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Wang Z, Kumaran M, Batsel E, Testor-Cabrera S, Beine Z, Ribelles AA, Tsoulfas P, Venkatesh I, Blackmore MG. Injury distance limits the transcriptional response to spinal injury. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.27.596075. [PMID: 38854133 PMCID: PMC11160615 DOI: 10.1101/2024.05.27.596075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
The ability of neurons to sense and respond to damage is fundamental to homeostasis and nervous system repair. For some cell types, notably dorsal root ganglia (DRG) and retinal ganglion cells (RGCs), extensive profiling has revealed a large transcriptional response to axon injury that determines survival and regenerative outcomes. In contrast, the injury response of most supraspinal cell types, whose limited regeneration constrains recovery from spinal injury, is mostly unknown. Here we employed single-nuclei sequencing in mice to profile the transcriptional responses of diverse supraspinal cell types to spinal injury. Surprisingly, thoracic spinal injury triggered only modest changes in gene expression across all populations, including corticospinal tract (CST) neurons. Moreover, CST neurons also responded minimally to cervical injury but much more strongly to intracortical axotomy, including upregulation of numerous regeneration and apoptosis-related transcripts shared with injured DRG and RGC neurons. Thus, the muted response of CST neuron to spinal injury is linked to the injury's distal location, rather than intrinsic cellular characteristics. More broadly, these findings indicate that a central challenge for enhancing regeneration after a spinal injury is the limited sensing of distant injuries and the subsequent modest baseline neuronal response.
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Affiliation(s)
- Zimei Wang
- Department of Biomedical Sciences, Marquette University, Milwaukee, WI
| | - Manojkumar Kumaran
- Council of Scientific and Industrial Research (CSIR) – Center for Cellular and Molecular Biology (CCMB), Hyderabad, Telangana, India
| | - Elizabeth Batsel
- Department of Biomedical Sciences, Marquette University, Milwaukee, WI
| | | | - Zac Beine
- Department of Biomedical Sciences, Marquette University, Milwaukee, WI
| | | | - Pantelis Tsoulfas
- Department of Neurological Surgery, Miami Project to Cure Paralysis, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Ishwariya Venkatesh
- Council of Scientific and Industrial Research (CSIR) – Center for Cellular and Molecular Biology (CCMB), Hyderabad, Telangana, India
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2
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Transcriptional Control of Peripheral Nerve Regeneration. Mol Neurobiol 2022; 60:329-341. [PMID: 36261692 DOI: 10.1007/s12035-022-03090-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 10/10/2022] [Indexed: 10/24/2022]
Abstract
Transcription factors are master regulators of various cellular processes under diverse physiological and pathological conditions. Many transcription factors that are differentially expressed after injury to peripheral nerves play important roles in nerve regeneration. Considering that rapid and timely regrowth of injured axons is a prerequisite for successful target reinnervation, here, we compile transcription factors that mediates axon elongation, including axon growth suppressor Klf4 and axon growth promoters c-Myc, Sox11, STAT3, Atf3, c-Jun, Smad1, C/EBPδ, and p53. Besides neuronal changes, Schwann cell phenotype modulation is also critical for nerve regeneration. The activation of Schwann cells at early time points post injury provides a permissive microenvironment whereas the re-differentiation of Schwann cells at later time points supports myelin sheath formation. Hence, c-Jun and Sox2, two critical drivers for Schwann cell reprogramming, as well as Krox-20 and Sox10, two essential regulators of Schwann cell myelination, are reviewed. These transcription factors may serve as promising targets for promoting the functional recovery of injured peripheral nerves.
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3
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Avraham O, Le J, Leahy K, Li T, Zhao G, Cavalli V. Analysis of neuronal injury transcriptional response identifies CTCF and YY1 as co-operating factors regulating axon regeneration. Front Mol Neurosci 2022; 15:967472. [PMID: 36081575 PMCID: PMC9446241 DOI: 10.3389/fnmol.2022.967472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2022] [Accepted: 07/28/2022] [Indexed: 11/13/2022] Open
Abstract
Injured sensory neurons activate a transcriptional program necessary for robust axon regeneration and eventual target reinnervation. Understanding the transcriptional regulators that govern this axon regenerative response may guide therapeutic strategies to promote axon regeneration in the injured nervous system. Here, we used cultured dorsal root ganglia neurons to identify pro-regenerative transcription factors. Using RNA sequencing, we first characterized this neuronal culture and determined that embryonic day 13.5 DRG (eDRG) neurons cultured for 7 days are similar to e15.5 DRG neurons in vivo and that all neuronal subtypes are represented. This eDRG neuronal culture does not contain other non-neuronal cell types. Next, we performed RNA sequencing at different time points after in vitro axotomy. Analysis of differentially expressed genes revealed upregulation of known regeneration associated transcription factors, including Jun, Atf3 and Rest, paralleling the axon injury response in vivo. Analysis of transcription factor binding sites in differentially expressed genes revealed other known transcription factors promoting axon regeneration, such as Myc, Hif1α, Pparγ, Ascl1a, Srf, and Ctcf, as well as other transcription factors not yet characterized in axon regeneration. We next tested if overexpression of novel candidate transcription factors alone or in combination promotes axon regeneration in vitro. Our results demonstrate that expression of Ctcf with Yy1 or E2f2 enhances in vitro axon regeneration. Our analysis highlights that transcription factor interaction and chromatin architecture play important roles as a regulator of axon regeneration.
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Affiliation(s)
- Oshri Avraham
- Department of Neuroscience, Washington University School of Medicine, St. Louis, MO, United States
| | - Jimmy Le
- Department of Neuroscience, Washington University School of Medicine, St. Louis, MO, United States
| | - Kathleen Leahy
- Department of Neuroscience, Washington University School of Medicine, St. Louis, MO, United States
| | - Tiandao Li
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, United States
- Center of Regenerative Medicine, Washington University School of Medicine, St. Louis, MO, United States
| | - Guoyan Zhao
- Department of Neuroscience, Washington University School of Medicine, St. Louis, MO, United States
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, United States
| | - Valeria Cavalli
- Department of Neuroscience, Washington University School of Medicine, St. Louis, MO, United States
- Center of Regenerative Medicine, Washington University School of Medicine, St. Louis, MO, United States
- Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO, United States
- *Correspondence: Valeria Cavalli,
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4
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Blackmore M, Batsel E, Tsoulfas P. Widening spinal injury research to consider all supraspinal cell types: Why we must and how we can. Exp Neurol 2021; 346:113862. [PMID: 34520726 PMCID: PMC8805209 DOI: 10.1016/j.expneurol.2021.113862] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 08/19/2021] [Accepted: 09/08/2021] [Indexed: 01/05/2023]
Abstract
The supraspinal connectome consists of dozens of neuronal populations that project axons from the brain to the spinal cord to influence a wide range of motor, autonomic, and sensory functions. The complexity and wide distribution of supraspinal neurons present significant technical challenges, leading most spinal cord injury research to focus on a handful of major pathways such as the corticospinal, rubrospinal, and raphespinal. Much less is known about many additional populations that carry information to modulate or compensate for these main pathways, or which carry pre-autonomic and other information of high value to individuals with spinal injury. A confluence of technical developments, however, now enables a whole-connectome study of spinal cord injury. Improved viral labeling, tissue clearing, and automated registration to 3D atlases can quantify supraspinal neurons throughout the murine brain, offering a practical means to track responses to injury and treatment on an unprecedented scale. Here we discuss the need for expanded connectome-wide analyses in spinal injury research, illustrate the potential by discussing a new web-based resource for brain-wide study of supraspinal neurons, and highlight future prospects for connectome analyses.
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Affiliation(s)
- Murray Blackmore
- Department of Biomedical Sciences, Marquette University, 53201, United States of America.
| | - Elizabeth Batsel
- Department of Biomedical Sciences, Marquette University, 53201, United States of America
| | - Pantelis Tsoulfas
- Department of Neurological Surgery, Miami Project to Cure Paralysis, University of Miami Miller School of Medicine, Miami, FL 33136, United States of America
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5
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DeFrates KG, Franco D, Heber-Katz E, Messersmith PB. Unlocking mammalian regeneration through hypoxia inducible factor one alpha signaling. Biomaterials 2021; 269:120646. [PMID: 33493769 PMCID: PMC8279430 DOI: 10.1016/j.biomaterials.2020.120646] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 12/19/2020] [Accepted: 12/29/2020] [Indexed: 02/08/2023]
Abstract
Historically, the field of regenerative medicine has aimed to heal damaged tissue through the use of biomaterials scaffolds or delivery of foreign progenitor cells. Despite 30 years of research, however, translation and commercialization of these techniques has been limited. To enable mammalian regeneration, a more practical approach may instead be to develop therapies that evoke endogenous processes reminiscent of those seen in innate regenerators. Recently, investigations into tadpole tail regrowth, zebrafish limb restoration, and the super-healing Murphy Roths Large (MRL) mouse strain, have identified ancient oxygen-sensing pathways as a possible target to achieve this goal. Specifically, upregulation of the transcription factor, hypoxia-inducible factor one alpha (HIF-1α) has been shown to modulate cell metabolism and plasticity, as well as inflammation and tissue remodeling, possibly priming injuries for regeneration. Since HIF-1α signaling is conserved across species, environmental or pharmacological manipulation of oxygen-dependent pathways may elicit a regenerative response in non-healing mammals. In this review, we will explore the emerging role of HIF-1α in mammalian healing and regeneration, as well as attempts to modulate protein stability through hyperbaric oxygen treatment, intermittent hypoxia therapy, and pharmacological targeting. We believe that these therapies could breathe new life into the field of regenerative medicine.
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Affiliation(s)
- Kelsey G DeFrates
- Department of Bioengineering and Materials Science and Engineering, University of California, Berkeley, CA, USA.
| | - Daniela Franco
- Department of Bioengineering and Materials Science and Engineering, University of California, Berkeley, CA, USA.
| | - Ellen Heber-Katz
- Laboratory of Regenerative Medicine, Lankenau Institute for Medical Research, Wynnewood, PA, USA.
| | - Phillip B Messersmith
- Department of Bioengineering and Materials Science and Engineering, University of California, Berkeley, CA, USA; Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
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6
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Ewan EE, Avraham O, Carlin D, Gonçalves TM, Zhao G, Cavalli V. Ascending dorsal column sensory neurons respond to spinal cord injury and downregulate genes related to lipid metabolism. Sci Rep 2021; 11:374. [PMID: 33431991 PMCID: PMC7801468 DOI: 10.1038/s41598-020-79624-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 12/07/2020] [Indexed: 02/08/2023] Open
Abstract
Regeneration failure after spinal cord injury (SCI) results in part from the lack of a pro-regenerative response in injured neurons, but the response to SCI has not been examined specifically in injured sensory neurons. Using RNA sequencing of dorsal root ganglion, we determined that thoracic SCI elicits a transcriptional response distinct from sciatic nerve injury (SNI). Both SNI and SCI induced upregulation of ATF3 and Jun, yet this response failed to promote growth in sensory neurons after SCI. RNA sequencing of purified sensory neurons one and three days after injury revealed that unlike SNI, the SCI response is not sustained. Both SCI and SNI elicited the expression of ATF3 target genes, with very little overlap between conditions. Pathway analysis of differentially expressed ATF3 target genes revealed that fatty acid biosynthesis and terpenoid backbone synthesis were downregulated after SCI but not SNI. Pharmacologic inhibition of fatty acid synthase, the enzyme generating palmitic acid, decreased axon growth and regeneration in vitro. These results support the notion that decreased expression of lipid metabolism-related genes after SCI, including fatty acid synthase, may restrict axon regenerative capacity after SCI.
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Affiliation(s)
- Eric E Ewan
- Department of Neuroscience, Washington University School of Medicine, 660 S. Euclid Ave, Campus Box 8108, St. Louis, MO, 63110-1093, USA
| | - Oshri Avraham
- Department of Neuroscience, Washington University School of Medicine, 660 S. Euclid Ave, Campus Box 8108, St. Louis, MO, 63110-1093, USA
| | - Dan Carlin
- Department of Neuroscience, Washington University School of Medicine, 660 S. Euclid Ave, Campus Box 8108, St. Louis, MO, 63110-1093, USA
| | - Tassia Mangetti Gonçalves
- Department of Neuroscience, Washington University School of Medicine, 660 S. Euclid Ave, Campus Box 8108, St. Louis, MO, 63110-1093, USA
| | - Guoyan Zhao
- Department of Neuroscience, Washington University School of Medicine, 660 S. Euclid Ave, Campus Box 8108, St. Louis, MO, 63110-1093, USA
| | - Valeria Cavalli
- Department of Neuroscience, Washington University School of Medicine, 660 S. Euclid Ave, Campus Box 8108, St. Louis, MO, 63110-1093, USA. .,Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO, 63110, USA. .,Center of Regenerative Medicine, Washington University School of Medicine, St. Louis, MO, 63110, USA.
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7
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Yang X, Xu X, Cai X, He J, Lu P, Guo Q, Wang G, Zhu H, Wang H, Xue C. Gene set enrichment analysis and protein-protein interaction network analysis after sciatic nerve injury. ANNALS OF TRANSLATIONAL MEDICINE 2020; 8:988. [PMID: 32953788 PMCID: PMC7475449 DOI: 10.21037/atm-20-4958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Background Peripheral nerves are able to regenerate spontaneously after injury. An increasing number of studies have investigated the mechanism of peripheral nerve regeneration and attempted to find potential therapeutic targets. The various bioinformatics analysis tools available, gene set enrichment analysis (GSEA) and protein-protein interaction (PPI) networks can effectively screen the crucial targets of neuroregeneration. Methods GSEA and PPI networks were constructed through ingenuity pathway analysis and sequential gene expression validation ex vitro to investigate the molecular processes at 1, 4, 7, and 14 days following sciatic nerve transection in rats. Results Immune response and the activation of related canonical pathways were classified as crucial biological events. Additionally, neural precursor cell expressed developmentally downregulated 4-like (NEDD4L), neuregulin 1 (NRG1), nuclear factor of activated T cells 2 (NFATC2), midline 1 (MID1), GLI family zinc finger 2 (GLI2), and ventral anterior homeobox 1 (VAX1), which were jointly involved in both immune response and axonal regeneration, were screened and their mRNA and protein expressions following nerve injury were validated. Among them, the expression of VAX1 continuously increased following nerve injury, and it was considered to be a potential therapeutic target. Conclusions The combined use of GSEA and PPI networks serves as a valuable way to identify potential therapeutic targets for neuroregeneration.
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Affiliation(s)
- Xiaoming Yang
- School of Biology and Basic Medical Sciences, Medical College of Soochow University, Suzhou, China.,Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Research Center of Clinical Medicine, Affiliated Hospital of Nantong University, Nantong, China.,Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, China
| | - Xi Xu
- Department of Rehabilitation Medicine, Affiliated Hospital of Nantong University, Nantong, China
| | - Xiaodong Cai
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, China
| | - Jin He
- School of Medicine, Nantong University, Nantong, China
| | - Panjian Lu
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, China
| | - Qi Guo
- Department of Hand Surgery, China-Japan Union Hospital, Jilin University, Changchun, China
| | - Gang Wang
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, China
| | - Hui Zhu
- Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Research Center of Clinical Medicine, Affiliated Hospital of Nantong University, Nantong, China.,Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, China
| | - Hongkui Wang
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, China
| | - Chengbin Xue
- Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Research Center of Clinical Medicine, Affiliated Hospital of Nantong University, Nantong, China.,Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, China
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8
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Li Y, Han W, Wu Y, Zhou K, Zheng Z, Wang H, Xie L, Li R, Xu K, Liu Y, Wang X, Xiao J. Stabilization of Hypoxia Inducible Factor-1α by Dimethyloxalylglycine Promotes Recovery from Acute Spinal Cord Injury by Inhibiting Neural Apoptosis and Enhancing Axon Regeneration. J Neurotrauma 2019; 36:3394-3409. [PMID: 31232175 DOI: 10.1089/neu.2018.6364] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Affiliation(s)
- Yao Li
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
- Molecular Pharmacology Research Center, School of Pharmaceutical Science, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Wen Han
- Molecular Pharmacology Research Center, School of Pharmaceutical Science, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Yanqing Wu
- The Institute of Life Sciences, Wenzhou University, Wenzhou, Zhejiang, China
| | - Kailiang Zhou
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
- Molecular Pharmacology Research Center, School of Pharmaceutical Science, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Zhilong Zheng
- Molecular Pharmacology Research Center, School of Pharmaceutical Science, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Haoli Wang
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
- Molecular Pharmacology Research Center, School of Pharmaceutical Science, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Ling Xie
- Molecular Pharmacology Research Center, School of Pharmaceutical Science, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Rui Li
- Molecular Pharmacology Research Center, School of Pharmaceutical Science, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Ke Xu
- The Institute of Life Sciences, Wenzhou University, Wenzhou, Zhejiang, China
| | - Yanlong Liu
- Molecular Pharmacology Research Center, School of Pharmaceutical Science, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Xiangyang Wang
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Jian Xiao
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
- Molecular Pharmacology Research Center, School of Pharmaceutical Science, Wenzhou Medical University, Wenzhou, Zhejiang, China
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9
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Abstract
Permanent disabilities following CNS injuries result from the failure of injured axons to regenerate and rebuild functional connections with their original targets. By contrast, injury to peripheral nerves is followed by robust regeneration, which can lead to recovery of sensory and motor functions. This regenerative response requires the induction of widespread transcriptional and epigenetic changes in injured neurons. Considerable progress has been made in recent years in understanding how peripheral axon injury elicits these widespread changes through the coordinated actions of transcription factors, epigenetic modifiers and, to a lesser extent, microRNAs. Although many questions remain about the interplay between these mechanisms, these new findings provide important insights into the pivotal role of coordinated gene expression and chromatin remodelling in the neuronal response to injury.
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Affiliation(s)
- Marcus Mahar
- Department of Neuroscience, Hope Center for Neurological Disorders and Center of Regenerative Medicine, Washington University School of Medicine, St Louis, MO, USA
| | - Valeria Cavalli
- Department of Neuroscience, Hope Center for Neurological Disorders and Center of Regenerative Medicine, Washington University School of Medicine, St Louis, MO, USA.
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10
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Wahane S, Halawani D, Zhou X, Zou H. Epigenetic Regulation Of Axon Regeneration and Glial Activation in Injury Responses. Front Genet 2019; 10:640. [PMID: 31354788 PMCID: PMC6629966 DOI: 10.3389/fgene.2019.00640] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 06/18/2019] [Indexed: 12/22/2022] Open
Abstract
Injury to the nervous system triggers a multicellular response in which epigenetic mechanisms play an important role in regulating cell type-specific transcriptional changes. Here, we summarize recent progress in characterizing neuronal intrinsic and extrinsic chromatin reconfigurations and epigenetic changes triggered by axonal injury that shape neuroplasticity and glial functions. We specifically discuss regeneration-associated transcriptional modules comprised of transcription factors and epigenetic regulators that control axon growth competence. We also review epigenetic regulation of neuroinflammation and astroglial responses that impact neural repair. These advances provide a framework for developing epigenetic strategies to maximize adaptive alterations while minimizing maladaptive stress responses in order to enhance axon regeneration and achieve functional recovery after injury.
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Affiliation(s)
- Shalaka Wahane
- Nash Family Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Dalia Halawani
- Nash Family Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Xiang Zhou
- Nash Family Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States.,Department of Orthopedics, Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Hongyan Zou
- Nash Family Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States.,Department of Neurosurgery, Icahn School of Medicine at Mount Sinai, New York, NY, United States
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11
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Epigenetic regulator UHRF1 inactivates REST and growth suppressor gene expression via DNA methylation to promote axon regeneration. Proc Natl Acad Sci U S A 2018; 115:E12417-E12426. [PMID: 30530687 DOI: 10.1073/pnas.1812518115] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Injured peripheral sensory neurons switch to a regenerative state after axon injury, which requires transcriptional and epigenetic changes. However, the roles and mechanisms of gene inactivation after injury are poorly understood. Here, we show that DNA methylation, which generally leads to gene silencing, is required for robust axon regeneration after peripheral nerve lesion. Ubiquitin-like containing PHD ring finger 1 (UHRF1), a critical epigenetic regulator involved in DNA methylation, increases upon axon injury and is required for robust axon regeneration. The increased level of UHRF1 results from a decrease in miR-9. The level of another target of miR-9, the transcriptional regulator RE1 silencing transcription factor (REST), transiently increases after injury and is required for axon regeneration. Mechanistically, UHRF1 interacts with DNA methyltransferases (DNMTs) and H3K9me3 at the promoter region to repress the expression of the tumor suppressor gene phosphatase and tensin homolog (PTEN) and REST. Our study reveals an epigenetic mechanism that silences tumor suppressor genes and restricts REST expression in time after injury to promote axon regeneration.
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12
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Venkatesh I, Mehra V, Wang Z, Califf B, Blackmore MG. Developmental Chromatin Restriction of Pro-Growth Gene Networks Acts as an Epigenetic Barrier to Axon Regeneration in Cortical Neurons. Dev Neurobiol 2018; 78:960-977. [PMID: 29786967 PMCID: PMC6204296 DOI: 10.1002/dneu.22605] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 05/01/2018] [Accepted: 05/04/2018] [Indexed: 12/21/2022]
Abstract
Axon regeneration in the central nervous system is prevented in part by a developmental decline in the intrinsic regenerative ability of maturing neurons. This loss of axon growth ability likely reflects widespread changes in gene expression, but the mechanisms that drive this shift remain unclear. Chromatin accessibility has emerged as a key regulatory mechanism in other cellular contexts, raising the possibility that chromatin structure may contribute to the age-dependent loss of regenerative potential. Here we establish an integrated bioinformatic pipeline that combines analysis of developmentally dynamic gene networks with transcription factor regulation and genome-wide maps of chromatin accessibility. When applied to the developing cortex, this pipeline detected overall closure of chromatin in sub-networks of genes associated with axon growth. We next analyzed mature CNS neurons that were supplied with various pro-regenerative transcription factors. Unlike prior results with SOX11 and KLF7, here we found that neither JUN nor an activated form of STAT3 promoted substantial corticospinal tract regeneration. Correspondingly, chromatin accessibility in JUN or STAT3 target genes was substantially lower than in predicted targets of SOX11 and KLF7. Finally, we used the pipeline to predict pioneer factors that could potentially relieve chromatin constraints at growth-associated loci. Overall this integrated analysis substantiates the hypothesis that dynamic chromatin accessibility contributes to the developmental decline in axon growth ability and influences the efficacy of pro-regenerative interventions in the adult, while also pointing toward selected pioneer factors as high-priority candidates for future combinatorial experiments. © 2018 Wiley Periodicals, Inc. Develop Neurobiol 00: 000-000, 2018.
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Affiliation(s)
| | - Vatsal Mehra
- Department of Biomedical Sciences, Marquette University, 53201
| | - Zimei Wang
- Department of Biomedical Sciences, Marquette University, 53201
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13
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KLF6 and STAT3 co-occupy regulatory DNA and functionally synergize to promote axon growth in CNS neurons. Sci Rep 2018; 8:12565. [PMID: 30135567 PMCID: PMC6105645 DOI: 10.1038/s41598-018-31101-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 08/10/2018] [Indexed: 11/26/2022] Open
Abstract
The failure of axon regeneration in the CNS limits recovery from damage and disease. Members of the KLF family of transcription factors can exert both positive and negative effects on axon regeneration, but the underlying mechanisms are unclear. Here we show that forced expression of KLF6 promotes axon regeneration by corticospinal tract neurons in the injured spinal cord. RNA sequencing identified 454 genes whose expression changed upon forced KLF6 expression in vitro, including sub-networks that were highly enriched for functions relevant to axon extension including cytoskeleton remodeling, lipid synthesis, and bioenergetics. In addition, promoter analysis predicted a functional interaction between KLF6 and a second transcription factor, STAT3, and genome-wide footprinting using ATAC-Seq data confirmed frequent co-occupancy. Co-expression of the two factors yielded a synergistic elevation of neurite growth in vitro. These data clarify the transcriptional control of axon growth and point the way toward novel interventions to promote CNS regeneration.
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14
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Herman PE, Papatheodorou A, Bryant SA, Waterbury CKM, Herdy JR, Arcese AA, Buxbaum JD, Smith JJ, Morgan JR, Bloom O. Highly conserved molecular pathways, including Wnt signaling, promote functional recovery from spinal cord injury in lampreys. Sci Rep 2018; 8:742. [PMID: 29335507 PMCID: PMC5768751 DOI: 10.1038/s41598-017-18757-1] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Accepted: 12/18/2017] [Indexed: 12/23/2022] Open
Abstract
In mammals, spinal cord injury (SCI) leads to dramatic losses in neurons and synaptic connections, and consequently function. Unlike mammals, lampreys are vertebrates that undergo spontaneous regeneration and achieve functional recovery after SCI. Therefore our goal was to determine the complete transcriptional responses that occur after SCI in lampreys and to identify deeply conserved pathways that promote regeneration. We performed RNA-Seq on lamprey spinal cord and brain throughout the course of functional recovery. We describe complex transcriptional responses in the injured spinal cord, and somewhat surprisingly, also in the brain. Transcriptional responses to SCI in lampreys included transcription factor networks that promote peripheral nerve regeneration in mammals such as Atf3 and Jun. Furthermore, a number of highly conserved axon guidance, extracellular matrix, and proliferation genes were also differentially expressed after SCI in lampreys. Strikingly, ~3% of differentially expressed transcripts belonged to the Wnt pathways. These included members of the Wnt and Frizzled gene families, and genes involved in downstream signaling. Pharmacological inhibition of Wnt signaling inhibited functional recovery, confirming a critical role for this pathway. These data indicate that molecular signals present in mammals are also involved in regeneration in lampreys, supporting translational relevance of the model.
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Affiliation(s)
- Paige E Herman
- The Feinstein Institute for Medical Research, Center for Autoimmune and Musculoskeletal Disease, Manhasset, NY, 11030, USA
| | - Angelos Papatheodorou
- The Feinstein Institute for Medical Research, Center for Autoimmune and Musculoskeletal Disease, Manhasset, NY, 11030, USA
| | - Stephanie A Bryant
- University of Kentucky, Department of Biology, Lexington, KY, 40506, USA
| | | | - Joseph R Herdy
- University of Kentucky, Department of Biology, Lexington, KY, 40506, USA
| | - Anthony A Arcese
- The Feinstein Institute for Medical Research, Center for Autoimmune and Musculoskeletal Disease, Manhasset, NY, 11030, USA
| | - Joseph D Buxbaum
- Icahn School of Medicine at Mount Sinai, Department of Psychiatry, New York, NY, 10029, USA
| | - Jeramiah J Smith
- University of Kentucky, Department of Biology, Lexington, KY, 40506, USA
| | - Jennifer R Morgan
- Marine Biological Laboratory, The Eugene Bell Center for Regenerative Biology and Tissue Engineering, Woods Hole, MA, 02543, USA.
| | - Ona Bloom
- The Feinstein Institute for Medical Research, Center for Autoimmune and Musculoskeletal Disease, Manhasset, NY, 11030, USA.
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15
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An S, Zhou M, Li Z, Feng M, Cao G, Lu S, Liu L. Administration of CoCl 2 Improves Functional Recovery in a Rat Model of Sciatic Nerve Transection Injury. Int J Med Sci 2018; 15:1423-1432. [PMID: 30443161 PMCID: PMC6216053 DOI: 10.7150/ijms.27867] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Accepted: 08/29/2018] [Indexed: 12/28/2022] Open
Abstract
Peripheral nerve injury is known to activate the hypoxia-inducible factor-1α (HIF-1α) pathway as one of pro-regenerative transcriptional programs, which could stimulate multiple injury-induced gene expression and contribute to axon regeneration and functional recovery. However, the role of HIF-1α in peripheral nerve regeneration remains to be fully elucidated. In this study, rats were divided into three groups and treated with sham surgery, surgery with cobalt chloride (CoCl2) and surgery with saline, respectively. Sciatic functional index, morphologic evaluations of muscle fibers, and never conduction velocity were performed to measure the functional recovery at 12 weeks postoperatively. In addition, the effects of CoCl2 on the expression of HIF-1α, glial cell line-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) were determined at mRNA levels; as well as HIF-1α, the dual leucine zipper kinase (DLK), the c-Jun N-terminal kinase (JNK), phosphorylated JNK (p-JNK), BDNF and NGF were measured at protein level at 4 weeks postoperatively. Systemic administration of CoCl2 (15 mg/kg/day intraperitoneally) significantly promoted functional recovery of rats with sciatic nerve transection injury. This study demonstrated in rats treated with CoCl2, the expression of HIF-1α, GDNF, BDNF and NGF was significantly increased at mRNA level, while HIF-1α, DLK, p-JNK, BDNF and NGF was significantly increased at protein level.
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Affiliation(s)
- Shuai An
- Department of Orthopedics, Xuanwu Hospital, Capital Medical University
| | - Meng Zhou
- Department of Orthopedics, Xuanwu Hospital, Capital Medical University
| | - Zheng Li
- Department of Orthopedics, Xuanwu Hospital, Capital Medical University
| | - Mingli Feng
- Department of Orthopedics, Xuanwu Hospital, Capital Medical University
| | - Guanglei Cao
- Department of Orthopedics, Xuanwu Hospital, Capital Medical University
| | - Shibao Lu
- Department of Orthopedics, Xuanwu Hospital, Capital Medical University
| | - Limin Liu
- Department of Orthopedics, Xuanwu Hospital, Capital Medical University
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16
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Enhanced axonal transport: A novel form of "plasticity" after primate and rodent spinal cord injury. Exp Neurol 2017; 301:59-69. [PMID: 29277625 DOI: 10.1016/j.expneurol.2017.12.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 12/09/2017] [Accepted: 12/21/2017] [Indexed: 11/22/2022]
Abstract
Deficient axonal transport after injury is believed to contribute to the failure of CNS regeneration. To better elucidate neural mechanisms associated with CNS responses to injury, we transected the dominant voluntary motor system, the corticospinal tract (CST), in the dorsolateral T10 spinal cord of rhesus monkeys. Three months later, a 4.5-fold increase in the number of CST axons located in the spared ventral corticospinal tract at both the lesion site and, surprisingly, remotely in the cervical spinal cord was observed. Additional studies of increases in corticospinal axon numbers in rat and primate models demonstrated that increases were transient and attributable to enhanced axonal transport rather than axonal sprouting. Accordingly, increases in axonal transport occur after CNS injury even in the longest projecting pathways of the non-human primate, likely representing an attempted adaptive response to injury as observed in the PNS.
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17
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Callif BL, Maunze B, Krueger NL, Simpson MT, Blackmore MG. The application of CRISPR technology to high content screening in primary neurons. Mol Cell Neurosci 2017; 80:170-179. [PMID: 28110021 DOI: 10.1016/j.mcn.2017.01.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 01/09/2017] [Accepted: 01/17/2017] [Indexed: 10/20/2022] Open
Abstract
Axon growth is coordinated by multiple interacting proteins that remain incompletely characterized. High content screening (HCS), in which manipulation of candidate genes is combined with rapid image analysis of phenotypic effects, has emerged as a powerful technique to identify key regulators of axon outgrowth. Here we explore the utility of a genome editing approach referred to as CRISPR (Clustered Regularly Interspersed Palindromic Repeats) for knockout screening in primary neurons. In the CRISPR approach a DNA-cleaving Cas enzyme is guided to genomic target sequences by user-created guide RNA (sgRNA), where it initiates a double-stranded break that ultimately results in frameshift mutation and loss of protein production. Using electroporation of plasmid DNA that co-expresses Cas9 enzyme and sgRNA, we first verified the ability of CRISPR targeting to achieve protein-level knockdown in cultured postnatal cortical neurons. Targeted proteins included NeuN (RbFox3) and PTEN, a well-studied regulator of axon growth. Effective knockdown lagged at least four days behind transfection, but targeted proteins were eventually undetectable by immunohistochemistry in >80% of transfected cells. Consistent with this, anti-PTEN sgRNA produced no changes in neurite outgrowth when assessed three days post-transfection. When week-long cultures were replated, however, PTEN knockdown consistently increased neurite lengths. These CRISPR-mediated PTEN effects were achieved using multi-well transfection and automated phenotypic analysis, indicating the suitability of PTEN as a positive control for future CRISPR-based screening efforts. Combined, these data establish an example of CRISPR-mediated protein knockdown in primary cortical neurons and its compatibility with HCS workflows.
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Affiliation(s)
- Ben L Callif
- Department of Biomedical Sciences, Marquette University, 53201, USA
| | - Brian Maunze
- Department of Biomedical Sciences, Marquette University, 53201, USA
| | - Nick L Krueger
- Department of Biomedical Sciences, Marquette University, 53201, USA
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18
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Selecting optimal combinations of transcription factors to promote axon regeneration: Why mechanisms matter. Neurosci Lett 2016; 652:64-73. [PMID: 28025113 DOI: 10.1016/j.neulet.2016.12.032] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Revised: 12/02/2016] [Accepted: 12/14/2016] [Indexed: 01/17/2023]
Abstract
Recovery from injuries to the central nervous system, including spinal cord injury, is constrained in part by the intrinsically low ability of many CNS neurons to mount an effective regenerative growth response. To improve outcomes, it is essential to understand and ultimately reverse these neuron-intrinsic constraints. Genetic manipulation of key transcription factors (TFs), which act to orchestrate production of multiple regeneration-associated genes, has emerged as a promising strategy. It is likely that no single TF will be sufficient to fully restore neuron-intrinsic growth potential, and that multiple, functionally interacting factors will be needed. An extensive literature, mostly from non-neural cell types, has identified potential mechanisms by which TFs can functionally synergize. Here we examine four potential mechanisms of TF/TF interaction; physical interaction, transcriptional cross-regulation, signaling-based cross regulation, and co-occupancy of regulatory DNA. For each mechanism, we consider how existing knowledge can be used to guide the discovery and effective use of TF combinations in the context of regenerative neuroscience. This mechanistic insight into TF interactions is needed to accelerate the design of effective TF-based interventions to relieve neuron-intrinsic constraints to regeneration and to foster recovery from CNS injury.
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19
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Wang Z, Winsor K, Nienhaus C, Hess E, Blackmore MG. Combined chondroitinase and KLF7 expression reduce net retraction of sensory and CST axons from sites of spinal injury. Neurobiol Dis 2016; 99:24-35. [PMID: 27988344 DOI: 10.1016/j.nbd.2016.12.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 12/02/2016] [Accepted: 12/13/2016] [Indexed: 11/26/2022] Open
Abstract
Axon regeneration in the central nervous system is limited both by inhibitory extracellular cues and by an intrinsically low capacity for axon growth in some CNS populations. Chondroitin sulfate proteoglycans (CSPGs) are well-studied inhibitors of axon growth in the CNS, and degradation of CSPGs by chondroitinase has been shown to improve the extension of injured axons. Alternatively, axon growth can be improved by targeting the neuron-intrinsic growth capacity through forced expression of regeneration-associated transcription factors. For example, a transcriptionally active chimera of Krüppel-like Factor 7 (KLF7) and a VP16 domain improves axon growth when expressed in corticospinal tract neurons. Here we tested the hypothesis that combined expression of chondroitinase and VP16-KLF7 would lead to further improvements in axon growth after spinal injury. Chondroitinase was expressed by viral transduction of cells in the spinal cord, while VP16-KLF7 was virally expressed in sensory neurons of the dorsal root ganglia or corticospinal tract (CST) neurons. After transection of the dorsal columns, both chondroitinase and VP16-KLF7 increased the proximity of severed sensory axons to the injury site. Similarly, after complete crush injuries, VP16-KLF7 expression increased the approach of CST axons to the injury site. In neither paradigm however, did single or combined treatment with chondroitinase or VP16-KLF7 enable regenerative growth distal to the injury. These results substantiate a role for CSPG inhibition and low KLF7 activity in determining the net retraction of axons from sites of spinal injury, while suggesting that additional factors act to limit a full regenerative response.
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Affiliation(s)
- Zimei Wang
- Department of Biomedical Sciences, Marquette University, 53201, USA
| | - Kristen Winsor
- Department of Biomedical Sciences, Marquette University, 53201, USA
| | | | - Evan Hess
- Department of Biomedical Sciences, Marquette University, 53201, USA
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20
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Venkatesh I, Simpson MT, Coley DM, Blackmore MG. Epigenetic profiling reveals a developmental decrease in promoter accessibility during cortical maturation in vivo. NEUROEPIGENETICS 2016; 8:19-26. [PMID: 27990351 PMCID: PMC5159751 DOI: 10.1016/j.nepig.2016.10.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Axon regeneration in adult central nervous system (CNS) is limited in part by a developmental decline in the ability of injured neurons to re-express needed regeneration associated genes (RAGs). Adult CNS neurons may lack appropriate pro-regenerative transcription factors, or may display chromatin structure that restricts transcriptional access to RAGs. Here we performed epigenetic profiling around the promoter regions of key RAGs, and found progressive restriction across a time course of cortical maturation. These data identify a potential intrinsic constraint to axon growth in adult CNS neurons. Neurite outgrowth from cultured postnatal cortical neurons, however, proved insensitive to treatments that improve axon growth in other cell types, including combinatorial overexpression of AP1 factors, overexpression of histone acetyltransferases, and pharmacological inhibitors of histone deacetylases. This insensitivity could be due to intermediate chromatin closure at the time of culture, and highlights important differences in cell culture models used to test potential pro-regenerative interventions.
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Affiliation(s)
| | | | - Denise M. Coley
- Department of Biomedical Sciences, Marquette University, 53201
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21
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Voelzmann A, Hahn I, Pearce SP, Sánchez-Soriano N, Prokop A. A conceptual view at microtubule plus end dynamics in neuronal axons. Brain Res Bull 2016; 126:226-237. [PMID: 27530065 PMCID: PMC5090033 DOI: 10.1016/j.brainresbull.2016.08.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 08/08/2016] [Accepted: 08/11/2016] [Indexed: 12/02/2022]
Abstract
Axons are the cable-like protrusions of neurons which wire up the nervous system. Polar bundles of microtubules (MTs) constitute their structural backbones and are highways for life-sustaining transport between proximal cell bodies and distal synapses. Any morphogenetic changes of axons during development, plastic rearrangement, regeneration or degeneration depend on dynamic changes of these MT bundles. A key mechanism for implementing such changes is the coordinated polymerisation and depolymerisation at the plus ends of MTs within these bundles. To gain an understanding of how such regulation can be achieved at the cellular level, we provide here an integrated overview of the extensive knowledge we have about the molecular mechanisms regulating MT de/polymerisation. We first summarise insights gained from work in vitro, then describe the machinery which supplies the essential tubulin building blocks, the protein complexes associating with MT plus ends, and MT shaft-based mechanisms that influence plus end dynamics. We briefly summarise the contribution of MT plus end dynamics to important cellular functions in axons, and conclude by discussing the challenges and potential strategies of integrating the existing molecular knowledge into conceptual understanding at the level of axons.
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Affiliation(s)
- André Voelzmann
- The University of Manchester, Faculty of Biology, Medicine and Health, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
| | - Ines Hahn
- The University of Manchester, Faculty of Biology, Medicine and Health, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
| | - Simon P Pearce
- The University of Manchester, Faculty of Biology, Medicine and Health, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK; The University of Manchester, School of Mathematics, Alan Turing Building, Oxford Road, Manchester M13 9PL, UK
| | - Natalia Sánchez-Soriano
- University of Liverpool, Institute of Translational Medicine, Department of Cellular and Molecular Physiology, Crown Street, Liverpool, L69 3BX, UK
| | - Andreas Prokop
- The University of Manchester, Faculty of Biology, Medicine and Health, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK.
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22
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Mironets E, Wu D, Tom VJ. Manipulating extrinsic and intrinsic obstacles to axonal regeneration after spinal cord injury. Neural Regen Res 2016; 11:224-5. [PMID: 27073365 PMCID: PMC4810976 DOI: 10.4103/1673-5374.177719] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Affiliation(s)
- Eugene Mironets
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania, PA, USA
| | - Di Wu
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania, PA, USA
| | - Veronica J Tom
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania, PA, USA
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23
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Abstract
UNLABELLED Understanding why adult CNS neurons fail to regenerate their axons following injury remains a central challenge of neuroscience research. A more complete appreciation of the biological mechanisms shaping the injured nervous system is a crucial prerequisite for the development of robust therapies to promote neural repair. Historically, the identification of regeneration associated signaling pathways has been impeded by the limitations of available genetic and molecular tools. As we progress into an era in which the high-throughput interrogation of gene expression is commonplace and our knowledge base of interactome data is rapidly expanding, we can now begin to assemble a more comprehensive view of the complex biology governing axon regeneration. Here, we highlight current and ongoing work featuring transcriptomic approaches toward the discovery of novel molecular mechanisms that can be manipulated to promote neural repair. SIGNIFICANCE STATEMENT Transcriptional profiling is a powerful technique with broad applications in the field of neuroscience. Recent advances such as single-cell transcriptomics, CNS cell type-specific and developmental stage-specific expression libraries are rapidly enhancing the power of transcriptomics for neuroscience applications. However, extracting biologically meaningful information from large transcriptomic datasets remains a formidable challenge. This mini-symposium will highlight current work using transcriptomic approaches to identify regulatory networks in the injured nervous system. We will discuss analytical strategies for transcriptomics data, the significance of noncoding RNA networks, and the utility of multiomic data integration. Though the studies featured here specifically focus on neural repair, the approaches highlighted in this mini-symposium will be of broad interest and utility to neuroscientists working in diverse areas of the field.
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24
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Cho Y, Shin JE, Ewan EE, Oh YM, Pita-Thomas W, Cavalli V. Activating Injury-Responsive Genes with Hypoxia Enhances Axon Regeneration through Neuronal HIF-1α. Neuron 2015; 88:720-34. [PMID: 26526390 DOI: 10.1016/j.neuron.2015.09.050] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Revised: 08/24/2015] [Accepted: 09/22/2015] [Indexed: 02/07/2023]
Abstract
Injured peripheral neurons successfully activate a proregenerative transcriptional program to enable axon regeneration and functional recovery. How transcriptional regulators coordinate the expression of such program remains unclear. Here we show that hypoxia-inducible factor 1α (HIF-1α) controls multiple injury-induced genes in sensory neurons and contribute to the preconditioning lesion effect. Knockdown of HIF-1α in vitro or conditional knock out in vivo impairs sensory axon regeneration. The HIF-1α target gene Vascular Endothelial Growth Factor A (VEGFA) is expressed in injured neurons and contributes to stimulate axon regeneration. Induction of HIF-1α using hypoxia enhances axon regeneration in vitro and in vivo in sensory neurons. Hypoxia also stimulates motor neuron regeneration and accelerates neuromuscular junction re-innervation. This study demonstrates that HIF-1α represents a critical transcriptional regulator in regenerating neurons and suggests hypoxia as a tool to stimulate axon regeneration.
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Affiliation(s)
- Yongcheol Cho
- Department of Anatomy and Neurobiology, School of Medicine, Washington University in St. Louis, St. Louis, MO 63110, USA
| | - Jung Eun Shin
- Department of Developmental Biology, School of Medicine, Washington University in St. Louis, St. Louis, MO 63110, USA
| | - Eric Edward Ewan
- Department of Anatomy and Neurobiology, School of Medicine, Washington University in St. Louis, St. Louis, MO 63110, USA
| | - Young Mi Oh
- Department of Anatomy and Neurobiology, School of Medicine, Washington University in St. Louis, St. Louis, MO 63110, USA
| | - Wolfgang Pita-Thomas
- Department of Anatomy and Neurobiology, School of Medicine, Washington University in St. Louis, St. Louis, MO 63110, USA
| | - Valeria Cavalli
- Department of Anatomy and Neurobiology, School of Medicine, Washington University in St. Louis, St. Louis, MO 63110, USA.
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25
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Marmor-Kollet N, Schuldiner O. Contrasting developmental axon regrowth and neurite sprouting of Drosophila mushroom body neurons reveals shared and unique molecular mechanisms. Dev Neurobiol 2015; 76:262-76. [PMID: 26037037 DOI: 10.1002/dneu.22312] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Revised: 05/14/2015] [Accepted: 05/28/2015] [Indexed: 11/06/2022]
Abstract
The molecular mechanisms regulating intrinsic axon growth potential during development or following injury remain largely unknown despite their vast importance. Here, we have established a neurite sprouting assay of primary cultured mushroom body (MB) neurons. We used the MARCM technique to both mark and manipulate MB neurons, enabling us to quantify the sprouting abilities of single WT and mutant neurons originating from flies at different developmental stages. Sprouting of dissociated MB neurons was dependent on wnd, the DLK ortholog, a conserved gene that is required for axon regeneration. Next, and as expected, we found that the sprouting ability of adult MB neurons was significantly decreased. In contrast, and to our surprise, we found that pupal-derived neurons exhibit increased sprouting compared with neurons derived from larvae, suggesting the existence of an elevated growth potential state. We then contrasted the molecular requirements of neurite sprouting to developmental axon regrowth of MB ɣ neurons, a process that we have previously shown requires the nuclear receptor UNF acting via the target of rapamycin (TOR) pathway. Strikingly, we found that while TOR was required for neurite sprouting, UNF was not. In contrast, we found that PTEN inhibits sprouting in adult neurons, suggesting that TOR is regulated by the PI3K/PTEN pathway during sprouting and by UNF during developmental regrowth. Interestingly, the PI3K pathway as well as Wnd were not required for developmental regrowth nor for initial axon outgrowth suggesting that axon growth during circuit formation, remodeling, and regeneration share some molecular components but differ in others.
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Affiliation(s)
- Neta Marmor-Kollet
- Department of Molecular Cell Biology, Weizmann Institute of Sciences, Rehovot, 76100, Israel
| | - Oren Schuldiner
- Department of Molecular Cell Biology, Weizmann Institute of Sciences, Rehovot, 76100, Israel
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26
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Overexpression of Sox11 promotes corticospinal tract regeneration after spinal injury while interfering with functional recovery. J Neurosci 2015; 35:3139-45. [PMID: 25698749 DOI: 10.1523/jneurosci.2832-14.2015] [Citation(s) in RCA: 111] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Embryonic neurons, peripheral neurons, and CNS neurons in zebrafish respond to axon injury by initiating pro-regenerative transcriptional programs that enable axons to extend, locate appropriate targets, and ultimately contribute to behavioral recovery. In contrast, many long-distance projection neurons in the adult mammalian CNS, notably corticospinal tract (CST) neurons, display a much lower regenerative capacity. To promote CNS repair, a long-standing goal has been to activate pro-regenerative mechanisms that are normally missing from injured CNS neurons. Sox11 is a transcription factor whose expression is common to a many types of regenerating neurons, but it is unknown whether suboptimal Sox11 expression contributes to low regenerative capacity in the adult mammalian CNS. Here we show in adult mice that dorsal root ganglion neurons (DRGs) and CST neurons fail to upregulate Sox11 after spinal axon injury. Furthermore, forced viral expression of Sox11 reduces axonal dieback of DRG axons, and promotes CST sprouting and regenerative axon growth in both acute and chronic injury paradigms. In tests of forelimb dexterity, however, Sox11 overexpression in the cortex caused a modest but consistent behavioral impairment. These data identify Sox11 as a key transcription factor that can confer an elevated innate regenerative capacity to CNS neurons. The results also demonstrate an unexpected dissociation between axon growth and behavioral outcome, highlighting the need for additional strategies to optimize the functional output of stimulated neurons.
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27
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Morrison BM, Tsingalia A, Vidensky S, Lee Y, Jin L, Farah MH, Lengacher S, Magistretti PJ, Pellerin L, Rothstein JD. Deficiency in monocarboxylate transporter 1 (MCT1) in mice delays regeneration of peripheral nerves following sciatic nerve crush. Exp Neurol 2014; 263:325-38. [PMID: 25447940 DOI: 10.1016/j.expneurol.2014.10.018] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Revised: 10/16/2014] [Accepted: 10/22/2014] [Indexed: 12/20/2022]
Abstract
Peripheral nerve regeneration following injury occurs spontaneously, but many of the processes require metabolic energy. The mechanism of energy supply to axons has not previously been determined. In the central nervous system, monocarboxylate transporter 1 (MCT1), expressed in oligodendroglia, is critical for supplying lactate or other energy metabolites to axons. In the current study, MCT1 is shown to localize within the peripheral nervous system to perineurial cells, dorsal root ganglion neurons, and Schwann cells by MCT1 immunofluorescence in wild-type mice and tdTomato fluorescence in MCT1 BAC reporter mice. To investigate whether MCT1 is necessary for peripheral nerve regeneration, sciatic nerves of MCT1 heterozygous null mice are crushed and peripheral nerve regeneration was quantified electrophysiologically and anatomically. Compound muscle action potential (CMAP) recovery is delayed from a median of 21 days in wild-type mice to greater than 38 days in MCT1 heterozygote null mice. In fact, half of the MCT1 heterozygote null mice have no recovery of CMAP at 42 days, while all of the wild-type mice recovered. In addition, muscle fibers remain 40% more atrophic and neuromuscular junctions 40% more denervated at 42 days post-crush in the MCT1 heterozygote null mice than wild-type mice. The delay in nerve regeneration is not only in motor axons, as the number of regenerated axons in the sural sensory nerve of MCT1 heterozygote null mice at 4 weeks and tibial mixed sensory and motor nerve at 3 weeks is also significantly reduced compared to wild-type mice. This delay in regeneration may be partly due to failed Schwann cell function, as there is reduced early phagocytosis of myelin debris and remyelination of axon segments. These data for the first time demonstrate that MCT1 is critical for regeneration of both sensory and motor axons in mice following sciatic nerve crush.
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Affiliation(s)
- Brett M Morrison
- Department of Neurology, School of Medicine, The Johns Hopkins University, 855 North Wolfe Street, Baltimore, MD 21205, USA.
| | - Akivaga Tsingalia
- Department of Neurology, School of Medicine, The Johns Hopkins University, 855 North Wolfe Street, Baltimore, MD 21205, USA.
| | - Svetlana Vidensky
- Department of Neurology, School of Medicine, The Johns Hopkins University, 855 North Wolfe Street, Baltimore, MD 21205, USA; Brain Science Institute, School of Medicine, The Johns Hopkins University, 855 North Wolfe Street, Baltimore, MD 21205, USA.
| | - Youngjin Lee
- Department of Neurology, School of Medicine, The Johns Hopkins University, 855 North Wolfe Street, Baltimore, MD 21205, USA; Brain Science Institute, School of Medicine, The Johns Hopkins University, 855 North Wolfe Street, Baltimore, MD 21205, USA.
| | - Lin Jin
- Department of Neurology, School of Medicine, The Johns Hopkins University, 855 North Wolfe Street, Baltimore, MD 21205, USA; Brain Science Institute, School of Medicine, The Johns Hopkins University, 855 North Wolfe Street, Baltimore, MD 21205, USA.
| | - Mohamed H Farah
- Department of Neurology, School of Medicine, The Johns Hopkins University, 855 North Wolfe Street, Baltimore, MD 21205, USA.
| | - Sylvain Lengacher
- Laboratory of Neuroenergetics and Cellular Dynamics, Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland.
| | - Pierre J Magistretti
- Division of Biological and Environmental Sciences and Engineering, KAUST, Thuwal, Saudi Arabia; Brain Mind Institute, Ecole Polytechnique Federale de Lausanne, SV2511, Station 19, CH-1015 Lausanne, Switzerland.
| | - Luc Pellerin
- Department of Fundamental Neurosciences, University of Lausanne, 7 Rue du Bugnon, 1005 Lausanne, Switzerland.
| | - Jeffrey D Rothstein
- Department of Neurology, School of Medicine, The Johns Hopkins University, 855 North Wolfe Street, Baltimore, MD 21205, USA; Brain Science Institute, School of Medicine, The Johns Hopkins University, 855 North Wolfe Street, Baltimore, MD 21205, USA.
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Xu C, Klaw MC, Lemay MA, Baas PW, Tom VJ. Pharmacologically inhibiting kinesin-5 activity with monastrol promotes axonal regeneration following spinal cord injury. Exp Neurol 2014; 263:172-6. [PMID: 25447935 DOI: 10.1016/j.expneurol.2014.10.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Revised: 10/14/2014] [Accepted: 10/19/2014] [Indexed: 10/24/2022]
Abstract
While it is well established that the axons of adult neurons have a lower capacity for regrowth, some regeneration of certain CNS populations after spinal cord injury (SCI) is possible if their axons are provided with a permissive substrate, such as an injured peripheral nerve. While some axons readily regenerate into a peripheral nerve graft (PNG), these axons almost always stall at the distal interface and fail to reinnervate spinal cord tissue. Treatment of the glial scar at the distal graft interface with chondroitinase ABC (ChABC) can improve regeneration, but most regenerated axons need further stimulation to extend beyond the interface. Previous studies demonstrate that pharmacologically inhibiting kinesin-5, a motor protein best known for its essential role in mitosis but also expressed in neurons, with the pharmacological agent monastrol increases axon growth on inhibitory substrates in vitro. We sought to determine if monastrol treatment after an SCI improves functional axon regeneration. Animals received complete thoracic level 7 (T7) transections and PNGs and were treated intrathecally with ChABC and either monastrol or DMSO vehicle. We found that combining ChABC with monastrol significantly enhanced axon regeneration. However, there were no further improvements in function or enhanced c-Fos induction upon stimulation of spinal cord rostral to the transection. This indicates that monastrol improves ChABC-mediated axon regeneration but that further treatments are needed to enhance the integration of these regrown axons.
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Affiliation(s)
- Chen Xu
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129
| | - Michelle C Klaw
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129
| | - Michel A Lemay
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129; Department of Bioengineering, Temple University, Philadelphia, PA 19122
| | - Peter W Baas
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129
| | - Veronica J Tom
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129.
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Roet KCD, Verhaagen J. Understanding the neural repair-promoting properties of olfactory ensheathing cells. Exp Neurol 2014; 261:594-609. [PMID: 24842489 DOI: 10.1016/j.expneurol.2014.05.007] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 05/02/2014] [Accepted: 05/06/2014] [Indexed: 12/13/2022]
Abstract
Olfactory ensheathing glial cells (OECs) are a specialized type of glia that form a continuously aligned cellular pathway that actively supports unprecedented regeneration of primary olfactory axons from the periphery into the central nervous system. Implantation of OECs stimulates neural repair in experimental models of spinal cord, brain and peripheral nerve injury and delays disease progression in animal models for neurodegenerative diseases like amyotrophic lateral sclerosis. OECs implanted in the injured spinal cord display a plethora of pro-regenerative effects; they promote axonal regeneration, reorganize the glial scar, remyelinate axons, stimulate blood vessel formation, have phagocytic properties and modulate the immune response. Recently genome wide transcriptional profiling and proteomics analysis combined with classical or larger scale "medium-throughput" bioassays have provided novel insights into the molecular mechanism that endow OECs with their pro-regenerative properties. Here we review these studies and show that the gaps that existed in our understanding of the molecular basis of the reparative properties of OECs are narrowing. OECs express functionally connected sets of genes that can be linked to at least 10 distinct processes directly relevant to neural repair. The data indicate that OECs exhibit a range of synergistic cellular activities, including active and passive stimulation of axon regeneration (by secretion of growth factors, axon guidance molecules and basement membrane components) and critical aspects of tissue repair (by structural remodeling and support, modulation of the immune system, enhancement of neurotrophic and antigenic stimuli and by metabolizing toxic macromolecules). Future experimentation will have to further explore the newly acquired knowledge to enhance the therapeutic potential of OECs.
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Affiliation(s)
- Kasper C D Roet
- Department of Neuroregeneration, Netherlands Institute for Neuroscience, An Institute of the Royal Netherlands Academy of Arts and Sciences, Meibergdreef 47, 1105BA Amsterdam, The Netherlands.
| | - Joost Verhaagen
- Department of Neuroregeneration, Netherlands Institute for Neuroscience, An Institute of the Royal Netherlands Academy of Arts and Sciences, Meibergdreef 47, 1105BA Amsterdam, The Netherlands; Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Boelelaan 1085, Amsterdam 1081HV, The Netherlands.
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Shin JE, Geisler S, DiAntonio A. Dynamic regulation of SCG10 in regenerating axons after injury. Exp Neurol 2013; 252:1-11. [PMID: 24246279 DOI: 10.1016/j.expneurol.2013.11.007] [Citation(s) in RCA: 130] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2013] [Revised: 11/03/2013] [Accepted: 11/05/2013] [Indexed: 10/26/2022]
Abstract
Peripheral axons can re-extend robustly after nerve injury. Soon after a nerve crush regenerating axons grow through the nerve segment distal to the lesion in close proximity to distal axons that are still morphologically and molecularly preserved. Hence, following the progress of regenerating axons necessitates markers that can distinguish between regenerating and degenerating axons. Here, we show that axonal levels of superior cervical ganglion 10 (SCG10) are dynamically regulated after axonal injury and provide an efficient method to label regenerating axons. In contrast to the rapid loss of SCG10 in distal axons (Shin et al., 2012b), we report that SCG10 accumulates in the proximal axons within an hour after injury, leading to a rapid identification of the lesion site. The increase in SCG10 levels is maintained during axon regeneration after nerve crush or nerve repair and allows for more selective labeling of regenerating axons than the commonly used markers growth-associated protein 43 (GAP43) and YFP. SCG10 is preferentially expressed in regenerating sensory axons rather than motor axons in the sciatic nerve. In a mouse model of slow Wallerian degeneration, SCG10 labeling remains selective for regenerating axons and allows for a quantitative analysis of delayed regeneration in this mutant. Taken together, these data demonstrate the utility of SCG10 as an efficient and selective marker of sensory axon regeneration.
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Affiliation(s)
- Jung Eun Shin
- Department of Developmental Biology, Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO 63110, USA.
| | - Stefanie Geisler
- Department of Developmental Biology, Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO 63110, USA.
| | - Aaron DiAntonio
- Department of Developmental Biology, Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO 63110, USA.
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Intraspinal AAV Injections Immediately Rostral to a Thoracic Spinal Cord Injury Site Efficiently Transduces Neurons in Spinal Cord and Brain. MOLECULAR THERAPY-NUCLEIC ACIDS 2013; 2:e108. [PMID: 23881451 PMCID: PMC3731889 DOI: 10.1038/mtna.2013.34] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 05/03/2013] [Indexed: 12/18/2022]
Abstract
In the vast majority of studies utilizing adeno-associated virus (AAV) in central nervous system applications, including those published with spinal cord injury (SCI) models, AAV has been administered at the level of the cell body of neurons targeted for genetic modification, resulting in transduction of neurons in the vicinity of the injection site. However, as SCI interrupts many axon tracts, it may be more beneficial to transduce a diverse pool of supraspinal neurons. We determined if descending axons severed by SCI are capable of retrogradely transporting AAV to remotely transduce a variety of brain regions. Different AAV serotypes encoding the reporter green fluorescent protein (GFP) were injected into gray and white matter immediately rostral to a spinal transection site. This resulted in the transduction of thousands of neurons within the spinal cord and in multiple regions within the brainstem that project to spinal cord. In addition, we established that different serotypes had disparate regional specificity and that AAV5 transduced the most brain and spinal cord neurons. This is the first demonstration that retrograde transport of AAV by axons severed by SCI is an effective means to transduce a collection of supraspinal neurons. Thus, we identify a novel, minimally invasive means to transduce a variety of neuronal populations within both the spinal cord and the brain following SCI. This paradigm to broadly distribute viral vectors has the potential to be an important component of a combinatorial strategy to promote functional axonal regeneration.
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Baas PW, Ahmad FJ. Beyond taxol: microtubule-based treatment of disease and injury of the nervous system. ACTA ACUST UNITED AC 2013; 136:2937-51. [PMID: 23811322 DOI: 10.1093/brain/awt153] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Contemporary research has revealed a great deal of information on the behaviours of microtubules that underlie critical events in the lives of neurons. Microtubules in the neuron undergo dynamic assembly and disassembly, bundling and splaying, severing, and rapid transport as well as integration with other cytoskeletal elements such as actin filaments. These various behaviours are regulated by signalling pathways that affect microtubule-related proteins such as molecular motor proteins and microtubule severing enzymes, as well as a variety of proteins that promote the assembly, stabilization and bundling of microtubules. In recent years, translational neuroscientists have earmarked microtubules as a promising target for therapy of injury and disease of the nervous system. Proof-of-principle has come mainly from studies using taxol and related drugs to pharmacologically stabilize microtubules in animal models of nerve injury and disease. However, concerns persist that the negative consequences of abnormal microtubule stabilization may outweigh the positive effects. Other potential approaches include microtubule-active drugs with somewhat different properties, but also expanding the therapeutic toolkit to include intervention at the level of microtubule regulatory proteins.
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Affiliation(s)
- Peter W Baas
- 1 Drexel University College of Medicine, Philadelphia, PA, USA
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