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Blum JA, Gitler AD. Singling out motor neurons in the age of single-cell transcriptomics. Trends Genet 2022; 38:904-919. [PMID: 35487823 PMCID: PMC9378604 DOI: 10.1016/j.tig.2022.03.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 03/24/2022] [Accepted: 03/28/2022] [Indexed: 01/07/2023]
Abstract
Motor neurons are a remarkably powerful cell type in the central nervous system. They innervate and control the contraction of virtually every muscle in the body and their dysfunction underlies numerous neuromuscular diseases. Some motor neurons seem resistant to degeneration whereas others are vulnerable. The intrinsic heterogeneity of motor neurons in adult organisms has remained elusive. The development of high-throughput single-cell transcriptomics has changed the paradigm, empowering rapid isolation and profiling of motor neuron nuclei, revealing remarkable transcriptional diversity within the skeletal and autonomic nervous systems. Here, we discuss emerging technologies for defining motor neuron heterogeneity in the adult motor system as well as implications for disease and spinal cord injury. We establish a roadmap for future applications of emerging techniques - such as epigenetic profiling, spatial RNA sequencing, and single-cell somatic mutational profiling to adult motor neurons, which will revolutionize our understanding of the healthy and degenerating adult motor system.
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Affiliation(s)
- Jacob A Blum
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA; Neurosciences Interdepartmental Program, Stanford University School of Medicine, Stanford, CA, USA.
| | - Aaron D Gitler
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA; Chan Zuckerberg Biohub, San Francisco, CA 94158, USA.
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2
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Kwan J, Vullaganti M. Amyotrophic lateral sclerosis mimics. Muscle Nerve 2022; 66:240-252. [PMID: 35607838 DOI: 10.1002/mus.27567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 04/25/2022] [Indexed: 11/10/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) is the most common adult-onset motor neuron disorder characterized by progressive degeneration of cortical, bulbar, and spinal motor neurons. When a patient presents with a progressive upper and/or lower motor syndrome, clinicians must pay particular attention to any atypical features in the history and/or clinical examination suggesting an alternate diagnosis, as up to 10% percent of patients initially diagnosed with ALS have a mimic of ALS. ALS is a clinical diagnosis and requires the exclusion of other disorders that may have similar presentations but a more favorable prognosis or an effective therapy. Because there is currently no specific diagnostic biomarker that is sensitive or specific for ALS, understanding the spectrum of clinical presentations of ALS and its mimics is paramount. While true mimics of ALS are rare, the clinician must correctly identify these disorders to avoid the misdiagnosis of ALS and to initiate effective treatment where available.
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Affiliation(s)
- Justin Kwan
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Mithila Vullaganti
- Department of Neurology, Tufts Medical Center, Tuft University School of Medicine, Boston, Massachusetts, USA
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Hardiman O, Al-Chalabi A, Chio A, Corr EM, Logroscino G, Robberecht W, Shaw PJ, Simmons Z, van den Berg LH. Amyotrophic lateral sclerosis. Nat Rev Dis Primers 2017; 3:17071. [PMID: 28980624 DOI: 10.1038/nrdp.2017.71] [Citation(s) in RCA: 811] [Impact Index Per Article: 115.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease, is characterized by the degeneration of both upper and lower motor neurons, which leads to muscle weakness and eventual paralysis. Until recently, ALS was classified primarily within the neuromuscular domain, although new imaging and neuropathological data have indicated the involvement of the non-motor neuraxis in disease pathology. In most patients, the mechanisms underlying the development of ALS are poorly understood, although a subset of patients have familial disease and harbour mutations in genes that have various roles in neuronal function. Two possible disease-modifying therapies that can slow disease progression are available for ALS, but patient management is largely mediated by symptomatic therapies, such as the use of muscle relaxants for spasticity and speech therapy for dysarthria.
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Affiliation(s)
- Orla Hardiman
- Academic Unit of Neurology, Room 5.41 Trinity Biomedical Science Institute, Trinity College Dublin, Pearse Street, Dublin 2, Ireland
| | - Ammar Al-Chalabi
- Department of Basic and Clinical Neuroscience, Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - Adriano Chio
- Rita Levi Montalcini Department of Neurosciences, University of Turin, Turin, Italy
| | - Emma M Corr
- Academic Unit of Neurology, Room 5.41 Trinity Biomedical Science Institute, Trinity College Dublin, Pearse Street, Dublin 2, Ireland
| | | | - Wim Robberecht
- KU Leuven-University of Leuven, University Hospitals Leuven, Department of Neurology, Leuven, Belgium
| | - Pamela J Shaw
- Sheffield Institute for Translational Neuroscience, University of Sheffield, Sheffield, UK
| | - Zachary Simmons
- Department of Neurology, Milton S. Hershey Medical Center, Penn State Health, Hershey, Pennsylvania, USA
| | - Leonard H van den Berg
- Department of Neurology, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht, The Netherlands
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Abstract
Progressive muscular atrophy (PMA) is a rare, sporadic, adult-onset motor neuron disease, clinically characterized by isolated lower motor neuron features; however, clinically evident upper motor neuron signs may emerge in some patients. Subclinical upper motor neuron involvement is identified pathologically, radiologically, and neurophysiologically in a substantial number of patients with PMA. Patients with subclinical upper motor neuron involvement do not fulfill the revised El Escorial criteria to participate in amyotrophic lateral sclerosis clinical trials. Intravenous immunoglobulin therapy is only marginally beneficial in a small subgroup of patients with lower motor neuron syndrome without conduction block.
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Affiliation(s)
- Teerin Liewluck
- Department of Neurology, University of Colorado School of Medicine, Anschutz Medical Campus, 12631 East 17th Avenue, Mail Stop B-185, Aurora, CO 80045, USA; Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
| | - David S Saperstein
- Phoenix Neurological Associates, University of Arizona College of Medicine, 5090 North 40th Street, Suite 250, Phoenix, AZ 85018, USA
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Züchner S. The genetics of hereditary spastic paraplegia and implications for drug therapy. Expert Opin Pharmacother 2007; 8:1433-9. [PMID: 17661726 DOI: 10.1517/14656566.8.10.1433] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Hereditary spastic paraplegia (HSP) comprises a group of clinically and genetically heterogeneous diseases that affect the upper motor neurons and their axonal projections. A total of 30 chromosomal loci have been identified for autosomal dominant, recessive and X-linked HSP. The underlying genes for 15 of these loci have been described. The molecular dissection of the cellular functions of the related gene products has already greatly advanced our understanding of the most critical pathways involved in HSP. It is hoped that in the foreseeable future this knowledge will begin to translate into novel pharmacological approaches for this devastating disease.
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Affiliation(s)
- Stephan Züchner
- University of Miami Miller School of Medicine, Miami Institute of Human Genomics, Miami, FL 33101, USA.
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Gopinath S, Blair IP, Kennerson ML, Durnall JC, Nicholson GA. A novel locus for distal motor neuron degeneration maps to chromosome 7q34-q36. Hum Genet 2007; 121:559-64. [PMID: 17354000 DOI: 10.1007/s00439-007-0348-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2007] [Accepted: 02/23/2007] [Indexed: 12/13/2022]
Abstract
The motor neuron diseases (MND) are a group of related neurodegenerative diseases that cause the relative selective progressive death of motor neurons. These diseases range from slowly progressive forms including hereditary motor neuropathy (HMN), to the rapidly progressive disorder amyotrophic lateral sclerosis (ALS). There is clinical and genetic overlap among these MNDs, implicating shared pathogenic mechanisms. We recruited a large family with a MND that was previously described as juvenile ALS and distal HMN. We identified a novel MND/HMN locus on chromosome 7q34-q36 following a genome-wide scan for linkage in this family. The disease causing mutation maps to a 26.2 cM (12.3 Mb) interval flanked by D7S2513 and D7S637 on chromosome 7q34-q36. Recombinant haplotype analysis including unaffected individuals suggests that the refined candidate interval spans 14.3 cM (6.3 Mb) flanked by D7S2511 and D7S798. One gene in the candidate interval, CDK5, was selected for immediate mutation analysis based upon its known association with an ALS-like phenotype in mice however, no mutations were identified. Identification of genes causing familial MND will lead to a greater understanding of the biological basis of both familial and sporadic motor neuron degeneration including ALS.
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Affiliation(s)
- Sumana Gopinath
- Northcott Neuroscience Laboratory, ANZAC Research Institute, Concord Hospital, and Faculty of Medicine, University of Sydney, NSW 2139, Australia
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Jacquier A, Buhler E, Schäfer MKE, Bohl D, Blanchard S, Beclin C, Haase G. Alsin/Rac1 signaling controls survival and growth of spinal motoneurons. Ann Neurol 2006; 60:105-17. [PMID: 16802292 DOI: 10.1002/ana.20886] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
OBJECTIVE Recessive mutations in alsin, a guanine-nucleotide exchange factor for the GTPases Rab5 and Rac1, cause juvenile amyotrophic lateral sclerosis (ALS2) and related motoneuron disorders. Alsin function in motoneurons remained unclear because alsin knock-out mice do not develop overt signs of motoneuron degeneration. METHODS To generate an alsin loss-of-function model in an ALS-relevant cell type, we developed a new small interfering RNA electroporation technique that allows efficient knock down of alsin in embryonic rat spinal motoneurons. RESULTS After small interfering RNA-mediated alsin knockdown, cultured motoneurons displayed a reduced apparent size of EEA1-labeled early endosomes and an increased intracellular accumulation of transferrin and L1CAM. Alsin knockdown induced cell death in 32 to 48% of motoneurons and significantly inhibited axon growth in the surviving neurons. Both cellular phenotypes were mimicked by expression of a dominant-negative Rac1 mutant and were completely blocked by expression of a constitutively active Rac1 mutant. Expression of dominant-negative or constitutively active forms of Rab5 had no such effects. INTERPRETATION Our data demonstrate that alsin controls the growth and survival of motoneurons in a Rac1-dependant manner. The strategy reported here illustrates how small interfering RNA electroporation can be used to generate cellular models of neurodegenerative disease involving a loss-of-function mechanism.
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Affiliation(s)
- Arnaud Jacquier
- Institut National de la Sante et de la Recherche Médicale, Marseille, France
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Züchner S, Vance JM. Emerging pathways for hereditary axonopathies. J Mol Med (Berl) 2005; 83:935-43. [PMID: 16133422 DOI: 10.1007/s00109-005-0694-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2005] [Accepted: 06/06/2005] [Indexed: 12/11/2022]
Abstract
Motor neurons are affected in a number of neurological diseases. Their unifying pathological signature is degeneration of extended projecting axons and loss of motor neurons in the prefrontal cortex and/or the spinal cord. Based on clinical criteria, hereditary forms have been traditionally divided into distinct entities, such as familial amyotrophic lateral sclerosis, hereditary motor neuropathy, spinal muscular atrophy, familial spinal paraplegia, and Charcot-Marie-Tooth disease type 2, also known as hereditary motor and sensory neuropathy II. Genetic research of the last decade has revealed remarkable heterogeneity within these disorders. Most of the identified genes to date cause disease in a classic Mendelian inheritance pattern with a high phenotypic penetrance. This rich source of molecular genetic data has already provided insight into the underlying major pathways of these diseases and should continue to do so in the future. This review attempts to cross the traditional clinical classifications in order to draw an emerging picture of common pathways between causative genes, providing a different perspective of this rapidly growing scientific field.
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Affiliation(s)
- Stephan Züchner
- Center for Human Genetics, Duke University Medical Center, 595 LaSalle Street, Box 3445 DUMC, Durham, NC 27710, USA.
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Sperfeld AD, Bretschneider V, Flaith L, Unrath A, Hanemann CO, Ludolph AC, Kassubek J. MR-Pathologic Comparison of the Upper Spinal Cord in Different Motor Neuron Diseases. Eur Neurol 2005; 53:74-7. [PMID: 15785072 DOI: 10.1159/000084650] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2004] [Accepted: 01/24/2005] [Indexed: 12/11/2022]
Abstract
This MRI study was performed to evaluate in vivo alterations of the spinal cord in defined subgroups of motor neuron diseases. Standard MRI examinations of the cervical and thoracic spinal cord in sporadic amyotrophic lateral sclerosis (ALS; n = 39), sporadic lower motor neuron disease (LMND; n = 19), Kennedy's disease (KD; n = 19) and a control group (n = 96) were analyzed with respect to spinal cord signal changes and the thickness of the spinal cord. No significant changes in thickness or signal alterations were observed when comparing ALS, LMND and control groups with one another. However, in KD patients significant upper spinal cord atrophy was detected at the cervical level as compared with all other groups. At the thoracic level, KD patients had significant upper cord atrophy as compared with controls and LMND. Marked atrophy of the upper spinal cord seems to be a feature of the KD-associated central-peripheral distal axonopathy.
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