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Kong L, Hassinan CW, Gerstner F, Buettner JM, Petigrow JB, Valdivia DO, Chan-Cortés MH, Mistri A, Cao A, McGaugh SA, Denton M, Brown S, Ross J, Schwab MH, Simon CM, Sumner CJ. Boosting neuregulin 1 type-III expression hastens SMA motor axon maturation. Acta Neuropathol Commun 2023; 11:53. [PMID: 36997967 PMCID: PMC10061791 DOI: 10.1186/s40478-023-01551-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Accepted: 03/12/2023] [Indexed: 04/01/2023] Open
Abstract
Intercellular communication between axons and Schwann cells is critical for attaining the complex morphological steps necessary for axon maturation. In the early onset motor neuron disease spinal muscular atrophy (SMA), many motor axons are not ensheathed by Schwann cells nor grow sufficiently in radial diameter to become myelinated. These developmentally arrested motor axons are dysfunctional and vulnerable to rapid degeneration, limiting efficacy of current SMA therapeutics. We hypothesized that accelerating SMA motor axon maturation would improve their function and reduce disease features. A principle regulator of peripheral axon development is neuregulin 1 type III (NRG1-III). Expressed on axon surfaces, it interacts with Schwann cell receptors to mediate axon ensheathment and myelination. We examined NRG1 mRNA and protein expression levels in human and mouse SMA tissues and observed reduced expression in SMA spinal cord and in ventral, but not dorsal root axons. To determine the impact of neuronal NRG1-III overexpression on SMA motor axon development, we bred NRG1-III overexpressing mice to SMA∆7 mice. Neonatally, elevated NRG1-III expression increased SMA ventral root size as well as axon segregation, diameter, and myelination resulting in improved motor axon conduction velocities. NRG1-III was not able to prevent distal axonal degeneration nor improve axon electrophysiology, motor behavior, or survival of older mice. Together these findings demonstrate that early SMA motor axon developmental impairments can be ameliorated by a molecular strategy independent of SMN replacement providing hope for future SMA combinatorial therapeutic approaches.
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Affiliation(s)
- Lingling Kong
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - Cera W Hassinan
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - Florian Gerstner
- Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig, Germany
| | - Jannik M Buettner
- Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig, Germany
| | - Jeffrey B Petigrow
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - David O Valdivia
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - Michelle H Chan-Cortés
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - Amy Mistri
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - Annie Cao
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - Scott Alan McGaugh
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - Madeline Denton
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - Stephen Brown
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - Joshua Ross
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA
| | - Markus H Schwab
- Department of Neuropathology, University Hospital Leipzig, Leipzig, Germany
| | - Christian M Simon
- Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig, Germany
| | - Charlotte J Sumner
- Departments of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Rangos Building Room 234, Baltimore, MD, 21205, USA.
- Departments of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
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Buettner JM, Sowoidnich L, Gerstner F, Blanco-Redondo B, Hallermann S, Simon CM. p53-dependent c-Fos expression is a marker but not executor for motor neuron death in spinal muscular atrophy mouse models. Front Cell Neurosci 2022; 16:1038276. [DOI: 10.3389/fncel.2022.1038276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Accepted: 10/18/2022] [Indexed: 11/09/2022] Open
Abstract
The activation of the p53 pathway has been associated with neuronal degeneration in different neurological disorders, including spinal muscular atrophy (SMA) where aberrant expression of p53 drives selective death of motor neurons destined to degenerate. Since direct p53 inhibition is an unsound therapeutic approach due carcinogenic effects, we investigated the expression of the cell death-associated p53 downstream targets c-fos, perp and fas in vulnerable motor neurons of SMA mice. Fluorescence in situ hybridization (FISH) of SMA motor neurons revealed c-fos RNA as a promising candidate. Accordingly, we identified p53-dependent nuclear upregulation of c-Fos protein in degenerating motor neurons from the severe SMNΔ7 and intermediate Smn2B/– SMA mouse models. Although motor neuron-specific c-fos genetic deletion in SMA mice did not improve motor neuron survival or motor behavior, p53-dependent c-Fos upregulation marks vulnerable motor neurons in different mouse models. Thus, nuclear c-Fos accumulation may serve as a readout for therapeutic approaches targeting neuronal death in SMA and possibly other p53-dependent neurodegenerative diseases.
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Abstract
Loss of synapses on spinal motor neurons is a major feature of several neurodegenerative diseases; however, analyzing these premotor synapses is challenging because of their small size and high density. This protocol describes confocal and Stimulated Emission Depletion (STED) imaging of murine spinal premotor synapses and their segment-specific quantification by confocal microscopy. We detail the preparation of spinal cord segments, followed by image acquisition and analysis. This protocol enables in-depth analysis of pathological changes in spinal premotor synapses during neurodegeneration. For complete details on the use and execution of this protocol, please refer to Buettner et al. (2021). Dissection and sectioning of identified murine spinal cord segments Fluorescent labeling of spinal premotor synapses and motor neurons Confocal and super-resolution acquisition of individual premotor synapses Quantification of premotor synapses onto motor neurons
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Affiliation(s)
- Jannik M. Buettner
- Carl-Ludwig-Institute for Physiology, Leipzig University, 04103 Leipzig, Germany
| | - Toni Kirmann
- Carl-Ludwig-Institute for Physiology, Leipzig University, 04103 Leipzig, Germany
| | - George Z. Mentis
- Center for Motor Neuron Biology and Disease, Columbia University, New York, NY 10032, USA
- Depts. of Pathology and Cell Biology and Neurology, Columbia University, New York, NY 10032, USA
| | - Stefan Hallermann
- Carl-Ludwig-Institute for Physiology, Leipzig University, 04103 Leipzig, Germany
| | - Christian M. Simon
- Carl-Ludwig-Institute for Physiology, Leipzig University, 04103 Leipzig, Germany
- Corresponding author
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Buettner JM, Sime Longang JK, Gerstner F, Apel KS, Blanco-Redondo B, Sowoidnich L, Janzen E, Langenhan T, Wirth B, Simon CM. Central synaptopathy is the most conserved feature of motor circuit pathology across spinal muscular atrophy mouse models. iScience 2021; 24:103376. [PMID: 34825141 PMCID: PMC8605199 DOI: 10.1016/j.isci.2021.103376] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 10/12/2021] [Accepted: 10/26/2021] [Indexed: 11/04/2022] Open
Abstract
Spinal muscular atrophy (SMA) is a neurodegenerative disease caused by reduced survival motor neuron (SMN) protein. Recently, SMN dysfunction has been linked to individual aspects of motor circuit pathology in a severe SMA mouse model. To determine whether these disease mechanisms are conserved, we directly compared the motor circuit pathology of three SMA mouse models. The severe SMNΔ7 model exhibits vast motor circuit defects, including degeneration of motor neurons, spinal excitatory synapses, and neuromuscular junctions (NMJs). In contrast, the Taiwanese model shows very mild motor neuron pathology, but early central synaptic loss. In the intermediate Smn2B/- model, strong pathology of central excitatory synapses and NMJs precedes the late onset of p53-dependent motor neuron death. These pathological events correlate with SMN-dependent splicing dysregulation of specific mRNAs. Our study provides a knowledge base for properly tailoring future studies and identifies central excitatory synaptopathy as a key feature of motor circuit pathology in SMA. Comparison of detailed motor circuit pathology across three SMA mouse models Motor circuit pathology correlates with dysregulation of specific mRNAs Motor neuron death in severe and intermediate SMA models is p53-dependent Central excitatory synaptopathy is the most conserved feature of SMA pathology
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Affiliation(s)
- Jannik M Buettner
- Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig 04103, Germany
| | | | - Florian Gerstner
- Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig 04103, Germany
| | - Katharina S Apel
- Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig 04103, Germany
| | - Beatriz Blanco-Redondo
- Rudolf Schönheimer Institute of Biochemistry, Division of General Biochemistry, Medical Faculty, Leipzig University, Leipzig 04103, Germany
| | - Leonie Sowoidnich
- Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig 04103, Germany
| | - Eva Janzen
- Institute of Human Genetics, Center for Molecular Medicine Cologne, Institute for Genetics, University of Cologne, Cologne, Germany
| | - Tobias Langenhan
- Rudolf Schönheimer Institute of Biochemistry, Division of General Biochemistry, Medical Faculty, Leipzig University, Leipzig 04103, Germany
| | - Brunhilde Wirth
- Institute of Human Genetics, Center for Molecular Medicine Cologne, Institute for Genetics, University of Cologne, Cologne, Germany.,Center for Rare Diseases Cologne, University Hospital of Cologne, Cologne, Germany
| | - Christian M Simon
- Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig 04103, Germany
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