Myelinating Schwann cells and Netrin-1 control intra-nervous vascularization of the developing mouse sciatic nerve.
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ABSTRACT:
SUBMITTER: Taib S
PROVIDER: S-EPMC8782568 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Transference of RNAs and ribosomes from Schwann cell-to-axon was demonstrated in normal and regenerating peripheral nerves. Previously, we have shown that RNAs transfer is dependent on F-actin cytoskeleton and Myosin Va. Here, we explored the contribution of microtubules to newly synthesized RNAs transport from Schwann cell nuclei up to nodal microvilli in sciatic nerves. Results using immunohistochemistry and quantitative confocal FRET analysis indicate that Schwann cell-derived RNAs co-localize with microtubules in Schwann cell cytoplasm. Additionally, transport of Schwann cell-derived RNAs is nocodazole and colchicine sensitive demonstrating its dependence on microtubule network integrity. Moreover, mRNAs codifying neuron-specific proteins are among Schwann cell newly synthesized RNAs population, and some of them are associated with KIF1B and KIF5B microtubules-based motors.
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Project description:Transient receptor potential vanilloid 4 (TRPV4) is a non-selective calcium-permeable cation channel that is widely expressed and activated in various neurons and glial cells in the nervous system. Schwann cells (SCs) are primary glia cells that wrap around axons to form the myelin sheath in the peripheral nervous system. However, whether TRPV4 is expressed and functions in SCs is unclear. Here, we demonstrate functional expression of TRPV4 in mouse SCs and investigated its physiological significance. Deletion of TRPV4 did not affect normal myelin development for SCs in sciatic nerves in mice. However, after sciatic nerve cut injury, TRPV4 expression levels were remarkably increased in SCs following nerve demyelination. Ablation of TRPV4 expression impaired the demyelinating process after nerve injury, resulting in delayed remyelination and functional recovery of sciatic nerves. These results suggest that local activation of TRPV4 could be an attractive pharmacological target for therapeutic intervention after peripheral nerve injury.
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Project description:BackgroundSchwann cells (SC) and macrophages play key roles in the response to peripheral nerve injury (PNI). Accurate isolation of such cells is essential for further analyses that can lead to better understanding of the repair process after PNI. Separation of live SC from the injury site without culture enrichment is necessary for targeted gene expression analysis.New methodsTwo flow cytometric techniques are presented for rapid enrichment of live SC and macrophages from injured murine peripheral nerve without the need for culture.ResultsSC were isolated by fluorescent activated cell sorting (FACS) using transgenic expression of eGFP in SC, or by exclusion of other cell types collected from the injury site.Comparison with existing method(s)Gene expression analyses of peripheral nerve repair have commonly used whole nerve lysates. Isolating SC allows more accurate understanding of their specific role in repair. SC are commonly enriched from nerve by culture, however this changes gene expression patterns and limits the utility for transcriptomic analysis. The surface marker p75-NTR has variable expression in different SC phenotypes and during the course of injury and repair. Using p75-NTR for SC isolation might enrich only a subset of SC. More stably expressed lineage markers for SC are intracellular and not suitable for sorting for gene expression. The methods used here avoid the requirement for surface marker labeling of SC.ConclusionGene expression analysis of sorted cells from both methods showed successful enrichment of SC. Lineage markers such as Map1b, p75-NTR and S100b were enriched in the sorted SC population. SC sorting by eGFP expression showed improved enrichment, particularly of mature myelinating genes, although this could represent sampling of a subset of SC.
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Project description:Schwann cells experience de-differentiation, proliferation, migration, re-differentiation and myelination, and participate in the repair and regeneration of injured peripheral nerves. Our previous sequencing analysis suggested that the gene expression level of matrix metalloproteinase 7 (MMP7), a Schwann cell-secreted proteolytic enzyme, was robustly elevated in rat sciatic nerve segments after nerve injury. However, the biological roles of MMP7 are poorly understood. Here, we exposed primary cultured Schwann cells with MMP7 recombinant protein and transfected siRNA against MMP7 into Schwann cells to examine the effect of exogenous and endogenous MMP7. Meanwhile, the effects of MMP7 in nerve regeneration after sciatic nerve crush in vivo were observed. Furthermore, RNA sequencing and bioinformatic analysis of Schwann cells were conducted to show the molecular mechanism behind the phenomenon. In vitro studies showed that MMP7 significantly elevated the migration rate of Schwann cells but did not affect the proliferation rate of Schwann cells. In vivo studies demonstrated that increased level of MMP7 contributed to Schwann cell migration and myelin sheaths formation after peripheral nerve injury. MMP7-mediated genetic changes were revealed by sequencing and bioinformatic analysis. Taken together, our current study demonstrated the promoting effect of MMP7 on Schwann cell migration and peripheral nerve regeneration, benefited the understanding of cellular and molecular mechanisms underlying peripheral nerve injury, and thus might facilitate the treatment of peripheral nerve regeneration in clinic.
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Project description:The peripheral nervous system (PNS) regenerates after injury. However regeneration is often compromised in case of large lesions, the speed of axon reconnection to their target being critical for successful functional recovery. After injury, mature Schwann cells (SCs) convert into repair cells that foster axonal regrowth, and redifferentiate to rebuild myelin. These processes require the regulation of several transcription factors, but the driving mechanisms remain partially understood. Here, we identify an early response to injury controlled by histone deacetylase (HDAC)2, which coordinates the action of other chromatin-remodeling enzymes to induce the upregulation of Oct6, a key transcription factor for Schwann cell development. Inactivating this mechanism using mouse genetics allows earlier conversion into repair cells and leads to faster axonal regrowth, but impairs remyelination. Consistently, short-term HDAC1/2 inhibitor treatment early after lesion accelerates functional recovery and enhances regeneration, thereby identifying a new therapeutic strategy to improve PNS regeneration after lesion.
2018-10-17 | PXD005383 | Pride
Project description:Lysine acetylation is a reversible Post-translational modification (PTM) involved in a broad array of physiological functions. Recent studies have demonstrated the involvement of protein acetylation in modulating Schwann cells' (SCs) biology and the peripheral nervous system (PNS) regeneration. However, the underlying mechanism is still under investigation. This descriptive study characterized the mouse sciatic nerve (SN) acetylome and explored their cellular distribution. Using a modified workflow for acetylome analysis, we identified 483 acetylated proteins containing 1,442 acetylation modification sites in the SN of adult C57BL/6. Notably, over 70% of identified peptides were acetylated. Bioinformatic analysis suggested that these acetylated proteins are mainly located in the myelin sheath, mitochondrial inner membrane, and actin cytoskeleton, and highlighted the remarkable differences between the mouse SN and brain (PXD027299）acetylome. Further manual annotation indicated that most acetylated proteins were mitochondrial and energy, and cytoskeleton and cell adhesion (> 45%). The acetylate modification of three novel myelin-related proteins were verified, including 2', 3' -cycling-nucleotide 3'-phosphodiesterase (CNP), Neurofilament light polypeptide (NEFL), neurofilament medium/high polypeptide (NFM/H), and periaxin (PRX). Immunofluorescence staining illustrated that, besides the nuclei, the acetylated proteins, including acetylated alpha-tubulin, were mainly co-localized with S100 positive SCs. Together, for the first time, this study provided a comprehensive mouse SN acetylome by using a simple but effective method. Moreover, we demonstrated that the acetylated SN proteins were predominantly located in SCs. These analyses and the method will contribute to understanding and uncovering the roles of protein acetylation in SCs development and PNS regeneration.
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Project description:Congenital peripheral nerve hyperexcitability (PNH) is usually associated with impaired function of voltage-gated K(+) channels (VGKCs) in neuromyotonia and demyelination in peripheral neuropathies. Schwartz-Jampel syndrome (SJS) is a form of PNH that is due to hypomorphic mutations of perlecan, the major proteoglycan of basement membranes. Schwann cell basement membrane and its cell receptors are critical for the myelination and organization of the nodes of Ranvier. We therefore studied a mouse model of SJS to determine whether a role for perlecan in these functions could account for PNH when perlecan is lacking. We revealed a role for perlecan in the longitudinal elongation and organization of myelinating Schwann cells because perlecan-deficient mice had shorter internodes, more numerous Schmidt-Lanterman incisures, and increased amounts of internodal fast VGKCs. Perlecan-deficient mice did not display demyelination events along the nerve trunk but developed dysmyelination of the preterminal segment associated with denervation processes at the neuromuscular junction. Investigating the excitability properties of the peripheral nerve suggested a persistent axonal depolarization during nerve firing in vitro, most likely due to defective K(+) homeostasis, and excluded the nerve trunk as the original site for PNH. Altogether, our data shed light on perlecan function by revealing critical roles in Schwann cell physiology and suggest that PNH in SJS originates distally from synergistic actions of peripheral nerve and neuromuscular junction changes.
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