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Sharma P, Lohiya S, Vagha K, Vagha JD, Raj H, Prasad R. Spinal Muscular Atrophy With Severe Hyperlordosis: A Case Report. Cureus 2024; 16:e53898. [PMID: 38465139 PMCID: PMC10924650 DOI: 10.7759/cureus.53898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2023] [Accepted: 02/09/2024] [Indexed: 03/12/2024] Open
Abstract
Spinal muscular atrophy (SMA) indicates a set of inherited autosomal recessive genetic disorders, where, specifically, the anterior horn cell motor neurons in the brain and spinal cord are affected, leading to a severe form of hypotonia and muscle weakness. The incidence is exceptionally rare, commonly manifesting as slowly progressive muscular weakness and atrophy of lower limbs. As per our existing knowledge, this is the first case of SMA associated with hyperlordosis in a patient. Hyperlordosis is a deformity in spinal curvature characterized by an excessive forward spinal curve in the region of the lower back, forming the characteristic C-shape curvature in the lumbar region, just above the buttocks. Parents brought an 11-year-old male child with complaints of inability to get up from a sitting position along with difficulty in walking for the past six months. Upon physical examination, deep tendon reflexes were absent; there was severe hyperlordosis, proximal limb weakness, and notable hypotonia. In our study, we aim to understand the clinical presentation, impact, and association of hyperlordosis in a child diagnosed with SMA. This case report describes the complaints and successful diagnosis of a patient of survivor motor neuron (SMN) gene-related SMA along with severe hyperlordosis backed by evidences of electrophysiology and neuropathology. However, a complete cure and normal lifestyle are not possible due to the lack of affordable and easily accessible therapies.
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Affiliation(s)
- Prachi Sharma
- Pediatrics, Jawaharlal Nehru Medical College, Datta Meghe Institute of Higher Education and Research, Wardha, IND
| | - Sham Lohiya
- Pediatrics, Jawaharlal Nehru Medical College, Datta Meghe Institute of Higher Education and Research, Wardha, IND
| | - Keta Vagha
- Pediatrics, Jawaharlal Nehru Medical College, Datta Meghe Institute of Higher Education and Research, Wardha, IND
| | - Jayant D Vagha
- Pediatrics, Jawaharlal Nehru Medical College, Datta Meghe Institute of Higher Education and Research, Wardha, IND
| | - Himanshu Raj
- Pediatrics, Jawaharlal Nehru Medical College, Datta Meghe Institute of Higher Education and Research, Wardha, IND
| | - Roshan Prasad
- Pediatrics and Neonatology, Jawaharlal Nehru Medical College, Datta Meghe Institute of Higher Education and Research, Wardha, IND
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Zhu X, Li H, Hu C, Wu M, Zhou S, Wang Y, Li W. Spinal muscular atrophy with hypoplasia of the corpus callosum: a case report. BMC Neurol 2023; 23:77. [PMID: 36803361 PMCID: PMC9938556 DOI: 10.1186/s12883-023-03121-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 02/14/2023] [Indexed: 02/20/2023] Open
Abstract
BACKGROUND Spinal Muscular Atrophy (SMA) is a severe neuromuscular disorder due to a defect in the survival motor neuron 1 (SMN1) gene. Hypoplasia of the corpus callosum is underdevelopment or thinness of the corpus callosum. SMA and callosal hypoplasia are relatively rare, and there is limited information sharing the diagnosis and treatment for SMA patients with callosal hypoplasia. CASE DESCRIPTION A boy with callosal hypoplasia, small penis, and small testes had been perceived with motor regression at 5 months. He was referred to the rehabilitation department and neurology department at 7 months. Physical examination showed absent deep tendon reflexes, proximal weakness and significant hypotonia. He was recommended to perform trio whole-exome sequencing (WES) and array comparative genomic hybridization (aCGH) for his complicated conditions. The subsequent nerve conduction study revealed some characteristics of motor neuron diseases. We identified a homozygous deletion in exon 7 of the SMN1 gene by multiplex ligation-dependent probe amplification and failed to find further pathogenic variations responsible for multiple malformations by trio WES and aCGH. He was diagnosed as SMA. Despite some concerns, he received the therapy of nusinersen for nearly 2 years. He gained the milestone of sitting without support, which he had never accomplished, after the seventh injection, and he continued to improve. During follow-up, there were no adverse events reported and no signs of hydrocephalus. CONCLUSIONS Some extra features which could not belong to neuromuscular manifestation made the diagnosis and treatment of SMA more complicated.
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Affiliation(s)
- Xiaomei Zhu
- grid.411333.70000 0004 0407 2968Department of Neurology, Children`s hospital of Fudan University, National Children`s Medical Center, 399 Wanyuan Road, Shanghai, 201102 China
| | - Hui Li
- grid.411333.70000 0004 0407 2968Department of Rehabilitation, Children`s hospital of Fudan University, National Children`s Medical Center, Shanghai, China
| | - Chaoping Hu
- grid.411333.70000 0004 0407 2968Department of Neurology, Children`s hospital of Fudan University, National Children`s Medical Center, 399 Wanyuan Road, Shanghai, 201102 China
| | - Min Wu
- grid.411333.70000 0004 0407 2968Department of Neurology, Children`s hospital of Fudan University, National Children`s Medical Center, 399 Wanyuan Road, Shanghai, 201102 China
| | - Shuizhen Zhou
- grid.411333.70000 0004 0407 2968Department of Neurology, Children`s hospital of Fudan University, National Children`s Medical Center, 399 Wanyuan Road, Shanghai, 201102 China
| | - Yi Wang
- grid.411333.70000 0004 0407 2968Department of Neurology, Children`s hospital of Fudan University, National Children`s Medical Center, 399 Wanyuan Road, Shanghai, 201102 China
| | - Wenhui Li
- Department of Neurology, Children`s hospital of Fudan University, National Children`s Medical Center, 399 Wanyuan Road, Shanghai, 201102, China.
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Mercuri E, Finkel RS, Muntoni F, Wirth B, Montes J, Main M, Mazzone ES, Vitale M, Snyder B, Quijano-Roy S, Bertini E, Davis RH, Meyer OH, Simonds AK, Schroth MK, Graham RJ, Kirschner J, Iannaccone ST, Crawford TO, Woods S, Qian Y, Sejersen T. Diagnosis and management of spinal muscular atrophy: Part 1: Recommendations for diagnosis, rehabilitation, orthopedic and nutritional care. Neuromuscul Disord 2017; 28:103-115. [PMID: 29290580 DOI: 10.1016/j.nmd.2017.11.005] [Citation(s) in RCA: 518] [Impact Index Per Article: 74.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2017] [Revised: 11/06/2017] [Accepted: 11/13/2017] [Indexed: 01/02/2023]
Abstract
Spinal muscular atrophy (SMA) is a severe neuromuscular disorder due to a defect in the survival motor neuron 1 (SMN1) gene. Its incidence is approximately 1 in 11,000 live births. In 2007, an International Conference on the Standard of Care for SMA published a consensus statement on SMA standard of care that has been widely used throughout the world. Here we report a two-part update of the topics covered in the previous recommendations. In part 1 we present the methods used to achieve these recommendations, and an update on diagnosis, rehabilitation, orthopedic and spinal management; and nutritional, swallowing and gastrointestinal management. Pulmonary management, acute care, other organ involvement, ethical issues, medications, and the impact of new treatments for SMA are discussed in part 2.
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Affiliation(s)
- Eugenio Mercuri
- Paediatric Neurology Unit, Catholic University, Rome, Italy; Centro Clinico Nemo, Policlinico Gemelli, Rome, Italy.
| | - Richard S Finkel
- Nemours Children's Hospital, University of Central Florida College of Medicine, Orlando, FL, USA
| | - Francesco Muntoni
- Dubowitz Neuromuscular Centre, UCL Great Ormond Street Institute of Child Health & Great Ormond Street Hospital, London, UK
| | - Brunhilde Wirth
- Institute of Human Genetics, Center for Molecular Medicine, Center for Rare Diseases and Institute for Genetics, University of Cologne, Germany
| | - Jacqueline Montes
- Departments of Rehabilitation and Regenerative Medicine and Neurology, Columbia University Medical Center, New York, NY, USA
| | - Marion Main
- Dubowitz Neuromuscular Centre, UCL Great Ormond Street Institute of Child Health & Great Ormond Street Hospital, London, UK
| | - Elena S Mazzone
- Paediatric Neurology Unit, Catholic University, Rome, Italy; Centro Clinico Nemo, Policlinico Gemelli, Rome, Italy
| | - Michael Vitale
- Department of Orthopaedic Surgery, Columbia University Medical Center, New York, NY, USA
| | - Brian Snyder
- Department of Orthopaedic Surgery, Children's Hospital, Harvard Medical School, Boston, USA
| | - Susana Quijano-Roy
- Assistance Publique des Hôpitaux de Paris (AP-HP), Unit of Neuromuscular Disorders, Department of Pediatric Intensive Care, Neurology and Rehabilitation, Hôpital Raymond Poincaré, Garches, France; Hôpitaux Universitaires Paris-Ile-de-France Ouest, INSERM U 1179, University of Versailles Saint-Quentin-en-Yvelines (UVSQ), Paris, France
| | - Enrico Bertini
- Unit of Neuromuscular & Neurodegenerative Disorders, Dept of Neurosciences & Neurorehabilitation, Bambino Gesù Children's Research Hospital, Rome, Italy
| | | | - Oscar H Meyer
- Division of Pulmonology, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Anita K Simonds
- NIHR Respiratory Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust, London, UK
| | - Mary K Schroth
- Division of Pediatric Pulmonary, Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, American Family Children's Hospital, Madison, WI, USA
| | - Robert J Graham
- Division of Critical Care, Dept of Anesthesiology, Perioperative & Pain Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Janbernd Kirschner
- Department of Neuropediatrics and Muscle Disorders, Medical Center, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Susan T Iannaccone
- Departments of Pediatrics and Neurology and Neurotherapeutics, Division of Pediatric Neurology, University of Texas Southwestern Medical Center and Children's Medical Center Dallas, USA
| | - Thomas O Crawford
- Department of Neurology, Johns Hopkins University, Baltimore, MD, USA
| | - Simon Woods
- Policy Ethics and Life Sciences Research Centre, Newcastle University, Newcastle, UK
| | | | - Thomas Sejersen
- Department of Women's and Children's Health, Paediatric Neurology, Karolinska Institute, Stockholm, Sweden
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Genetisches Modell der autosomal-rezessiv erblichen proximalen spinalen Muskelatrophie. MED GENET-BERLIN 2013. [DOI: 10.1007/s11825-013-0402-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Zusammenfassung
Die proximale infantile und juvenile spinale Muskelatrophie (SMA) ist eine der häufigsten autosomal-rezessive Erbkrankheiten. Man unterteilt die Patienten in 3 Gruppen, SMA Typ I-III, abhängig von der Schwere der Erkrankung (den erreichten Meilensteinen). Das hauptsächlich verantwortliche Gen, das Survival-motor-neuron(SMN1)-Gen, ist auf Chromosom 5 lokalisiert. Während das Normalallel meist mit einer oder 2 SMN1-Kopien vorliegt, sind die Defektallele bei den meisten Patienten von einer Deletion betroffen; bei einigen liegen Punktmutationen vor. Bei den Deletionen wiederum unterscheidet man zwischen einfacher und großer Deletion, die über das SMN1-Gen hinausgeht. Ein homozygotes Auftreten letzterer führt zu pränataler Letalität.
Für die vorliegende Arbeit wurden zahlreiche in der Literatur verfügbare Daten zur SMA Typ I-III zusammengetragen und in ihrer Abhängigkeit in einem genetischen Modell zusammengefasst. So war es möglich, fehlende Parameter zu schätzen, um genauere Aussagen über Genotypen machen zu können. Die einzelnen Allelfrequenzen konnten wie folgt geschätzt werden:
Normalallel b (1 SMN1-Kopie): ≈ 0,9527; Normalallel c (2 SMN1-Kopien): ≈ 0,0362; einfache Deletion a (0 SMN1-Kopien): ≈ 0,0104; Punktmutation d (1 SMN1-Kopie): ≈ 0,0003; große Deletion g (0 SMN1-Kopien): ≈ 0,0004. Die Genhäufigkeit beträgt etwa 1:90 mit einer Heterozygtenfrequenz von 1:46.
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de Souza Godinho FM, Bock H, Gheno TC, Saraiva-Pereira ML. Molecular Analysis of Spinal Muscular Atrophy: A genotyping protocol based on TaqMan(®) real-time PCR. Genet Mol Biol 2012; 35:955-9. [PMID: 23412967 PMCID: PMC3571419 DOI: 10.1590/s1415-47572012000600010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Spinal muscular atrophy (SMA) is an autosomal recessive inherited disorder caused by alterations in the survival motor neuron I (SMN1) gene. SMA patients are classified as type I-IV based on severity of symptoms and age of onset. About 95% of SMA cases are caused by the homozygous absence of SMN1 due to gene deletion or conversion into SMN2. PCR-based methods have been widely used in genetic testing for SMA. In this work, we introduce a new approach based on TaqMan(®)real-time PCR for research and diagnostic settings. DNA samples from 100 individuals with clinical signs and symptoms suggestive of SMA were analyzed. Mutant DNA samples as well as controls were confirmed by DNA sequencing. We detected 58 SMA cases (58.0%) by showing deletion of SMN1 exon 7. Considering clinical information available from 56 of them, the patient distribution was 26 (46.4%) SMA type I, 16 (28.6%) SMA type II and 14 (25.0%) SMA type III. Results generated by the new method was confirmed by PCR-RFLP and by DNA sequencing when required. In conclusion, a protocol based on real-time PCR was shown to be effective and specific for molecular analysis of SMA patients.
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Affiliation(s)
- Fernanda Marques de Souza Godinho
- Laboratório de Identificação Genética, Centro de Pesquisa Experimental e Serviço de Genética Médica, Hospital de Clínicas de Porto Alegre, RS, Brazil. ; Programa de Pós-Graduação em Bioquímica, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
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Hasanzad M, Golkar Z, Kariminejad R, Hadavi V, Almadani N, Afroozan F, Salahshurifar I, Shafeghati Y, Kahrizi K, Najmabadi H. Deletions in the Survival Motor Neuron Gene in Iranian Patients with Spinal Muscular Atrophy. ANNALS OF THE ACADEMY OF MEDICINE, SINGAPORE 2009. [DOI: 10.47102/annals-acadmedsg.v38n2p139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/11/2023]
Abstract
Introduction: Spinal muscular atrophy (SMA) is a common neuromuscular disorder with progressive paralysis caused by the loss of -motor neurons in the spinal cord. The survival motor neuron (SMN) protein is encoded by 2 genes, SMN1 and SMN2. The most frequent mutation is the biallelic deletion of exon 7 of the SMN1 gene. In SMA, SMN2 cannot compensate for the loss of SMN1, due to the exclusion of exon 7. The aim of our study was to estimate the frequency of the common SMN1 exon 7 deletion in patients referred to our centre for carrier detection and prenatal diagnosis. Materials and Methods: We performed the detection of exon 7 deletion of the SMN1 gene for the affected patients and fetuses suspected to have SMA. Results: Of 243 families, 195 were classified as SMA type I, 30 as type II, and 18 as type III according to their family histories. The analysis of exon 7 deletion among living affected children showed that 94% of the patients with SMA type I, 95% with type II families and 100% with type III had homozygous deletions. Of the prenatal diagnoses, 21 (22.8%) of the 92 fetuses were found to be affected and these pregnancies were terminated. Conclusions: The homozygosity frequency for the deletion of SMN1 exon 7 for all 3 types was (94%), similar to those of Western Europe, China, Japan and Kuwait. Key words: Iranian patients, SMN1
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Affiliation(s)
- Mandana Hasanzad
- Kariminejad-Najmabadi Pathology & Genetics Center, 14665/154, Tehran, Iran
| | - Zahra Golkar
- Kariminejad-Najmabadi Pathology & Genetics Center, 14665/154, Tehran, Iran
| | - Roxana Kariminejad
- Kariminejad-Najmabadi Pathology & Genetics Center, 14665/154, Tehran, Iran
| | - Valeh Hadavi
- Kariminejad-Najmabadi Pathology & Genetics Center, 14665/154, Tehran, Iran
| | - Navid Almadani
- Kariminejad-Najmabadi Pathology & Genetics Center, 14665/154, Tehran, Iran
| | - Fariba Afroozan
- Kariminejad-Najmabadi Pathology & Genetics Center, 14665/154, Tehran, Iran
| | - Iman Salahshurifar
- Kariminejad-Najmabadi Pathology & Genetics Center, 14665/154, Tehran, Iran
| | - Yousef Shafeghati
- University of Social Welfare & Rehabilitation Sciences, Tehran, Iran
| | - Kimia Kahrizi
- University of Social Welfare & Rehabilitation Sciences, Tehran, Iran
| | - Hossein Najmabadi
- Kariminejad-Najmabadi Pathology & Genetics Center, 14665/154, Tehran, Iran
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Tran VK, Sasongko TH, Hong DD, Hoan NT, Dung VC, Lee MJ, Gunadi, Takeshima Y, Matsuo M, Nishio H. SMN2 and NAIP gene dosages in Vietnamese patients with spinal muscular atrophy. Pediatr Int 2008; 50:346-51. [PMID: 18533950 DOI: 10.1111/j.1442-200x.2008.02590.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND The SMN1 gene is now recognized as a spinal muscular atrophy (SMA)-causing gene, while SMN2 and NAIP have been characterized as a modifying factor of the clinical severity of SMA. Gene dosage of SMN2 is associated with clinical severity of SMA. But the relationship between gene dosage of NAIP and clinical severity of SMA remains to be clarified, although complete deletion of NAIP is frequent in type I patients. METHODS To evaluate the contribution of the SMN2 and NAIP gene dosages to SMA, quantitative real-time polymerase chain reaction was used to measure copy numbers of SMN2 and NAIP in 34 Vietnamese SMA patients lacking SMN1 (13 type I, 11 type II and 10 type III patients). RESULTS The SMN2 copy number in type I patients was significantly lower than that in type II-III patients, which was compatible with the previous reports. In contrast, 25 out of 34 patients had only zero or one copy of NAIP, while 50 out of 52 controls had two or more copies. For NAIP (+) genotype, six out of 13 type I patients, eight out of 11 type II patients and six out of 10 type III patients carried one NAIP copy. CONCLUSIONS The SMN2 copy number was related to the clinical severity of SMA among Vietnamese patients. The presence of one NAIP copy, that is, heterozygous NAIP deletion, was common in Vietnamese SMA, regardless of clinical phenotype.
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Affiliation(s)
- Van Khanh Tran
- Department of Pediatrics, Graduate School of Medicine, Kobe University, Japan
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Labrum R, Rodda J, Krause A. The molecular basis of spinal muscular atrophy (SMA) in South African black patients. Neuromuscul Disord 2007; 17:684-92. [PMID: 17627822 DOI: 10.1016/j.nmd.2007.05.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2006] [Revised: 05/08/2007] [Accepted: 05/16/2007] [Indexed: 11/21/2022]
Abstract
SMA is an autosomal recessive disorder that results in symmetrical muscle weakness and wasting due to degeneration of the anterior horns of the spinal cord. The gene for SMA, the survival motor neuron (SMN) gene is found on chromosome 5q13, in a region harbouring a 500kb duplication, resulting in two copies (a telomeric and a centromeric) of each of the genes found within the duplication. SMN1 is homozygously deleted in approximately 95% of patients worldwide. Results of the current study show that only 51% (42/92) of South African black SMA patients have homozygous deletions of the SMN1 gene. This frequency is significantly lower than observed in the South African white patient group and in other international populations. The pattern of deletions in the South African black patients is also significantly different. In order to elucidate the molecular basis of SMA in the black population, a dosage assay enabling the detection of SMN1 deletion heterozygotes was independently developed. This assay confirmed SMN1 heterozygosity in at least 70% of black non-deletion SMA patients. However, no second disease-causing mutation or a common chromosomal background for this mutation could be identified in these patients. The frequency of SMA in both the black and white population was also determined using the SMN1 gene dosage assay. Results showed that SMA is more common than previously thought with carrier rates of 1 in 50 and 1 in 23 and a predicted birth incidence of 1 in 3574 and 1 in 1945 in the black population and the white population, respectively. Development and incorporation of the SMN1 dosage assay into the molecular diagnostic service will increase the percentage of cases in which the diagnosis of SMA can be confirmed and allow preclinical and prenatal diagnosis. Further gene characterisation and functional studies would need to be performed in order to further define the molecular basis of SMA in the South African black population.
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Affiliation(s)
- R Labrum
- Division of Human Genetics, School of Pathology, National Health Laboratory Service and University of the Witwatersrand, P.O. Box 1038, Johannesburg 2000, South Africa
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Wirth B, Brichta L, Hahnen E. Spinal muscular atrophy and therapeutic prospects. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2007; 44:109-32. [PMID: 17076267 DOI: 10.1007/978-3-540-34449-0_6] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The molecular genetic basis of spinal muscular atrophy (SMA), an autosomal recessive neuromuscular disorder, is the loss of function of the survival motor neuron gene (SMN1). The SMN2 gene, a nearly identical copy of SMN1, has been detected as a promising target for SMA therapy. Both genes are ubiquitously expressed and encode identical proteins, but markedly differ in their splicing patterns: While SMN1 produces full-length (FL)-SMN transcripts only, the majority of SMN2 transcripts lacks exon 7. Transcriptional SMN2 activation or modulation of its splicing pattern to increase FL-SMN levels is believed to be clinically beneficial and therefore a crucial challenge in SMA research. Drugs such as valproic acid, phenylbutyrate, sodium butyrate, M344 and SAHA that mainly act as histone deacetylase inhibitors can mediate both: they stimulate the SMN2 gene transcription and/or restore the splicing pattern, thereby elevating the levels of FL-SMN2 protein. Preliminary phase II clinical trials and individual experimental curative approaches SMA patients show promising results. However, phase III double-blind placebo controlled clinical trials have to finally prove the efficacy of these drugs.
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Affiliation(s)
- Brunhilde Wirth
- Institute of Human Genetics, Institute of Genetics, and Center for Molecular Medicine Cologne, University of Cologne, Kerpener Str. 34, 50931 Cologne, Germany
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Dupré N, Bouchard JP, Brais B, Rouleau GA. Hereditary ataxia, spastic paraparesis and neuropathy in the French-Canadian population. Can J Neurol Sci 2006; 33:149-57. [PMID: 16736723 DOI: 10.1017/s031716710000490x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Historical events have shaped the various regional gene pools of the French-Canadian (FC) population, leading to increased prevalence of some rare diseases. The first studies of these founder effects were performed in large part by astute clinicians such as André Barbeau. In collaboration with others, he contributed greatly to the delineation of phenotypic subtypes of these conditions. As such, the following neurogenetic disorders were first identified in patients of FC origin: AOA2, ARSACS, HSAN2, RAB, and HMSN/ACC. We have summarized our current knowledge of the main hereditary ataxias, spastic parapareses and neuropathies that are particular to the FC population. The initial genetic characterization of the more common and homogeneous of these diseases has been largely completed. We predict that the regional populations of Canada will allow the identification of new rare forms of hereditary ataxias, spastic parapareses and neuropathies, and contribute to the unravelling of the genetic basis of these entities.
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Affiliation(s)
- Nicolas Dupré
- Department of Neurological Sciences, CHAUQ-Enfant-Jésus, Quebec City, QC, Canada
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Abstract
The molecular basis of spinal muscular atrophy (SMA), an autosomal recessive neuromuscular disorder, is the homozygous loss of the survival motor neuron gene 1 (SMN1). A nearly identical copy of the SMN1 gene, called SMN2, modulates the disease severity. The functional difference between both genes is a translationally silent mutation that, however, disrupts an exonic splicing enhancer causing exon 7 skipping in most SMN2 transcripts. Only 10% of SMN2 transcripts encode functional full-length protein identical to SMN1. Transcriptional activation, facilitation of correct SMN2 splicing, or stabilization of the protein are considered as strategies for SMA therapy. Among various drugs, histone deacetylase inhibitors such as valproic acid (VPA) or 4-phenylbutyrate (PBA) have been shown to increase SMN2-derived RNA and protein levels. Recently, in vivo activation of the SMN gene was shown in VPA-treated SMA patients and carriers. Clinical trials are underway to investigate the effect of VPA and PBA on motor function in SMA patients.
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Affiliation(s)
- Brunhilde Wirth
- Institute of Human Genetics, Institute of Genetics and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany.
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Kesari A, Misra UK, Kalita J, Mishra VN, Pradhan S, Patil SJ, Phadke SR, Mittal B. Study of survival of motor neuron (SMN) and neuronal apoptosis inhibitory protein (NAIP) gene deletions in SMA patients. J Neurol 2005; 252:667-71. [PMID: 15772743 DOI: 10.1007/s00415-005-0714-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2004] [Revised: 10/14/2004] [Accepted: 10/26/2004] [Indexed: 12/22/2022]
Abstract
In view of the paucity of deletion studies of survival of motor neuron (SMN) and neuronal apoptosis inhibitor protein (NAIP) genes in Indian SMA patients, this study has been undertaken to determine the status of SMN1, SMN2 and NAIP gene deletions in Indian SMA patients. Clinically and neurophysiologically diagnosed SMA patients were included in the study. A gene deletion study was carried out in 45 proximal SMA patients and 50 controls of the same ethnic group. Both SMN1 and NAIP genes showed homozygous absence in 76% and 31% respectively in proximal SMA patients. It is proposed that the lower deletion frequency of SMN1 gene in Indian patients may be due to mutations present in other genes or population variation, which need further study.
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Affiliation(s)
- Akanchha Kesari
- Dept. of Genetics, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Raebareli Road, Lucknow-226014, India
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Miyaso H, Okumura M, Kondo S, Higashide S, Miyajima H, Imaizumi K. An intronic splicing enhancer element in survival motor neuron (SMN) pre-mRNA. J Biol Chem 2003; 278:15825-31. [PMID: 12604607 DOI: 10.1074/jbc.m209271200] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Spinal muscular atrophy is caused by the homozygous loss of survival motor neuron 1 (SMN1). SMN2, a nearly identical copy gene, differs from SMN1 only by a single nonpolymorphic C to T transition in exon 7, which leads to alteration of exon 7 splicing; SMN2 leads to exon 7 skipping and expression of a nonfunctional gene product and fails to compensate for the loss of SMN1. The exclusion of SMN exon 7 is critical for the onset of this disease. Regulation of SMN exon 7 splicing was determined by analyzing the roles of the cis-acting element in intron 7 (element 2), which we previously identified as a splicing enhancer element of SMN exon 7 containing the C to T transition. The minimum sequence essential for activation of the splicing was determined to be 24 nucleotides, and RNA structural analyses showed a stem-loop structure. Deletion of this element or disruption of the stem-loop structure resulted in a decrease in exon 7 inclusion. A gel shift assay using element 2 revealed formation of RNA-protein complexes, suggesting that the binding of the trans-acting proteins to element 2 plays a crucial role in the splicing of SMN exon 7 containing the C to T transition.
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Affiliation(s)
- Hidenobu Miyaso
- Division of Structural Cellular Biology, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0101, Japan
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14
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Savas S, Eraslan S, Kantarci S, Karaman B, Acarsoz D, Tükel T, Cogulu O, Ozkinay F, Basaran S, Aydinli K, Yuksel-Apak M, Kirdar B. Prenatal prediction of childhood-onset spinal muscular atrophy (SMA) in Turkish families. Prenat Diagn 2002; 22:703-9. [PMID: 12210580 DOI: 10.1002/pd.384] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Childhood-onset spinal muscular atrophy (SMA) is one of the most common neurodegenerative genetic disorders. SMN1 is the SMA-determining gene deleted or mutated in the majority of SMA cases. There is no effective cure or treatment for this disease yet. Thus, the availability of prenatal testing is important. Here we report prenatal prediction for 68 fetuses in 63 Turkish SMA families using direct deletion analysis of the SMN1 gene by restriction digestion. The genotype of the index case was known in 40 families (Group A) but unknown in the remaining 23 families (Group B). A total of ten fetuses were predicted to be affected. Eight of these fetuses were derived from Group A and two of these fetuses were from Group B families. Two fetuses from the same family in Group A had the SMNhyb1 gene in addition to homozygous deletion of the NAIP gene. One fetus from Group A was homozygously deleted for only exon 8 of the SMN2 gene, and further analysis showed the presence of both the SMN1 and SMNhyb1 genes but not the SMN2 gene. In addition, one carrier with a homozygous deletion of only exon 8 of the SMN1 gene was detected to have a SMNhyb2 gene, which was also found in the fetus. To our knowledge, these are the first prenatal cases with SMNhyb genes. Follow-up studies demonstrated that the prenatal predictions and the phenotype of the fetuses correlated well in 33 type I pregnancies demonstrating that a careful molecular analysis of the SMN genes is very useful in predicting the phenotype of the fetus in families at risk for SMA.
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Affiliation(s)
- S Savas
- Department of Molecular Biology and Genetics, Bogazici University, Istanbul, Turkey.
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15
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Miyajima H, Miyaso H, Okumura M, Kurisu J, Imaizumi K. Identification of a cis-acting element for the regulation of SMN exon 7 splicing. J Biol Chem 2002; 277:23271-7. [PMID: 11956196 DOI: 10.1074/jbc.m200851200] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Spinal muscular atrophy results from the loss of functional survival motor neuron (SMN1) alleles. Two nearly identical copies of SMN exist and differ only by a single non-polymorphic C to T transition in exon 7. This transition leads to alteration of exon 7 splicing; that is, SMN1 produces a full-length transcript, whereas SMN2 expresses a low level of full-length transcript and predominantly an isoform lacking exon 7. The truncated transcript of SMN encodes a less stable protein with reduced self-oligomerization activity that fails to compensate for the loss of SMN1. In this paper, we identified a cis-acting element (element 1), which is composed of 45 bp in intron 6 responsible for the regulation of SMN exon 7 splicing. Mutations in element 1 or treatment with antisense oligonucleotides directed toward element 1 caused an increase in exon 7 inclusion. An approximately 33-kDa protein was demonstrated to associate with a pre-mRNA sequence containing both element 1 and the C to T transition in SMN exon 7 but not with the sequence containing mutated element 1, suggesting that the binding of the approximately 33-kDa protein plays crucial roles in the skipping of SMN exon 7 containing the C to T transition.
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Affiliation(s)
- Hiroshi Miyajima
- Division of Structural Cellular Biology, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama, Ikoma, Nara 630-0101, Japan
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16
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Diep Tran T, Kroepfl T, Saito M, Nagura M, Ichiseki H, Kubota M, Toda T, Sakakihara Y. The gene copy ratios of SMN1/SMN2 in Japanese carriers with type I spinal muscular atrophy. Brain Dev 2001; 23:321-6. [PMID: 11504604 DOI: 10.1016/s0387-7604(01)00234-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Spinal muscular atrophy is an autosomal recessive neurodegenerative disorder with progressive weakness and atrophy of voluntary muscles. The survival motor neuron gene (SMN) is present in two highly homologous copies (SMN1 and SMN2) on chromosome 5q13. Homozygous deletion of exons 7 and 8 of SMN1 is responsible for spinal muscular atrophy. In spinal muscular atrophy patients, SMN2 partially compensates for the lack of SMN1. Previously, we reported the relatively high incidence of a large deletion including the SMN1 region in Japanese spinal muscular atrophy type I patients. In order to further establish the genetic background of Japanese spinal muscular atrophy type I patients, we investigated the SMN1/SMN2 ratio in the carriers. In normal individuals, there is one copy of each gene on the chromosome (the SMN1/SMN2 ratio was 1). Among 15 carriers (14 parents and one carrier sibling of Japanese type I spinal muscular atrophy patients with homozygous deletion of exons 7 and 8 of SMN1), we found that the SMN1/SMN2 ratio was 0.5 or 1 in 11 (73.3%) carriers. The remaining four carriers had an SMN1/SMN2 ratio of 1/3. This finding supports the idea that deletion rather than conversion is the main genetic event in type I spinal muscular atrophy. In addition, the ratio of SMN1/SMN2 among Japanese carriers, which was thought to be higher than that of the Western population, was compatible with the results obtained in Western populations. For further insight into the characteristic genetic background of spinal muscular atrophy in Japanese, determination of the gene copy number is essential.
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Affiliation(s)
- T Diep Tran
- Department of Pediatrics, Faculty of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, 113-8655, Tokyo, Japan
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17
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Abstract
The profile of disorders presenting with neonatal hypotonia to the neonatal intensive care unit has not been studied previously. An 11-year retrospective cohort study of neonates, who were identified through computer database records and were admitted to the Neonatal Intensive Care Unit from January 1989 to December 1999 at the Montreal Children's Hospital (Montreal, Québec), is presented. The final diagnoses, tests obtained, and outcome were determined from a structured review of the subject's hospital record. The database search generated 95 records, of which 50 neonates met the inclusion criteria. The hypotonia was classified as central in 33 patients (66%) and peripheral in 17 (34%). Hypoxic-ischemic encephalopathy (n = 13), Prader-Willi syndrome (n = 6), myotonic dystrophy (n = 6), other muscle disorders (n = 6), chromosomal disorders (n = 4), and peripheral nerve disorders (n = 3) were the most common diagnoses. The genetic tests of highest yield were fluorescent in situ hybridization for Prader-Willi syndrome, DNA methylation studies for Prader-Willi syndrome, trinucleotide repeat testing for myotonic dystrophy, and karyotype analysis. A diagnostic approach is proposed based on the results.
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Affiliation(s)
- L P Richer
- Department of Neurology, McGill University, Montreal, Québec, Canada
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18
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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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19
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Abstract
Our understanding of the neuromuscular disorders of childhood has been rapidly expanding. This is mostly because of the discovery of the underlying genetic loci for the vast majority of these diseases and the abnormal proteins produced caused by these mutations. Spinal muscular atrophy is the second most frequent autosomal recessive disease of childhood and the most fatal. It has been mapped to chromosome 5q11.2-13.3, an area with three distinct genes associated with spinal muscular atrophy. Charcot-Marie-Tooth is the most common inherited peripheral neuropathy. Three genes encoding for myelin proteins and one for a nuclear protein have been associated with this group of disorders. Finally, since dystrophin was cloned in 1986, many proteins assisting dystrophin in anchoring the muscle cytoskeleton to the extracellular matrix have been discovered. Mutations in these genes lead to various forms of muscular dystrophy.
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Affiliation(s)
- J B Strober
- Pediatrics and Neurology, Division of Child Neurology, University of California at San Francisco, 94143-0136, USA.
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20
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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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21
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Sato K, Eguchi Y, Kodama TS, Tsujimoto Y. Regions essential for the interaction between Bcl-2 and SMN, the spinal muscular atrophy disease gene product. Cell Death Differ 2000; 7:374-83. [PMID: 10773822 DOI: 10.1038/sj.cdd.4400660] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The SMN gene is implicated in spinal muscular atrophy (SMA), and its product has been shown to interact with Bcl-2 protein to enhance its anti-apoptotic activity. In this study, we determined the regions that were essential for the interaction of Bcl-2 and SMN by co-immunoprecipitation of deletion mutants. Bcl-2 lacking its amino-terminal 20 amino acid residues or its carboxyl-terminal membrane-anchoring domain showed no or greatly reduced binding with SMN, respectively. However, Bcl-2 lacking other regions could still bind to SMN. Because Bcl-2 lacking the membrane-anchoring domain could bind to SMN in a yeast two-hybrid system, the amino-terminal region of Bcl-2 seems to be the most important domain for binding with SMN. A fragment of SMN encoded by exon 6 could bind to Bcl-2, but SMN lacking this region could not. From these results, we concluded that Bcl-2 and SMN proteins bound with each other at the amino-terminal region near the BH4 domain of Bcl-2 and the region encoded by exon 6 of SMN, both regions known to be important for their function.
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Affiliation(s)
- K Sato
- Department of Medical Genetics, Biomedical Research Center (B8), Osaka University Graduate School of Medicine, and CREST, Japan Science and Technology Corp., 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan
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22
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Stevens G, Yawitch T, Rodda J, Verhaart S, Krause A. Different molecular basis for spinal muscular atrophy in South African black patients. ACTA ACUST UNITED AC 1999. [DOI: 10.1002/(sici)1096-8628(19991029)86:5<420::aid-ajmg5>3.0.co;2-s] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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23
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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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24
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Wirth B, Herz M, Wetter A, Moskau S, Hahnen E, Rudnik-Schöneborn S, Wienker T, Zerres K. Quantitative analysis of survival motor neuron copies: identification of subtle SMN1 mutations in patients with spinal muscular atrophy, genotype-phenotype correlation, and implications for genetic counseling. Am J Hum Genet 1999; 64:1340-56. [PMID: 10205265 PMCID: PMC1377870 DOI: 10.1086/302369] [Citation(s) in RCA: 272] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Problems with diagnosis and genetic counseling occur for patients with autosomal recessive proximal spinal muscular atrophy (SMA) who do not show the most common mutation: homozygous absence of at least exon 7 of the telomeric survival motor neuron gene (SMN1). Here we present molecular genetic data for 42 independent nondeleted SMA patients. A nonradioactive quantitative PCR test showed one SMN1 copy in 19 patients (45%). By sequencing cloned reverse-transcription (RT) PCR products or genomic fragments of SMN1, we identified nine different mutations in 18 of the 19 patients, six described for the first time: three missense mutations (Y272C, T274I, S262I), three frameshift mutations in exons 2a, 2b, and 4 (124insT, 241-242ins4, 591delA), one nonsense mutation in exon 1 (Q15X), one Alu-mediated deletion from intron 4 to intron 6, and one donor splice site mutation in intron 7 (c.922+6T-->G). The most frequent mutation, Y272C, was found in 6 (33%) of 18 patients. Each intragenic mutation found in at least two patients occurred on the same haplotype background, indicating founder mutations. Genotype-phenotype correlation allowed inference of the effect of each mutation on the function of the SMN1 protein and the role of the SMN2 copy number in modulating the SMA phenotype. In 14 of 23 SMA patients with two SMN1 copies, at least one intact SMN1 copy was sequenced, which excludes a 5q-SMA and suggests the existence of further gene(s) responsible for approximately 4%-5% of phenotypes indistinguishable from SMA. We determined the validity of the test, and we discuss its practical implications and limitations.
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Affiliation(s)
- B Wirth
- Institute of Human Genetics, Wilhelmstrasse 31, D-53111 Bonn, Germany.
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25
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Parsons DW, McAndrew PE, Iannaccone ST, Mendell JR, Burghes AH, Prior TW. Intragenic telSMN mutations: frequency, distribution, evidence of a founder effect, and modification of the spinal muscular atrophy phenotype by cenSMN copy number. Am J Hum Genet 1998; 63:1712-23. [PMID: 9837824 PMCID: PMC1377643 DOI: 10.1086/302160] [Citation(s) in RCA: 144] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
The autosomal recessive neuromuscular disorder proximal spinal muscular atrophy (SMA) is caused by the loss or mutation of the survival motor neuron (SMN) gene, which exists in two nearly identical copies, telomeric SMN (telSMN) and centromeric SMN (cenSMN). Exon 7 of the telSMN gene is homozygously absent in approximately 95% of SMA patients, whereas loss of cenSMN does not cause SMA. We searched for other telSMN mutations among 23 SMA compound heterozygotes, using heteroduplex analysis. We identified telSMN mutations in 11 of these unrelated SMA-like individuals who carry a single copy of telSMN: these include two frameshift mutations (800ins11 and 542delGT) and three missense mutations (A2G, S262I, and T274I). The telSMN mutations identified to date cluster at the 3' end, in a region containing sites for SMN oligomerization and binding of Sm proteins. Interestingly, the novel A2G missense mutation occurs outside this conserved carboxy-terminal domain, closely upstream of an SIP1 (SMN-interacting protein 1) binding site. In three patients, the A2G mutation was found to be on the same allele as a rare polymorphism in the 5' UTR, providing evidence for a founder chromosome; Ag1-CA marker data also support evidence of an ancestral origin for the 800ins11 and 542delGT mutations. We note that telSMN missense mutations are associated with milder disease in our patients and that the severe type I SMA phenotype caused by frameshift mutations can be ameliorated by an increase in cenSMN gene copy number.
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Affiliation(s)
- D W Parsons
- Department of Pathology, Ohio State University, Columbus, Ohio, USA
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26
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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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27
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DiDonato CJ, Chen XN, Noya D, Korenberg JR, Nadeau JH, Simard LR. Cloning, characterization, and copy number of the murine survival motor neuron gene: homolog of the spinal muscular atrophy-determining gene. Genome Res 1997; 7:339-52. [PMID: 9110173 DOI: 10.1101/gr.7.4.339] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Because of a 500-kb inverted duplication, there are two copies of the survival motor neuron (SMN) gene in humans, cenSMN and telSMN. Both genes produce identical ubiquitously expressed transcripts; however, only mutations in telSMN are responsible for spinal muscular atrophy (SMA), the second most common autosomal recessive childhood disease. We have cloned the murine homolog Smn and mapped the gene to Chromosome 13 within the conserved syntenic region of human chromosome 5q13. We show that the Smn transcript (1.4 kb) is expressed as early as embryonic day 7. In contrast to humans, we found no evidence of alternative splicing. The predicted amino acid sequence between mouse and human SMN is 82% identical, and a putative nuclear localization signal is conserved. FISH data indicate that the duplication of the SMA region observed in humans is not present in the mouse. We also found no evidence of multiple Smn genes using Southern blot hybridization and single-strand conformation analysis. Using these methods, we detected at least four copies of Naip exon 5 clustering distal to Smn. Finally, three biallelic markers were identified within the Smn coding region; two are silent polymorphisms, whereas the third changes a cysteine residue to a tyrosine residue in exon 7. Overall, our results indicate that Smn is single copy within the mouse genome, which should facilitate gene disruption experiments to create an animal model of SMA.
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MESH Headings
- Amino Acid Sequence
- Animals
- Base Sequence
- Blotting, Northern
- Chromosome Mapping/methods
- Chromosomes, Artificial, Yeast
- Chromosomes, Bacterial
- Chromosomes, Human, Pair 5
- Cloning, Molecular
- Cyclic AMP Response Element-Binding Protein
- Female
- Gene Amplification
- Humans
- In Situ Hybridization, Fluorescence
- Mice
- Mice, Inbred C57BL
- Mice, Inbred Strains
- Molecular Sequence Data
- Muscular Atrophy, Spinal/genetics
- Nerve Tissue Proteins/genetics
- Polymorphism, Single-Stranded Conformational
- RNA-Binding Proteins
- SMN Complex Proteins
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Tissue Distribution
- Transcription, Genetic
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Affiliation(s)
- C J DiDonato
- Service de Génétique Médicale, Hôpital Ste-Justine, Québec, Canada
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