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Kong L, Valdivia DO, Simon CM, Hassinan CW, Delestrée N, Ramos DM, Park JH, Pilato CM, Xu X, Crowder M, Grzyb CC, King ZA, Petrillo M, Swoboda KJ, Davis C, Lutz CM, Stephan AH, Zhao X, Weetall M, Naryshkin NA, Crawford TO, Mentis GZ, Sumner CJ. Impaired prenatal motor axon development necessitates early therapeutic intervention in severe SMA. Sci Transl Med 2021; 13:13/578/eabb6871. [PMID: 33504650 DOI: 10.1126/scitranslmed.abb6871] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Accepted: 09/18/2020] [Indexed: 12/21/2022]
Abstract
Gene replacement and pre-mRNA splicing modifier therapies represent breakthrough gene targeting treatments for the neuromuscular disease spinal muscular atrophy (SMA), but mechanisms underlying variable efficacy of treatment are incompletely understood. Our examination of severe infantile onset human SMA tissues obtained at expedited autopsy revealed persistence of developmentally immature motor neuron axons, many of which are actively degenerating. We identified similar features in a mouse model of severe SMA, in which impaired radial growth and Schwann cell ensheathment of motor axons began during embryogenesis and resulted in reduced acquisition of myelinated axons that impeded motor axon function neonatally. Axons that failed to ensheath degenerated rapidly postnatally, specifically releasing neurofilament light chain protein into the blood. Genetic restoration of survival motor neuron protein (SMN) expression in mouse motor neurons, but not in Schwann cells or muscle, improved SMA motor axon development and maintenance. Treatment with small-molecule SMN2 splice modifiers beginning immediately after birth in mice increased radial growth of the already myelinated axons, but in utero treatment was required to restore axonal growth and associated maturation, prevent subsequent neonatal axon degeneration, and enhance motor axon function. Together, these data reveal a cellular basis for the fulminant neonatal worsening of patients with infantile onset SMA and identify a temporal window for more effective treatment. These findings suggest that minimizing treatment delay is critical to achieve optimal therapeutic efficacy.
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Affiliation(s)
- Lingling Kong
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - David O Valdivia
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Christian M Simon
- Center for Motor Neuron Biology and Disease, Department of Pathology and Cell Biology, Columbia University, New York, NY 10032, USA
| | - Cera W Hassinan
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Nicolas Delestrée
- Center for Motor Neuron Biology and Disease, Department of Pathology and Cell Biology, Columbia University, New York, NY 10032, USA
| | - Daniel M Ramos
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Jae Hong Park
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Celeste M Pilato
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Xixi Xu
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Melissa Crowder
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Chloe C Grzyb
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Zachary A King
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | | | - Kathryn J Swoboda
- Center for Genomic Medicine, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | - Crystal Davis
- Genetic Resource Science, The Jackson Laboratory, Bar Harbor, ME 04609, USA
| | - Cathleen M Lutz
- Genetic Resource Science, The Jackson Laboratory, Bar Harbor, ME 04609, USA
| | - Alexander H Stephan
- F. Hoffmann-La Roche Ltd., pRED, Pharma & Early Development, Roche Innovation Center Basel, Basel CH-4070, Switzerland
| | - Xin Zhao
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | - Marla Weetall
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | | | - Thomas O Crawford
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.,Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - George Z Mentis
- Center for Motor Neuron Biology and Disease, Department of Pathology and Cell Biology, Columbia University, New York, NY 10032, USA.,Department of Neurology, Columbia University, New York, NY 10032, USA
| | - Charlotte J Sumner
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. .,Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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Ram S, Devapriya IA, Fenton G, Mcvay L, Nguyen DV, Tassone F, Maselli RA, Hagerman RJ. Axonal neuropathy in female carriers of the fragile X premutation with fragile x-associated tremor ataxia syndrome. Muscle Nerve 2014; 52:234-9. [PMID: 25388402 DOI: 10.1002/mus.24515] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 10/22/2014] [Accepted: 11/07/2014] [Indexed: 12/12/2022]
Abstract
INTRODUCTION In this study we examined whether females with the fragile X-associated tremor ataxia syndrome (FXTAS) and non-FXTAS premutation carriers have electrophysiological signs of underlying peripheral neuropathy. METHODS Nerve conduction studies (NCS) were performed on 19 women with FXTAS, 20 non-FXTAS carriers, and 26 age-matched controls. The results were compared with existing data on corresponding male carriers. RESULTS Women with FXTAS and non-FXTAS carriers had reduced sensory nerve action potential amplitudes. Also, there was a strong trend for reduced compound muscle action potential amplitudes in women with FXTAS, but not in non-FXTAS carriers. No significant slowing of nerve conduction velocities, prolongation of F-wave latencies, or associations with molecular measures was observed. CONCLUSIONS This study suggests an underlying axonal neuropathy in women with FXTAS. However, in comparison to men with FXTAS, the NCS abnormalities in women were less severe, possibly due to the effect of a normal X chromosome.
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Affiliation(s)
- Suresh Ram
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California Davis Medical Center, 2825 50th Street, Sacramento, California, 95817, USA
| | - Inoka A Devapriya
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California Davis Medical Center, 2825 50th Street, Sacramento, California, 95817, USA
| | - Grace Fenton
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California Davis Medical Center, 2825 50th Street, Sacramento, California, 95817, USA.,Department of Neurology, University of California Davis Health System, Sacramento, California, USA
| | - Lindsey Mcvay
- Division of Biostatistics, University of California Davis, Davis, California, USA
| | - Danh V Nguyen
- Department of Medicine, University of California Irvine, Orange, California, USA
| | - Flora Tassone
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California Davis Medical Center, 2825 50th Street, Sacramento, California, 95817, USA.,Department of Biochemistry and Molecular Medicine, University of California Davis, Davis, California, USA
| | - Ricardo A Maselli
- Department of Neurology, University of California Davis Health System, Sacramento, California, USA
| | - Randi J Hagerman
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California Davis Medical Center, 2825 50th Street, Sacramento, California, 95817, USA.,Department of Pediatrics, University of California Davis Health System, Sacramento, California, USA
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Abstract
Spinal muscular atrophies (SMA) are genetic disorders characterized by degeneration of lower motor neurons. The most frequent form is caused by mutations of the survival motor neuron 1 gene (SMN1). The identification of this gene greatly improved diagnostic testing and family-planning options of SMA families. SMN plays a key role in metabolism of RNA. However, the link between RNA metabolism and motor neuron degeneration remains unknown. A defect in mRNA processing likely generates either a loss of function of some critical RNA or abnormal transcripts with toxic property for motor neurons. Mutations of SMN in various organisms highlighted an essential role of SMN in motor axon and neuromuscular junction development or maintenance. The quality of life of patients has greatly improved over recent decades through the improvement of care and management of patients. In addition, major advances in translational research have been made in the field of SMA. Various therapeutic strategies have been successfully developed aiming at acting on SMN2, a partially functional copy of the SMN1 gene which remains present in patients. Drugs have been identified and some are already at preclinical stages. Identifying molecules involved in the SMA degenerative process should represent additional attractive targets for therapeutics in SMA.
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Affiliation(s)
- Louis Viollet
- Hôpital Necker-Enfants Malades and Université Paris Descartes, Paris, France
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King AE, Blizzard CA, Southam KA, Vickers JC, Dickson TC. Degeneration of axons in spinal white matter in G93A mSOD1 mouse characterized by NFL and α-internexin immunoreactivity. Brain Res 2012; 1465:90-100. [PMID: 22609817 DOI: 10.1016/j.brainres.2012.05.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Revised: 05/03/2012] [Accepted: 05/09/2012] [Indexed: 12/14/2022]
Abstract
Axonal degeneration is a prominent feature of amyotrophic lateral sclerosis (ALS) both in lower motor nerves as well as descending white matter axons in the spinal cord of human patients. Although the pathology of lower motor axonal degeneration has been described in both human ALS and related transgenic animal models, few studies have examined the pathological features of descending axon degeneration, particularly in mouse models of ALS. We have examined the degeneration of white matter tracts in the G93A mutant superoxide dismutase-1 (mSOD1+) mouse spinal cord white matter from 12 weeks of age to end-stage disease. In a G93A mSOD1 mouse model where green fluorescent protein was expressed in neurons (mSOD1+/GFP+), degeneration of white matter tracts was present from the ventral to dorsolateral funiculi. This pattern of axonal pathology occurred from 16 weeks of age. However, the dorsal funiculus, the site of the major corticospinal tract in mice, showed relatively less degeneration. Immunohistochemical analysis demonstrated that the neurofilament light chain (NFL) and neuronal intermediate filament protein alpha-internexin accumulated in axon swellings in the spinal white matter. Increased levels of alpha-internexin protein, in mSOD1+ mouse spinal cord tissue, were demonstrated by Western blotting. In contrast, degenerating axons did not show obvious accumulations of neurofilament medium and heavy chain proteins (NFM and NFH). These data suggest that white matter degeneration in this mouse model of ALS is widespread and involves a specific molecular signature, particularly the accumulation of NFL and alpha-internexin proteins.
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Affiliation(s)
- Anna E King
- Wicking Dementia Research and Education Centre and Menzies Research Institute Tasmania, University of Tasmania, Hobart, Tasmania 7000, Australia.
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Han JJ, McDonald CM. Diagnosis and clinical management of spinal muscular atrophy. Phys Med Rehabil Clin N Am 2008; 19:661-80, xii. [PMID: 18625423 DOI: 10.1016/j.pmr.2008.02.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease characterized by degeneration of lower motor neurons, with resulting progressive muscle weakness. The clinical phenotype and disease severity can be varied and occupy a wide spectrum. Although many advances have been made regarding our understanding of SMA, no cure is yet available. The care of patients who have SMA can often be complex, with many medical issues to consider. When possible, a multidisciplinary team approach is effective. The current understanding of SMA, and the clinical management and rehabilitative care of patients who have SMA, are discussed in this article.
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Affiliation(s)
- Jay J Han
- Department of Physical Medicine and Rehabilitation, University of California-Davis, 4860 Y Street, Suite 3850, Sacramento, CA 95817, USA.
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Abstract
Spinal muscular atrophy (SMA) is a hereditary neurodegenerative disease caused by homozygous deletions or mutations in the SMN1 gene on Chr.5q13. SMA spans from severe Werdnig-Hoffmann disease (SMA 1) to relatively benign Kugelberg-Welander disease (SMA 3). Onset before birth possibly aggravates the clinical course, because immature motoneurons do not show compensatory sprouting and collateral reinnervation, and motor units in SMA 1, in contrast to those in SMA 3, are not enlarged. Genetic evidence indicates that SMN2, a gene 99% identical to SMN1, can attenuate SMA severity: in patients, more SMN2 copies and higher SMN protein levels are correlated with milder SMA. There is evidence that SMN plays a role in motoneuron RNA metabolism, but it has also been linked to apoptosis. Several mouse models with motoneuron disease have been successfully treated with neurotrophic factors. None of these models is, however, homologous to SMA. Recently, genetic mouse models of SMA have been created by introducing human SMN2 transgenes into Smn knockout mice or by targeting the Smn gene knockout to neurons. These mice not only provide important insights into the pathogenesis of SMA but are also crucial for testing new therapeutic strategies. These include SMN gene transfer, molecules capable to up-regulate SMN expression and trophic or antiapoptotic factors.
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Affiliation(s)
- H Schmalbruch
- Department of Medical Physiology, University of Copenhagen, Denmark.
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