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Cottam NC, Bamfo T, Harrington MA, Charvet CJ, Hekmatyar K, Tulin N, Sun J. Cerebellar structural, astrocytic, and neuronal abnormalities in the SMNΔ7 mouse model of spinal muscular atrophy. Brain Pathol 2023; 33:e13162. [PMID: 37218083 PMCID: PMC10467044 DOI: 10.1111/bpa.13162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Accepted: 04/18/2023] [Indexed: 05/24/2023] Open
Abstract
Spinalmuscular atrophy (SMA) is a neuromuscular disease that affects as many as 1 in 6000 individuals at birth, making it the leading genetic cause of infant mortality. A growing number of studies indicate that SMA is a multi-system disease. The cerebellum has received little attention even though it plays an important role in motor function and widespread pathology has been reported in the cerebella of SMA patients. In this study, we assessed SMA pathology in the cerebellum using structural and diffusion magnetic resonance imaging, immunohistochemistry, and electrophysiology with the SMNΔ7 mouse model. We found a significant disproportionate loss in cerebellar volume, decrease in afferent cerebellar tracts, selective lobule-specific degeneration of Purkinje cells, abnormal lobule foliation and astrocyte integrity, and a decrease in spontaneous firing of cerebellar output neurons in the SMA mice compared to controls. Our data suggest that defects in cerebellar structure and function due to decreased survival motor neuron (SMN) levels impair the functional cerebellar output affecting motor control, and that cerebellar pathology should be addressed to achieve comprehensive treatment and therapy for SMA patients.
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Affiliation(s)
- Nicholas C. Cottam
- Department of Biological SciencesDelaware State UniversityDoverDelawareUSA
| | - Tiffany Bamfo
- Department of Biological SciencesDelaware State UniversityDoverDelawareUSA
| | | | - Christine J. Charvet
- Delaware Center for Neuroscience ResearchDelaware State UniversityDoverDelawareUSA
- Department of Anatomy, Physiology and PharmacologyAuburn UniversityAuburnAlabamaUSA
- Department of PsychologyDelaware State UniversityDoverDEUnited States
| | - Khan Hekmatyar
- Center for Biomedical and Brain ImagingUniversity of DelawareNewarkDelawareUSA
- Bioimaging Research Center for Biomedical and Brain ImagingUniversity of GeorgiaAthensGeorgiaUSA
| | - Nikita Tulin
- Department of NeuroscienceTemple UniversityPhiladelphiaPennsylvaniaUSA
| | - Jianli Sun
- Department of Biological SciencesDelaware State UniversityDoverDelawareUSA
- Delaware Center for Neuroscience ResearchDelaware State UniversityDoverDelawareUSA
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Nancy M, Andrea OC, Tarannum B, Maryam O. Brain Magnetic Resonance Imaging (MRI) in Spinal Muscular Atrophy: A Scoping Review. J Neuromuscul Dis 2023:JND221567. [PMID: 37125560 DOI: 10.3233/jnd-221567] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
BACKGROUND 5q Spinal Muscular Atrophy (SMA) is a prototypical lower motor neuron disorder. However, the characteristic early motor impairment raises the question on the scope of brain involvement with implications for further investigations on the brain as a potential therapeutic target. OBJECTIVE To review changes across the SMA clinical spectrum reported on brain magnetic resonance imaging (MRI). METHODS We conducted a scoping review of existing literature on PubMed and EMBASE. Two reviewers searched and retrieved relevant articles on magnetic resonance brain imaging in individuals with SMA censoring to April 2022. Full-text articles published in peer-reviewed journals or abstracts accepted to conferences in English and French were included. RESULTS Twelve articles were identified describing a total of 39 patients [age range: 11 days to 41 years old, type 0 (n = 5), type 1 (n = 4), type 2 (n = 2), type 3 (n = 22), type 4 (n = 6)]. All reported structural changes and did not explore other MRI modalities. In individuals with infantile onset SMA, cortical and subcortical brain abnormalities in white matter, basal ganglia, thalamus, hippocampus, and high intensity areas around lateral ventricles and thalami were reported over time. In individuals with later-onset SMA, reduced cerebellar and lobular volume were observed as well as increased grey matter density in motor areas. CONCLUSIONS Limited data on brain imaging in SMA highlights both cortical and subcortical involvement in SMA, supporting the hypothesis that changes are not restricted to lower motor neuron pathways. Further studies are needed to determine the extent and prevalence of structural and functional brain changes across SMA types.
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Affiliation(s)
- Mugisha Nancy
- Research Institute of the McGill University Health Centre, McGill University, Montreal, Quebec, Canada
| | - Oliveira-Carneiro Andrea
- Research Institute of the McGill University Health Centre, McGill University, Montreal, Quebec, Canada
| | - Behlim Tarannum
- Research Institute of the McGill University Health Centre, McGill University, Montreal, Quebec, Canada
| | - Oskoui Maryam
- Research Institute of the McGill University Health Centre, McGill University, Montreal, Quebec, Canada
- Departments of Pediatrics and Neurology Neurosurgery, McGill University, Montreal, Quebec, Canada
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Abstract
Spinal muscular atrophy (SMA) is caused by biallelic mutations in the SMN1 (survival motor neuron 1) gene on chromosome 5q13.2, which leads to a progressive degeneration of alpha motor neurons in the spinal cord and in motor nerve nuclei in the caudal brainstem. It is characterized by progressive proximally accentuated muscle weakness with loss of already acquired motor skills, areflexia and, depending on the phenotype, varying degrees of weakness of the respiratory and bulbar muscles. Over the past decade, disease-modifying therapies have become available based on splicing modulation of the SMN2 with SMN1 gene replacement, which if initiated significantly modifies the natural course of the disease. Newborn screening for SMA has been implemented in an increasing number of centers; however, available evidence for these new treatments is often limited to a small spectrum of patients concerning age and disease stage.
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Affiliation(s)
- David S Younger
- Department of Clinical Medicine and Neuroscience, CUNY School of Medicine, New York, NY, United States; Department of Medicine, Section of Internal Medicine and Neurology, White Plains Hospital, White Plains, NY, United States.
| | - Jerry R Mendell
- Department of Neurology and Pediatrics, Center for Gene Therapy, Abigail Wexner Research Institute, The Ohio State University, Nationwide Children's Hospital, Columbus, OH, United States
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Butchbach MER. Genomic Variability in the Survival Motor Neuron Genes ( SMN1 and SMN2): Implications for Spinal Muscular Atrophy Phenotype and Therapeutics Development. Int J Mol Sci 2021; 22:ijms22157896. [PMID: 34360669 PMCID: PMC8348669 DOI: 10.3390/ijms22157896] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 07/14/2021] [Accepted: 07/21/2021] [Indexed: 02/07/2023] Open
Abstract
Spinal muscular atrophy (SMA) is a leading genetic cause of infant death worldwide that is characterized by loss of spinal motor neurons leading to muscle weakness and atrophy. SMA results from the loss of survival motor neuron 1 (SMN1) gene but retention of its paralog SMN2. The copy numbers of SMN1 and SMN2 are variable within the human population with SMN2 copy number inversely correlating with SMA severity. Current therapeutic options for SMA focus on increasing SMN2 expression and alternative splicing so as to increase the amount of SMN protein. Recent work has demonstrated that not all SMN2, or SMN1, genes are equivalent and there is a high degree of genomic heterogeneity with respect to the SMN genes. Because SMA is now an actionable disease with SMN2 being the primary target, it is imperative to have a comprehensive understanding of this genomic heterogeneity with respect to hybrid SMN1–SMN2 genes generated by gene conversion events as well as partial deletions of the SMN genes. This review will describe this genetic heterogeneity in SMA and its impact on disease phenotype as well as therapeutic efficacy.
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Affiliation(s)
- Matthew E. R. Butchbach
- Center for Applied Clinical Genomics, Nemours Children’s Health Delaware, Wilmington, DE 19803, USA;
- Center for Pediatric Research, Nemours Children’s Health Delaware, Wilmington, DE 19803, USA
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
- Department of Pediatrics, Thomas Jefferson University, Philadelphia, PA 19107, USA
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Masson R, Brusa C, Scoto M, Baranello G. Brain, cognition, and language development in spinal muscular atrophy type 1: a scoping review. Dev Med Child Neurol 2021; 63:527-536. [PMID: 33452688 DOI: 10.1111/dmcn.14798] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/30/2020] [Indexed: 01/01/2023]
Abstract
AIM To summarize the current knowledge on brain involvement in spinal muscular atrophy (SMA) type 1, focusing on brain pathology, cognition, and speech/language development. METHOD A scoping review was performed using the methodology of the Joanna Briggs Institute. Five databases and references from relevant articles were searched up to December 2019. Articles were screened on the basis of titles and abstracts. Full-text papers published in peer-reviewed journals in English were selected. RESULTS Nineteen articles met eligibility criteria. Eight case series/reports on brain pathology showed abnormalities in few SMA type 0/1 cases, supported by findings in three post-mortem examinations in mice. Four studies (three case-control, one cross-sectional) on cognition reported contradictory results, with impaired cognitive performances in recent, small groups with SMA type 1. Four studies (three cross-sectional, one observational) on speech/language showed that untreated SMA type 1 patients rarely achieve functional and intelligible speech, with data limited to parent reports/non-formal evaluations. INTERPRETATION Brain involvement is an under-investigated aspect of SMA type 1, requiring further exploration in longitudinal studies. A deeper knowledge of brain involvement would improve the interpretation of clinical phenotypes and the personalization of rehabilitation programmes supporting patients' autonomies and quality of life. Additionally, it may help to define further outcome measures testing the efficacy of current and new developing drugs on this domain. WHAT THIS PAPER ADDS Brain involvement is under-investigated in spinal muscular atrophy (SMA) type 1. Neuropathological data suggest progressive brain involvement in severe forms of SMA. Impaired cognitive performances are reported in small groups with SMA type 1. Data on language in those with SMA type 1 are limited to parent reports and non-formal assessments.
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Affiliation(s)
- Riccardo Masson
- Developmental Neurology Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Chiara Brusa
- The Dubowitz Neuromuscular Centre, UCL NIHR GOSH Biomedical Research Centre, UCL Great Ormond Street Institute of Child Health, London, UK.,Department of Neurosciences "Rita Levi Montalcini", University of Turin, Turin, Italy.,Department of Public Health and Paediatric Sciences, Section of Child and Adolescent Neuropsychiatry, University of Turin, Turin, Italy
| | - Mariacristina Scoto
- The Dubowitz Neuromuscular Centre, UCL NIHR GOSH Biomedical Research Centre, UCL Great Ormond Street Institute of Child Health, London, UK
| | - Giovanni Baranello
- Developmental Neurology Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy.,The Dubowitz Neuromuscular Centre, UCL NIHR GOSH Biomedical Research Centre, UCL Great Ormond Street Institute of Child Health, London, UK
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Cerebellar degeneration in adult spinal muscular atrophy patients. J Neurol 2020; 267:2625-2631. [PMID: 32388834 DOI: 10.1007/s00415-020-09875-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2020] [Revised: 04/27/2020] [Accepted: 04/29/2020] [Indexed: 12/13/2022]
Abstract
BACKGROUND Spinal muscular atrophy (SMA) is a genetic motor neuron disease related to deletions in the SMN1 gene. There is mounting evidence that the disease is not restricted to motor neurons. In this neuroimaging study, we aimed to investigate the presence of in-vivo cerebellar damage in adult SMA patients not treated with disease-modifying treatment. METHODS Twenty-five molecularly confirmed patients with SMA type III or IV and 25 healthy controls underwent MRI with cerebellar focused structural analysis by the CERES automated pipeline. Volumetry (total and gray matter-GM) as well as cortical thickness of the cerebellar lobules were compared in both groups. Full clinical and demographic data were then assessed for correlations with cerebellar imaging findings. RESULTS Volumes of cerebellar lobules VIIIB (right), IX and X were significantly smaller in patients with SMA. Lobule IX also had GM atrophy in comparison to controls. We found no significant correlation between clinical findings and cerebellar damage. CONCLUSIONS Neuroimaging detects cerebellar structural changes in adult SMA patients, suggesting that neurodegeneration is not confined to the lower motor neurons in the disease.
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Mendonça RH, Rocha AJ, Lozano‐Arango A, Diaz AB, Castiglioni C, Silva AMS, Reed UC, Kulikowski L, Paramonov I, Cuscó I, Tizzano EF, Zanoteli E. Severe brain involvement in 5q spinal muscular atrophy type 0. Ann Neurol 2019; 86:458-462. [DOI: 10.1002/ana.25549] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2019] [Revised: 07/09/2019] [Accepted: 07/09/2019] [Indexed: 01/26/2023]
Affiliation(s)
- Rodrigo H. Mendonça
- Department of Neurology, Faculdade de MedicinaUniversidade de São Paulo (FMUSP) São Paulo Brazil
| | - Antônio J. Rocha
- Neuroradiology SectionHigh Diagnostic Excellence (DASA Group) São Paulo Brazil
| | | | - Astry B. Diaz
- Hernan Henriquez Aravena Regional Hospital Temuco Chile
| | | | - André M. S. Silva
- Department of Neurology, Faculdade de MedicinaUniversidade de São Paulo (FMUSP) São Paulo Brazil
| | - Umbertina C. Reed
- Department of Neurology, Faculdade de MedicinaUniversidade de São Paulo (FMUSP) São Paulo Brazil
| | - Leslie Kulikowski
- Department of Pathology, Faculdade de MedicinaUniversidade de São Paulo (FMUSP) São Paulo Brazil
| | - Ida Paramonov
- Department of Clinical and Molecular Genetics, Valle Hebron University HospitalMedicine Genetics Group, Valle Hebron Research Institute Barcelona Spain
| | - Ivon Cuscó
- Department of Clinical and Molecular Genetics, Valle Hebron University HospitalMedicine Genetics Group, Valle Hebron Research Institute Barcelona Spain
| | - Eduardo F. Tizzano
- Department of Clinical and Molecular Genetics, Valle Hebron University HospitalMedicine Genetics Group, Valle Hebron Research Institute Barcelona Spain
| | - Edmar Zanoteli
- Department of Neurology, Faculdade de MedicinaUniversidade de São Paulo (FMUSP) São Paulo Brazil
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Adam S, Coetzee M, Honey EM. Pena-Shokeir syndrome: current management strategies and palliative care. APPLICATION OF CLINICAL GENETICS 2018; 11:111-120. [PMID: 30498368 PMCID: PMC6207248 DOI: 10.2147/tacg.s154643] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Pena-Shokeir syndrome (PSS) type 1, also known as fetal akinesia deformation sequence, is a rare genetic syndrome that almost always results in intrauterine or early neonatal death. It is characterized by markedly decreased fetal movements, intrauterine growth restriction, joint contractures, short umbilical cord, and features of pulmonary hypoplasia. Antenatal diagnosis can be difficult. Ultrasound features are varied and may overlap with those of Trisomy 18. The poor prognosis of PSS is due to pulmonary hypoplasia, which is an important feature that distinguishes PSS from arthrogryposis multiplex congenital without pulmonary hypoplasia, which has a better prognosis. If diagnosed in the antenatal period, a late termination of pregnancy can be considered following ethical discussion (if the law allows). In most cases, a diagnosis is only made in the neonatal period. Parents of a baby affected with PSS require detailed counseling that includes information on the imprecise recurrence risks and a plan for subsequent pregnancies.
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Affiliation(s)
- Sumaiya Adam
- Department of Obstetrics and Gynaecology, Steve Biko Academic Hospital, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa,
| | - Melantha Coetzee
- Division of Neonatology, Department of Pediatrics and Child Health, Steve Biko Academic Hospital, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
| | - Engela Magdalena Honey
- Department of Biochemistry, Genetics and Microbiology, Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria, South Africa
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Wijngaarde CA, Blank AC, Stam M, Wadman RI, van den Berg LH, van der Pol WL. Cardiac pathology in spinal muscular atrophy: a systematic review. Orphanet J Rare Dis 2017; 12:67. [PMID: 28399889 PMCID: PMC5387385 DOI: 10.1186/s13023-017-0613-5] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2016] [Accepted: 03/14/2017] [Indexed: 01/09/2023] Open
Abstract
Background Hereditary proximal spinal muscular atrophy (SMA) is a severe neuromuscular disease of childhood caused by homozygous loss of function of the survival motor neuron (SMN) 1 gene. The presence of a second, nearly identical SMN gene (SMN2) in the human genome ensures production of residual levels of the ubiquitously expressed SMN protein. Alpha-motor neurons in the ventral horns of the spinal cord are most vulnerable to reduced SMN concentrations but the development or function of other tissues may also be affected, and cardiovascular abnormalities have frequently been reported both in patients and SMA mouse models. Methods We systematically reviewed reported cardiac pathology in relation to SMN deficiency. To investigate the relevance of the possible association in more detail, we used clinical classification systems to characterize structural cardiac defects and arrhythmias. Conclusions Seventy-two studies with a total of 264 SMA patients with reported cardiac pathology were identified, along with 14 publications on SMA mouse models with abnormalities of the heart. Structural cardiac pathology, mainly septal defects and abnormalities of the cardiac outflow tract, was reported predominantly in the most severely affected patients (i.e. SMA type 1). Cardiac rhythm disorders were most frequently reported in patients with milder SMA types (e.g. SMA type 3). All included studies lacked control groups and a standardized approach for cardiac evaluation. The convergence to specific abnormalities of cardiac structure and function may indicate vulnerability of specific cell types or developmental processes relevant for cardiogenesis. Future studies would benefit from a controlled and standardized approach for cardiac evaluation in patients with SMA. Electronic supplementary material The online version of this article (doi:10.1186/s13023-017-0613-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- C A Wijngaarde
- Department of Neurology and Neurosurgery, F02.230, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Heidelberglaan 100, 3508 GA, Utrecht, The Netherlands.
| | - A C Blank
- Department of Pediatric Cardiology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, The Netherlands
| | - M Stam
- Department of Neurology and Neurosurgery, F02.230, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Heidelberglaan 100, 3508 GA, Utrecht, The Netherlands
| | - R I Wadman
- Department of Neurology and Neurosurgery, F02.230, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Heidelberglaan 100, 3508 GA, Utrecht, The Netherlands
| | - L H van den Berg
- Department of Neurology and Neurosurgery, F02.230, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Heidelberglaan 100, 3508 GA, Utrecht, The Netherlands
| | - W L van der Pol
- Department of Neurology and Neurosurgery, F02.230, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Heidelberglaan 100, 3508 GA, Utrecht, The Netherlands.
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Grotto S, Cuisset JM, Marret S, Drunat S, Faure P, Audebert-Bellanger S, Desguerre I, Flurin V, Grebille AG, Guerrot AM, Journel H, Morin G, Plessis G, Renolleau S, Roume J, Simon-Bouy B, Touraine R, Willems M, Frébourg T, Verspyck E, Saugier-Veber P. Type 0 Spinal Muscular Atrophy: Further Delineation of Prenatal and Postnatal Features in 16 Patients. J Neuromuscul Dis 2016; 3:487-495. [DOI: 10.3233/jnd-160177] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Sarah Grotto
- Department of Genetics, Normandy Center for Medical Genomics and Personalized Medicine, Rouen University Hospital, Rouen, France
| | - Jean-Marie Cuisset
- Department of Pediatric Neurology, Roger Salengro Hospital, Lille Regional University Hospital, Lille, France
| | - Stéphane Marret
- Department of Pediatric Intensive Care, Rouen University Hospital, Rouen, France
- Inserm ERI 28, Institute for Research and Innovation in Biomedicine, Rouen University, France
| | - Séverine Drunat
- Department of Genetics, Robert Debre University Hospital, APHP, Paris, France
| | - Patricia Faure
- Inserm U1079, Institute for Research and Innovation in Biomedicine, Rouen University, Rouen, France
| | | | - Isabelle Desguerre
- Department of Pediatric Neurology, Necker-Enfants Malades Hospital, APHP, Paris, France
| | - Vincent Flurin
- Department of Pediatric Intensive Care, Le Mans Hospital, Le Mans, France
| | - Anne-Gaëlle Grebille
- Department of Obstetrics and Gynecology, Saint-Brieuc Hospital, Saint-Brieuc, France
| | - Anne-Marie Guerrot
- Department of Genetics, Normandy Center for Medical Genomics and Personalized Medicine, Rouen University Hospital, Rouen, France
| | - Hubert Journel
- Department of Genetics, Vannes Bretagne-Atlantique Hospital, Vannes, France
| | - Gilles Morin
- Department of Genetics, Amiens University Hospital, Amiens, France
| | | | - Sylvain Renolleau
- Department of Pediatric Intensive Care, Armand-Trousseau Children’s Hospital, APHP, Paris, France
| | - Joëlle Roume
- Department of Genetics, Poissy-Saint-Germain-en-Laye Hospital, Poissy, France
| | | | - Renaud Touraine
- Department of Genetics, Saint-Etienne University Hospital, Saint-Priest-en-Jarez, France
| | - Marjolaine Willems
- Department of Genetics, Necker-Enfants Malades Hospital, APHP, Paris, France
| | - Thierry Frébourg
- Department of Genetics, Normandy Center for Medical Genomics and Personalized Medicine, Rouen University Hospital, Rouen, France
- Inserm U1079, Institute for Research and Innovation in Biomedicine, Rouen University, Rouen, France
| | - Eric Verspyck
- Department of Obstetrics and Gynecology, Rouen University Hospital, Rouen, France
| | - Pascale Saugier-Veber
- Department of Genetics, Normandy Center for Medical Genomics and Personalized Medicine, Rouen University Hospital, Rouen, France
- Inserm U1079, Institute for Research and Innovation in Biomedicine, Rouen University, Rouen, France
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Noguchi Y, Onishi A, Nakamachi Y, Hayashi N, Harahap NIF, Rochmah MA, Shima A, Yanagisawa S, Morisada N, Nakagawa T, Iijima K, Kasagi S, Saegusa J, Kawano S, Shinohara M, Tairaku S, Saito T, Kubo Y, Saito K, Nishio H. Telomeric Region of the Spinal Muscular Atrophy Locus Is Susceptible to Structural Variations. Pediatr Neurol 2016; 58:83-9. [PMID: 27268759 DOI: 10.1016/j.pediatrneurol.2016.01.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 01/18/2016] [Accepted: 01/22/2016] [Indexed: 01/11/2023]
Abstract
BACKGROUND Most patients with spinal muscular atrophy lack the survival motor neuron 1 gene (SMN1) in the telomeric region of the spinal muscular atrophy locus on chromosome 5q13. On the other hand, the copy number of SMN2, a centromeric homolog of SMN1, is increased in many of these patients. This study aimed to clarify the mechanism underlying these structural variations. METHODS We determined the copy numbers of telomeric and centromeric genes in the spinal muscular atrophy locus of 86 patients and 22 control subjects using multiplex ligation-dependent probe amplification analysis. Then, we chose 74 patients lacking SMN1 exons 7 and 8, and compared their dataset with that of 22 control subjects retaining SMN1 exons 7 and 8. RESULTS The SMN2 copy number was shown to vary widely and to correlate with the disease severity of the patients. Interestingly, telomeric NAIP and telomeric GTF2H2 showed similar tendencies. We also noted positive correlations among the copy number of SMN2 and the telomeric genes of the spinal muscular atrophy locus. However, the copy numbers of centromeric NAIP and centromeric GTF2H2 were stable among the patients, with both approximating a value of two. CONCLUSION Our findings suggested that the telomeric region of the spinal muscular atrophy locus appears to be susceptible to structural variation, whereas the centromeric region is stable. Moreover, according to our results, new SMN2 copies may be generated in the telomeric region of the spinal muscular atrophy locus, supporting the SMN1-to-SMN2 gene conversion theory.
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Affiliation(s)
- Yoriko Noguchi
- Department of Clinical Laboratory, Kobe University Hospital, Kobe, Japan
| | - Akira Onishi
- Department of Rheumatology and Clinical Immunology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Yuji Nakamachi
- Department of Clinical Laboratory, Kobe University Hospital, Kobe, Japan
| | - Nobuhide Hayashi
- Department of Clinical Laboratory, Kobe University Hospital, Kobe, Japan
| | - Nur Imma Fatimah Harahap
- Department of Community Medicine and Social Health Care, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Mawaddah Ar Rochmah
- Department of Community Medicine and Social Health Care, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Ai Shima
- Department of Community Medicine and Social Health Care, Kobe University Graduate School of Medicine, Kobe, Japan
| | | | - Naoya Morisada
- Department of Community Medicine and Social Health Care, Kobe University Graduate School of Medicine, Kobe, Japan; Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Taku Nakagawa
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Kazumoto Iijima
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Shimpei Kasagi
- Department of Clinical Laboratory, Kobe University Hospital, Kobe, Japan
| | - Jun Saegusa
- Department of Clinical Laboratory, Kobe University Hospital, Kobe, Japan; Department of Rheumatology and Clinical Immunology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Seiji Kawano
- Department of Medical Education, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Masakazu Shinohara
- Department of Community Medicine and Social Health Care, Kobe University Graduate School of Medicine, Kobe, Japan; The Integrated Center for Mass Spectrometry, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Shinya Tairaku
- Department of Obstetrics and Gynecology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Toshio Saito
- Division of Child Neurology, Department of Neurology, National Hospital Organization Toneyama National Hospital, Toyonaka, Japan
| | - Yuji Kubo
- Institute of Medical Genetics, Tokyo Women's Medical University, Tokyo, Japan
| | - Kayoko Saito
- Institute of Medical Genetics, Tokyo Women's Medical University, Tokyo, Japan
| | - Hisahide Nishio
- Department of Community Medicine and Social Health Care, Kobe University Graduate School of Medicine, Kobe, Japan; Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan.
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12
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Butchbach MER. Copy Number Variations in the Survival Motor Neuron Genes: Implications for Spinal Muscular Atrophy and Other Neurodegenerative Diseases. Front Mol Biosci 2016; 3:7. [PMID: 27014701 PMCID: PMC4785180 DOI: 10.3389/fmolb.2016.00007] [Citation(s) in RCA: 110] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 02/25/2016] [Indexed: 12/11/2022] Open
Abstract
Proximal spinal muscular atrophy (SMA), a leading genetic cause of infant death worldwide, is an early-onset, autosomal recessive neurodegenerative disease characterized by the loss of spinal α-motor neurons. This loss of α-motor neurons is associated with muscle weakness and atrophy. SMA can be classified into five clinical grades based on age of onset and severity of the disease. Regardless of clinical grade, proximal SMA results from the loss or mutation of SMN1 (survival motor neuron 1) on chromosome 5q13. In humans a large tandem chromosomal duplication has lead to a second copy of the SMN gene locus known as SMN2. SMN2 is distinguishable from SMN1 by a single nucleotide difference that disrupts an exonic splice enhancer in exon 7. As a result, most of SMN2 mRNAs lack exon 7 (SMNΔ7) and produce a protein that is both unstable and less than fully functional. Although only 10–20% of the SMN2 gene product is fully functional, increased genomic copies of SMN2 inversely correlates with disease severity among individuals with SMA. Because SMN2 copy number influences disease severity in SMA, there is prognostic value in accurate measurement of SMN2 copy number from patients being evaluated for SMA. This prognostic value is especially important given that SMN2 copy number is now being used as an inclusion criterion for SMA clinical trials. In addition to SMA, copy number variations (CNVs) in the SMN genes can affect the clinical severity of other neurological disorders including amyotrophic lateral sclerosis (ALS) and progressive muscular atrophy (PMA). This review will discuss how SMN1 and SMN2 CNVs are detected and why accurate measurement of SMN1 and SMN2 copy numbers is relevant for SMA and other neurodegenerative diseases.
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Affiliation(s)
- Matthew E R Butchbach
- Center for Applied Clinical Genomics, Nemours Biomedical Research, Nemours Alfred I. duPont Hospital for ChildrenWilmington, DE, USA; Center for Pediatric Research, Nemours Biomedical Research, Nemours Alfred I. duPont Hospital for ChildrenWilmington, DE, USA; Department of Biological Sciences, University of DelawareNewark, DE, USA; Department of Pediatrics, Thomas Jefferson UniversityPhiladelphia, PA, USA
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Abstract
Neuropathologic findings within the central and peripheral nervous systems in patients with spinal muscular atrophy type I (SMA-I) were examined in relation to genetic, clinical, and electrophysiologic features. Five infants representing the full clinical spectrum of SMA-I were examined clinically for compound motor action potential amplitude and SMN2 gene copy number; morphologic analyses of postmortem central nervous system, neuromuscular junction, and muscle tissue samples were performed and SMN protein was assessed in muscle samples. The 2 clinically most severely affected patients had a single copy of the SMN2 gene; in addition to anterior horn cells, dorsal root ganglia, and thalamus, neuronal degeneration in them was widespread in the cerebral cortex, basal ganglia, pigmented nuclei, brainstem, and cerebellum. Two typical SMA-I patients and a milder case each had 2 copies of the SMN2 gene and more restricted neuropathologic abnormalities. Maturation of acetylcholine receptor subunits was delayed and the neuromuscular junctions were abnormally formed in the SMA-I patients. Thus, the neuropathologic findings in human SMA-I are similar to many findings in animal models; factors other than SMN2 copy number modify disease severity. We present a pathophysiologic model for SMA-I as a protein deficiency disease affecting a neuronal network with variable clinical thresholds. Because new treatment strategies improve survival of infants with SMA-I, a better understanding of these factors will guide future treatments.
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Locatelli D, d'Errico P, Capra S, Finardi A, Colciaghi F, Setola V, Terao M, Garattini E, Battaglia G. Spinal muscular atrophy pathogenic mutations impair the axonogenic properties of axonal-survival of motor neuron. J Neurochem 2012; 121:465-74. [PMID: 22324632 DOI: 10.1111/j.1471-4159.2012.07689.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The axonal survival of motor neuron (a-SMN) protein is a truncated isoform of SMN1, the spinal muscular atrophy (SMA) disease gene. a-SMN is selectively localized in axons and endowed with remarkable axonogenic properties. At present, the role of a-SMN in SMA is unknown. As a first step to verify a link between a-SMN and SMA, we investigated by means of over-expression experiments in neuroblastoma-spinal cord hybrid cell line (NSC34) whether SMA pathogenic mutations located in the N-terminal part of the protein affected a-SMN function. We demonstrated here that either SMN1 missense mutations or small intragenic re-arrangements located in the Tudor domain consistently altered the a-SMN capability of inducing axonal elongation in vitro. Mutated human a-SMN proteins determined in almost all NSC34 motor neurons the growth of short axons with prominent morphologic abnormalities. Our data indicate that the Tudor domain is critical in dictating a-SMN function possibly because it is an association domain for proteins involved in axon growth. They also indicate that Tudor domain mutations are functionally relevant not only for FL-SMN but also for a-SMN, raising the possibility that also a-SMN loss of function may contribute to the pathogenic steps leading to SMA.
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Affiliation(s)
- Denise Locatelli
- Molecular Neuroanatomy and Pathogenesis Unit, Neurological Institute 'C. Besta', Milano, Italy
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Hypoplastisch linkerhartsyndroom als uiting van een bijzondere vorm van de ziekte van Werdnig-Hoffmann. ACTA ACUST UNITED AC 2006. [DOI: 10.1007/bf03061635] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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16
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Giavazzi A, Setola V, Simonati A, Battaglia G. Neuronal-specific roles of the survival motor neuron protein: evidence from survival motor neuron expression patterns in the developing human central nervous system. J Neuropathol Exp Neurol 2006; 65:267-77. [PMID: 16651888 DOI: 10.1097/01.jnen.0000205144.54457.a3] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Despite recent data on the cellular function of the survival motor neuron (SMN) gene, the spinal muscular atrophy (SMA) disease gene, the role of the SMN protein in motor neurons and hence in the pathogenesis of SMA is still unclear. The spatial and temporal expression of SMN in neurons, particularly during development, could help in verifying the hypotheses on the SMN protein functions so far proposed. We have therefore investigated the expression and subcellular localization of the SMN protein in the human central nervous system (CNS) during ontogenesis with immunocytochemical, confocal immunofluorescence, and Western blot experiments using a panel of anti-SMN antibodies recognizing the full-length SMN protein. The experiments not only revealed the early SMN expression in all neurons, but also demonstrated the progressive shift in SMN subcellular localization from mainly nuclear to cytoplasmic and then to axons during CNS maturation. This finding was present in selected neuronal cell populations and it was particularly conspicuous in motor neurons. Our data support the idea of a specific role for SMN in axons, which becomes predominant in the ontogenetic period encompassing axonogenesis and axonal sprouting. In addition, the asymmetric SMN staining demonstrated in the germinative neuroepithelium suggests a possible role for SMN in neuronal migration and/or differentiation.
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Affiliation(s)
- Alessio Giavazzi
- Molecular Neuroanatomy Lab, Department of Neurophysiology, Neurological Institute C. Besta, Milano, Italy
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17
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El-Matary W, Kotagiri S, Cameron D, Peart I. Spinal muscle atrophy type 1 (Werdnig-Hoffman disease) with complex cardiac malformation. Eur J Pediatr 2004; 163:331-2. [PMID: 15346918 DOI: 10.1007/s00431-004-1437-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Wael El-Matary
- Department of Paediatrics, Glan Clwyd Hospital, LL18 5UJ Rhyl, UK
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Markowitz JA, Tinkle MB, Fischbeck KH. Spinal Muscular Atrophy in the Neonate. J Obstet Gynecol Neonatal Nurs 2004; 33:12-20. [PMID: 14971549 DOI: 10.1177/0884217503261125] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Spinal muscular atrophy (SMA) type I is an autosomal recessive disorder characterized by loss of lower motor neurons in the spinal cord. This severe hereditary neurodegenerative disorder is an important cause of morbidity in the neonate and the leading hereditary cause of infant mortality. The characteristic degeneration of anterior horn cells in the spinal cord leads to progressive muscular weakness and atrophy of the skeletal muscles. In SMA type I, the most severe form of SMA, death usually ensues by 2 years of age from respiratory failure or infection. Accurate diagnosis is now available through genetic testing, and progress is being made toward the development of therapy based on understanding of the disease mechanism. The neonatal nurse plays a pivotal role in identifying and caring for these medically fragile infants and in providing support and education for parents and families.
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Affiliation(s)
- Jennifer A Markowitz
- Clinical Research Training Program, National Institute of Neurological Diseases and Stroke, Neurogenetics Branch, National Institutes of Health, Bethesda, MD 20892-2178, USA
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Rudnik-Schöneborn S, Sztriha L, Aithala GR, Houge G, Laegreid LM, Seeger J, Huppke M, Wirth B, Zerres K. Extended phenotype of pontocerebellar hypoplasia with infantile spinal muscular atrophy. Am J Med Genet A 2003; 117A:10-7. [PMID: 12548734 DOI: 10.1002/ajmg.a.10863] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Pontocerebellar hypoplasia (PCH) is rarely associated with anterior horn cell disease and designated as PCH-1. This phenotype is characterized by severe muscle weakness and hypotonia starting prenatally or at birth with a life span not exceeding a few months in most cases. Milder disease courses with later onset and longer survival are normally not diagnosed as PCH-1. We describe the clinical and neuroradiological findings in nine patients out of six siblingships with evidence of cerebellar defects and early onset spinal muscular atrophy (SMA), representing a broad spectrum of clinical variability. In all patients, the diagnosis of SMA (Werdnig-Hoffmann disease) was made on the basis of electrophysiological data and muscle biopsy; however, genetic testing failed to confirm the diagnosis of infantile SMA with a gene defect on chromosome 5q and resulted in clinical reevaluation. Age at onset was after a normal period in the first months of life in three siblingships and pre- and postnatally in the other three families. Life span was 2-4 years in patients with later onset, and age at death occurred after birth or within months in the more severe group. Two siblingships showed discordant ages at death despite similar treatment. In contrast to the previous definition of PCH-1, our observations suggest the existence of milder phenotypes with pontocerebellar hypoplasia or olivopontocerebellar atrophy in combination with anterior horn cell loss. A pontine involvement is not necessarily seen by neuroimaging methods. The genetic basis of PCH-1 remains to be determined. The gene locus for infantile SMA on chromosome 5q could be excluded by linkage studies. Parental consanguinity and affected siblings make autosomal recessive inheritance most likely.
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Witters I, Moerman P, Fryns JP. Fetal akinesia deformation sequence: a study of 30 consecutive in utero diagnoses. AMERICAN JOURNAL OF MEDICAL GENETICS 2002; 113:23-8. [PMID: 12400062 DOI: 10.1002/ajmg.10698] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The etiology of the fetal akinesia deformation sequence (FADS) is heterogeneous and can be the result of neurogenic and myopathic disorders, restrictive dermopathy, teratogen exposure, and intrauterine constraint. We present the prenatal and fetopathological findings in a consecutive series of 30 affected fetuses with normal chromosomal results. According to the in utero time of onset of the fetal akinesia, the severity of the phenotype varied from a severe, generalized FADS in the early-onset group to milder defects, as isolated distal arthrogryposis in the late-onset group. No more than 10% (3/30) were diagnosed in the first trimester of pregnancy and all presented a severe phenotype. Twenty-seven of the thirty (90%) were diagnosed after the first trimester, with a severe FADS in 15/27 and a milder phenotype of distal arthrogryposis in 12/27. In all 30 patients, extensive neuropathological studies (brain, spinal cord, and muscles) were performed. In 16 patients (53%) a specific diagnosis could be made (central nervous system abnormalities 9/16; spinal cord 1/16; primary myopathy 3/16; syndromic 3/16). In 10 others (33%), pathological neuromuscular findings were present but no definitive diagnosis was established. In 4 patients (13%), neuromuscular findings were normal, and the etiology of the FADS remained unexplained.
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Affiliation(s)
- Ingrid Witters
- Department of Obstetrics and Gynecology, University of Leuven, Belgium
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21
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Importancia diagnóstica de los signos de hipocinesia fetal en la atrofia muscular espinal de presentación neonatal. An Pediatr (Barc) 2002. [DOI: 10.1016/s1695-4033(02)77788-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Mailman MD, Heinz JW, Papp AC, Snyder PJ, Sedra MS, Wirth B, Burghes AHM, Prior TW. Molecular analysis of spinal muscular atrophy and modification of the phenotype by SMN2. Genet Med 2002; 4:20-6. [PMID: 11839954 DOI: 10.1097/00125817-200201000-00004] [Citation(s) in RCA: 233] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
PURPOSE This study describes SMN1 deletion frequency, carrier studies, and the effect of the modifying SMN2 gene on the spinal muscular atrophy (SMA) phenotype. A novel allele-specific intragenic mutation panel increases the sensitivity of SMN1 testing. METHODS From 1995 to 2001, 610 patients were tested for SMN1 deletions and 399 relatives of probands have been tested for carrier status. SMN2 copy number was compared between 52 type I and 90 type III patients, and between type I and type III patients with chimeric SMN genes. A fluorescent allele-specific polymerase chain reaction (PCR) -based strategy detected intragenic mutations in potential compound heterozygotes and was used on 366 patients. RESULTS Less than half of the patients tested were homozygously deleted for SMN1. A PCR-based panel detected the seven most common intragenic mutations. SMN2 copy number was significantly different between mild and severely affected patients. CONCLUSIONS SMN1 molecular testing is essential for the diagnosis of SMA and allows for accurate carrier testing. Screening for intragenic mutations in SMN1 increases the sensitivity of diagnostic testing. Finally, SMN2 copy number is conclusively shown to ameliorate the phenotype and provide valuable prognostic information.
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Affiliation(s)
- Matthew D Mailman
- Department of Pathology, The Ohio State University, Columbus 43210, USA
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23
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Haider MZ, Moosa A, Dalal H, Habib Y, Reynold L. Gene deletion patterns in spinal muscular atrophy patients with different clinical phenotypes. J Biomed Sci 2001; 8:191-6. [PMID: 11287750 DOI: 10.1007/bf02256412] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
Spinal muscular atrophy (SMA) is an autosomal recessive disorder characterized by degeneration of lower motor neurons. We have assayed deletions in two candidate genes, the survival motor neuron (SMN) and neuronal apoptosis inhibitory protein (NAIP) genes, in 108 samples, of which 46 were from SMA patients, and 62 were from unaffected subjects. The SMA patients included 3 from Bahrain, 9 from South Africa, 2 from India, 5 from Oman, 1 from Saudi Arabia, and 26 from Kuwait. SMN gene exons 7 and 8 were deleted in all type I SMA patients. NAIP gene exons 5 and 6 were deleted in 22 of 23 type I SMA patients. SMN gene exon 7 was deleted in all type II SMA patients while exon 8 was deleted in 19 of 21 type II patients. In 1 type II SMA patient, both centromeric and telomeric copies of SMN exon 8 were deleted. NAIP gene exons 5 and 6 were deleted in only 1 type II SMA patient. In 1 of the 2 type III SMA patients, SMN gene exons 7 and 8 were deleted with no deletion in the NAIP gene, while in the second patient, deletions were detected in both SMN and NAIP genes. None of the 62 unaffected subjects had deletions in either the SMN or NAIP gene. The incidence of biallelic polymorphism in SMN gene exon 7 (BsmAI) was found to be similar (97%) to that (98%) reported in a Spanish population but was significantly different from that reported from Taiwan (0%). The incidence of a second polymorphism in SMN gene exon 8 (presence of the sequence ATGGCCT) was markedly different in our population (97%) and those reported from Spain (50%) and Taiwan (0%).
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Affiliation(s)
- M Z Haider
- Paediatrics Department, Faculty of Medicine, Kuwait University, PO Box 24923, Safat 13110, Kuwait.
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24
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Biomedical vignette. J Biomed Sci 2001. [DOI: 10.1007/bf02256406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Gérard B, Ginet N, Matthijs G, Evrard P, Baumann C, Da Silva F, Gérard-Blanluet M, Mayer M, Grandchamp B, Elion J. Genotype determination at the survival motor neuron locus in a normal population and SMA carriers using competitive PCR and primer extension. Hum Mutat 2000; 16:253-63. [PMID: 10980532 DOI: 10.1002/1098-1004(200009)16:3<253::aid-humu8>3.0.co;2-8] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Precise quantitation of SMN1 copy number is of great interest in many clinical applications such as direct detection of SMA carriers or detection of an SMA-affected patient with a hemizygous deletion of the SMN1 gene. We describe a method that combines two independent nonradioactive PCR assays: determination of the relative ratio of the SMN1 and SMN2 genes using a primer extension assay and of the total SMN copy number using competitive PCR. Consistency of the results of two independent approaches ensures the reliability of the deduced genotype and thus avoids false interpretation of borderline results that can occur in quantitative assays. In all, 135 subjects were tested, including 91 normal controls and 44 SMA-affected children or SMA carriers. Two main genotypes were observed in controls: 2T/2C (45%) and 2T/1C (32%). A wide variability at the SMN locus is observed with nine different genotypes and up to six SMN genes. SMA carriers showed three frequent genotypes, 1T/2C (50%), 1T/3C (29%), and 1T/1C (18%). Normal chromosomes with two SMN1 genes per chromosome are not infrequent and thus, about 3% of SMA carriers are not detected using SMN1 copy number quantitation. Finally, as this method does not detect point mutations (4% of SMN1 gene mutations), reliability ranges from 93% to 100% depending on data available from the propositus.
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Affiliation(s)
- B Gérard
- Service de Biochimie Génétique, Hôpital Robert Debré, Paris, France.
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26
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Abstract
Spinal muscular atrophy (SMA) is characterized by degeneration of motor neurons in the spinal cord, causing progressive weakness of the limbs and trunk, followed by muscle atrophy. SMA is one of the most frequent autosomal recessive diseases, with a carrier frequency of 1 in 50 and the most common genetic cause of childhood mortality. The phenotype is extremely variable, and patients have been classified in type I-III SMA based on age at onset and clinical course. All three types of SMA are caused by mutations in the survival motor neuron gene (SMN1). There are two almost identical copies, SMN1 and SMN2, present on chromosome 5q13. Only homozygous absence of SMN1 is responsible for SMA, while homozygous absence of SMN2, found in about 5% of controls, has no clinical phenotype. Ninety-six percent of SMA patients display mutations in SMN1, while 4% are unlinked to 5q13. Of the 5q13-linked SMA patients, 96.4% show homozygous absence of SMN1 exons 7 and 8 or exon 7 only, whereas 3. 6% present a compound heterozygosity with a subtle mutation on one chromosome and a deletion/gene conversion on the other chromosome. Among the 23 different subtle mutations described so far, the Y272C missense mutation is the most frequent one, at 20%. Given this uniform mutation spectrum, direct molecular genetic testing is an easy and rapid analysis for most of the SMA patients. Direct testing of heterozygotes, while not trivial, is compromised by the presence of two SMN1 copies per chromosome in about 4% of individuals. The number of SMN2 copies modulates the SMA phenotype. Nevertheless, it should not be used for prediction of severity of the SMA.
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Affiliation(s)
- B Wirth
- Institute of Human Genetics, Bonn, Germany.
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27
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Nishio H, Horikawa H, Yakura H, Sugie K, Nakamuro T, Koterazawa K, Ishikawa Y, Lee MJ, Wada H, Takeshima Y, Matsuo M, Sumino K. Hybrid survival motor neuron genes in Japanese patients with spinal muscular atrophy. Acta Neurol Scand 1999; 99:374-80. [PMID: 10577272 DOI: 10.1111/j.1600-0404.1999.tb07367.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Spinal muscular atrophy (SMA) is a frequently occurring autosomal recessive disease, characterized by the degeneration of spinal cord anterior horn cells, leading to muscular atrophy. Most SMA patients carry homozygous deletions of the telomeric survival motor neuron gene (SMN) exons 7 and 8. In the study presented here, we examined 20 Japanese SMA patients and found that 4 of these patients were lacking in telomeric SMN exon 7, but retained exon 8. In these 4 patients, who exhibited all grades of disease severity, direct sequencing analysis demonstrated the presence of a hybrid SMN gene in which centromeric SMN exon 7 was adjacent to telomeric SMN exon 8. In an SMA family, a combination of polymerase chain reaction and enzyme-digestion analysis and haplotype analysis with the polymorphic multicopy marker Agl-CA indicated that the patient inherited the hybrid gene from her father. In conclusion, hybrid SMN genes can be present in all grades of disease severity and inherited from generation to generation in an SMA family.
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Affiliation(s)
- H Nishio
- Department of Public Health, Kobe University School of Medicine, Japan
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28
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Zerres K, Davies KE. 59th ENMC International Workshop: Spinal Muscular Atrophies: recent progress and revised diagnostic criteria 17-19 April 1998, Soestduinen, The Netherlands. Neuromuscul Disord 1999; 9:272-8. [PMID: 10399757 DOI: 10.1016/s0960-8966(99)00016-4] [Citation(s) in RCA: 116] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Affiliation(s)
- K Zerres
- Institute for Human Genetics, Technical University, Aachen Germany
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29
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Abstract
Spinal muscular atrophy is an autosomal recessive disease characterized by motor neurone loss, muscle atrophy and weakness. Deletion or mutation of the SMN1 gene reduces intracellular survival motor neurone protein levels causes spinal muscular atrophy, most likely by interfering with spliceosome assembly. A range of clinical severity and corresponding survival motor neurone levels is seen because of the presence of copies of the transcriptionally inefficient SMN2 gene and possibly other modifying genes. The delineation of SMN1 as the gene that causes spinal muscular atrophy and the identification of genes that modify spinal muscular atrophy raise the prospect of gene therapy or in-vivo gene activation treatment for this frequently fatal disorder.
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Affiliation(s)
- N H Gendron
- Children's Hospital of Eastern Ontario Research Institute, Solange Gauthier Karsh Laboratory, Ottawa, Canada.
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30
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Béchade C, Rostaing P, Cisterni C, Kalisch R, La Bella V, Pettmann B, Triller A. Subcellular distribution of survival motor neuron (SMN) protein: possible involvement in nucleocytoplasmic and dendritic transport. Eur J Neurosci 1999; 11:293-304. [PMID: 9987032 DOI: 10.1046/j.1460-9568.1999.00428.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Spinal muscular atrophy (SMA) is among the most common recessive autosomal diseases and is characterized by the loss of spinal motor neurons. A gene termed 'Survival of Motor Neurons' (SMN) has been identified as the SMA-determining gene. Recent work indicates the involvement of the SMN protein and its associated protein SIP1 in spliceosomal snRNP biogenesis. However, the function of SMN remains unknown. Here, we have studied the subcellular localization of SMN in the rat spinal cord and more generally in the central nervous system (CNS), by light fluorescence and electron microscopy. SMN immunoreactivity (IR) was found in the different regions of the spinal cord but also in various regions of the CNS such as the brainstem, cerebellum, thalamus, cortex and hippocampus. In most neurons, we observed a speckled labelling of the cytoplasm and a discontinuous staining of the nuclear envelope. For some neurons (e.g. brainstem nuclei, dentate gyrus, cortex: layer V) and, in particular in motoneurons, SMN-IR was also present as prominent nuclear dot-like-structures. In these nuclear dots, SMN colocalized with SIP1 and with fibrillarin, a marker of coiled bodies. Ultrastructural studies in the anterior horn of the spinal cord confirmed the presence of SMN in the coiled bodies and also revealed the protein at the external side of nuclear pores complexes, in association with polyribosomes, and in dendrites, associated with microtubules. These localizations suggest that, in addition to its involvement in the spliceosome biogenesis, the SMN protein could also play a part in nucleocytoplasmic and dendritic transport.
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Affiliation(s)
- C Béchade
- Laboratoire de Biologie Cellulaire de la Synapse Normale et Pathologique (INSERM U497), Paris, France
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31
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Mäkelä-Bengs P, Järvinen N, Vuopala K, Suomalainen A, Ignatius J, Sipilä M, Herva R, Palotie A, Peltonen L. Assignment of the disease locus for lethal congenital contracture syndrome to a restricted region of chromosome 9q34, by genome scan using five affected individuals. Am J Hum Genet 1998; 63:506-16. [PMID: 9683599 PMCID: PMC1377309 DOI: 10.1086/301968] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Lethal congenital contracture syndrome (LCCS) is an autosomal recessive disease leading to death before the 32d gestational week. It is characterized by the fetal akinesia phenotype, with highly focused degeneration of motoneurons in the spinal cord as the main neuropathological finding. We report here the assignment of the LCCS locus to a defined region of chromosome 9q34, between markers D9S1825 and D9S1830. The initial genome scan was performed with the DNA samples of only five affected individuals from two unrelated LCCS families. The conventional linkage analysis performed with 20 affected individuals and their families was focused on those chromosomal regions in which the affected siblings were identical by descent in the initial scan. One core haplotype of 3 cM was observed in LCCS alleles, supporting the assumption of one major mutation underlying LCCS, and linkage disequilibrium analysis restricted the critical chromosomal region to <100 kb in the vicinity of marker D9S61. Two genes, NGAL (neutrophil gelatinase-associated lipocalin and NOTCH 1, were excluded as causative genes for LCCS
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Affiliation(s)
- P Mäkelä-Bengs
- Department of Human Molecular Genetics, National Public Health Institute, helsinki, Finland
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Campbell L, Daniels RJ, Dubowitz V, Davies KE. Maternal mosaicism for a second mutational event in a type I spinal muscular atrophy family. Am J Hum Genet 1998; 63:37-44. [PMID: 9634516 PMCID: PMC1377239 DOI: 10.1086/301918] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Spinal muscular atrophy (SMA) is a common fatal motor-neuron disorder characterized by degeneration of the anterior horn cells of the spinal cord, which results in proximal muscle weakness. Three forms of the disease, exhibiting differing phenotypic severity, map to chromosome 5q13 in a region of unusually high genomic variability. The SMA-determining gene (SMN) is deleted or rearranged in patients with SMA of all levels of severity. A high de novo mutation rate has been estimated for SMA, based on the deletion of multicopy microsatellite markers. We present a type I SMA family in which a mutant SMA chromosome has undergone a second mutation event. Both the occurrence of three affected siblings harboring this same mutation in one generation of this family and the obligate-carrier status of their mother indicate the existence of maternal germ-line mosaicism for cells carrying the second mutation. The existence of secondary mutational events and of germ-line mosaicism has implications for the counseling of SMA families undergoing prenatal genetic analysis.
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Affiliation(s)
- L Campbell
- Genetics Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
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Abstract
Advances in molecular genetics have disclosed many different explanations for allelic heterogeneity, how different clinical syndromes arise from mutations in the same gene. The converse, how similar clinical syndromes arise from mutations of different genes on different chromosomes is called locus heterogeneity. Both, however, give rise to some disease-defining mutations, as in childhood spinal muscular atrophy or Duchenne muscular dystrophy. Nevertheless, new problems have been created, including what might be called "diagnosis by the number," diverse syndromes from mutations in the same gene without current explanation, or siblings with different clinical syndromes. These discoveries have transformed the clinical neurology of heritable diseases. They also provide clinicians with new responsibilities and opportunities in defining clinical syndromes and influencing the evolution of our clinical language.
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Affiliation(s)
- L P Rowland
- Department of Neurology, Columbia University College of Physicians and Surgeons, New York, NY, USA
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Battaglia G, Princivalle A, Forti F, Lizier C, Zeviani M. Expression of the SMN gene, the spinal muscular atrophy determining gene, in the mammalian central nervous system. Hum Mol Genet 1997; 6:1961-71. [PMID: 9302277 DOI: 10.1093/hmg/6.11.1961] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The survival motor neuron (SMN) gene is the putative disease gene for human spinal muscular atrophy (SMA), an autosomal recessive disorder characterized by progressive degeneration of lower motor neurons. Two copies of the gene, centromeric and telomeric, are present in the same 5q13 chromosomal region in humans. However, only the telomeric gene is affected in SMA. The SMN gene(s) encode(s) a novel protein of unknown function. To gain insights into the role of SMN in neurons, we have identified the SMN gene ortholog in the rat, and investigated SMN expression in the CNS of rat, monkey and humans by immunocytochemistry and in situ hybridization experiments. Antibodies against the SMN amino-terminus specifically recognized a single protein identical to the in vitro translation products of human and rat SMN cDNAs. The SMN gene transcript and product were widely but unevenly expressed throughout cerebral and spinal cord areas. The SMN protein was localized mainly in the cytoplasm of specific neuronal systems, and it was particularly expressed in lower motor neurons of newborn and adult animals. Likewise, a strong hybridization signal was detected in lamina IX of the spinal ventral horn. These results support the relevance of SMN for the motor neuron function and the pathogenetic role of the SMN gene in the neuronal degeneration associated with SMA.
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Affiliation(s)
- G Battaglia
- Department of Neurophysiology, Istituto Neurologico C. Besta, Milano, Italy
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Campbell L, Potter A, Ignatius J, Dubowitz V, Davies K. Genomic variation and gene conversion in spinal muscular atrophy: implications for disease process and clinical phenotype. Am J Hum Genet 1997; 61:40-50. [PMID: 9245983 PMCID: PMC1715870 DOI: 10.1086/513886] [Citation(s) in RCA: 228] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Autosomal recessive spinal muscular atrophy (SMA) is classified, on the basis of age at onset and severity, into three types: type I, severe; type II, intermediate; and type III, mild. The critical region in 5q13 contains an inverted repeat harboring several genes, including the survival motor neuron (SMN) gene, the neuronal apoptosis inhibitory protein (NAIP) gene, and the p44 gene, which encodes a transcription-factor subunit. Deletion of NAIP and p44 is observed more often in severe SMA, but there is no evidence that these genes play a role in the pathology of the disease. In > 90% of all SMA patients, exons 7 and 8 of the telomeric SMN gene (SMNtel) are not detectable, and this is also observed in some normal siblings and parents. Point mutations and gene conversions in SMNtel suggest that it plays a major role in the disease. To define a correlation between genotype and phenotype, we mapped deletions, using pulsed-field gel electrophoresis. Surprisingly, our data show that mutations in SMA types II and III, previously classed as deletions, are in fact due to gene-conversion events in which SMNtel is replaced by its centromeric counterpart, SMNcen. This results in a greater number of SMNcen copies in type II and type III patients compared with type I patients and enables a genotype/phenotype correlation to be made. We also demonstrate individual DNA-content variations of several hundred kilobases, even in a relatively isolated population from Finland. This explains why no consensus map of this region has been produced. This DNA variation may be due to a midisatellite repeat array, which would promote the observed high deletion and gene-conversion rate.
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Affiliation(s)
- L Campbell
- Department of Biochemistry, University of Oxford, United Kingdom
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