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Kutikov AB, Moore SW, Layer RT, Podell PE, Sridhar N, Santamaria AJ, Aimetti AA, Hofstetter CP, Ulich TR, Guest JD. Method and Apparatus for the Automated Delivery of Continuous Neural Stem Cell Trails Into the Spinal Cord of Small and Large Animals. Neurosurgery 2020; 85:560-573. [PMID: 30169668 DOI: 10.1093/neuros/nyy379] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Accepted: 07/19/2018] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Immature neurons can extend processes after transplantation in adult animals. Neuronal relays can form between injected neural stem cells (NSCs) and surviving neurons, possibly improving recovery after spinal cord injury (SCI). Cell delivery methods of single or multiple bolus injections of concentrated cell suspensions thus far tested in preclinical and clinical experiments are suboptimal for new tract formation. Nonuniform injectate dispersal is often seen due to gravitational cell settling and clumping. Multiple injections have additive risks of hemorrhage, parenchymal damage, and cellular reflux and require additional surgical exposure. The deposition of multiply delivered cells boluses may be uneven and discontinuous. OBJECTIVE To develop an injection apparatus and methodology to deliver continuous cellular trails bridging spinal cord lesions. METHODS We improved the uniformity of cellular trails by formulating NSCs in hyaluronic acid. The TrailmakerTM stereotaxic injection device was automatized to extend a shape memory needle from a single-entry point in the spinal cord longitudinal axis to "pioneer" a new trail space and then retract while depositing an hyaluronic acid-NSC suspension. We conducted testing in a collagen spinal models, and animal testing using human NSCs (hNSCs) in rats and minipigs. RESULTS Continuous surviving trails of hNSCs within rat and minipig naive spinal cords were 12 and 40 mm in length. hNSC trails were delivered across semi-acute contusion injuries in rats. Transplanted hNSCs survived and were able to differentiate into neural lineage cells and astrocytes. CONCLUSION The TrailmakerTM creates longitudinal cellular trails spanning multiple levels from a single-entry point. This may enhance the ability of therapeutics to promote functional relays after SCI.
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Affiliation(s)
| | - Simon W Moore
- InVivo Therapeutics Corporation, Cambridge, Massachusetts
| | | | | | - Nithya Sridhar
- InVivo Therapeutics Corporation, Cambridge, Massachusetts
| | | | - Alex A Aimetti
- InVivo Therapeutics Corporation, Cambridge, Massachusetts
| | | | - Thomas R Ulich
- InVivo Therapeutics Corporation, Cambridge, Massachusetts
| | - James D Guest
- The Miami Project to Cure Paralysis, University of Miami, Miami, Florida.,Department of Neurosurgery, University of Miami, Miami, Florida
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Zhuang M, Li X, Zhu J, Zhang J, Niu F, Liang F, Chen M, Li D, Han P, Ji SJ. The m6A reader YTHDF1 regulates axon guidance through translational control of Robo3.1 expression. Nucleic Acids Res 2019; 47:4765-4777. [PMID: 30843071 PMCID: PMC6511866 DOI: 10.1093/nar/gkz157] [Citation(s) in RCA: 122] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2018] [Revised: 02/25/2019] [Accepted: 02/27/2019] [Indexed: 12/02/2022] Open
Abstract
N6-Methyladenosine (m6A) is a dynamic mRNA modification which regulates protein expression in various posttranscriptional levels. Functional studies of m6A in nervous system have focused on its writers and erasers so far, whether and how m6A readers mediate m6A functions through recognizing and binding their target mRNA remains poorly understood. Here, we find that the expression of axon guidance receptor Robo3.1 which plays important roles in midline crossing of spinal commissural axons is regulated precisely at translational level. The m6A reader YTHDF1 binds to and positively regulates translation of m6A-modified Robo3.1 mRNA. Either mutation of m6A sites in Robo3.1 mRNA or YTHDF1 knockdown or knockout leads to dramatic reduction of Robo3.1 protein without affecting Robo3.1 mRNA level. Specific ablation of Ythdf1 in spinal commissural neurons results in pre-crossing axon guidance defects. Our findings identify a mechanism that YTHDF1-mediated translation of m6A-modified Robo3.1 mRNA controls pre-crossing axon guidance in spinal cord.
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Affiliation(s)
- Mengru Zhuang
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China.,SUSTech-HKUST Joint PhD Program, Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Xinbei Li
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Junda Zhu
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Jian Zhang
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Fugui Niu
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China.,SUSTech-HIT Joint Graduate Program, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Fanghao Liang
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China.,SUSTech-HIT Joint Graduate Program, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Mengxian Chen
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Duo Li
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Peng Han
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Sheng-Jian Ji
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China.,Institute of Neuroscience, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
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Fisher M, Grainger RM. Special Considerations for Making Explants and Transplants with Xenopus tropicalis. Cold Spring Harb Protoc 2019; 2019:pdb.prot097428. [PMID: 31010887 DOI: 10.1101/pdb.prot097428] [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: 06/09/2023]
Abstract
Although Xenopus laevis is an important model organism for embryological experimentation, the smaller, more genetically tractable, and faster developing Xenopus tropicalis provides advantages for using genetic approaches to understand developmental mechanisms. Explant cultures and transplants of X. tropicalis embryonic tissues present unique opportunities to examine embryonic tissue determination in a simplified setting. Here we demonstrate preparation of explants and transplants of preplacodal head ectoderm in order to illustrate these approaches; however, these methods apply broadly to tissues throughout the embryo. We focus on technical adjustments to accommodate the differences in size, tissue character, and rate of development between X. laevis and X. tropicalis With only modest modifications, X. tropicalis embryos are quite amenable to the same kinds of experimental manipulations as X. laevis.
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Affiliation(s)
- Marilyn Fisher
- Biology Department, University of Virginia, Charlottesville, Virginia 22904
| | - Robert M Grainger
- Biology Department, University of Virginia, Charlottesville, Virginia 22904
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K + Channel Kv3.4 Is Essential for Axon Growth by Limiting the Influx of Ca 2+ into Growth Cones. J Neurosci 2017; 37:4433-4449. [PMID: 28320840 DOI: 10.1523/jneurosci.1076-16.2017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Revised: 03/10/2017] [Accepted: 03/13/2017] [Indexed: 11/21/2022] Open
Abstract
Membrane excitability in the axonal growth cones of embryonic neurons influences axon growth. Voltage-gated K+ (Kv) channels are key factors in controlling membrane excitability, but whether they regulate axon growth remains unclear. Here, we report that Kv3.4 is expressed in the axonal growth cones of embryonic spinal commissural neurons, motoneurons, dorsal root ganglion neurons, retinal ganglion cells, and callosal projection neurons during axon growth. Our in vitro (cultured dorsal spinal neurons of chick embryos) and in vivo (developing chick spinal commissural axons and rat callosal axons) findings demonstrate that knockdown of Kv3.4 by a specific shRNA impedes axon initiation, elongation, pathfinding, and fasciculation. In cultured dorsal spinal neurons, blockade of Kv3.4 by blood depressing substance II suppresses axon growth via an increase in the amplitude and frequency of Ca2+ influx through T-type and L-type Ca2+ channels. Electrophysiological results show that Kv3.4, the major Kv channel in the axonal growth cones of embryonic dorsal spinal neurons, is activated at more hyperpolarized potentials and inactivated more slowly than it is in postnatal and adult neurons. The opening of Kv3.4 channels effectively reduces growth cone membrane excitability, thereby limiting excessive Ca2+ influx at subthreshold potentials or during Ca2+-dependent action potentials. Furthermore, excessive Ca2+ influx induced by an optogenetic approach also inhibits axon growth. Our findings suggest that Kv3.4 reduces growth cone membrane excitability and maintains [Ca2+]i at an optimal concentration for normal axon growth.SIGNIFICANCE STATEMENT Accumulating evidence supports the idea that impairments in axon growth contribute to many clinical disorders, such as autism spectrum disorders, corpus callosum agenesis, Joubert syndrome, Kallmann syndrome, and horizontal gaze palsy with progressive scoliosis. Membrane excitability in the growth cone, which is mainly controlled by voltage-gated Ca2+ (Cav) and K+ (Kv) channels, modulates axon growth. The role of Cav channels during axon growth is well understood, but it is unclear whether Kv channels control axon outgrowth by regulating Ca2+ influx. This report shows that Kv3.4, which is transiently expressed in the axonal growth cones of many types of embryonic neurons, acts to reduce excessive Ca2+ influx through Cav channels and thus permits normal axon outgrowth.
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Rappaz B, Lai Wing Sun K, Correia JP, Wiseman PW, Kennedy TE. FLIM FRET Visualization of Cdc42 Activation by Netrin-1 in Embryonic Spinal Commissural Neuron Growth Cones. PLoS One 2016; 11:e0159405. [PMID: 27482713 PMCID: PMC4970703 DOI: 10.1371/journal.pone.0159405] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 07/02/2016] [Indexed: 12/29/2022] Open
Abstract
Netrin-1 is an essential extracellular chemoattractant that signals through its receptor DCC to guide commissural axon extension in the embryonic spinal cord. DCC directs the organization of F-actin in growth cones by activating an intracellular protein complex that includes the Rho GTPase Cdc42, a critical regulator of cell polarity and directional migration. To address the spatial distribution of signaling events downstream of netrin-1, we expressed the FRET biosensor Raichu-Cdc42 in cultured embryonic rat spinal commissural neurons. Using FLIM-FRET imaging we detected rapid activation of Cdc42 in neuronal growth cones following application of netrin-1. Investigating the signaling mechanisms that control Cdc42 activation by netrin-1, we demonstrate that netrin-1 rapidly enriches DCC at the leading edge of commissural neuron growth cones and that netrin-1 induced activation of Cdc42 in the growth cone is blocked by inhibiting src family kinase signaling. These findings reveal the activation of Cdc42 in embryonic spinal commissural axon growth cones and support the conclusion that src family kinase activation downstream of DCC is required for Cdc42 activation by netrin-1.
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Affiliation(s)
- Benjamin Rappaz
- Program in NeuroEngineering, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Neurology and Neurosurgery, Montréal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Physics, McGill University, Montreal, QC, H3A 2T8, Canada
| | - Karen Lai Wing Sun
- Program in NeuroEngineering, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Neurology and Neurosurgery, Montréal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada
| | - James P. Correia
- Program in NeuroEngineering, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Neurology and Neurosurgery, Montréal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada
| | - Paul W. Wiseman
- Program in NeuroEngineering, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Physics, McGill University, Montreal, QC, H3A 2T8, Canada
- Department of Chemistry, McGill University, Montreal, QC, H3A 0B8, Canada
| | - Timothy E. Kennedy
- Program in NeuroEngineering, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Neurology and Neurosurgery, Montréal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada
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Chen X, Yang H, Zhou X, Zhang L, Lu X. MiR-93 Targeting EphA4 Promotes Neurite Outgrowth from Spinal Cord Neurons. J Mol Neurosci 2016; 58:517-24. [PMID: 26798048 DOI: 10.1007/s12031-015-0709-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2015] [Accepted: 12/28/2015] [Indexed: 11/26/2022]
Abstract
The failure of neurite outgrowth in the adult mammalian spinal cord injury is thought to be attributed to the intrinsic growth ability of mature neurons. Ephrin/Eph system is a major growth regulator of many axonal guidance processes. EphA4 is expressed specifically in traumatic central nervous system (CNS) and dynamically regulate target gene expression, suggesting that it may be associated with neural regeneration. Here, we found an alteration in temporal expression of miR-93 following a contusive spinal cord injury (SCI) in adult rats. The messenger RNA (mRNA) expression level of miR-93 was upregulated and the protein expression levels of EphA4, p-Ephexin, and active RhoA were all decreased in traumatic spinal cord relative to those with an intact spinal cord. Infection of cultured spinal cord neurons (SCNs) with miR-93 mimic led to neuronal growth promotion and decreased levels of EphA4, p-Ephexin, and active RhoA protein expression. Dual-luciferase reporter assay confirmed that miR-93 bound to the three prime untranslated region (3' UTR) of EphA4 and inhibited the expression of EphA4 mRNA. These findings provide evidence that miR-93 inhibits EphA4 expression, decreased EphA4 expression could promote neurite outgrowth in SCNs due to reduced levels of p-Ephexin and active RhoA.
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Affiliation(s)
- Xiaogang Chen
- Department of Orthopedic Surgery, The First Affiliated Hospital of Soochow University, 188 Shizi Street, Suzhou, 215006, Jiangsu Province, China
- Department of Orthopedic Surgery, Huai'an NO.2 People's Hospital, Affiliated Huai'an Hospital of Xuzhou Medical College, Huai'an, 223002, Jiangsu Province, China
| | - Huilin Yang
- Department of Orthopedic Surgery, The First Affiliated Hospital of Soochow University, 188 Shizi Street, Suzhou, 215006, Jiangsu Province, China.
| | - Xiaoqing Zhou
- Department of Orthopedic Surgery, Huai'an NO.2 People's Hospital, Affiliated Huai'an Hospital of Xuzhou Medical College, Huai'an, 223002, Jiangsu Province, China
| | - Lin Zhang
- Department of Orthopedic Surgery, Huai'an NO.2 People's Hospital, Affiliated Huai'an Hospital of Xuzhou Medical College, Huai'an, 223002, Jiangsu Province, China
| | - Xiaoqing Lu
- Department of Orthopedic Surgery, Huai'an NO.2 People's Hospital, Affiliated Huai'an Hospital of Xuzhou Medical College, Huai'an, 223002, Jiangsu Province, China
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Colak D, Ji SJ, Porse BT, Jaffrey SR. Regulation of axon guidance by compartmentalized nonsense-mediated mRNA decay. Cell 2013; 153:1252-65. [PMID: 23746841 PMCID: PMC3685487 DOI: 10.1016/j.cell.2013.04.056] [Citation(s) in RCA: 147] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Revised: 03/05/2013] [Accepted: 04/30/2013] [Indexed: 12/13/2022]
Abstract
Growth cones enable axons to navigate toward their targets by responding to extracellular signaling molecules. Growth-cone responses are mediated in part by the local translation of axonal messenger RNAs (mRNAs). However, the mechanisms that regulate local translation are poorly understood. Here we show that Robo3.2, a receptor for the Slit family of guidance cues, is synthesized locally within axons of commissural neurons. Robo3.2 translation is induced by floor-plate-derived signals as axons cross the spinal cord midline. Robo3.2 is also a predicted target of the nonsense-mediated mRNA decay (NMD) pathway. We find that NMD regulates Robo3.2 synthesis by inducing the degradation of Robo3.2 transcripts in axons that encounter the floor plate. Commissural neurons deficient in NMD proteins exhibit aberrant axonal trajectories after crossing the midline, consistent with misregulation of Robo3.2 expression. These data show that local translation is regulated by mRNA stability and that NMD acts locally to influence axonal pathfinding.
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Affiliation(s)
- Dilek Colak
- Department of Pharmacology, Weill Medical College, Cornell University, New York, NY 10065, USA
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