scholarly journals Cell Shrinkage, Cytoskeletal Pathologies, and Neurodegeneration: Myelin Sheath Formation and Remodeling

2021 ◽  
Vol 01 (01) ◽  
Author(s):  
Rajiv Kumar
Keyword(s):  
Myelin Sheath ◽  
Cell Shrinkage ◽  
Sheath Formation

scholarly journals Individual neuronal subtypes control initial myelin sheath growth and stabilization

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Heather N. Nelson ◽  
Anthony J. Treichel ◽  
Erin N. Eggum ◽  
Madeline R. Martell ◽  
Amanda J. Kaiser ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Central Nervous System ◽  
Nervous System ◽  
Myelin Sheath ◽  
Time Lapse ◽  
Marked Individual ◽  
Larval Zebrafish ◽  
Sheath Formation ◽  
Time Lapse Imaging

Abstract Background In the developing central nervous system, pre-myelinating oligodendrocytes sample candidate nerve axons by extending and retracting process extensions. Some contacts stabilize, leading to the initiation of axon wrapping, nascent myelin sheath formation, concentric wrapping and sheath elongation, and sheath stabilization or pruning by oligodendrocytes. Although axonal signals influence the overall process of myelination, the precise oligodendrocyte behaviors that require signaling from axons are not completely understood. In this study, we investigated whether oligodendrocyte behaviors during the early events of myelination are mediated by an oligodendrocyte-intrinsic myelination program or are over-ridden by axonal factors. Methods To address this, we utilized in vivo time-lapse imaging in embryonic and larval zebrafish spinal cord during the initial hours and days of axon wrapping and myelination. Transgenic reporter lines marked individual axon subtypes or oligodendrocyte membranes. Results In the larval zebrafish spinal cord, individual axon subtypes supported distinct nascent sheath growth rates and stabilization frequencies. Oligodendrocytes ensheathed individual axon subtypes at different rates during a two-day period after initial axon wrapping. When descending reticulospinal axons were ablated, local spinal axons supported a constant ensheathment rate despite the increased ratio of oligodendrocytes to target axons. Conclusion We conclude that properties of individual axon subtypes instruct oligodendrocyte behaviors during initial stages of myelination by differentially controlling nascent sheath growth and stabilization.

scholarly journals Translation of myelin basic protein mRNA in oligodendrocytes is regulated by integrin activation and hnRNP-K

2011 ◽  
Vol 192 (5) ◽  
pp. 797-811 ◽  
Author(s):  
Lisbeth S. Laursen ◽  
Colin W. Chan ◽  
Charles ffrench-Constant
Keyword(s):  
Protein Synthesis ◽  
Myelin Basic Protein ◽  
Myelin Sheath ◽  
Basic Protein ◽  
Inhibitory Effect ◽  
Integrin Activation ◽  
Hnrnp K ◽  
Sheath Formation ◽  
The Central Nervous System ◽  
Mrna Binding

Myelination in the central nervous system provides a unique example of how cells establish asymmetry. The myelinating cell, the oligodendrocyte, extends processes to and wraps multiple axons of different diameter, keeping the number of wraps proportional to the axon diameter. Local regulation of protein synthesis represents one mechanism used to control the different requirements for myelin sheath at each axo–glia interaction. Prior work has established that β1-integrins are involved in the axoglial interactions that initiate myelination. Here, we show that integrin activation regulates translation of a key sheath protein, myelin basic protein (MBP), by reversing the inhibitory effect of the mRNA 3′UTR. During oligodendrocyte differentiation and myelination α6β1-integrin interacts with hnRNP-K, an mRNA-binding protein, which binds to MBP mRNA and translocates from the nucleus to the myelin sheath. Furthermore, knockdown of hnRNP-K inhibits MBP protein synthesis during myelination. Together, these results identify a novel pathway by which axoglial adhesion molecules coordinate MBP synthesis with myelin sheath formation.

scholarly journals Ca2+ activity signatures of myelin sheath formation and growth in vivo

2017 ◽  
Vol 21 (1) ◽  
pp. 19-23 ◽  
Author(s):  
Marion Baraban ◽  
Sigrid Koudelka ◽  
David A. Lyons
Keyword(s):  
Myelin Sheath ◽  
Sheath Formation

scholarly journals Oligodendrocytes express synaptic proteins that modulate myelin sheath formation

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Alexandria N. Hughes ◽  
Bruce Appel
Keyword(s):  
Membrane Fusion ◽  
Myelin Sheath ◽  
Synaptic Vesicles ◽  
Fusion Proteins ◽  
Synaptic Proteins ◽  
Synaptic Protein ◽  
Site Location ◽  
Myelin Sheaths ◽  
Vesicular Release ◽  
Sheath Formation

Abstract Vesicular release from neurons promotes myelin sheath growth on axons. Oligodendrocytes express proteins that allow dendrites to respond to vesicular release at synapses, suggesting that axon-myelin contacts use similar communication mechanisms as synapses to form myelin sheaths. To test this, we used fusion proteins to track synaptic vesicle localization and membrane fusion in zebrafish during developmental myelination and investigated expression and localization of PSD95, a dendritic post-synaptic protein, within oligodendrocytes. Synaptic vesicles accumulate and exocytose at ensheathment sites with variable patterning and most sheaths localize PSD95 with patterning similar to exocytosis site location. Disruption of candidate PDZ-binding transsynaptic adhesion proteins in oligodendrocytes cause variable effects on sheath length and number. One candidate, Cadm1b, localizes to myelin sheaths where both PDZ binding and extracellular adhesion to axons mediate sheath growth. Our work raises the possibility that axon-glial communication contributes to myelin plasticity, providing new targets for mechanistic unraveling of developmental myelination.

Clobetasol Attenuates White Matter Injury by Promoting Oligodendrocyte Precursor Cell Differentiation

2020 ◽  
Vol 55 (4) ◽  
pp. 188-196
Author(s):  
Xuewen Su ◽  
Haifeng Yuan ◽  
Yuxin Bai ◽  
Junlong Chen ◽  
Mingze Sui ◽  
...  
Keyword(s):  
White Matter ◽  
Rat Model ◽  
Myelin Sheath ◽  
White Matter Injury ◽  
Neurological Deficits ◽  
Treatment Groups ◽  
Myelin Sheaths ◽  
Neurobehavioral Function ◽  
Sheath Formation ◽  
Oligodendrocyte Precursor

<b><i>Introduction:</i></b> White matter injury (WMI) is the most common brain injury in preterm infants and can result in life-long neurological deficits. The main cause of WMI is damage to the oligodendrocyte precursor cells (OPC) in the brain that results in delayed myelin sheath formation, or the destruction of existing myelin sheaths. OPC undergo highly regulated and strictly timed developmental changes that result in their transformation to mature oligodendrocytes capable of myelin production. <b><i>Objective:</i></b> Studies have shown that clobetasol strongly promotes differentiation of OPC into myelin sheaths. Therefore, we hypothesized that clobetasol may be a therapeutic option for the treatment of preterm WMI. <b><i>Methods:</i></b> We induced a WMI rat model and observed white matter damage under an optical microscope. Rats subjected to WMI were injected intraperitoneally with clobetasol (2 or 5 mg/kg daily) from day 1 to day 5 in the early treatment groups, or from day 6 to day 10 in the late treatment groups. After 17 days, the rats were sacrificed and the expression of myelin basic protein (MBP) was visualized using immunofluorescence. In addition, we evaluated myelin sheath formation using electron microscopy. The rats were also subjected to the suspension test, ramp test, and open field test to evaluate neurobehavioral functions. <b><i>Results:</i></b> A rat model of WMI was successfully induced. It was found that clobetasol significantly induced MBP expression and myelin sheath formation and improved neurobehavioral function in the rats subjected to WMI. <b><i>Conclusions:</i></b> Our results indicate that clobetasol attenuates WMI by promoting OPC differentiation, and it may be an effective therapeutic agent for the treatment of preterm WMI.

scholarly journals Myosin II has distinct functions in PNS and CNS myelin sheath formation

2008 ◽  
Vol 182 (6) ◽  
pp. 1171-1184 ◽  
Author(s):  
Haibo Wang ◽  
Ambika Tewari ◽  
Steven Einheber ◽  
James L. Salzer ◽  
Carmen V. Melendez-Vasquez
Keyword(s):  
Nervous System ◽  
Schwann Cells ◽  
Myelin Sheath ◽  
Actin Polymerization ◽  
Myosin Ii ◽  
Myelin Formation ◽  
Sheath Formation ◽  
Central Nervous Systems ◽  
Glial Membrane ◽  
Cytoskeleton Dynamics

The myelin sheath forms by the spiral wrapping of a glial membrane around the axon. The mechanisms responsible for this process are unknown but are likely to involve coordinated changes in the glial cell cytoskeleton. We have found that inhibition of myosin II, a key regulator of actin cytoskeleton dynamics, has remarkably opposite effects on myelin formation by Schwann cells (SC) and oligodendrocytes (OL). Myosin II is necessary for initial interactions between SC and axons, and its inhibition or down-regulation impairs their ability to segregate axons and elongate along them, preventing the formation of a 1:1 relationship, which is critical for peripheral nervous system myelination. In contrast, OL branching, differentiation, and myelin formation are potentiated by inhibition of myosin II. Thus, by controlling the spatial and localized activation of actin polymerization, myosin II regulates SC polarization and OL branching, and by extension their ability to form myelin. Our data indicate that the mechanisms regulating myelination in the peripheral and central nervous systems are distinct.

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