Neuroscience, College of Medicine, University of Kentucky, KY 40536, USA
- Markey Cancer Center, Lexington, KY 40536, USA
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY 40536, USA
- Department of Biochemistry and Molecular Biology, University of Florida, College of Medicine, Gainesville, FL 32611, USA
- Center for Advanced Spatial Biomolecule Research, University of Florida, College of Medicine, Gainesville, FL 32611, USA
| | - Douglas A. Andres
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, KY 40536, USA
- Markey Cancer Center, Lexington, KY 40536, USA
- Spinal Cord and Brain Injury Research Center, College of Medicine, University of Kentucky, KY 40536, USA
- Gill Heart and Vascular Institute, College of Medicine, University of Kentucky, Lexington, KY 40536, USA
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22
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Anagnostou E, Xirou S, Aristeidou S, Koutsoudaki P, Kokotis P, Karandreas N, Zambelis T. The Rise Slope of the Compound Sensory Nerve Action Potential in Normal and Pathological Human Nerves. Neurodiagn J 2023; 63:190-204. [PMID: 37549426 DOI: 10.1080/21646821.2023.2235956] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2023] [Accepted: 07/10/2023] [Indexed: 08/09/2023]
Abstract
In spite of the diagnostic importance of the early phase of the sensory nerve action potential (SNAP), reliable electrodiagnostic metrics for this part of the recorded waveform are lacking. The average rise slope of the SNAP appreciates the steepness of the initial negative deflection of the waveform, which might be a useful metric for the first part of the potential. Sural nerve sensory neurography was performed in patients with various axonal neuropathies, and median nerve sensory studies were carried out in patients with carpal tunnel syndrome. Age-matched healthy individuals served as controls. The rise slope was compared to conventional SNAP parameters such as conduction velocity, latency, duration, and rise time. Overall, 537 sensory studies were prospectively analyzed. The rise slope of the sural SNAP demonstrated superior classification performance in terms of sensitivity (92.5%), specificity (97%), and area under the receiver operating characteristic curve (0.986), as compared to conventional SNAP parameters. Its diagnostic power was similarly excellent in median nerve studies, whereas here a slightly better classification performance was obtained by SNAP latency and conduction velocity. The average rise slope appears to do justice to the tight interplay between amplitude and rise time of the initial negative spike deflection, outperforming many conventional measures. This composite metric proved high diagnostic potency in particular with regard to axonal sensory nerve dysfunction.
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Affiliation(s)
- Evangelos Anagnostou
- Department of Neurology National and Kapodistrian University of Athens, Eginition Hospital, Athens, Greece
| | - Sophia Xirou
- Department of Neurology National and Kapodistrian University of Athens, Eginition Hospital, Athens, Greece
| | - Stavroula Aristeidou
- Department of Neurology National and Kapodistrian University of Athens, Eginition Hospital, Athens, Greece
| | - Pinelopi Koutsoudaki
- Department of Neurology National and Kapodistrian University of Athens, Eginition Hospital, Athens, Greece
| | - Panagiotis Kokotis
- Department of Neurology National and Kapodistrian University of Athens, Eginition Hospital, Athens, Greece
| | - Nikos Karandreas
- Department of Neurology National and Kapodistrian University of Athens, Eginition Hospital, Athens, Greece
| | - Thomas Zambelis
- Department of Neurology National and Kapodistrian University of Athens, Eginition Hospital, Athens, Greece
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23
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Pukos N, Marion CM, Arnold WD, Noble BT, Popovich PG, McTigue DM. Chronic demyelination and myelin repair after spinal cord injury in mice: A potential link for glutamatergic axon activity. Glia 2023; 71:2096-2116. [PMID: 37208933 PMCID: PMC10330449 DOI: 10.1002/glia.24382] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Revised: 04/08/2023] [Accepted: 04/20/2023] [Indexed: 05/21/2023]
Abstract
Our prior work examining endogenous repair after spinal cord injury (SCI) in mice revealed that large numbers of new oligodendrocytes (OLs) are generated in the injured spinal cord, with peak oligodendrogenesis between 4 and 7 weeks post-injury (wpi). We also detected new myelin formation over 2 months post-injury (mpi). Our current work significantly extends these results, including quantification of new myelin through 6 mpi and concomitant examination of indices of demyelination. We also examined electrophysiological changes during peak oligogenesis and a potential mechanism driving OL progenitor cell (OPC) contact with axons. Results reveal peak in remyelination occurs during the 3rd mpi, and that myelin generation continues for at least 6 mpi. Further, motor evoked potentials significantly increased during peak remyelination, suggesting enhanced axon potential conduction. Interestingly, two indices of demyelination, nodal protein spreading and Nav1.2 upregulation, were also present chronically after SCI. Nav1.2 was expressed through 10 wpi and nodal protein disorganization was detectable throughout 6 mpi suggesting chronic demyelination, which was confirmed with EM. Thus, demyelination may continue chronically, which could trigger the long-term remyelination response. To examine a potential mechanism that may initiate post-injury myelination, we show that OPC processes contact glutamatergic axons in the injured spinal cord in an activity-dependent manner. Notably, these OPC/axon contacts were increased 2-fold when axons were activated chemogenetically, revealing a potential therapeutic target to enhance post-SCI myelin repair. Collectively, results show the surprisingly dynamic nature of the injured spinal cord over time and that the tissue may be amenable to treatments targeting chronic demyelination.
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Affiliation(s)
- Nicole Pukos
- Neuroscience Graduate Program, Ohio State University, Columbus, Ohio, USA
- Belford Center for Spinal Cord Injury, Ohio State University, Columbus, Ohio, USA
| | - Christina M Marion
- Belford Center for Spinal Cord Injury, Ohio State University, Columbus, Ohio, USA
- Department of Neuroscience, College of Medicine, Ohio State University, Columbus, Ohio, USA
| | - W David Arnold
- Department of Neuroscience, College of Medicine, Ohio State University, Columbus, Ohio, USA
- Division of Neuromuscular Disorders, Department of Neurology, Wexner Medical Center, Ohio State University, Columbus, Ohio, USA
- Department of Physical Medicine and Rehabilitation, Wexner Medical Center, Ohio State University, Columbus, Ohio, USA
- Department of Physiology and Cell Biology, College of Medicine, Ohio State University, Columbus, Ohio, USA
| | - Benjamin T Noble
- Neuroscience Graduate Program, Ohio State University, Columbus, Ohio, USA
- Belford Center for Spinal Cord Injury, Ohio State University, Columbus, Ohio, USA
| | - Phillip G Popovich
- Belford Center for Spinal Cord Injury, Ohio State University, Columbus, Ohio, USA
- Department of Neuroscience, College of Medicine, Ohio State University, Columbus, Ohio, USA
| | - Dana M McTigue
- Belford Center for Spinal Cord Injury, Ohio State University, Columbus, Ohio, USA
- Department of Neuroscience, College of Medicine, Ohio State University, Columbus, Ohio, USA
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24
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Ibañez S, Sengupta N, Luebke JI, Wimmer K, Weaver CM. Myelin dystrophy in the aging prefrontal cortex leads to impaired signal transmission and working memory decline: a multiscale computational study. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.30.555476. [PMID: 37693412 PMCID: PMC10491254 DOI: 10.1101/2023.08.30.555476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
Normal aging leads to myelin alternations in the rhesus monkey dorsolateral prefrontal cortex (dlPFC), which are often correlated with cognitive impairment. It is hypothesized that remyelination with shorter and thinner myelin sheaths partially compensates for myelin degradation, but computational modeling has not yet explored these two phenomena together systematically. Here, we used a two-pronged modeling approach to determine how age-related myelin changes affect a core cognitive function: spatial working memory. First we built a multicompartment pyramidal neuron model fit to monkey dlPFC data, with axon including myelinated segments having paranodes, juxtaparanodes, internodes, and tight junctions, to quantify conduction velocity (CV) changes and action potential (AP) failures after demyelination and subsequent remyelination in a population of neurons. Lasso regression identified distinctive parameter sets likely to modulate an axon's susceptibility to CV changes following demyelination versus remyelination. Next we incorporated the single neuron results into a spiking neural network model of working memory. While complete remyelination nearly recovered axonal transmission and network function to unperturbed levels, our models predict that biologically plausible levels of myelin dystrophy, if uncompensated by other factors, can account for substantial working memory impairment with aging. The present computational study unites empirical data from electron microscopy up to behavior on aging, and has broader implications for many demyelinating conditions, such as multiple sclerosis or schizophrenia.
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Affiliation(s)
- Sara Ibañez
- Department of Anatomy & Neurobiology, Boston University Chobanian & Avedisian School of Medicine, Boston, MA USA 02118
- Centre de Recerca Matemàtica, Edifici C, Campus Bellaterra, 08193 Bellaterra, Spain
| | - Nilapratim Sengupta
- Department of Anatomy & Neurobiology, Boston University Chobanian & Avedisian School of Medicine, Boston, MA USA 02118
- Department of Mathematics, Franklin and Marshall College, Lancaster, PA, USA 17604
| | - Jennifer I Luebke
- Department of Anatomy & Neurobiology, Boston University Chobanian & Avedisian School of Medicine, Boston, MA USA 02118
| | - Klaus Wimmer
- Centre de Recerca Matemàtica, Edifici C, Campus Bellaterra, 08193 Bellaterra, Spain
| | - Christina M Weaver
- Department of Mathematics, Franklin and Marshall College, Lancaster, PA, USA 17604
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25
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Radivojevic M, Rostedt Punga A. Functional imaging of conduction dynamics in cortical and spinal axons. eLife 2023; 12:e86512. [PMID: 37606618 PMCID: PMC10444024 DOI: 10.7554/elife.86512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 08/09/2023] [Indexed: 08/23/2023] Open
Abstract
Mammalian axons are specialized for transmitting action potentials to targets within the central and peripheral nervous system. A growing body of evidence suggests that, besides signal conduction, axons play essential roles in neural information processing, and their malfunctions are common hallmarks of neurodegenerative diseases. The technologies available to study axonal function and structure integrally limit the comprehension of axon neurobiology. High-density microelectrode arrays (HD-MEAs) allow for accessing axonal action potentials at high spatiotemporal resolution, but provide no insights on axonal morphology. Here, we demonstrate a method for electrical visualization of axonal morphologies based on extracellular action potentials recorded from cortical and motor neurons using HD-MEAs. The method enabled us to reconstruct up to 5-cm-long axonal arbors and directly monitor axonal conduction across thousands of recording sites. We reconstructed 1.86 m of cortical and spinal axons in total and found specific features in their structure and function.
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26
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Castaldo F, Páscoa Dos Santos F, Timms RC, Cabral J, Vohryzek J, Deco G, Woolrich M, Friston K, Verschure P, Litvak V. Multi-modal and multi-model interrogation of large-scale functional brain networks. Neuroimage 2023; 277:120236. [PMID: 37355200 PMCID: PMC10958139 DOI: 10.1016/j.neuroimage.2023.120236] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 06/14/2023] [Accepted: 06/16/2023] [Indexed: 06/26/2023] Open
Abstract
Existing whole-brain models are generally tailored to the modelling of a particular data modality (e.g., fMRI or MEG/EEG). We propose that despite the differing aspects of neural activity each modality captures, they originate from shared network dynamics. Building on the universal principles of self-organising delay-coupled nonlinear systems, we aim to link distinct features of brain activity - captured across modalities - to the dynamics unfolding on a macroscopic structural connectome. To jointly predict connectivity, spatiotemporal and transient features of distinct signal modalities, we consider two large-scale models - the Stuart Landau and Wilson and Cowan models - which generate short-lived 40 Hz oscillations with varying levels of realism. To this end, we measure features of functional connectivity and metastable oscillatory modes (MOMs) in fMRI and MEG signals - and compare them against simulated data. We show that both models can represent MEG functional connectivity (FC), functional connectivity dynamics (FCD) and generate MOMs to a comparable degree. This is achieved by adjusting the global coupling and mean conduction time delay and, in the WC model, through the inclusion of balance between excitation and inhibition. For both models, the omission of delays dramatically decreased the performance. For fMRI, the SL model performed worse for FCD and MOMs, highlighting the importance of balanced dynamics for the emergence of spatiotemporal and transient patterns of ultra-slow dynamics. Notably, optimal working points varied across modalities and no model was able to achieve a correlation with empirical FC higher than 0.4 across modalities for the same set of parameters. Nonetheless, both displayed the emergence of FC patterns that extended beyond the constraints of the anatomical structure. Finally, we show that both models can generate MOMs with empirical-like properties such as size (number of brain regions engaging in a mode) and duration (continuous time interval during which a mode appears). Our results demonstrate the emergence of static and dynamic properties of neural activity at different timescales from networks of delay-coupled oscillators at 40 Hz. Given the higher dependence of simulated FC on the underlying structural connectivity, we suggest that mesoscale heterogeneities in neural circuitry may be critical for the emergence of parallel cross-modal functional networks and should be accounted for in future modelling endeavours.
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Affiliation(s)
- Francesca Castaldo
- Wellcome Centre for Human Neuroimaging, UCL Queen Square Institute of Neurology, London, United Kingdom.
| | - Francisco Páscoa Dos Santos
- Eodyne Systems SL, Barcelona, Spain; Department of Information and Communication Technologies, Universitat Pompeu Fabra, Barcelona, Spain
| | - Ryan C Timms
- Wellcome Centre for Human Neuroimaging, UCL Queen Square Institute of Neurology, London, United Kingdom
| | - Joana Cabral
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal; ICVS/3B's - Portuguese Government Associate Laboratory, Braga/Guimarães, Portugal; Centre for Eudaimonia and Human Flourishing, Linacre College, University of Oxford, United United Kingdom
| | - Jakub Vohryzek
- Centre for Eudaimonia and Human Flourishing, Linacre College, University of Oxford, United United Kingdom; Centre for Brain and Cognition, Computational Neuroscience Group, Universitat Pompeu Fabra, Barcelona, Spain
| | - Gustavo Deco
- Centre for Brain and Cognition, Computational Neuroscience Group, Universitat Pompeu Fabra, Barcelona, Spain; Institució Catalana de la Recerca i Estudis Avançats (ICREA), Barcelona, Spain; Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; School of Psychological Sciences, Monash University, Melbourne, Australia
| | - Mark Woolrich
- Wellcome Centre for Integrative Neuroimaging, University of Oxford, Oxford, United Kingdom
| | - Karl Friston
- Wellcome Centre for Human Neuroimaging, UCL Queen Square Institute of Neurology, London, United Kingdom
| | - Paul Verschure
- Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, The Netherlands
| | - Vladimir Litvak
- Wellcome Centre for Human Neuroimaging, UCL Queen Square Institute of Neurology, London, United Kingdom
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27
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Kempe PRG, de Castro MV, Khuriyeh VC, Barraviera B, Ferreira RS, de Oliveira ALR. Ultrastructural Evidence of Synapse Preservation and Axonal Regeneration Following Spinal Root Repair with Fibrin Biopolymer and Therapy with Dimethyl Fumarate. Polymers (Basel) 2023; 15:3171. [PMID: 37571065 PMCID: PMC10421511 DOI: 10.3390/polym15153171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 07/16/2023] [Accepted: 07/19/2023] [Indexed: 08/13/2023] Open
Abstract
Spinal cord injury causes critical loss in motor and sensory function. Ventral root avulsion is an experimental model in which there is the tearing of the ventral (motor) roots from the surface of the spinal cord, resulting in several morphological changes, including motoneuron degeneration and local spinal cord circuitry rearrangements. Therefore, our goal was to test the combination of surgical repair of lesioned roots with a fibrin biopolymer and the pharmacological treatment with dimethyl fumarate, an immunomodulatory drug. Thus, adult female Lewis rats were subjected to unilateral ventral root avulsion of L4-L6 roots followed by repair with fibrin biopolymer and daily treatment with dimethyl fumarate (15 mg/Kg; gavage) for 4 weeks, the survival time post-surgery being 12 weeks; n = 5/group/technique. Treatments were evaluated by immunofluorescence and transmission electron microscopy, morphometry of the sciatic nerve, and motor function recovery. Our results indicate that the combination between fibrin biopolymer and dimethyl fumarate is neuroprotective since most of the synapses apposed to alfa motoneurons were preserved in clusters. Also, nerve sprouting occurred, and the restoration of the 'g' ratio and large axon diameter was achieved with the combined treatment. Such parameters were combined with up to 50% of gait recovery, observed by the walking track test. Altogether, our results indicate that combining root restoration with fibrin biopolymer and dimethyl fumarate administration can enhance motoneuron survival and regeneration after proximal lesions.
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Affiliation(s)
- Paula Regina Gelinski Kempe
- Laboratory of Nerve Regeneration, Department of Structural and Functional Biology, Institute of Biology, University of Campinas, Campinas 13083-862, SP, Brazil; (P.R.G.K.); (M.V.d.C.); (V.C.K.)
| | - Mateus Vidigal de Castro
- Laboratory of Nerve Regeneration, Department of Structural and Functional Biology, Institute of Biology, University of Campinas, Campinas 13083-862, SP, Brazil; (P.R.G.K.); (M.V.d.C.); (V.C.K.)
| | - Victor Campos Khuriyeh
- Laboratory of Nerve Regeneration, Department of Structural and Functional Biology, Institute of Biology, University of Campinas, Campinas 13083-862, SP, Brazil; (P.R.G.K.); (M.V.d.C.); (V.C.K.)
| | - Benedito Barraviera
- Center for the Study of Venoms and Venomous Animals (CEVAP), São Paulo State University (UNESP), Botucatu 18610-307, SP, Brazil; (B.B.); (R.S.F.J.)
| | - Rui Seabra Ferreira
- Center for the Study of Venoms and Venomous Animals (CEVAP), São Paulo State University (UNESP), Botucatu 18610-307, SP, Brazil; (B.B.); (R.S.F.J.)
| | - Alexandre Leite Rodrigues de Oliveira
- Laboratory of Nerve Regeneration, Department of Structural and Functional Biology, Institute of Biology, University of Campinas, Campinas 13083-862, SP, Brazil; (P.R.G.K.); (M.V.d.C.); (V.C.K.)
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28
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Griswold JM, Bonilla-Quintana M, Pepper R, Lee CT, Raychaudhuri S, Ma S, Gan Q, Syed S, Zhu C, Bell M, Suga M, Yamaguchi Y, Chéreau R, Nägerl UV, Knott G, Rangamani P, Watanabe S. Membrane mechanics dictate axonal morphology and function. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.20.549958. [PMID: 37503105 PMCID: PMC10370128 DOI: 10.1101/2023.07.20.549958] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Axons are thought to be ultrathin membrane cables of a relatively uniform diameter, designed to conduct electrical signals, or action potentials. Here, we demonstrate that unmyelinated axons are not simple cylindrical tubes. Rather, axons have nanoscopic boutons repeatedly along their length interspersed with a thin cable with a diameter of ∼60 nm like pearls-on-a-string. These boutons are only ∼200 nm in diameter and do not have synaptic contacts or a cluster of synaptic vesicles, hence non-synaptic. Our in silico modeling suggests that axon pearling can be explained by the mechanical properties of the membrane including the bending modulus and tension. Consistent with modeling predictions, treatments that disrupt these parameters like hyper- or hypo-tonic solutions, cholesterol removal, and non-muscle myosin II inhibition all alter the degree of axon pearling, suggesting that axon morphology is indeed determined by the membrane mechanics. Intriguingly, neuronal activity modulates the cholesterol level of plasma membrane, leading to shrinkage of axon pearls. Consequently, the conduction velocity of action potentials becomes slower. These data reveal that biophysical forces dictate axon morphology and function and that modulation of membrane mechanics likely underlies plasticity of unmyelinated axons.
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29
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Gast H, Horowitz A, Krupnik R, Barazany D, Lifshits S, Ben-Amitay S, Assaf Y. A Method for In-Vivo Mapping of Axonal Diameter Distributions in the Human Brain Using Diffusion-Based Axonal Spectrum Imaging (AxSI). Neuroinformatics 2023; 21:469-482. [PMID: 37036548 PMCID: PMC10406702 DOI: 10.1007/s12021-023-09630-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/24/2023] [Indexed: 04/11/2023]
Abstract
In this paper we demonstrate a generalized and simplified pipeline called axonal spectrum imaging (AxSI) for in-vivo estimation of axonal characteristics in the human brain. Whole-brain estimation of the axon diameter, in-vivo and non-invasively, across all fiber systems will allow exploring uncharted aspects of brain structure and function relations with emphasis on connectivity and connectome analysis. While axon diameter mapping is important in and of itself, its correlation with conduction velocity will allow, for the first time, the explorations of information transfer mechanisms within the brain. We demonstrate various well-known aspects of axonal morphometry (e.g., the corpus callosum axon diameter variation) as well as other aspects that are less explored (e.g., axon diameter-based separation of the superior longitudinal fasciculus into segments). Moreover, we have created an MNI based mean axon diameter map over the entire brain for a large cohort of subjects providing the reference basis for future studies exploring relation between axon properties, its connectome representation, and other functional and behavioral aspects of the brain.
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Affiliation(s)
- Hila Gast
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.
| | - Assaf Horowitz
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Ronnie Krupnik
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Daniel Barazany
- The Strauss center for neuroimaging, Tel Aviv University, Tel Aviv, Israel
| | - Shlomi Lifshits
- Department of Statistics and Operations Research, Faculty of Exact Sciences, Tel Aviv University, Tel-Aviv, Israel
| | - Shani Ben-Amitay
- School of Neurobiology, Biochemistry and Biophysics, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Yaniv Assaf
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
- The Strauss center for neuroimaging, Tel Aviv University, Tel Aviv, Israel
- School of Neurobiology, Biochemistry and Biophysics, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
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30
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Spirou GA, Kersting M, Carr S, Razzaq B, Yamamoto Alves Pinto C, Dawson M, Ellisman MH, Manis PB. High-resolution volumetric imaging constrains compartmental models to explore synaptic integration and temporal processing by cochlear nucleus globular bushy cells. eLife 2023; 12:e83393. [PMID: 37288824 PMCID: PMC10435236 DOI: 10.7554/elife.83393] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 06/07/2023] [Indexed: 06/09/2023] Open
Abstract
Globular bushy cells (GBCs) of the cochlear nucleus play central roles in the temporal processing of sound. Despite investigation over many decades, fundamental questions remain about their dendrite structure, afferent innervation, and integration of synaptic inputs. Here, we use volume electron microscopy (EM) of the mouse cochlear nucleus to construct synaptic maps that precisely specify convergence ratios and synaptic weights for auditory nerve innervation and accurate surface areas of all postsynaptic compartments. Detailed biophysically based compartmental models can help develop hypotheses regarding how GBCs integrate inputs to yield their recorded responses to sound. We established a pipeline to export a precise reconstruction of auditory nerve axons and their endbulb terminals together with high-resolution dendrite, soma, and axon reconstructions into biophysically detailed compartmental models that could be activated by a standard cochlear transduction model. With these constraints, the models predict auditory nerve input profiles whereby all endbulbs onto a GBC are subthreshold (coincidence detection mode), or one or two inputs are suprathreshold (mixed mode). The models also predict the relative importance of dendrite geometry, soma size, and axon initial segment length in setting action potential threshold and generating heterogeneity in sound-evoked responses, and thereby propose mechanisms by which GBCs may homeostatically adjust their excitability. Volume EM also reveals new dendritic structures and dendrites that lack innervation. This framework defines a pathway from subcellular morphology to synaptic connectivity, and facilitates investigation into the roles of specific cellular features in sound encoding. We also clarify the need for new experimental measurements to provide missing cellular parameters, and predict responses to sound for further in vivo studies, thereby serving as a template for investigation of other neuron classes.
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Affiliation(s)
- George A Spirou
- Department of Medical Engineering, University of South FloridaTampaUnited States
| | - Matthew Kersting
- Department of Medical Engineering, University of South FloridaTampaUnited States
| | - Sean Carr
- Department of Medical Engineering, University of South FloridaTampaUnited States
| | - Bayan Razzaq
- Department of Otolaryngology, Head and Neck Surgery, West Virginia UniversityMorgantownUnited States
| | | | - Mariah Dawson
- Department of Otolaryngology, Head and Neck Surgery, West Virginia UniversityMorgantownUnited States
| | - Mark H Ellisman
- Department of Neurosciences, University of California, San DiegoSan DiegoUnited States
- National Center for Microscopy and Imaging Research,University of California, San DiegoSan DiegoUnited States
| | - Paul B Manis
- Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel HillChapel HillUnited States
- Department of Cell Biology and Physiology, University of North CarolinaChapel HillUnited States
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31
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Ciotu CI, Kistner K, Kaindl U, Millesi F, Weiss T, Radtke C, Kremer A, Schmidt K, Fischer MJM. Schwann cell stimulation induces functional and structural changes in peripheral nerves. Glia 2023; 71:945-956. [PMID: 36495059 DOI: 10.1002/glia.24316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 11/19/2022] [Accepted: 11/24/2022] [Indexed: 12/14/2022]
Abstract
Signal propagation is the essential function of nerves. Lysophosphatidic acid 18:1 (LPA) allows the selective stimulation of calcium signaling in Schwann cells but not neurons. Here, the time course of slowing and amplitude reduction on compound action potentials due to LPA exposure was observed in myelinated and unmyelinated fibers of the mouse, indicating a clear change of axonal function. Teased nerve fiber imaging showed that Schwann cell activation is also present in axon-attached Schwann cells in freshly isolated peripheral rat nerves. The LPA receptor 1 was primarily localized at the cell extensions in isolated rat Schwann cells, suggesting a role in cell migration. Structural investigation of rat C-fibers demonstrated that LPA leads to an evagination of the axons from their Schwann cells. In A-fibers, the nodes of Ranvier appeared unchanged, but the Schmidt-Lanterman incisures were shortened and myelination reduced. The latter might increase leak current, reducing the potential spread to the next node of Ranvier and explain the changes in conduction velocity. The observed structural changes provide a plausible explanation for the functional changes in myelinated and unmyelinated axons of peripheral nerves and the reported sensory sensations such as itch and pain.
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Affiliation(s)
- Cosmin I Ciotu
- Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Katrin Kistner
- Institute of Physiology and Pathophysiology, University of Erlangen-Nürnberg, Erlangen, Germany
| | - Ulrich Kaindl
- Department of Anatomy and Cell Biology, Medical University of Vienna, Vienna, Austria
| | - Flavia Millesi
- Department of Plastic, Reconstructive and Aesthetic Surgery, Medical University of Vienna, Vienna, Austria
| | - Tamara Weiss
- Department of Plastic, Reconstructive and Aesthetic Surgery, Medical University of Vienna, Vienna, Austria
| | - Christine Radtke
- Department of Plastic, Reconstructive and Aesthetic Surgery, Medical University of Vienna, Vienna, Austria
| | - Andreas Kremer
- Department of Gastroenterology and Hepatology, University Hospital Zürich, Zürich, Switzerland
| | - Katy Schmidt
- Department of Anatomy and Cell Biology, Medical University of Vienna, Vienna, Austria
| | - Michael J M Fischer
- Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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Rao MV, Darji S, Stavrides PH, Goulbourne CN, Kumar A, Yang DS, Yoo L, Peddy J, Lee JH, Yuan A, Nixon RA. Autophagy is a novel pathway for neurofilament protein degradation in vivo. Autophagy 2023; 19:1277-1292. [PMID: 36131358 PMCID: PMC10012948 DOI: 10.1080/15548627.2022.2124500] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
Abstract
How macroautophagy/autophagy influences neurofilament (NF) proteins in neurons, a frequent target in neurodegenerative diseases and injury, is not known. NFs in axons have exceptionally long half-lives in vivo enabling formation of large stable supporting networks, but they can be rapidly degraded during Wallerian degeneration initiated by a limited calpain cleavage. Here, we identify autophagy as a previously unrecognized pathway for NF subunit protein degradation that modulates constitutive and inducible NF turnover in vivo. Levels of NEFL/NF-L, NEFM/NF-M, and NEFH/NF-H subunits rise substantially in neuroblastoma (N2a) cells after blocking autophagy either with the phosphatidylinositol 3-kinase (PtdIns3K) inhibitor 3-methyladenine (3-MA), by depleting ATG5 expression with shRNA, or by using both treatments. In contrast, activating autophagy with rapamycin significantly lowers NF levels in N2a cells. In the mouse brain, NF subunit levels increase in vivo after intracerebroventricular infusion of 3-MA. Furthermore, using tomographic confocal microscopy, immunoelectron microscopy, and biochemical fractionation, we demonstrate the presence of NF proteins intra-lumenally within autophagosomes (APs), autolysosomes (ALs), and lysosomes (LYs). Our findings establish a prominent role for autophagy in NF proteolysis. Autophagy may regulate axon cytoskeleton size and responses of the NF cytoskeleton to injury and disease.
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Affiliation(s)
- Mala V Rao
- Center for Dementia Research, Nathan Kline Institute, Orangeburg, NY, USA.,Department of Psychiatry, New York University Langone Medical Center, New York, NY, USA
| | - Sandipkumar Darji
- Center for Dementia Research, Nathan Kline Institute, Orangeburg, NY, USA
| | - Philip H Stavrides
- Center for Dementia Research, Nathan Kline Institute, Orangeburg, NY, USA
| | - Chris N Goulbourne
- Center for Dementia Research, Nathan Kline Institute, Orangeburg, NY, USA
| | - Asok Kumar
- Center for Dementia Research, Nathan Kline Institute, Orangeburg, NY, USA
| | - Dun-Sheng Yang
- Center for Dementia Research, Nathan Kline Institute, Orangeburg, NY, USA.,Department of Psychiatry, New York University Langone Medical Center, New York, NY, USA
| | - Lang Yoo
- Center for Dementia Research, Nathan Kline Institute, Orangeburg, NY, USA
| | - James Peddy
- Center for Dementia Research, Nathan Kline Institute, Orangeburg, NY, USA.,Department of Psychiatry, New York University Langone Medical Center, New York, NY, USA
| | - Ju-Hyun Lee
- Center for Dementia Research, Nathan Kline Institute, Orangeburg, NY, USA.,Department of Psychiatry, New York University Langone Medical Center, New York, NY, USA
| | - Aidong Yuan
- Center for Dementia Research, Nathan Kline Institute, Orangeburg, NY, USA
| | - Ralph A Nixon
- Center for Dementia Research, Nathan Kline Institute, Orangeburg, NY, USA.,Department of Psychiatry, New York University Langone Medical Center, New York, NY, USA.,Cell Biology, NewYork University Langone Medical Center, NY, USA.,NYU Neuroscience Institute, New York University, New York, NY, USA
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33
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Theodosiadou A, Henry M, Duchateau J, Baudry S. Revisiting the use of Hoffmann reflex in motor control research on humans. Eur J Appl Physiol 2023; 123:695-710. [PMID: 36571622 DOI: 10.1007/s00421-022-05119-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 12/17/2022] [Indexed: 12/27/2022]
Abstract
Research in movement science aims at unravelling mechanisms and designing methods for restoring and maximizing human functional capacity, and many techniques provide access to neural adjustments (acute changes) or long-term adaptations (chronic changes) underlying changes in movement capabilities. First described by Paul Hoffmann over a century ago, when an electrical stimulus is applied to a peripheral nerve, this causes action potentials in afferent axons, primarily the Ia afferents of the muscle spindles, which recruit homonymous motor neurons, thereby causing an electromyographic response known as the Hoffmann (H) reflex. This technique is a valuable tool in the study of the neuromuscular function in humans and has provided relevant information in the neural control of movement. The large use of the H reflex in motor control research on humans relies in part to its relative simplicity. However, such simplicity masks subtleties that require rigorous experimental protocols and careful data interpretation. After highlighting basic properties and methodological aspects that should be considered for the correct use of the H-reflex technique, this brief narrative review discusses the purpose of the H reflex and emphasizes its use as a tool to assess the effectiveness of Ia afferents in discharging motor neurones. The review also aims to reconsider the link between H-reflex modulation and Ia presynaptic inhibition, the use of the H-reflex technique in motor control studies, and the effects of ageing. These aspects are summarized as recommendations for the use of the H reflex in motor control research on humans.
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Affiliation(s)
- Anastasia Theodosiadou
- Laboratory of Applied Biology, Research Unit in Applied Neurophysiology (LABNeuro), Faculty of Motor Sciences, ULB-Neurosciences Institute (UNI), Université Libre de Bruxelles (ULB), 808 Route de Lennik, CP 640, 1070, Brussels, Belgium
| | - Mélanie Henry
- Laboratory of Applied Biology, Research Unit in Applied Neurophysiology (LABNeuro), Faculty of Motor Sciences, ULB-Neurosciences Institute (UNI), Université Libre de Bruxelles (ULB), 808 Route de Lennik, CP 640, 1070, Brussels, Belgium
| | - Jacques Duchateau
- Laboratory of Applied Biology, Research Unit in Applied Neurophysiology (LABNeuro), Faculty of Motor Sciences, ULB-Neurosciences Institute (UNI), Université Libre de Bruxelles (ULB), 808 Route de Lennik, CP 640, 1070, Brussels, Belgium
| | - Stéphane Baudry
- Laboratory of Applied Biology, Research Unit in Applied Neurophysiology (LABNeuro), Faculty of Motor Sciences, ULB-Neurosciences Institute (UNI), Université Libre de Bruxelles (ULB), 808 Route de Lennik, CP 640, 1070, Brussels, Belgium.
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Fenn JD, Li Y, Julien JP, Jung P, Brown A. The Mobility of Neurofilaments in Mature Myelinated Axons of Adult Mice. eNeuro 2023; 10:ENEURO.0029-23.2023. [PMID: 36882311 PMCID: PMC10035772 DOI: 10.1523/eneuro.0029-23.2023] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 02/20/2023] [Accepted: 02/26/2023] [Indexed: 03/09/2023] Open
Abstract
Studies in cultured neurons have shown that neurofilaments are cargoes of axonal transport that move rapidly but intermittently along microtubule tracks. However, the extent to which axonal neurofilaments move in vivo has been controversial. Some researchers have proposed that most axonally transported neurofilaments are deposited into a persistently stationary network and that only a small proportion of axonal neurofilaments are transported in mature axons. Here we use the fluorescence photoactivation pulse-escape technique to test this hypothesis in intact peripheral nerves of adult male hThy1-paGFP-NFM mice, which express low levels of mouse neurofilament protein M tagged with photoactivatable GFP. Neurofilaments were photoactivated in short segments of large, myelinated axons, and the mobility of these fluorescently tagged polymers was determined by analyzing the kinetics of their departure. Our results show that >80% of the fluorescence departed the window within 3 h after activation, indicating a highly mobile neurofilament population. The movement was blocked by glycolytic inhibitors, confirming that it was an active transport process. Thus, we find no evidence for a substantial stationary neurofilament population. By extrapolation of the decay kinetics, we predict that 99% of the neurofilaments would have exited the activation window after 10 h. These data support a dynamic view of the neuronal cytoskeleton in which neurofilaments cycle repeatedly between moving and pausing states throughout their journey along the axon, even in mature myelinated axons. The filaments spend a large proportion of their time pausing, but on a timescale of hours, most of them move.
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Affiliation(s)
- J Daniel Fenn
- Department of Neuroscience, The Ohio State University, Columbus, Ohio 43210
- Medical Scientist Training Program, The Ohio State University, Columbus, Ohio 43210
| | - Yinyun Li
- Quantitative Biology Institute and Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701
| | - Jean-Pierre Julien
- CERVO Brain Research Centre, Department of Psychiatry and Neuroscience, Laval University, Quebec, Quebec G1J 2G3, Canada
| | - Peter Jung
- Quantitative Biology Institute and Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701
| | - Anthony Brown
- Department of Neuroscience, The Ohio State University, Columbus, Ohio 43210
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35
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Petkoski S, Ritter P, Jirsa VK. White-matter degradation and dynamical compensation support age-related functional alterations in human brain. Cereb Cortex 2023; 33:6241-6256. [PMID: 36611231 PMCID: PMC10183745 DOI: 10.1093/cercor/bhac500] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 11/02/2022] [Accepted: 11/03/2022] [Indexed: 01/09/2023] Open
Abstract
Structural connectivity of the brain at different ages is analyzed using diffusion-weighted magnetic resonance imaging (MRI) data. The largest decrease of streamlines is found in frontal regions and for long inter-hemispheric links. The average length of the tracts also decreases, but the clustering is unaffected. From functional MRI we identify age-related changes of dynamic functional connectivity (dFC) and spatial covariation features of functional connectivity (FC) links captured by metaconnectivity. They indicate more stable dFC, but wider range and variance of MC, whereas static features of FC did not show any significant differences with age. We implement individual connectivity in whole-brain models and test several hypotheses for the mechanisms of operation among underlying neural system. We demonstrate that age-related functional fingerprints are only supported if the model accounts for: (i) compensation of the individual brains for the overall loss of structural connectivity and (ii) decrease of propagation velocity due to the loss of myelination. We also show that with these 2 conditions, it is sufficient to decompose the time-delays as bimodal distribution that only distinguishes between intra- and inter-hemispheric delays, and that the same working point also captures the static FC the best, and produces the largest variability at slow time-scales.
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Affiliation(s)
- Spase Petkoski
- Aix Marseille Univ, INSERM, INS, Inst Neurosci Syst, Marseille, France
| | - Petra Ritter
- Berlin Institute of Health at Charité - Universitätsmedizin Berlin, Berlin, Germany.,Department of Neurology with Experimental Neurology, Brain Simulation Section, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany.,Bernstein Focus State Dependencies of Learning, Bernstein Center for Computational Neuroscience, Berlin, Germany
| | - Viktor K Jirsa
- Aix Marseille Univ, INSERM, INS, Inst Neurosci Syst, Marseille, France
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36
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Murray CJ, Vecchiarelli HA, Tremblay MÈ. Enhancing axonal myelination in seniors: A review exploring the potential impact cannabis has on myelination in the aged brain. Front Aging Neurosci 2023; 15:1119552. [PMID: 37032821 PMCID: PMC10073480 DOI: 10.3389/fnagi.2023.1119552] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Accepted: 02/22/2023] [Indexed: 04/11/2023] Open
Abstract
Consumption of cannabis is on the rise as public opinion trends toward acceptance and its consequent legalization. Specifically, the senior population is one of the demographics increasing their use of cannabis the fastest, but research aimed at understanding cannabis' impact on the aged brain is still scarce. Aging is characterized by many brain changes that slowly alter cognitive ability. One process that is greatly impacted during aging is axonal myelination. The slow degradation and loss of myelin (i.e., demyelination) in the brain with age has been shown to associate with cognitive decline and, furthermore, is a common characteristic of numerous neurological diseases experienced in aging. It is currently not known what causes this age-dependent degradation, but it is likely due to numerous confounding factors (i.e., heightened inflammation, reduced blood flow, cellular senescence) that impact the many cells responsible for maintaining overall homeostasis and myelin integrity. Importantly, animal studies using non-human primates and rodents have also revealed demyelination with age, providing a reliable model for researchers to try and understand the cellular mechanisms at play. In rodents, cannabis was recently shown to modulate the myelination process. Furthermore, studies looking at the direct modulatory impact cannabis has on microglia, astrocytes and oligodendrocyte lineage cells hint at potential mechanisms to prevent some of the more damaging activities performed by these cells that contribute to demyelination in aging. However, research focusing on how cannabis impacts myelination in the aged brain is lacking. Therefore, this review will explore the evidence thus far accumulated to show how cannabis impacts myelination and will extrapolate what this knowledge may mean for the aged brain.
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Affiliation(s)
- Colin J. Murray
- Neuroscience Graduate Program, University of Victoria, Victoria, BC, Canada
- Division of Medical Sciences, University of Victoria, Victoria, BC, Canada
- *Correspondence: Colin J. Murray,
| | | | - Marie-Ève Tremblay
- Division of Medical Sciences, University of Victoria, Victoria, BC, Canada
- Départment de Médicine Moléculaire, Université Laval, Québec City, QC, Canada
- Axe Neurosciences, Center de Recherche du CHU de Québec, Université Laval, Québec City, QC, Canada
- Neurology and Neurosurgery Department, McGill University, Montréal, QC, Canada
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
- Centre for Advanced Materials and Related Technology (CAMTEC), University of Victoria, Victoria, BC, Canada
- Institute for Aging and Lifelong Health, University of Victoria, Victoria, BC, Canada
- Marie-Ève Tremblay,
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37
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Schwann cell functions in peripheral nerve development and repair. Neurobiol Dis 2023; 176:105952. [PMID: 36493976 DOI: 10.1016/j.nbd.2022.105952] [Citation(s) in RCA: 47] [Impact Index Per Article: 47.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 11/23/2022] [Accepted: 12/05/2022] [Indexed: 12/12/2022] Open
Abstract
The glial cell of the peripheral nervous system (PNS), the Schwann cell (SC), counts among the most multifaceted cells of the body. During development, SCs secure neuronal survival and participate in axonal path finding. Simultaneously, they orchestrate the architectural set up of the developing nerves, including the blood vessels and the endo-, peri- and epineurial layers. Perinatally, in rodents, SCs radially sort and subsequently myelinate individual axons larger than 1 μm in diameter, while small calibre axons become organised in non-myelinating Remak bundles. SCs have a vital role in maintaining axonal health throughout life and several specialized SC types perform essential functions at specific locations, such as terminal SC at the neuromuscular junction (NMJ) or SC within cutaneous sensory end organs. In addition, neural crest derived satellite glia maintain a tight communication with the soma of sensory, sympathetic, and parasympathetic neurons and neural crest derivatives are furthermore an indispensable part of the enteric nervous system. The remarkable plasticity of SCs becomes evident in the context of a nerve injury, where SC transdifferentiate into intriguing repair cells, which orchestrate a regenerative response that promotes nerve repair. Indeed, the multiple adaptations of SCs are captivating, but remain often ill-resolved on the molecular level. Here, we summarize and discuss the knowns and unknowns of the vast array of functions that this single cell type can cover in peripheral nervous system development, maintenance, and repair.
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38
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Sharmin S, Karal MAS, Mahbub ZB, Rabbani KSE. Increase in conduction velocity in myelinated nerves due to stretch - An experimental verification. Front Neurosci 2023; 17:1084004. [PMID: 37139532 PMCID: PMC10149795 DOI: 10.3389/fnins.2023.1084004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Accepted: 03/28/2023] [Indexed: 05/05/2023] Open
Abstract
Background Based on published experimental evidence, a recent publication revealed an anomalous phenomenon in nerve conduction: for myelinated nerves the nerve conduction velocity (NCV) increases with stretch, which should have been the opposite according to existing concepts and theories since the diameter decreases on stretching. To resolve the anomaly, a new conduction mechanism for myelinated nerves was proposed based on physiological changes in the nodal region, introducing a new electrical resistance at the node. The earlier experimental measurements of NCV were performed on the ulnar nerve at different angles of flexion, focusing at the elbow region, but left some uncertainty for not reporting the lengths of nerve segments involved so that the magnitudes of stretch could not be estimated. Aims The aim of the present study was to relate NCV of myelinated nerves with different magnitudes of stretch through careful measurements. Method Essentially, we duplicated the earlier published NCV measurements on ulnar nerves at different angles of flexion but recording appropriate distances between nerve stimulation points on the skin carefully and assuming that the lengths of the underlying nerve segment undergoes the same percentages of changes as that on the skin outside. Results We found that the percentage of nerve stretch across the elbow is directly proportional to the angle of flexion and that the percentage increase in NCV is directly proportional to the percentage increase in nerve stretch. Page's L Trend test also supported the above trends of changes through obtained p values. Discussion Our experimental findings on myelinated nerves agree with those of some recent publications which measured changes in CV of single fibres, both myelinated and unmyelinated, on stretch. Analyzing all the observed results, we may infer that the new conduction mechanism based on the nodal resistance and proposed by the recent publication mentioned above is the most plausible one to explain the increase in CV with nerve stretch. Furthermore, interpreting the experimental results in the light of the new mechanism, we may suggest that the ulnar nerve at the forearm is always under a mild stretch, with slightly increased NCV of the myelinated nerves.
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Affiliation(s)
- Sabrina Sharmin
- Department of Physics, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh
- Department of Arts and Sciences, Ahsanullah University of Science and Technology, Dhaka, Bangladesh
- *Correspondence: Sabrina Sharmin,
| | - Mohammad Abu Sayem Karal
- Department of Physics, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh
- Mohammad Abu Sayem Karal,
| | - Zaid Bin Mahbub
- Department of Mathematics and Physics, North South University, Dhaka, Bangladesh
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Fernandez-Alvarez M, Atienza M, Cantero JL. Effects of non-modifiable risk factors of Alzheimer's disease on intracortical myelin content. Alzheimers Res Ther 2022; 14:202. [PMID: 36587227 PMCID: PMC9805254 DOI: 10.1186/s13195-022-01152-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 12/25/2022] [Indexed: 01/01/2023]
Abstract
BACKGROUND Non-modifiable risk factors of Alzheimer's disease (AD) have lifelong effects on cortical integrity that could be mitigated if identified at early stages. However, it remains unknown whether cortical microstructure is affected in older individuals with non-modifiable AD risk factors and whether altered cortical tissue integrity produces abnormalities in brain functional networks in this AD-risk population. METHODS Using relative T1w/T2w (rT1w/T2w) ratio maps, we have compared tissue integrity of normal-appearing cortical GM between controls and cognitively normal older adults with either APOE4 (N = 50), with a first-degree family history (FH) of AD (N = 52), or with the co-occurrence of both AD risk factors (APOE4+FH) (N = 35). Additionally, individuals with only one risk factor (APOE4 or FH) were combined into one group (N = 102) and compared with controls. The same number of controls matched in age, sex, and years of education was employed for each of these comparisons. Group differences in resting state functional connectivity (rs-FC) patterns were also investigated, using as FC seeds those cortical regions showing significant changes in rT1w/T2w ratios. RESULTS Overall, individuals with non-modifiable AD risk factors exhibited significant variations in rT1w/T2w ratios compared to controls, being APOE4 and APOE4+FH at opposite ends of a continuum. The co-occurrence of APOE4 and FH was further accompanied by altered patterns of rs-FC. CONCLUSIONS These findings may have practical implications for early detection of cortical abnormalities in older populations with APOE4 and/or FH of AD and open new avenues to monitor changes in cortical tissue integrity associated with non-modifiable AD risk factors.
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Affiliation(s)
- Marina Fernandez-Alvarez
- grid.15449.3d0000 0001 2200 2355Laboratory of Functional Neuroscience, Pablo de Olavide University, Ctra. de Utrera Km 1, 41013 Seville, Spain ,grid.418264.d0000 0004 1762 4012CIBERNED, Network Center for Biomedical Research in Neurodegenerative Diseases, Madrid, Spain
| | - Mercedes Atienza
- grid.15449.3d0000 0001 2200 2355Laboratory of Functional Neuroscience, Pablo de Olavide University, Ctra. de Utrera Km 1, 41013 Seville, Spain ,grid.418264.d0000 0004 1762 4012CIBERNED, Network Center for Biomedical Research in Neurodegenerative Diseases, Madrid, Spain
| | - Jose L. Cantero
- grid.15449.3d0000 0001 2200 2355Laboratory of Functional Neuroscience, Pablo de Olavide University, Ctra. de Utrera Km 1, 41013 Seville, Spain ,grid.418264.d0000 0004 1762 4012CIBERNED, Network Center for Biomedical Research in Neurodegenerative Diseases, Madrid, Spain
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40
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Sessler CD, Zhou Y, Wang W, Hartley ND, Fu Z, Graykowski D, Sheng M, Wang X, Liu J. Optogenetic polymerization and assembly of electrically functional polymers for modulation of single-neuron excitability. SCIENCE ADVANCES 2022; 8:eade1136. [PMID: 36475786 PMCID: PMC9728971 DOI: 10.1126/sciadv.ade1136] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Accepted: 10/28/2022] [Indexed: 06/17/2023]
Abstract
Ionic conductivity and membrane capacitance are two foundational parameters that govern neuron excitability. Conventional optogenetics has emerged as a powerful tool to temporarily manipulate membrane ionic conductivity in intact biological systems. However, no analogous method exists for precisely manipulating cell membrane capacitance to enable long-lasting modulation of neuronal excitability. Genetically targetable chemical assembly of conductive and insulating polymers can modulate cell membrane capacitance, but further development of this technique has been hindered by poor spatiotemporal control of the polymer deposition and cytotoxicity from the widely diffused peroxide. We address these issues by harnessing genetically targetable photosensitizer proteins to assemble electrically functional polymers in neurons with precise spatiotemporal control. Using whole-cell patch-clamp recordings, we demonstrate that this optogenetic polymerization can achieve stepwise modulation of both neuron membrane capacitance and intrinsic excitability. Furthermore, cytotoxicity can be limited by controlling light exposure, demonstrating a promising new method for precisely modulating cell excitability.
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Affiliation(s)
- Chanan D. Sessler
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Yiming Zhou
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Wenbo Wang
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Nolan D. Hartley
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Zhanyan Fu
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - David Graykowski
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Morgan Sheng
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Xiao Wang
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Jia Liu
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
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41
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A macroscopic link between interhemispheric tract myelination and cortico-cortical interactions during action reprogramming. Nat Commun 2022; 13:4253. [PMID: 35869067 PMCID: PMC9307658 DOI: 10.1038/s41467-022-31687-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 06/16/2022] [Indexed: 11/15/2022] Open
Abstract
Myelination has been increasingly implicated in the function and dysfunction of the adult human brain. Although it is known that axon myelination shapes axon physiology in animal models, it is unclear whether a similar principle applies in the living human brain, and at the level of whole axon bundles in white matter tracts. Here, we hypothesised that in humans, cortico-cortical interactions between two brain areas may be shaped by the amount of myelin in the white matter tract connecting them. As a test bed for this hypothesis, we use a well-defined interhemispheric premotor-to-motor circuit. We combined TMS-derived physiological measures of cortico-cortical interactions during action reprogramming with multimodal myelin markers (MT, R1, R2* and FA), in a large cohort of healthy subjects. We found that physiological metrics of premotor-to-motor interaction are broadly associated with multiple myelin markers, suggesting interindividual differences in tract myelination may play a role in motor network physiology. Moreover, we also demonstrate that myelination metrics link indirectly to action switching by influencing local primary motor cortex dynamics. These findings suggest that myelination levels in white matter tracts may influence millisecond-level cortico-cortical interactions during tasks. They also unveil a link between the physiology of the motor network and the myelination of tracts connecting its components, and provide a putative mechanism mediating the relationship between brain myelination and human behaviour. Myelination is a key regulator of brain function. Here the authors use MR-based myelin measures to examine if cortico-cortical interactions, as assessed by paired pulse transcranial magnetic stimulation, are affected by variations in myelin in the human brain.
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Abstract
Within the past decade, multiple lines of evidence have converged to identify a critical role for activity-regulated myelination in tuning the function of neural networks. In this Review, we provide an overview of accumulating evidence that activity-regulated myelination is required for brain adaptation and learning across multiple domains. We then discuss dysregulation of activity-dependent myelination in the context of neurological disease, a novel frontier with the potential to uncover new mechanisms of disease pathogenesis and to develop new therapeutic strategies. Alterations in myelination and neural network function can result from deficient myelin plasticity that impairs neurological function or from maladaptive myelination, in which intact activity-dependent myelination contributes to the disease process by promoting pathological patterns of neuronal activity. These emerging mechanisms suggest new avenues for therapeutic intervention that could more fully address the complex interactions between neurons and oligodendroglia.
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43
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Osanai Y, Yamazaki R, Shinohara Y, Ohno N. Heterogeneity and regulation of oligodendrocyte morphology. Front Cell Dev Biol 2022; 10:1030486. [PMID: 36393856 PMCID: PMC9644283 DOI: 10.3389/fcell.2022.1030486] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 10/10/2022] [Indexed: 09/24/2023] Open
Abstract
Oligodendrocytes form multiple myelin sheaths in the central nervous system (CNS), which increase nerve conduction velocity and are necessary for basic and higher brain functions such as sensory function, motor control, and learning. Structures of the myelin sheath such as myelin internodal length and myelin thickness regulate nerve conduction. Various parts of the central nervous system exhibit different myelin structures and oligodendrocyte morphologies. Recent studies supported that oligodendrocytes are a heterogenous population of cells and myelin sheaths formed by some oligodendrocytes can be biased to particular groups of axons, and myelin structures are dynamically modulated in certain classes of neurons by specific experiences. Structures of oligodendrocyte/myelin are also affected in pathological conditions such as demyelinating and neuropsychiatric disorders. This review summarizes our understanding of heterogeneity and regulation of oligodendrocyte morphology concerning central nervous system regions, neuronal classes, experiences, diseases, and how oligodendrocytes are optimized to execute central nervous system functions.
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Affiliation(s)
- Yasuyuki Osanai
- Department of Anatomy, Division of Histology and Cell Biology, School of Medicine, Jichi Medical University, Shimotsuke, Japan
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC, Australia
| | - Reiji Yamazaki
- Department of Anatomy, Division of Histology and Cell Biology, School of Medicine, Jichi Medical University, Shimotsuke, Japan
| | - Yoshiaki Shinohara
- Department of Anatomy, Division of Histology and Cell Biology, School of Medicine, Jichi Medical University, Shimotsuke, Japan
- Department of Anatomy and Cell Biology, Faculty of Medicine, University of Yamanashi, Chuo, Japan
| | - Nobuhiko Ohno
- Department of Anatomy, Division of Histology and Cell Biology, School of Medicine, Jichi Medical University, Shimotsuke, Japan
- Division of Ultrastructural Research, National Institute for Physiological Sciences, Okazaki, Japan
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44
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Deck M, Van Hameren G, Campbell G, Bernard-Marissal N, Devaux J, Berthelot J, Lattard A, Médard JJ, Gautier B, Guelfi S, Abbou S, Quintana P, Chao de la Barca JM, Reynier P, Lenaers G, Chrast R, Tricaud N. Physiology of PNS axons relies on glycolytic metabolism in myelinating Schwann cells. PLoS One 2022; 17:e0272097. [PMID: 36194565 PMCID: PMC9531822 DOI: 10.1371/journal.pone.0272097] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2022] [Accepted: 07/12/2022] [Indexed: 11/18/2022] Open
Abstract
While lactate shuttle theory states that glial cells metabolize glucose into lactate to shuttle it to neurons, how glial cells support axonal metabolism and function remains unclear. Lactate production is a common occurrence following anaerobic glycolysis in muscles. However, several other cell types, including some stem cells, activated macrophages and tumor cells, can produce lactate in presence of oxygen and cellular respiration, using Pyruvate Kinase 2 (PKM2) to divert pyruvate to lactate dehydrogenase. We show here that PKM2 is also upregulated in myelinating Schwann cells (mSC) of mature mouse sciatic nerve versus postnatal immature nerve. Deletion of this isoform in PLP-expressing cells in mice leads to a deficit of lactate in mSC and in peripheral nerves. While the structure of myelin sheath was preserved, mutant mice developed a peripheral neuropathy. Peripheral nerve axons of mutant mice failed to maintain lactate homeostasis upon activity, resulting in an impaired production of mitochondrial ATP. Action potential propagation was not altered but axonal mitochondria transport was slowed down, muscle axon terminals retracted and motor neurons displayed cellular stress. Additional reduction of lactate availability through dichloroacetate treatment, which diverts pyruvate to mitochondrial oxidative phosphorylation, further aggravated motor dysfunction in mutant mice. Thus, lactate production through PKM2 enzyme and aerobic glycolysis is essential in mSC for the long-term maintenance of peripheral nerve axon physiology and function.
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Affiliation(s)
- Marie Deck
- INM, INSERM, Université de Montpellier, Montpellier, France
- * E-mail: (NT); (MD)
| | | | | | | | - Jérôme Devaux
- INM, INSERM, Université de Montpellier, Montpellier, France
| | - Jade Berthelot
- INM, INSERM, Université de Montpellier, Montpellier, France
| | - Alise Lattard
- INM, INSERM, Université de Montpellier, Montpellier, France
| | - Jean-Jacques Médard
- Departments of Clinical Neuroscience and Neuroscience, Karolinska Intitutet, Stockholm, Sweden
| | - Benoît Gautier
- INM, INSERM, Université de Montpellier, Montpellier, France
| | - Sophie Guelfi
- INM, INSERM, Université de Montpellier, Montpellier, France
| | | | | | - Juan Manuel Chao de la Barca
- Département de Biochimie et Génétique, Centre Hospitalier Universitaire, Angers, France
- Equipe Mitolab, MITOVASC, CNRS 6015, INSERM U1083, Université d’Angers, Angers, France
| | - Pascal Reynier
- Département de Biochimie et Génétique, Centre Hospitalier Universitaire, Angers, France
- Equipe Mitolab, MITOVASC, CNRS 6015, INSERM U1083, Université d’Angers, Angers, France
| | - Guy Lenaers
- Equipe Mitolab, MITOVASC, CNRS 6015, INSERM U1083, Université d’Angers, Angers, France
| | - Roman Chrast
- Departments of Clinical Neuroscience and Neuroscience, Karolinska Intitutet, Stockholm, Sweden
| | - Nicolas Tricaud
- I-Stem, UEVE/UPS U861, INSERM, AFM, Corbeil-Essonnes, France
- * E-mail: (NT); (MD)
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45
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Clark IA, Mohammadi S, Callaghan MF, Maguire EA. Conduction velocity along a key white matter tract is associated with autobiographical memory recall ability. eLife 2022; 11:e79303. [PMID: 36166372 PMCID: PMC9514844 DOI: 10.7554/elife.79303] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 09/12/2022] [Indexed: 12/01/2022] Open
Abstract
Conduction velocity is the speed at which electrical signals travel along axons and is a crucial determinant of neural communication. Inferences about conduction velocity can now be made in vivo in humans using a measure called the magnetic resonance (MR) g-ratio. This is the ratio of the inner axon diameter relative to that of the axon plus the myelin sheath that encases it. Here, in the first application to cognition, we found that variations in MR g-ratio, and by inference conduction velocity, of the parahippocampal cingulum bundle were associated with autobiographical memory recall ability in 217 healthy adults. This tract connects the hippocampus with a range of other brain areas. We further observed that the association seemed to be with inner axon diameter rather than myelin content. The extent to which neurites were coherently organised within the parahippocampal cingulum bundle was also linked with autobiographical memory recall ability. Moreover, these findings were specific to autobiographical memory recall and were not apparent for laboratory-based memory tests. Our results offer a new perspective on individual differences in autobiographical memory recall ability, highlighting the possible influence of specific white matter microstructure features on conduction velocity when recalling detailed memories of real-life past experiences.
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Affiliation(s)
- Ian A Clark
- Wellcome Centre for Human Neuroimaging, Department of Imaging Neuroscience, UCL Queen Square Institute of Neurology, University College LondonLondonUnited Kingdom
| | - Siawoosh Mohammadi
- Institute of Systems Neuroscience, University Medical Centre Hamburg-EppendorfHamburgGermany
| | - Martina F Callaghan
- Wellcome Centre for Human Neuroimaging, Department of Imaging Neuroscience, UCL Queen Square Institute of Neurology, University College LondonLondonUnited Kingdom
| | - Eleanor A Maguire
- Wellcome Centre for Human Neuroimaging, Department of Imaging Neuroscience, UCL Queen Square Institute of Neurology, University College LondonLondonUnited Kingdom
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46
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Zhang Z, Qu Z. Bistable nerve conduction. Biophys J 2022; 121:3499-3507. [PMID: 35962548 PMCID: PMC9515125 DOI: 10.1016/j.bpj.2022.08.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 07/16/2022] [Accepted: 08/09/2022] [Indexed: 11/02/2022] Open
Abstract
It has been demonstrated experimentally that slow and fast conduction waves with distinct conduction velocities can occur in the same nerve system depending on the strength or the form of the stimulus, which give rise to two modes of nerve functions. However, the mechanisms remain to be elucidated. In this study, we use computer simulations of the cable equation with modified Hodgkin-Huxley kinetics and analytical solutions of a simplified model to show that stimulus-dependent slow and fast waves recapitulating the experimental observations can occur in the cable, which are the two stable conduction states of a bistable conduction behavior. The bistable conduction is caused by a positive feedback loop of the wavefront upstroke speed, mediated by the sodium channel inactivation properties. Although the occurrence of bistable conduction only requires the presence of the sodium current, adding a calcium current to the model further promotes bistable conduction by potentiating the slow wave. We also show that the bistable conduction is robust, occurring for sodium and calcium activation thresholds well within the experimentally determined ones of the known sodium and calcium channel families. Since bistable conduction can occur in the cable equation of Hodgkin-Huxley kinetics with a single inward current, i.e., the sodium current, it can be a generic mechanism applicable to stimulus-dependent fast and slow conduction not only in the nerve systems but also in other electrically excitable systems, such as cardiac muscles.
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Affiliation(s)
- Zhaoyang Zhang
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Zhilin Qu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California; Department of Computational Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California.
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47
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Fernández-Castañeda A, Lu P, Geraghty AC, Song E, Lee MH, Wood J, O'Dea MR, Dutton S, Shamardani K, Nwangwu K, Mancusi R, Yalçın B, Taylor KR, Acosta-Alvarez L, Malacon K, Keough MB, Ni L, Woo PJ, Contreras-Esquivel D, Toland AMS, Gehlhausen JR, Klein J, Takahashi T, Silva J, Israelow B, Lucas C, Mao T, Peña-Hernández MA, Tabachnikova A, Homer RJ, Tabacof L, Tosto-Mancuso J, Breyman E, Kontorovich A, McCarthy D, Quezado M, Vogel H, Hefti MM, Perl DP, Liddelow S, Folkerth R, Putrino D, Nath A, Iwasaki A, Monje M. Mild respiratory COVID can cause multi-lineage neural cell and myelin dysregulation. Cell 2022; 185:2452-2468.e16. [PMID: 35768006 PMCID: PMC9189143 DOI: 10.1016/j.cell.2022.06.008] [Citation(s) in RCA: 242] [Impact Index Per Article: 121.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 05/04/2022] [Accepted: 06/07/2022] [Indexed: 12/13/2022]
Abstract
COVID survivors frequently experience lingering neurological symptoms that resemble cancer-therapy-related cognitive impairment, a syndrome for which white matter microglial reactivity and consequent neural dysregulation is central. Here, we explored the neurobiological effects of respiratory SARS-CoV-2 infection and found white-matter-selective microglial reactivity in mice and humans. Following mild respiratory COVID in mice, persistently impaired hippocampal neurogenesis, decreased oligodendrocytes, and myelin loss were evident together with elevated CSF cytokines/chemokines including CCL11. Systemic CCL11 administration specifically caused hippocampal microglial reactivity and impaired neurogenesis. Concordantly, humans with lasting cognitive symptoms post-COVID exhibit elevated CCL11 levels. Compared with SARS-CoV-2, mild respiratory influenza in mice caused similar patterns of white-matter-selective microglial reactivity, oligodendrocyte loss, impaired neurogenesis, and elevated CCL11 at early time points, but after influenza, only elevated CCL11 and hippocampal pathology persisted. These findings illustrate similar neuropathophysiology after cancer therapy and respiratory SARS-CoV-2 infection which may contribute to cognitive impairment following even mild COVID.
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Affiliation(s)
| | - Peiwen Lu
- Department of Immunobiology, Yale University, New Haven, CT, USA
| | - Anna C Geraghty
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | - Eric Song
- Department of Immunobiology, Yale University, New Haven, CT, USA
| | - Myoung-Hwa Lee
- National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA
| | - Jamie Wood
- Abilities Research Center, Department of Rehabilitation and Human Performance, Mount Sinai School of Medicine, New York, NY, USA
| | - Michael R O'Dea
- Neuroscience Institute, NYU Grossman School of Medicine, New York, NY, USA
| | - Selena Dutton
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | - Kiarash Shamardani
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | - Kamsi Nwangwu
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | - Rebecca Mancusi
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | - Belgin Yalçın
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | - Kathryn R Taylor
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | - Lehi Acosta-Alvarez
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | - Karen Malacon
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | - Michael B Keough
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | - Lijun Ni
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | - Pamelyn J Woo
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | | | | | | | - Jon Klein
- Department of Immunobiology, Yale University, New Haven, CT, USA
| | | | - Julio Silva
- Department of Immunobiology, Yale University, New Haven, CT, USA
| | | | - Carolina Lucas
- Department of Immunobiology, Yale University, New Haven, CT, USA
| | - Tianyang Mao
- Department of Immunobiology, Yale University, New Haven, CT, USA
| | | | | | - Robert J Homer
- Department of Pathology, Yale University, New Haven, CT, USA
| | - Laura Tabacof
- Abilities Research Center, Department of Rehabilitation and Human Performance, Mount Sinai School of Medicine, New York, NY, USA
| | - Jenna Tosto-Mancuso
- Abilities Research Center, Department of Rehabilitation and Human Performance, Mount Sinai School of Medicine, New York, NY, USA
| | - Erica Breyman
- Abilities Research Center, Department of Rehabilitation and Human Performance, Mount Sinai School of Medicine, New York, NY, USA
| | - Amy Kontorovich
- Cardiovascular Research Institute, Mount Sinai School of Medicine, New York, NY, USA
| | - Dayna McCarthy
- Abilities Research Center, Department of Rehabilitation and Human Performance, Mount Sinai School of Medicine, New York, NY, USA
| | | | - Hannes Vogel
- Department of Pathology, Stanford University, Stanford, CA, USA
| | - Marco M Hefti
- Department of Pathology, University of Iowa, Iowa City, IA, USA
| | - Daniel P Perl
- Department of Pathology, Uniformed Services University of Health Sciences, Bethesda, MD, USA
| | - Shane Liddelow
- Neuroscience Institute, NYU Grossman School of Medicine, New York, NY, USA; Departments of Neuroscience & Physiology and of Ophthalmology, NYU Grossman School of Medicine, New York, NY, USA; Parekh Center for Interdisciplinary Neurology, NYU Grossman School of Medicine, New York, NY, USA
| | | | - David Putrino
- Abilities Research Center, Department of Rehabilitation and Human Performance, Mount Sinai School of Medicine, New York, NY, USA
| | - Avindra Nath
- National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA
| | - Akiko Iwasaki
- Department of Immunobiology, Yale University, New Haven, CT, USA; Howard Hughes Medical Institute, Yale University, New Haven, CT, USA.
| | - Michelle Monje
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA; Department of Pathology, Stanford University, Stanford, CA, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA.
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48
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Fernandez-Alvarez M, Atienza M, Zallo F, Matute C, Capetillo-Zarate E, Cantero JL. Linking Plasma Amyloid Beta and Neurofilament Light Chain to Intracortical Myelin Content in Cognitively Normal Older Adults. Front Aging Neurosci 2022; 14:896848. [PMID: 35783126 PMCID: PMC9247578 DOI: 10.3389/fnagi.2022.896848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Accepted: 05/23/2022] [Indexed: 11/29/2022] Open
Abstract
Evidence suggests that lightly myelinated cortical regions are vulnerable to aging and Alzheimer’s disease (AD). However, it remains unknown whether plasma markers of amyloid and neurodegeneration are related to deficits in intracortical myelin content, and whether this relationship, in turn, is associated with altered patterns of resting-state functional connectivity (rs-FC). To shed light into these questions, plasma levels of amyloid-β fragment 1–42 (Aβ1–42) and neurofilament light chain (NfL) were measured using ultra-sensitive single-molecule array (Simoa) assays, and the intracortical myelin content was estimated with the ratio T1-weigthed/T2-weighted (T1w/T2w) in 133 cognitively normal older adults. We assessed: (i) whether plasma Aβ1–42 and/or NfL levels were associated with intracortical myelin content at different cortical depths and (ii) whether cortical regions showing myelin reductions also exhibited altered rs-FC patterns. Surface-based multiple regression analyses revealed that lower plasma Aβ1–42 and higher plasma NfL were associated with lower myelin content in temporo-parietal-occipital regions and the insular cortex, respectively. Whereas the association with Aβ1–42 decreased with depth, the NfL-myelin relationship was most evident in the innermost layer. Older individuals with higher plasma NfL levels also exhibited altered rs-FC between the insula and medial orbitofrontal cortex. Together, these findings establish a link between plasma markers of amyloid/neurodegeneration and intracortical myelin content in cognitively normal older adults, and support the role of plasma NfL in boosting aberrant FC patterns of the insular cortex, a central brain hub highly vulnerable to aging and neurodegeneration.
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Affiliation(s)
- Marina Fernandez-Alvarez
- Laboratory of Functional Neuroscience, Pablo de Olavide University, Seville, Spain
- Network Center for Biomedical Research in Neurodegenerative Diseases (CIBERNED), Madrid, Spain
| | - Mercedes Atienza
- Laboratory of Functional Neuroscience, Pablo de Olavide University, Seville, Spain
- Network Center for Biomedical Research in Neurodegenerative Diseases (CIBERNED), Madrid, Spain
| | - Fatima Zallo
- Departamento de Neurociencias, Achucarro Basque Center for Neuroscience, Universidad del País Vasco, Leioa, Spain
| | - Carlos Matute
- Network Center for Biomedical Research in Neurodegenerative Diseases (CIBERNED), Madrid, Spain
- Departamento de Neurociencias, Achucarro Basque Center for Neuroscience, Universidad del País Vasco, Leioa, Spain
| | - Estibaliz Capetillo-Zarate
- Network Center for Biomedical Research in Neurodegenerative Diseases (CIBERNED), Madrid, Spain
- Departamento de Neurociencias, Achucarro Basque Center for Neuroscience, Universidad del País Vasco, Leioa, Spain
- Ikerbasque, Basque Foundation for Science, Bilbao, Spain
| | - Jose L. Cantero
- Laboratory of Functional Neuroscience, Pablo de Olavide University, Seville, Spain
- Network Center for Biomedical Research in Neurodegenerative Diseases (CIBERNED), Madrid, Spain
- *Correspondence: Jose L. Cantero,
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49
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Radomski KL, Zi X, Lischka FW, Noble MD, Galdzicki Z, Armstrong RC. Acute axon damage and demyelination are mitigated by 4-aminopyridine (4-AP) therapy after experimental traumatic brain injury. Acta Neuropathol Commun 2022; 10:67. [PMID: 35501931 PMCID: PMC9059462 DOI: 10.1186/s40478-022-01366-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Accepted: 04/11/2022] [Indexed: 11/10/2022] Open
Abstract
Damage to long axons in white matter tracts is a major pathology in closed head traumatic brain injury (TBI). Acute TBI treatments are needed that protect against axon damage and promote recovery of axon function to prevent long term symptoms and neurodegeneration. Our prior characterization of axon damage and demyelination after TBI led us to examine repurposing of 4-aminopyridine (4-AP), an FDA-approved inhibitor of voltage-gated potassium (Kv) channels. 4-AP is currently indicated to provide symptomatic relief for patients with chronic stage multiple sclerosis, which involves axon damage and demyelination. We tested clinically relevant dosage of 4-AP as an acute treatment for experimental TBI and found multiple benefits in corpus callosum axons. This randomized, controlled pre-clinical study focused on the first week after TBI, when axons are particularly vulnerable. 4-AP treatment initiated one day post-injury dramatically reduced axon damage detected by intra-axonal fluorescence accumulations in Thy1-YFP mice of both sexes. Detailed electron microscopy in C57BL/6 mice showed that 4-AP reduced pathological features of mitochondrial swelling, cytoskeletal disruption, and demyelination at 7 days post-injury. Furthermore, 4-AP improved the molecular organization of axon nodal regions by restoring disrupted paranode domains and reducing Kv1.2 channel dispersion. 4-AP treatment did not resolve deficits in action potential conduction across the corpus callosum, based on ex vivo electrophysiological recordings at 7 days post-TBI. Thus, this first study of 4-AP effects on axon damage in the acute period demonstrates a significant decrease in multiple pathological hallmarks of axon damage after experimental TBI.
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Affiliation(s)
- Kryslaine L. Radomski
- Department of Anatomy, Physiology and Genetics, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814 USA
- Center for Neuroscience and Regenerative Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814 USA
| | - Xiaomei Zi
- Department of Anatomy, Physiology and Genetics, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814 USA
- Center for Neuroscience and Regenerative Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814 USA
| | - Fritz W. Lischka
- Department of Anatomy, Physiology and Genetics, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814 USA
- Biomedical Instrumentation Center, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814 USA
| | - Mark D. Noble
- Department of Biomedical Genetics, School of Medicine and Dentistry, University of Rochester, 601 Elmwood Ave, Box 633, Rochester, NY 14642 USA
| | - Zygmunt Galdzicki
- Department of Anatomy, Physiology and Genetics, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814 USA
- Center for Neuroscience and Regenerative Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814 USA
| | - Regina C. Armstrong
- Department of Anatomy, Physiology and Genetics, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814 USA
- Center for Neuroscience and Regenerative Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814 USA
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50
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Knowles JK, Xu H, Soane C, Batra A, Saucedo T, Frost E, Tam LT, Fraga D, Ni L, Villar K, Talmi S, Huguenard JR, Monje M. Maladaptive myelination promotes generalized epilepsy progression. Nat Neurosci 2022; 25:596-606. [PMID: 35501379 PMCID: PMC9076538 DOI: 10.1038/s41593-022-01052-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Accepted: 03/14/2022] [Indexed: 12/18/2022]
Abstract
Activity-dependent myelination can fine-tune neural network dynamics. Conversely, aberrant neuronal activity, as occurs in disorders of recurrent seizures (epilepsy), could promote maladaptive myelination, contributing to pathogenesis. In this study, we tested the hypothesis that activity-dependent myelination resulting from absence seizures, which manifest as frequent behavioral arrests with generalized electroencephalography (EEG) spike-wave discharges, promote thalamocortical network hypersynchrony and contribute to epilepsy progression. We found increased oligodendrogenesis and myelination specifically within the seizure network in two models of generalized epilepsy with absence seizures (Wag/Rij rats and Scn8a+/mut mice), evident only after epilepsy onset. Aberrant myelination was prevented by pharmacological seizure inhibition in Wag/Rij rats. Blocking activity-dependent myelination decreased seizure burden over time and reduced ictal synchrony as assessed by EEG coherence. These findings indicate that activity-dependent myelination driven by absence seizures contributes to epilepsy progression; maladaptive myelination may be pathogenic in some forms of epilepsy and other neurological diseases.
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Affiliation(s)
- Juliet K Knowles
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA.
| | - Haojun Xu
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
- Ph.D. Program in Human Biology, School of Integrative and Global Majors, University of Tsukuba, Tsukuba, Japan
| | - Caroline Soane
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | - Ankita Batra
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | - Tristan Saucedo
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | - Eleanor Frost
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | - Lydia T Tam
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | - Danielle Fraga
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | - Lijun Ni
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | - Katlin Villar
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | - Sydney Talmi
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | - John R Huguenard
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA.
| | - Michelle Monje
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA.
- Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA.
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