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Smith CE, Lorson MA, Ricardez Hernandez SM, Al Rawi Z, Mao J, Marquez J, Villalón E, Keilholz AN, Smith CL, Garro-Kacher MO, Morcos T, Davis DJ, Bryda EC, Nichols NL, Lorson CL. The Ighmbp2D564N mouse model is the first SMARD1 model to demonstrate respiratory defects. Hum Mol Genet 2022; 31:1293-1307. [PMID: 34726235 PMCID: PMC9029233 DOI: 10.1093/hmg/ddab317] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 09/30/2021] [Accepted: 10/26/2021] [Indexed: 11/12/2022] Open
Abstract
Spinal muscular atrophy with respiratory distress type I (SMARD1) is a neurodegenerative disease defined by respiratory distress, muscle atrophy and sensory and autonomic nervous system defects. SMARD1 is a result of mutations within the IGHMBP2 gene. We have generated six Ighmbp2 mouse models based on patient-derived mutations that result in SMARD1 and/or Charcot-Marie Tooth Type 2 (CMT2S). Here we describe the characterization of one of these models, Ighmbp2D564N (human D565N). The Ighmbp2D564N/D564N mouse model mimics important aspects of the SMARD1 disease phenotype, including motor neuron degeneration and muscle atrophy. Ighmbp2D564N/D564N is the first SMARD1 mouse model to demonstrate respiratory defects based on quantified plethysmography analyses. SMARD1 disease phenotypes, including the respiratory defects, are significantly diminished by intracerebroventricular (ICV) injection of ssAAV9-IGHMBP2 and the extent of phenotypic restoration is dose-dependent. Collectively, this model provides important biological insight into SMARD1 disease development.
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Affiliation(s)
- Caley E Smith
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
- Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
| | - Monique A Lorson
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
- Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
| | - Sara M Ricardez Hernandez
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
- Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
| | - Zayd Al Rawi
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
- Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
| | - Jiude Mao
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
- Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
| | - Jose Marquez
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
- Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
| | - Eric Villalón
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
- Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
| | - Amy N Keilholz
- Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
| | - Catherine L Smith
- Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
| | - Mona O Garro-Kacher
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
- Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
| | - Toni Morcos
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
- Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
| | - Daniel J Davis
- Animal Modeling Core, University of Missouri, Columbia, MO 65211, USA
| | - Elizabeth C Bryda
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
- Animal Modeling Core, University of Missouri, Columbia, MO 65211, USA
| | - Nicole L Nichols
- Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
| | - Christian L Lorson
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
- Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
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2
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Villalón E, Lee NN, Marquez J, Lorson CL. Muscle fiber-type selective propensity to pathology in the nmd mouse model of SMARD1. Biochem Biophys Res Commun 2019; 516:313-319. [PMID: 31256932 DOI: 10.1016/j.bbrc.2019.06.117] [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: 06/11/2019] [Accepted: 06/21/2019] [Indexed: 12/01/2022]
Abstract
Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is an autosomal recessive disease that causes distal limb muscle atrophy, due to motor neuron degeneration. Similar to other motor neuron diseases, SMARD1 shows differential vulnerability to denervation in various muscle groups, which is recapitulated in the nmd mouse, a model of SMARD1. In multiple neurodegenerative disease models, transcriptomic analysis has identified differentially expressed genes between vulnerable motor neuron populations, but the mechanism leading to susceptibility is largely unknown. To investigate if denervation vulnerability is linked to intrinsic muscle properties, we analyzed muscle fiber-type composition in muscles from motor units that show different degrees of denervation in nmd mice: gastrocnemius, tibialis anterior (TA), and extensor digitorum longus (EDL). Our results revealed that denervation vulnerability correlated with atrophy and loss of MyHC-IIb and MyHC-IIx muscle fiber types. Interestingly, increased vulnerability also correlated with an increased abundance of MyHC-I and MyHC-IIa muscle fibers. These results indicated that MyHC-IIx muscle fibers are the most vulnerable to denervation, followed by MyHC-IIb muscle fibers. Moreover, our data indicate that type MyHC-IIa and MyHC-IIb muscle fibers show resistance to denervation and compensate for the loss of MyHC-IIx and MyHC-IIb muscle fibers in the most vulnerable muscles. Taken together these results provide a basis for the selective vulnerability to denervation of specific muscles in nmd mice and identifies new targets for potential therapeutic intervention.
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Affiliation(s)
- Eric Villalón
- Bond Life Sciences Center, University of Missouri, Columbia, MO, 65211, USA; Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO, 65211, USA
| | - Naomi N Lee
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO, 65211, USA
| | - Jose Marquez
- Bond Life Sciences Center, University of Missouri, Columbia, MO, 65211, USA; Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO, 65211, USA
| | - Christian L Lorson
- Bond Life Sciences Center, University of Missouri, Columbia, MO, 65211, USA; Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO, 65211, USA.
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Villalón E, Shababi M, Kline R, Lorson ZC, Florea KM, Lorson CL. Selective vulnerability in neuronal populations in nmd/SMARD1 mice. Hum Mol Genet 2019; 27:679-690. [PMID: 29272405 DOI: 10.1093/hmg/ddx434] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 12/15/2017] [Indexed: 12/12/2022] Open
Abstract
Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is an autosomal recessive motor neuron disease causing distal limb muscle atrophy that progresses proximally and is accompanied by diaphragmatic paralysis. Neuromuscular junction (NMJ) alterations have been reported in muscles of SMARD1 model mice, known as nmd mice, with varying degrees of severity, suggesting that different muscles are specifically and selectively resistant or susceptible to denervation. To evaluate the extent of NMJ pathology in a broad range of muscles, a panel of axial and appendicular muscles were isolated and immunostained from nmd mice. These analyses revealed that selective distal appendage muscles were highly vulnerable to denervation. Susceptibility to pathology was not limited to NMJ alterations, but included defects in myelination within those neurons innervating susceptible muscles. Interestingly, end plate fragmentation was present within all muscles independent of the extent of NMJ alterations, suggesting that end plate fragmentation is an early hallmark of SMARD1 pathogenesis. Expressing the full-length IGHMBP2 cDNA using an adeno-associated virus (AAV9) significantly decreased all aspects of muscle and nerve disease pathology. These results shed new light onto the pathogenesis of SMARD1 by identifying specific motor units that are resistant and susceptible to neurodegeneration in an important model of SMARD1.
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Affiliation(s)
- Eric Villalón
- Department of Veterinary Pathobiology, Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA.,Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
| | - Monir Shababi
- Department of Veterinary Pathobiology, Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA.,Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
| | - Rachel Kline
- Department of Veterinary Pathobiology, Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA.,Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
| | - Zachary C Lorson
- Department of Veterinary Pathobiology, Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA.,Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
| | - Kyra M Florea
- Department of Veterinary Pathobiology, Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA.,Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
| | - Christian L Lorson
- Department of Veterinary Pathobiology, Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA.,Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
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Surrey V, Zöller C, Lork AA, Moradi M, Balk S, Dombert B, Saal-Bauernschubert L, Briese M, Appenzeller S, Fischer U, Jablonka S. Impaired Local Translation of β-actin mRNA in Ighmbp2-Deficient Motoneurons: Implications for Spinal Muscular Atrophy with respiratory Distress (SMARD1). Neuroscience 2018; 386:24-40. [DOI: 10.1016/j.neuroscience.2018.06.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 06/03/2018] [Accepted: 06/11/2018] [Indexed: 12/31/2022]
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Ikeda A, Yamashita S, Tsuyusaki Y, Tanaka M, Tanaka Y, Hashiguchi A, Takashima H, Goto T. Peripheral nerve pathology at fixed stage in spinal muscular atrophy with respiratory distress type 1. Brain Dev 2018; 40:155-158. [PMID: 28899595 DOI: 10.1016/j.braindev.2017.08.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 08/16/2017] [Accepted: 08/23/2017] [Indexed: 10/18/2022]
Abstract
Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is characterized by severe respiratory failure due to diaphragmatic paralysis and distal muscular weakness in early infancy. After an initial decline in respiratory state and motor function until 1-2years of age, residual capabilities reach a plateau. We report the peripheral neuropathological findings of a patient with SMARD1 at 1year and 1month of age, when his muscle strength and respiratory symptoms had deteriorated and then stabilized for several months. Peripheral nerve biopsy revealed severely progressed axonal degeneration. This finding suggests the rapid progression of peripheral axonal neuropathy in SMARD1 that leads to its characteristic clinical course of respiratory failure and paralysis in the early infantile period.
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Affiliation(s)
- Azusa Ikeda
- Department of Neurology, Kanagawa Children's Medical Center, Japan.
| | | | - Yu Tsuyusaki
- Department of Neurology, Kanagawa Children's Medical Center, Japan
| | - Mio Tanaka
- Department of Pathology, Kanagawa Children's Medical Center, Japan
| | - Yukichi Tanaka
- Department of Pathology, Kanagawa Children's Medical Center, Japan
| | - Akihiro Hashiguchi
- Department of Neurology and Geriatrics, Kagoshima University Graduate School of Medical and Dental Sciences, Japan
| | - Hiroshi Takashima
- Department of Neurology and Geriatrics, Kagoshima University Graduate School of Medical and Dental Sciences, Japan
| | - Tomohide Goto
- Department of Neurology, Kanagawa Children's Medical Center, Japan
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Abstract
Spinal muscular atrophy (SMA) is a motor neuron disease caused by mutations/deletions within the survival of motor neuron 1 (SMN1) gene that lead to a pathological reduction of SMN protein levels. SMN is part of a multiprotein complex, functioning as a molecular chaperone that facilitates the assembly of spliceosomal small nuclear ribonucleoproteins (snRNP). In addition to its role in spliceosome formation, SMN has also been found to interact with mRNA-binding proteins (mRBPs), and facilitate their assembly into mRNP transport granules. The association of protein and RNA in RNP complexes plays an important role in an extensive and diverse set of cellular processes that regulate neuronal growth, differentiation, and the maturation and plasticity of synapses. This review discusses the role of SMN in RNP assembly and localization, focusing on molecular defects that affect mRNA processing and may contribute to SMA pathology.
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Abstract
Paediatric motor neuron diseases encompass a group of neurodegenerative diseases characterised by the onset of muscle weakness and atrophy before the age of 18 years, attributable to motor neuron loss across various neuronal networks in the brain and spinal cord. While the genetic underpinnings are diverse, advances in next generation sequencing have transformed diagnostic paradigms. This has reinforced the clinical phenotyping and molecular genetic expertise required to navigate the complexities of such diagnoses. In turn, improved genetic technology and subsequent gene identification have enabled further insights into the mechanisms of motor neuron degeneration and how these diseases form part of a neurodegenerative disorder spectrum. Common pathophysiologies include abnormalities in axonal architecture and function, RNA processing, and protein quality control. This review incorporates an overview of the clinical manifestations, genetics, and pathophysiology of inherited paediatric motor neuron disorders beyond classic SMN1-related spinal muscular atrophy and describes recent advances in next generation sequencing and its clinical application. Specific disease-modifying treatment is becoming a clinical reality in some disorders of the motor neuron highlighting the importance of a timely and specific diagnosis.
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Infantile spinal muscular atrophy with respiratory distress type I presenting without respiratory involvement: Novel mutations and review of the literature. Brain Dev 2016; 38:685-9. [PMID: 26922252 DOI: 10.1016/j.braindev.2016.02.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Revised: 01/31/2016] [Accepted: 02/01/2016] [Indexed: 11/24/2022]
Abstract
Spinal muscular atrophy with respiratory distress type 1 (SMARD1), also known as distal spinal muscular atrophy 1 (DSMA1) or distal hereditary motor neuropathies type 6 (dHMN6), is a rare autosomal recessive motor neuron disorder that affects infants and is characterized by diaphragmatic palsy, distal muscular weakness and muscle atrophy. The disease is caused by mutations in the gene encoding immunoglobulinm-binding protein 2 (IGHMBP2). We present a female child with novel compound heterozygous mutations in IGHMBP2 gene c.344C>T (p.115T>M) and c.1737C>A (p.579F>L), displaying distal limbs weakness and atrophy without signs of diaphragmatic palsy or respiratory insufficiency. We review 20 reported SMARD1 cases that have no respiratory involvement or have late onsets. We propose that IGHMBP2 gene mutations are characterized by significant phenotypic heterogeneity. Diaphragmatic palsy and respiratory distress may be absent and SMARD1 should be considered in infantile with the onset of peripheral neuropathies.
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Rescue of a Mouse Model of Spinal Muscular Atrophy With Respiratory Distress Type 1 by AAV9-IGHMBP2 Is Dose Dependent. Mol Ther 2016; 24:855-66. [PMID: 26860981 DOI: 10.1038/mt.2016.33] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Accepted: 01/17/2016] [Indexed: 01/07/2023] Open
Abstract
Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is an autosomal recessive disease occurring during childhood. The gene responsible for disease development is a ubiquitously expressed protein, IGHMBP2. Mutations in IGHMBP2 result in the loss of α-motor neurons leading to muscle atrophy in the distal limbs accompanied by respiratory complications. Although genetically and clinically distinct, proximal SMA is also caused by the loss of a ubiquitously expressed gene (SMN). Significant preclinical success has been achieved in proximal SMA using viral-based gene replacement strategies. We leveraged the technologies employed in SMA to demonstrate gene replacement efficacy in an SMARD1 animal model. Intracerebroventricular (ICV) injection of single-stranded AAV9 expressing the full-length cDNA of IGHMBP2 in a low dose led to a significant level of rescue in treated SMARD1 animals. Consistent with drastically increased survival, weight gain, and strength, the rescued animals demonstrated a significant improvement in muscle, NMJ, motor neurons, and axonal pathology. In addition, increased levels of IGHMBP2 in lumbar motor neurons verified the efficacy of the virus to transduce the target tissues. Our results indicate that AAV9-based gene replacement is a viable strategy for SMARD1, although dosing effects and potential negative impacts of high dose and ICV injection should be thoroughly investigated.
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Cottenie E, Kochanski A, Jordanova A, Bansagi B, Zimon M, Horga A, Jaunmuktane Z, Saveri P, Rasic VM, Baets J, Bartsakoulia M, Ploski R, Teterycz P, Nikolic M, Quinlivan R, Laura M, Sweeney MG, Taroni F, Lunn MP, Moroni I, Gonzalez M, Hanna MG, Bettencourt C, Chabrol E, Franke A, von Au K, Schilhabel M, Kabzińska D, Hausmanowa-Petrusewicz I, Brandner S, Lim SC, Song H, Choi BO, Horvath R, Chung KW, Zuchner S, Pareyson D, Harms M, Reilly MM, Houlden H. Truncating and missense mutations in IGHMBP2 cause Charcot-Marie Tooth disease type 2. Am J Hum Genet 2014; 95:590-601. [PMID: 25439726 PMCID: PMC4225647 DOI: 10.1016/j.ajhg.2014.10.002] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Accepted: 10/01/2014] [Indexed: 11/18/2022] Open
Abstract
Using a combination of exome sequencing and linkage analysis, we investigated an English family with two affected siblings in their 40s with recessive Charcot-Marie Tooth disease type 2 (CMT2). Compound heterozygous mutations in the immunoglobulin-helicase-μ-binding protein 2 (IGHMBP2) gene were identified. Further sequencing revealed a total of 11 CMT2 families with recessively inherited IGHMBP2 gene mutations. IGHMBP2 mutations usually lead to spinal muscular atrophy with respiratory distress type 1 (SMARD1), where most infants die before 1 year of age. The individuals with CMT2 described here, have slowly progressive weakness, wasting and sensory loss, with an axonal neuropathy typical of CMT2, but no significant respiratory compromise. Segregating IGHMBP2 mutations in CMT2 were mainly loss-of-function nonsense in the 5' region of the gene in combination with a truncating frameshift, missense, or homozygous frameshift mutations in the last exon. Mutations in CMT2 were predicted to be less aggressive as compared to those in SMARD1, and fibroblast and lymphoblast studies indicate that the IGHMBP2 protein levels are significantly higher in CMT2 than SMARD1, but lower than controls, suggesting that the clinical phenotype differences are related to the IGHMBP2 protein levels.
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Affiliation(s)
- Ellen Cottenie
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK; Department of Molecular Neurosciences, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
| | - Andrzej Kochanski
- Neuromuscular Unit, Mossakowski Medical Research Centre Polish Academy of Sciences, Centre of Biostructure, Medical University of Warsaw, Pawinskiego 5, 02-106 Warsaw, Poland
| | - Albena Jordanova
- VIB Department of Molecular Genetics, University of Antwerp, Antwerpen 2610, Belgium
| | - Boglarka Bansagi
- Institute of Genetic Medicine, MRC Centre for Neuromuscular Diseases, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - Magdalena Zimon
- VIB Department of Molecular Genetics, University of Antwerp, Antwerpen 2610, Belgium
| | - Alejandro Horga
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK; Department of Molecular Neurosciences, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
| | - Zane Jaunmuktane
- Division of Neuropathology and Department of Neurodegenerative Disease, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
| | - Paola Saveri
- Clinic of Central and Peripheral Degenerative Neuropathies Unit, IRCCS Foundation, C. Besta Neurological Institute, Via Celoria 11, 20133 Milan, Italy
| | - Vedrana Milic Rasic
- Clinic for Neurology and Psychiatry for Children and Youth, Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
| | - Jonathan Baets
- VIB Department of Molecular Genetics, University of Antwerp, Antwerpen 2610, Belgium; Laboratory of Neurogenetics, University of Antwerp, Antwerpen 2610, Belgium; Department of Neurology, Antwerp University Hospital, Antwerpen, Belgium
| | - Marina Bartsakoulia
- Institute of Genetic Medicine, MRC Centre for Neuromuscular Diseases, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - Rafal Ploski
- Department of Medical Genetics, Centre of Biostructure, Medical University of Warsaw, Pawinskiego 5, 02-106 Warsaw, Poland
| | - Pawel Teterycz
- Department of Medical Genetics, Centre of Biostructure, Medical University of Warsaw, Pawinskiego 5, 02-106 Warsaw, Poland
| | - Milos Nikolic
- University of Belgrade, Faculty of Medicine, 11000 Belgrade, Serbia
| | - Ros Quinlivan
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
| | - Matilde Laura
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK; Department of Molecular Neurosciences, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
| | - Mary G Sweeney
- Neurogenetics Laboratory, The National Hospital for Neurology and Neurosurgery and UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
| | - Franco Taroni
- Unit of Genetics of Neurodegenerative and Metabolic Disease IRCCS Foundation, C. Besta Neurological Institute, Via Celoria 11, 20133 Milan, Italy
| | - Michael P Lunn
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
| | - Isabella Moroni
- Child Neurology Unit, IRCCS Foundation, C. Besta Neurological Institute, Via Celoria 11, 20133 Milan, Italy
| | - Michael Gonzalez
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, FL 33136, USA
| | - Michael G Hanna
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK; Department of Molecular Neurosciences, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
| | - Conceicao Bettencourt
- Department of Molecular Neurosciences, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
| | - Elodie Chabrol
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
| | - Andre Franke
- Christian-Albrechts-University, 24118 Kiel, Germany
| | - Katja von Au
- SPZ Pediatric Neurology, Charité - Universitätsmedizin Berlin, 13353 Berlin, Germany
| | | | - Dagmara Kabzińska
- Neuromuscular Unit, Mossakowski Medical Research Centre Polish Academy of Sciences, Centre of Biostructure, Medical University of Warsaw, Pawinskiego 5, 02-106 Warsaw, Poland
| | - Irena Hausmanowa-Petrusewicz
- Neuromuscular Unit, Mossakowski Medical Research Centre Polish Academy of Sciences, Centre of Biostructure, Medical University of Warsaw, Pawinskiego 5, 02-106 Warsaw, Poland
| | - Sebastian Brandner
- Division of Neuropathology and Department of Neurodegenerative Disease, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
| | - Siew Choo Lim
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673
| | - Haiwei Song
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673; Life Sciences Institute, Zhejiang University, Hangzhou 310058, People's Republic of China
| | - Byung-Ok Choi
- Department of Neurology, Sungkyunkwan University School of Medicine, Seoul 137-710, Korea
| | - Rita Horvath
- Institute of Genetic Medicine, MRC Centre for Neuromuscular Diseases, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - Ki-Wha Chung
- Department of Biological Science, Kongju National University, Chungnam 134-701, Korea
| | - Stephan Zuchner
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, FL 33136, USA
| | - Davide Pareyson
- Clinic of Central and Peripheral Degenerative Neuropathies Unit, IRCCS Foundation, C. Besta Neurological Institute, Via Celoria 11, 20133 Milan, Italy
| | - Matthew Harms
- Department of Neurology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Mary M Reilly
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK; Department of Molecular Neurosciences, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
| | - Henry Houlden
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK; Department of Molecular Neurosciences, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK; Neurogenetics Laboratory, The National Hospital for Neurology and Neurosurgery and UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK.
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Porro F, Rinchetti P, Magri F, Riboldi G, Nizzardo M, Simone C, Zanetta C, Faravelli I, Corti S. The wide spectrum of clinical phenotypes of spinal muscular atrophy with respiratory distress type 1: A systematic review. J Neurol Sci 2014; 346:35-42. [DOI: 10.1016/j.jns.2014.09.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Revised: 09/05/2014] [Accepted: 09/08/2014] [Indexed: 12/13/2022]
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Krieger F, Metzger F, Jablonka S. Differentiation defects in primary motoneurons from a SMARD1 mouse model that are insensitive to treatment with low dose PEGylated IGF1. Rare Dis 2014; 2:e29415. [PMID: 25083343 PMCID: PMC4116388 DOI: 10.4161/rdis.29415] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Revised: 05/26/2014] [Accepted: 05/30/2014] [Indexed: 11/21/2022] Open
Abstract
Muscle atrophy and diaphragmatic palsy are the clinical characteristics of spinal muscular atrophy with respiratory distress type 1 (SMARD1), and are well represented in the neuromuscular degeneration (Nmd2J) mouse, modeling the juvenile form of SMARD1. Both in humans and mice mutations in the IGHMBP2 gene lead to motoneuron degeneration. We could previously demonstrate that treatment with a polyethylene glycol-coupled variant of IGF1 (PEG-IGF1) improves motor functions accompanied by reduced fiber degeneration in the gastrocnemius muscle and the diaphragm, but has no beneficial effect on motoneuron survival. These data raised the question which cell autonomous disease mechanisms contribute to dysfunction and loss of Ighmbp2-deficient motoneurons. An analysis of primary Ighmbp2-deficient motoneurons exhibited differentiation deficits such as reduced spontaneous Ca2+ transients and altered axon elongation, which was not compensated by PEG-IGF1. This points to an IGF1 independent mechanism of motoneuron degeneration that deserves treatment approaches in addition to IGF1.
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Affiliation(s)
- Frank Krieger
- Institute for Clinical Neurobiology; University of Wuerzburg; Wuerzburg, Germany
| | - Friedrich Metzger
- Roche Pharmaceutical Research and Early Development; Roche Innovation Center Basel; F. Hoffmann-La Roche Ltd.; Basel, Switzerland
| | - Sibylle Jablonka
- Institute for Clinical Neurobiology; University of Wuerzburg; Wuerzburg, Germany
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Jędrzejowska M, Madej-Pilarczyk A, Fidziańska A, Mierzewska H, Pronicka E, Obersztyn E, Gos M, Pronicki M, Kmieć T, Migdał M, Mierzewska-Schmidt M, Walczak-Wojtkowska I, Konopka E, Hausmanowa-Petrusewicz I. Severe phenotypes of SMARD1 associated with novel mutations of the IGHMBP2 gene and nuclear degeneration of muscle and Schwann cells. Eur J Paediatr Neurol 2014; 18:183-92. [PMID: 24388491 DOI: 10.1016/j.ejpn.2013.11.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 11/04/2013] [Indexed: 01/25/2023]
Abstract
Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is a very rare autosomal recessive form of spinal muscular atrophy manifested in low birth weight, diaphragmatic palsy and distal muscular atrophy. Caused by a mutation in the IGHMBP2 gene, the disease is addressed here by reference to five Polish patients in which SMARD1 has been confirmed genetically. All presented a severe form of the disease and had evident symptoms during the second month of life; with four displaying weak cries, feeding difficulties and hypotonia from birth. Two were afflicted by severe dysfunction of the autonomic nervous system. Ultrastructural analysis of a muscle biopsy revealed progressive degeneration within the nuclei of the muscle cells and Schwann cells. Neuromuscular junctions were also defective. It proved possible to identify in our patients 6 novel IGHMBP2 mutations: three missense (c.595G>C, c.1682T>C and c.1794C>A), two nonsense (c.94C>T and c.1336C>T) and one in-frame deletion (c.1615_1623del). One nonsense mutation (c.429C>T) that had been described previously was also identified. Observation of our patients makes it clear that clinical picture is still the most important factor suggesting diagnosis of SMARD1, though further investigations concerning some of the symptoms are required. As the IGHMBP2 gene is characterized by significant heterogeneity, genetic counseling of affected families is rendered more complex. IGHMBP2 protein deficiency can lead to the degeneration of nuclei, in both muscle and Schwann cells.
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Affiliation(s)
- Maria Jędrzejowska
- Neuromuscular Unit, Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland.
| | | | - Anna Fidziańska
- Neuromuscular Unit, Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland
| | - Hanna Mierzewska
- Department of Child and Adolescent Neurology, Institute of Mother and Child, Warsaw, Poland
| | - Ewa Pronicka
- Department of Metabolic Diseases, The Children's Memorial Health Institute, Warsaw, Poland
| | - Ewa Obersztyn
- Department of Medical Genetics, Institute of Mother and Child, Warsaw, Poland
| | - Monika Gos
- Department of Medical Genetics, Institute of Mother and Child, Warsaw, Poland
| | - Maciej Pronicki
- Department of Pathology, The Children's Memorial Health Institute, Warsaw, Poland
| | - Tomasz Kmieć
- Department of Neurology and Epileptology, The Children's Memorial Health Institute, Warsaw, Poland
| | - Marek Migdał
- Department of Anaesthesiology and Intensive Care, The Children's Memorial Health Institute, Warsaw, Poland
| | | | - Iwona Walczak-Wojtkowska
- Department of Paediatric Anaesthesiology and Intensive Care, Institute of Mother and Child, Warsaw, Poland
| | - Elżbieta Konopka
- Department of Paediatric Anaesthesiology and Intensive Care, Institute of Mother and Child, Warsaw, Poland
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Murray L, Gillingwater TH, Kothary R. Dissection of the transversus abdominis muscle for whole-mount neuromuscular junction analysis. J Vis Exp 2014:e51162. [PMID: 24457471 PMCID: PMC4089412 DOI: 10.3791/51162] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Analysis of neuromuscular junction morphology can give important insight into the physiological status of a given motor neuron. Analysis of thin flat muscles can offer significant advantage over traditionally used thicker muscles, such as those from the hind limb (e.g. gastrocnemius). Thin muscles allow for comprehensive overview of the entire innervation pattern for a given muscle, which in turn permits identification of selectively vulnerable pools of motor neurons. These muscles also allow analysis of parameters such as motor unit size, axonal branching, and terminal/nodal sprouting. A common obstacle in using such muscles is gaining the technical expertise to dissect them. In this video, we detail the protocol for dissecting the transversus abdominis (TVA) muscle from young mice and performing immunofluorescence to visualize axons and neuromuscular junctions (NMJs). We demonstrate that this technique gives a complete overview of the innervation pattern of the TVA muscle and can be used to investigate NMJ pathology in a mouse model of the childhood motor neuron disease, spinal muscular atrophy.
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Affiliation(s)
- Lyndsay Murray
- Regenerative Medicine Program, Ottawa Hospital Research Institute
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15
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van der Pol WL, Talim B, Pitt M, von Au K. 190th ENMC international workshop: Spinal muscular atrophy with respiratory distress/distal spinal muscular atrophy type 1. Neuromuscul Disord 2013; 23:602-9. [PMID: 23726377 DOI: 10.1016/j.nmd.2013.04.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 04/23/2013] [Indexed: 11/25/2022]
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16
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Gitiaux C, Bergounioux J, Magen M, Quijano-Roy S, Blanc T, Bonnefont JP, Desguerre I. Diaphragmatic weakness with progressive sensory and motor polyneuropathy: case report of a neonatal IGHMBP2-related neuropathy. J Child Neurol 2013; 28:787-90. [PMID: 22791546 DOI: 10.1177/0883073812450209] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The authors present a child affected with diaphragmatic paralysis in the early neonatal period. Although no electroneuromyographic abnormalities were reported, the patient developed dramatic motor and respiratory impairment with impossibility to wean from mechanical ventilation. Repeated electroneuromyographic study at age 4 months revealed severe neurogenic changes and sensory nerve abnormalities with more preserved nerve conduction velocities. Genetic studies identified 2 mutations in the gene IGHMBP2. These results support the consideration of this entity as a form of sensory-motor rapidly progressive polyneuropathy rather than a primary anterior horn disease (IGHMBP2-related neuropathy). A review of the series of mutated patients in the French National Database gives new insights of the incidence of this disease in France.
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Affiliation(s)
- Cyril Gitiaux
- Service de Neurologie Pédiatrique et Maladies métaboliques, hôpital Necker Enfants Malades, Assistance Publique-Hôpitaux de Paris, Université Paris-Descartes, Paris, France.
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17
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Fast motor axon loss in SMARD1 does not correspond to morphological and functional alterations of the NMJ. Neurobiol Dis 2013; 54:169-82. [PMID: 23295857 DOI: 10.1016/j.nbd.2012.12.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2012] [Revised: 11/30/2012] [Accepted: 12/21/2012] [Indexed: 11/20/2022] Open
Abstract
Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is a childhood motoneuron disease caused by mutations in the gene encoding for IGHMBP2, an ATPase/Helicase. Paralysis of the diaphragm is an early and prominent clinical sign resulting both from denervation and myopathy. In skeletal muscles, muscle atrophy mainly results from loss of motoneuron cell bodies and axonal degeneration. Although it is well known that loss of motoneurons at the lumbar spinal cord is an early event in the pathogenesis of the disease, it is not clear whether the corresponding proximal axons and NMJs are also early affected. In order to address this question, we have investigated the time course of the disease progression at the level of the motoneuron cell body, proximal axon (ventral root), distal axon (sciatic nerve), NMJ, and muscle fiber in Nmd(2J) mice, a mouse model for SMARD1. Our results show an early and apparently parallel loss of motoneurons, proximal axons, and NMJs. In affected muscles, however, denervated fibers coexist with NMJs with normal morphology and unaltered neurotransmission. Furthermore, unaffected axons are able to sprout and reinnervate muscle fibers, suggesting selective vulnerability of neurons to Ighmbp2 deficiency. The preservation of the NMJ morphology and neurotransmission in the Nmd(2J) mouse until motor axon loss takes place, differs from that observed in SMA mouse models in which NMJ impairment is an early and more general phenomenon in affected muscles.
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18
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Yiu EM, Ryan MM. Genetic axonal neuropathies and neuronopathies of pre-natal and infantile onset. J Peripher Nerv Syst 2012; 17:285-300. [DOI: 10.1111/j.1529-8027.2012.00412.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Rossoll W, Bassell GJ. Spinal muscular atrophy and a model for survival of motor neuron protein function in axonal ribonucleoprotein complexes. Results Probl Cell Differ 2009; 48:289-326. [PMID: 19343312 PMCID: PMC3718852 DOI: 10.1007/400_2009_4] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Spinal muscular atrophy (SMA) is a neurodegenerative disease that results from loss of function of the SMN1 gene, encoding the ubiquitously expressed survival of motor neuron (SMN) protein, a protein best known for its housekeeping role in the SMN-Gemin multiprotein complex involved in spliceosomal small nuclear ribonucleoprotein (snRNP) assembly. However, numerous studies reveal that SMN has many interaction partners, including mRNA binding proteins and actin regulators, suggesting its diverse role as a molecular chaperone involved in mRNA metabolism. This review focuses on studies suggesting an important role of SMN in regulating the assembly, localization, or stability of axonal messenger ribonucleoprotein (mRNP) complexes. Various animal models for SMA are discussed, and phenotypes described that indicate a predominant function for SMN in neuronal development and synapse formation. These models have begun to be used to test different therapeutic strategies that have the potential to restore SMN function. Further work to elucidate SMN mechanisms within motor neurons and other cell types involved in neuromuscular circuitry hold promise for the potential treatment of SMA.
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Affiliation(s)
- Wilfried Rossoll
- Departments of Cell Biology and Neurology, Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, GA 30322, USA.
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Kaindl AM, Guenther UP, Rudnik-Schöneborn S, Varon R, Zerres K, Gressens P, Schuelke M, Hubner C, von Au K. [Distal spinal-muscular atrophy 1 (DSMA1 or SMARD1)]. Arch Pediatr 2008; 15:1568-72. [PMID: 18804971 DOI: 10.1016/j.arcped.2008.07.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2007] [Revised: 05/20/2008] [Accepted: 07/22/2008] [Indexed: 11/24/2022]
Abstract
In this article, we review the clinical, neuropathological and genetic aspects of distal spinal-muscular atrophy 1 (DSMA1; MIM#604320), formerly designated as autosomal recessive spinal muscular atrophy with respiratory distress type 1 (SMARD1) and also known as distal hereditary-motor neuropathy type 6 (dHMN6 or HMN6).
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Affiliation(s)
- A M Kaindl
- Charité, service de neuropédiatrie, hôpital universitaire, campus Virchow-Klinikum, Augustenburger Platz 1, 13353 Berlin, Allemagne.
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21
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Kaindl AM, Guenther UP, Rudnik-Schöneborn S, Varon R, Zerres K, Schuelke M, Hübner C, von Au K. Spinal muscular atrophy with respiratory distress type 1 (SMARD1). J Child Neurol 2008; 23:199-204. [PMID: 18263757 DOI: 10.1177/0883073807310989] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Autosomal recessive spinal muscular atrophy with respiratory distress type 1 (SMARD1), recently referred to as distal spinal muscular atrophy 1 (DSMA1; MIM#604320) and also known as distal hereditary motor neuropathy type 6 (dHMN6 or HMN6), results from mutations in the IGHMBP2 gene on chromosome 11q13.3 encoding the immunoglobulin micro-binding protein 2. In contrast to the infantile spinal muscular atrophy type 1 (SMA1; Werdnig-Hoffmann disease) with weakness predominantly of proximal muscles and bell-shaped thorax deformities due to intercostal muscle atrophy, infants with distal spinal muscular atrophy 1 usually present with distal muscle weakness, foot deformities, and sudden respiratory failure due to diaphragmatic paralysis that often requires urgent intubation. In this article, the authors review the clinical, neuropathological, and genetic aspects of distal spinal muscular atrophy 1 and discuss differential diagnoses.
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Affiliation(s)
- Angela M Kaindl
- Department of Pediatric Neurology, Charité, University Medical Center, Berlin, Germany
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Talbot K, Davies KE. Chapter 7 Spinal muscular atrophies and hereditary motor neuropathies. HANDBOOK OF CLINICAL NEUROLOGY 2007; 82:141-153. [PMID: 18808892 DOI: 10.1016/s0072-9752(07)80010-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Affiliation(s)
- Kevin Talbot
- Department of Human Anatomy and Genetics, University of Oxford, UK; Department of Clinical Neurology, University of Oxford, UK
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Giannini A, Pinto AM, Rossetti G, Prandi E, Tiziano D, Brahe C, Nardocci N. Respiratory failure in infants due to spinal muscular atrophy with respiratory distress type 1. Intensive Care Med 2006; 32:1851-5. [PMID: 16964485 DOI: 10.1007/s00134-006-0346-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2006] [Accepted: 07/24/2006] [Indexed: 02/05/2023]
Abstract
BACKGROUND Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is a rare autosomal recessive neuromuscular disease of unknown prevalence characterized by degeneration of anterior horn alpha-motoneurons and manifesting in the first 6months of life as life-threatening irreversible diaphragmatic paralysis associated with progressive symmetrical muscular weakness (distal lower limbs mainly involved), muscle atrophy, and peripheral sensory neuropathy. SETTING Pediatric intensive care unit of tertiary care hospital. PATIENTS We present two new cases of SMARD1 and report two new mutations in the gene IGHMBP2 which encodes immunoglobulin mu-binding protein 2 on chromosome 11q13. CONCLUSIONS SMARD1 is a poor-prognosis disease that should be considered when acute respiratory insufficiency, of suspected neuromuscular or unclear cause, develops during the first 6months of life. Diaphragmatic paralysis, manifesting as dyspnea and paradoxical respiration, is the most prominent presenting sign and diaphragmatic motility should be investigated early by fluoroscopy or ultrasound. Electromyography and nerve conduction studies revealing peripheral motor and sensory neuropathy then suggest the diagnosis which should be confirmed by genetic analysis.
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Affiliation(s)
- Alberto Giannini
- Pediatric Intensive Care Unit, Fondazione IRCCS Ospedale Maggiore Policlinico, Mangiagalli e Regina Elena, Via della Commenda 9, 20122, Milan, Italy.
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Irobi J, Dierick I, Jordanova A, Claeys KG, De Jonghe P, Timmerman V. Unraveling the genetics of distal hereditary motor neuronopathies. Neuromolecular Med 2006; 8:131-46. [PMID: 16775372 DOI: 10.1385/nmm:8:1-2:131] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/1999] [Revised: 11/30/1999] [Accepted: 11/30/1999] [Indexed: 02/02/2023]
Abstract
The hereditary motor neuronopathies (HMN [MIM 158590]) are a heterogeneous group of disorders characterized by an exclusive involvement of the motor part of the peripheral nervous system. They are usually subdivided in proximal HMN, i.e., the classical spinal muscular atrophy syndromes and distal hereditary motor neuronopathies (distal HMN) that clinically resemble Charcot-Marie-Tooth syndromes. In this review, we concentrate on distal HMN. The distal HMN are clinically and genetically heterogeneous and were initially subdivided in seven subtypes according to mode of inheritance, age at onset, and clinical evolution. Recent studies have shown that these subtypes are still heterogeneous at the molecular genetic level and novel clinical and genetic entities have been delineated. Since the introduction of positional cloning, 13 chromosomal loci and seven disease-associated genes have been identified for autosomal-dominant, autosomal-recessive, and X-linked recessive distal HMN. Most of the genes involved encode protein with housekeeping functions, such as RNA processing, translation synthesis, stress response, apoptosis, and others code for proteins involved in retrograde survival. Motor neurons of the anterior horn of the spinal cord seems to be vulnerable to defects in these housekeeping proteins, likely because their large axons have higher metabolic requirements for maintenance, transport over long distances and precise connectivity. Understanding the molecular pathomechanisms for mutations in these genes that are ubiquitous expressed will help unravel the neuronal mechanisms that underlie motor neuropathies leading to denervation of distal limb muscles, and might generate new insights for future therapeutic strategies.
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Affiliation(s)
- Joy Irobi
- Peripheral Neuropathy Group, Department of Molecular Genetics, Flanders Interuniversity Institute for Biotechnology, University of Antwerp, Antwerpen, Belgium
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