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Schreml J, Riessland M, Paterno M, Garbes L, Roßbach K, Ackermann B, Krämer J, Somers E, Parson SH, Heller R, Berkessel A, Sterner-Kock A, Wirth B. Severe SMA mice show organ impairment that cannot be rescued by therapy with the HDACi JNJ-26481585. Eur J Hum Genet 2012; 21:643-52. [PMID: 23073311 DOI: 10.1038/ejhg.2012.222] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Spinal muscular atrophy (SMA) is the leading genetic cause of early childhood death worldwide and no therapy is available today. Many drugs, especially histone deacetylase inhibitors (HDACi), increase SMN levels. As all HDACi tested so far only mildly ameliorate the SMA phenotype or are unsuitable for use in humans, there is still need to identify more potent drugs. Here, we assessed the therapeutic power of the pan-HDACi JNJ-26481585 for SMA, which is currently used in various clinical cancer trials. When administered for 64 h at 100 nM, JNJ-26481585 upregulated SMN levels in SMA fibroblast cell lines, including those from non-responders to valproic acid. Oral treatment of Taiwanese SMA mice and control littermates starting at P0 showed no overt extension of lifespan, despite mild improvements in motor abilities and weight progression. Many treated and untreated animals showed a very rapid decline or unexpected sudden death. We performed exploratory autopsy and histological assessment at different disease stages and found consistent abnormalities in the intestine, heart and lung and skeletal muscle vasculature of SMA animals, which were not prevented by JNJ-26481585 treatment. Interestingly, some of these features may be only indirectly caused by α-motoneuron function loss but may be major life-limiting factors in the course of disease. A better understanding of - primary or secondary - non-neuromuscular organ involvement in SMA patients may improve standard of care and may lead to reassessment of how to investigate SMA patients clinically.
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Affiliation(s)
- Julia Schreml
- Institute of Human Genetics, University of Cologne, Cologne, Germany
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Yu-Jin Q, Juan D, Er-zhen L, Jin-li B, Yu-wei J, Hong W, Fang S. Subtle mutations in the SMN1 gene in Chinese patients with SMA: p.Arg288Met mutation causing SMN1 transcript exclusion of exon7. BMC MEDICAL GENETICS 2012; 13:86. [PMID: 22994313 PMCID: PMC3523059 DOI: 10.1186/1471-2350-13-86] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Accepted: 09/14/2012] [Indexed: 11/17/2022]
Abstract
Background Proximal spinal muscular atrophy (SMA) is a common neuromuscular disorder resulting in death during childhood. Around 81 ~ 95% of SMA cases are a result of homozygous deletions of survival motor neuron gene 1 (SMN1) gene or gene conversions from SMN1 to SMN2. Less than 5% of cases showed rare subtle mutations in SMN1. Our aim was to identify subtle mutations in Chinese SMA patients carrying a single SMN1 copy. Methods We examined 14 patients from 13 unrelated families. Multiplex ligation-dependent probe amplification analysis was carried out to determine the copy numbers of SMN1 and SMN2. Reverse transcription polymerase chain reaction (RT-PCR) and clone sequencing were used to detect subtle mutations in SMN1. SMN transcript levels were determined using quantitative RT-PCR. Results Six subtle mutations (p.Ser8LysfsX23, p.Glu134Lys, p.Leu228X, p.Ser230Leu, p.Tyr277Cys, and p.Arg288Met) were identified in 12 patients. The p.Tyr277Cys mutation has not been reported previously. The p.Ser8LysfsX23, p.Leu228X, and p.Tyr277Cys mutations have only been reported in Chinese SMA patients and the first two mutations seem to be the common ones. Levels of full length SMN1 (fl-SMN1) transcripts were very low in patients carrying p.Ser8LysfsX23, p.Leu228X or p.Arg288Met compared with healthy carriers. In patients carrying p.Glu134Lys or p.Ser230Leu, levels of fl-SMN1 transcripts were reduced but not significant. The SMN1 transcript almost skipped exon 7 entirely in patients with the p.Arg288Met mutation. Conclusions Our study reveals a distinct spectrum of subtle mutations in SMN1 of Chinese SMA patients from that of other ethnicities. The p.Arg288Met missense mutation possibly influences the correct splicing of exon 7 in SMN1. Mutation analysis of the SMN1 gene in Chinese patients may contribute to the identification of potential ethnic differences and enrich the SMN1 subtle mutation database.
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Affiliation(s)
- Qu Yu-Jin
- Department of Medical Genetics, Capital Institute of Pediatrics, Beijing, China
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103
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Parra J, Tizzano EF. Raising obstetricians' awareness of spinal muscular atrophy: towards early detection and reproductive planning. J Matern Fetal Neonatal Med 2012; 25:2555-8. [PMID: 22712688 DOI: 10.3109/14767058.2012.703720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder that is caused by degeneration of α motor neurons in the spinal cord anterior horns. This degeneration can lead to progressive atrophy of proximal muscles, weakness, respiratory failure and death in severe cases. SMA is the most common neuromuscular disease of childhood and one of the main causes of infant death, with no cure in sight. This review highlights the impact of the disease in families, summarizes genetics and ultrasound advances, discusses how obstetricians can work towards its early detection and explores the options for reproductive planning.
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Affiliation(s)
- Juan Parra
- Department of Obstetrics and Gynecology, Hospital Sant Pau, and Ciberer U-705(3), Barcelona, Spain
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104
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Thauvin-Robinet C, Drunat S, Saugier Veber P, Chantereau D, Cossée M, Cassini C, Soichot P, Masurel-Paulet A, De Monléon JV, Sagot P, Huet F, Antin M, Calmels N, Faivre L, Gérard B. Homozygous SMN1 exons 1-6 deletion: pitfalls in genetic counseling and general recommendations for spinal muscular atrophy molecular diagnosis. Am J Med Genet A 2012; 158A:1735-41. [PMID: 22678974 DOI: 10.1002/ajmg.a.35402] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Accepted: 03/14/2012] [Indexed: 11/10/2022]
Abstract
We report on a rare homozygous intragenic deletion encompassing exons 1-6 of the SMN1 gene in a patient with spinal muscular atrophy (SMA) born into a consanguineous family. This exceptional configuration induced misinterpretation of the molecular defect involved in this patient, who was first reported as having a classic SMN1 exon 7 deletion. This case points out the possible pitfalls in molecular diagnosis of SMA in affected patients and their relatives: exploration of the SMN1 exon 7 (c.840C/T alleles) may be disturbed by several non-pathological or pathological variants around the SMN1 exon 7. In order to accurately describe the molecular defect in an SMA-affected patient, we propose to apply the Human Genome Variation Society nomenclature. This widely accepted nomenclature would improve the reporting of the molecular defect observed in SMA patients and thus would avoid the commonly used but imprecise terminology "absence of SMN1 exon 7."
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105
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Rudnik-Schöneborn S, Eggermann T, Kress W, Lemmink HH, Cobben JM, Zerres K. Clinical utility gene card for: proximal spinal muscular atrophy. Eur J Hum Genet 2012; 20:ejhg201262. [PMID: 22510849 DOI: 10.1038/ejhg.2012.62] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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106
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Dobrowolski SF, Pham HT, Downes FP, Prior TW, Naylor EW, Swoboda KJ. Newborn screening for spinal muscular atrophy by calibrated short-amplicon melt profiling. Clin Chem 2012; 58:1033-9. [PMID: 22490618 DOI: 10.1373/clinchem.2012.183038] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
BACKGROUND The management options for the autosomal recessive neurodegenerative disorder spinal muscular atrophy (SMA) are evolving; however, their efficacy may require presymptom diagnosis and continuous treatment. To identify presymptomatic SMA patients, we created a DNA-based newborn screening assay to identify the homozygous deletions of the SMN1 (survival of motor neuron 1, telomeric) gene observed in 95%-98% of affected patients. METHODS We developed primers that amplify a 52-bp PCR product from homologous regions in the SMN1 and SMN2 (survival of motor neuron 2, centromeric) genes that flank a divergent site at site c.840. Post-PCR high-resolution melt profiling assessed the amplification product, and we used a unique means of melt calibration to normalize profiles. Samples that we had previously characterized for the numbers of SMN1 and SMN2 copies established genotypes associated with particular profiles. The system was evaluated with approximately 1000 purified DNA samples, 100 self-created dried blood spots, and >1200 dried blood spots from newborn screening tests. RESULTS Homozygous deletion of SMN1 exon 7 produced a distinctive melt profile that identified SMA patients. Samples with different numbers of SMN1 and SMN2 copies were resolved by their profiles. All samples with homozygous deletions were unambiguously recognized, and no normal sample was misidentified as a positive. CONCLUSIONS This assay has characteristics suitable for population-based screening. A reliable screening test will facilitate the identification of an SMA-affected cohort to receive early intervention to maximize the benefit from treatment. A prospective screening trial will allow the efficacy of treatment options to be assessed, which may justify the inclusion of SMA as a target for population screening.
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Affiliation(s)
- Steven F Dobrowolski
- Department of Pathology, Children's Hospital of Pittsburgh, Pittsburgh, PA, USA.
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107
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Workman E, Kolb SJ, Battle DJ. Spliceosomal small nuclear ribonucleoprotein biogenesis defects and motor neuron selectivity in spinal muscular atrophy. Brain Res 2012; 1462:93-9. [PMID: 22424789 DOI: 10.1016/j.brainres.2012.02.051] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Revised: 02/17/2012] [Accepted: 02/21/2012] [Indexed: 12/22/2022]
Abstract
The SMN protein is essential and participates in the assembly of macromolecular complexes of RNA and protein in all cells. The best-characterized function of SMN is as an assembler of spliceosomal small nuclear ribonucleoproteins (snRNPs). SMN performs this function as part of a complex with several other proteins called Gemins. snRNPs are assembled in the cytoplasm in a stepwise manner and then are imported to the nucleus where they participate globally in the splicing of pre-mRNA. Mutations in the SMN1 gene result in the motor neuron disease, spinal muscular atrophy (SMA). Most of these mutations result in a reduction in the expression levels of the SMN protein, which, in turn, results in a reduction in snRNP assembly capacity. This review highlights current studies that have investigated the mechanism of SMN-dependent snRNP assembly, as well as the downstream effects on pre-mRNA splicing that result from a decrease in SMN. This article is part of a Special Issue entitled "RNA-Binding Proteins".
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Affiliation(s)
- Eileen Workman
- Department of Molecular and Cellular Biochemistry, Wexner Medical Center at The Ohio State University, Columbus, OH 43210, USA
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108
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Reorganization of Cajal bodies and nucleolar targeting of coilin in motor neurons of type I spinal muscular atrophy. Histochem Cell Biol 2012; 137:657-67. [DOI: 10.1007/s00418-012-0921-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/13/2012] [Indexed: 12/21/2022]
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109
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Abstract
Spinal muscular atrophy is a common autosomal recessive neuromuscular disorder caused by mutations in the survival motor neuron (SMN1) gene, affecting approximately 1 in 10,000 live births. The disease is characterized by progressive symmetrical muscle weakness resulting from the degeneration and loss of anterior horn cells in the spinal cord and brainstem nuclei. The disease is classified on the basis of age of onset and clinical course. Two almost identical SMN genes are present on 5q13: the SMN1 gene, which is the spinal muscular atrophy-determining gene, and the SMN2 gene. The homozygous absence of the SMN1 exon 7 has been observed in the majority of patients and is being used as a reliable and sensitive spinal muscular atrophy diagnostic test. Although SMN2 produces less full-length transcript than SMN1, the number of SMN2 copies has been shown to modulate the clinical phenotype. Carrier detection relies on the accurate determination of the SMN1 gene copies. This document follows the outline format of the general Standards and Guidelines for Clinical Laboratories. It is designed to be a checklist for genetic testing professionals who are already familiar with the disease and methods of analysis.
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110
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Parra J, Alias L, Also-Rallo E, Martínez-Hernández R, Senosiain R, Medina C, Alejos O, Rams N, Amenedo M, Ormo F, Jesús Barceló M, Calaf J, Baiget M, Bernal S, Tizzano EF. Evaluation of fetal nuchal translucency in 98 pregnancies at risk for severe spinal muscular atrophy: possible relevance of the SMN2 copy number. J Matern Fetal Neonatal Med 2011; 25:1246-9. [PMID: 22082206 DOI: 10.3109/14767058.2011.636101] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE To study fetal nuchal translucency (NT) thickness as a possible early marker in fetuses at risk for severe spinal muscular atrophy (SMA). To investigate the significance of the survival motor neuron (SMN) 2 gene copy number in affected fetuses. METHODS We performed 2D-ultrasound in 98 pregnancies at risk for SMA, all of which underwent prenatal molecular testing of the SMN1 gene. Crown-rump length (CRL) and NT measurements were obtained in all cases before chorionic villus sampling. Fetuses were diagnosed as healthy, carriers or affected according to the SMN1 molecular testing results. SMN2 copies were also tested in all affected fetuses. RESULTS Nineteen fetuses were predicted to be affected due to the absence of the SMN1 gene, 18 of which had two SMN2 copies. Mean CRL and NT values did not differ between healthy, carrier and affected fetuses. In the remaining affected case who had only one SMN2 copy, the ultrasound examination showed a NT value of 4.98 mm and findings compatible with hypoplastic left heart. CONCLUSIONS Most affected SMA fetuses have normal NT values. Our findings support the idea that SMN2 copy number in SMA fetuses is relevant for the development of congenital heart defects and increased NT values.
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Affiliation(s)
- Juan Parra
- Department of Obstetrics and Gynecology, Hospital Sant Pau, Universitat Autonoma de Barcelona, Spain
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111
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Zhong Q, Bhattacharya S, Kotsopoulos S, Olson J, Taly V, Griffiths AD, Link DR, Larson JW. Multiplex digital PCR: breaking the one target per color barrier of quantitative PCR. LAB ON A CHIP 2011; 11:2167-74. [PMID: 21584334 DOI: 10.1039/c1lc20126c] [Citation(s) in RCA: 220] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Quantitative polymerase chain reactions (qPCR) based on real-time PCR constitute a powerful and sensitive method for the analysis of nucleic acids. However, in qPCR, the ability to multiplex targets using differently colored fluorescent probes is typically limited to 4-fold by the spectral overlap of the fluorophores. Furthermore, multiplexing qPCR assays requires expensive instrumentation and most often lengthy assay development cycles. Digital PCR (dPCR), which is based on the amplification of single target DNA molecules in many separate reactions, is an attractive alternative to qPCR. Here we report a novel and easy method for multiplexing dPCR in picolitre droplets within emulsions-generated and read out in microfluidic devices-that takes advantage of both the very high numbers of reactions possible within emulsions (>10(6)) as well as the high likelihood that the amplification of only a single target DNA molecule will initiate within each droplet. By varying the concentration of different fluorogenic probes of the same color, it is possible to identify the different probes on the basis of fluorescence intensity. Adding multiple colors increases the number of possible reactions geometrically, rather than linearly as with qPCR. Accurate and precise copy numbers of up to sixteen per cell were measured using a model system. A 5-plex assay for spinal muscular atrophy was demonstrated with just two fluorophores to simultaneously measure the copy number of two genes (SMN1 and SMN2) and to genotype a single nucleotide polymorphism (c.815A>G, SMN1). Results of a pilot study with SMA patients are presented.
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Affiliation(s)
- Qun Zhong
- RainDance Technologies, Inc., 44 Hartwell Ave., Lexington, MA 02150, USA.
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112
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Also-Rallo E, Alías L, Martínez-Hernández R, Caselles L, Barceló MJ, Baiget M, Bernal S, Tizzano EF. Treatment of spinal muscular atrophy cells with drugs that upregulate SMN expression reveals inter- and intra-patient variability. Eur J Hum Genet 2011; 19:1059-65. [PMID: 21610752 DOI: 10.1038/ejhg.2011.89] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Spinal muscular atrophy (SMA) is a genetic neuromuscular disorder caused by mutations in the SMN1 gene. The homologous copy (SMN2) is always present in SMA patients. SMN1 gene transcripts are usually full-length (FL), but exon 7 is spliced out in a high proportion of SMN2 transcripts (delta7) (Δ7). Advances in drug therapy for SMA have shown that an increase in SMN mRNA and protein levels can be achieved in vitro. We performed a systematic analysis of SMN expression in primary fibroblasts and EBV-transformed lymphoblasts from seven SMA patients with varying clinical severity and different SMN1 genotypes to determine expression differences in two accessible tissues (skin and blood). The basal expression of SMN mRNA FL and Δ7 in fibroblasts and lymphoblasts was analyzed by quantitative real-time PCR. The FL-SMN and FL/Δ7 SMN ratios were higher in control cells than in patients. Furthermore, we investigated the response of these cell lines to hydroxyurea, valproate and phenylbutyrate, drugs previously reported to upregulate SMN2. The response to treatments with these compounds was heterogeneous. We found both intra-patient and inter-patient variability even within haploidentical siblings, suggesting that tissue and individual factors may affect the response to these compounds. To optimize the stratification of patients in clinical trials, in vitro studies should be performed before enrolment so as to define each patient as a responder or non-responder to the compound under investigation.
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Affiliation(s)
- Eva Also-Rallo
- Department of Genetics and CIBERER U-705 ISCIII, Hospital de Santa Creu i Sant Pau, Barcelona, Spain
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113
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Alías L, Bernal S, Barceló MJ, Also-Rallo E, Martínez-Hernández R, Rodríguez-Alvarez FJ, Hernández-Chico C, Baiget M, Tizzano EF. Accuracy of marker analysis, quantitative real-time polymerase chain reaction, and multiple ligation-dependent probe amplification to determine SMN2 copy number in patients with spinal muscular atrophy. Genet Test Mol Biomarkers 2011; 15:587-94. [PMID: 21548796 DOI: 10.1089/gtmb.2010.0253] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder caused by absence of or mutations in the survival motor neuron1 gene (SMN1). All SMA patients have a highly homologous copy of SMN1, the SMN2 gene. Severe (type I) SMA patients present one or two SMN2 copies, whereas milder chronic forms (type II-III) usually have three or four SMN2 copies. SMN2 dosage is important to stratify patients for motor function tests and clinical trials. Our aim was to compare three methods, marker analysis, real-time quantitative polymerase chain reaction using the LightCycler instrument, and multiple ligation-dependent probe amplification (MLPA), to characterize their accuracy in quantifying SMN2 genes. We studied a group of 62 genetically confirmed SMA patients, 54 with homozygous absence of exons 7 and 8 of SMN1 and 8 with SMN2-SMN1 hybrid genes. A complete correlation using the three methods was observed in 32 patients (51.6%). In the remaining 30 patients, discordances between the three methods were found, including under or overestimation of SMN2 copies by marker analysis with respect to the quantitative methods (LightCycler and MLPA) because of lack of informativeness of markers, 3' deletions of SMN genes, and breakpoints in SMN2-SMN1 hybrid genes. The technical limitations and advantages and disadvantages of these methods are discussed. We conclude that the three methods complement each other in estimating the SMN2 copy number in most cases. However, MLPA offers additional information to characterize SMA cases with particular rearrangements such as partial deletions and hybrid genes.
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Affiliation(s)
- Laura Alías
- Servicio de Genética, Hospital de la Santa Creu i Sant Pau, CIBERER (U705), Barcelona, Spain
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114
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Gonçalves-Rocha M, Oliveira J, Rodrigues L, Santos R. New approaches in molecular diagnosis and population carrier screening for spinal muscular atrophy. Genet Test Mol Biomarkers 2011; 15:319-26. [PMID: 21329463 DOI: 10.1089/gtmb.2010.0164] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Autosomal recessive spinal muscular atrophy, the leading genetic cause of infant death, is due to loss of functional SMN1 genes, mainly as a result of homozygous deletions. Carrier frequency in the general population varies widely from 1/50 to 1/125 and has significant counseling implications. In a cohort of 210 patients with spinal muscular atrophy confirmed at the molecular level, 91.9% had a homozygous deletion and 14 were compound heterozygotes. Two novel point mutations were detected (c.524delC and c.734dupC) and the 11 bp duplication c.770_780dup was found at a high frequency. We describe the development of a simple and robust method for homozygous deletion detection, which enabled us to simplify the diagnostic workup. Further, carrier frequency in our population was established by direct quantification with the commercially available MLPA kit, following optimization for the use of dried blood spots as sample specimens.
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Affiliation(s)
- Miguel Gonçalves-Rocha
- Unidade de Genética Médica, Centro de Genética Médica, Dr. Jacinto de Magalhães, INSA-IP, Praça Pedro Nunes 88, Porto, Portugal
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115
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Hammond SM, Gogliotti RG, Rao V, Beauvais A, Kothary R, DiDonato CJ. Mouse survival motor neuron alleles that mimic SMN2 splicing and are inducible rescue embryonic lethality early in development but not late. PLoS One 2010; 5:e15887. [PMID: 21249120 PMCID: PMC3012126 DOI: 10.1371/journal.pone.0015887] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 11/27/2010] [Indexed: 11/25/2022] Open
Abstract
Spinal muscular atrophy (SMA) is caused by low survival motor neuron (SMN) levels and patients represent a clinical spectrum due primarily to varying copies of the survival motor neuron-2 (SMN2) gene. Patient and animals studies show that disease severity is abrogated as SMN levels increase. Since therapies currently being pursued target the induction of SMN, it will be important to understand the dosage, timing and cellular requirements of SMN for disease etiology and potential therapeutic intervention. This requires new mouse models that can induce SMN temporally and/or spatially. Here we describe the generation of two hypomorphic Smn alleles, SmnC-T-Neo and Smn2B-Neo. These alleles mimic SMN2 exon 7 splicing, titre Smn levels and are inducible. They were specifically designed so that up to three independent lines of mice could be generated, herein we describe two. In a homozygous state each allele results in embryonic lethality. Analysis of these mutants indicates that greater than 5% of Smn protein is required for normal development. The severe hypomorphic nature of these alleles is caused by inclusion of a loxP-flanked neomycin gene selection cassette in Smn intron 7, which can be removed with Cre recombinase. In vitro and in vivo experiments demonstrate these as inducible Smn alleles. When combined with an inducible Cre mouse, embryonic lethality caused by low Smn levels can be rescued early in gestation but not late. This provides direct genetic evidence that a therapeutic window for SMN inductive therapies may exist. Importantly, these lines fill a void for inducible Smn alleles. They also provide a base from which to generate a large repertoire of SMA models of varying disease severities when combined with other Smn alleles or SMN2-containing mice.
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Affiliation(s)
- Suzan M. Hammond
- Human Molecular Genetics Program, Children's Memorial Research Center, Chicago, Illinois, United States of America
- Department of Pediatrics, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Rocky G. Gogliotti
- Human Molecular Genetics Program, Children's Memorial Research Center, Chicago, Illinois, United States of America
- Department of Pediatrics, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Vamshi Rao
- Human Molecular Genetics Program, Children's Memorial Research Center, Chicago, Illinois, United States of America
- Department of Pediatrics, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Ariane Beauvais
- Ottawa Hospital Research Institute, Ottawa, Canada
- The University of Ottawa Center for Neuromuscular Disease, Ottawa, Canada
| | - Rashmi Kothary
- Ottawa Hospital Research Institute, Ottawa, Canada
- The University of Ottawa Center for Neuromuscular Disease, Ottawa, Canada
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Canada
- Department of Medicine, University of Ottawa, Ottawa, Canada
| | - Christine J. DiDonato
- Human Molecular Genetics Program, Children's Memorial Research Center, Chicago, Illinois, United States of America
- Department of Pediatrics, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
- * E-mail:
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Chitramuthu BP, Baranowski DC, Kay DG, Bateman A, Bennett HP. Progranulin modulates zebrafish motoneuron development in vivo and rescues truncation defects associated with knockdown of Survival motor neuron 1. Mol Neurodegener 2010; 5:41. [PMID: 20946666 PMCID: PMC2974670 DOI: 10.1186/1750-1326-5-41] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2010] [Accepted: 10/14/2010] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND Progranulin (PGRN) encoded by the GRN gene, is a secreted glycoprotein growth factor that has been implicated in many physiological and pathophysiological processes. PGRN haploinsufficiency caused by autosomal dominant mutations within the GRN gene leads to progressive neuronal atrophy in the form of frontotemporal lobar degeneration (FTLD). This form of the disease is associated with neuronal inclusions that bear the ubiquitinated TAR DNA Binding Protein-43 (TDP-43) molecular signature (FTLD-U). The neurotrophic properties of PGRN in vitro have recently been reported but the role of PGRN in neurons is not well understood. Here we document the neuronal expression and functions of PGRN in spinal cord motoneuron (MN) maturation and branching in vivo using zebrafish, a well established model of vertebrate embryonic development. RESULTS Whole-mount in situ hybridization and immunohistochemical analyses of zebrafish embryos revealed that zfPGRN-A is expressed within the peripheral and central nervous systems including the caudal primary (CaP) MNs within the spinal cord. Knockdown of zfPGRN-A mRNA translation mediated by antisense morpholino oligonucleotides disrupted normal CaP MN development resulting in both truncated MNs and inappropriate early branching. Ectopic over-expression of zfPGRN-A mRNA resulted in increased MN branching and rescued the truncation defects brought about by knockdown of zfPGRN-A expression. The ability of PGRN to interact with established MN developmental pathways was tested. PGRN over-expression was found to reverse the truncation defect resulting from knockdown of Survival of motor neuron 1 (smn1). This is involved in small ribonucleoprotein biogenesis RNA processing, mutations of which cause Spinal Muscular Atrophy (SMA) in humans. It did not reverse the MN defects caused by interfering with the neuronal guidance pathway by knockdown of expression of NRP-1, a semaphorin co-receptor. CONCLUSIONS Expression of PGRN within MNs and the observed phenotypes resulting from mRNA knockdown and over-expression are consistent with a role in the regulation of spinal cord MN development and branching. This study presents the first in vivo demonstration of the neurotrophic properties of PGRN and suggests possible future therapeutic applications in the treatment of neurodegenerative diseases.
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Affiliation(s)
- Babykumari P Chitramuthu
- Endocrine Research Laboratory and Department of Medicine, Royal Victoria Hospital and McGill University Health Centre Research Institute, Montreal, Quebec, H3A 1A1, Canada.
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Prior TW. Spinal muscular atrophy: newborn and carrier screening. Obstet Gynecol Clin North Am 2010; 37:23-36, Table of Contents. [PMID: 20494255 DOI: 10.1016/j.ogc.2010.03.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Spinal muscular atrophy (SMA) is a common autosomal-recessive neuromuscular disorder caused by mutations in the survival motor neuron (SMN1) gene, affecting approximately 1 in 10,000 live births. The disease is characterized by progressive symmetric muscle weakness resulting from the degeneration and loss of anterior horn cells in the spinal cord and brainstem nuclei. The management of SMA involves supportive and preventive strategies. New treatments based on increasing the expression of full-length SMN protein levels from the SMN2 gene are being investigated and may be dependent on early detection of the disorder, before the irreversible loss of motor neurons. This article focuses on the prevention of SMA through population carrier screening and newborn screening as a means of ensuring early intervention for SMA.
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Affiliation(s)
- Thomas W Prior
- Department of Pathology, The Ohio State University, 125 Hamilton Hall, 1645 Neil Avenue, Columbus, OH 43210, USA.
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Prior TW, Snyder PJ, Rink BD, Pearl DK, Pyatt RE, Mihal DC, Conlan T, Schmalz B, Montgomery L, Ziegler K, Noonan C, Hashimoto S, Garner S. Newborn and carrier screening for spinal muscular atrophy. Am J Med Genet A 2010; 152A:1608-16. [DOI: 10.1002/ajmg.a.33474] [Citation(s) in RCA: 185] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Abstract
During the past five years, copy number variation (CNV) has emerged as a highly prevalent form of genomic variation, bridging the interval between long-recognised microscopic chromosomal alterations and single-nucleotide changes. These genomic segmental differences among humans reflect the dynamic nature of genomes, and account for both normal variations among us and variations that predispose to conditions of medical consequence. Here, we place CNVs into their historical and medical contexts, focusing on how these variations can be recognised, documented, characterised and interpreted in clinical diagnostics. We also discuss how they can cause disease or influence adaptation to an environment. Various clinical exemplars are drawn out to illustrate salient characteristics and residual enigmas of CNVs, particularly the complexity of the data and information associated with CNVs relative to that of single-nucleotide variation. The potential is immense for CNVs to explain and predict disorders and traits that have long resisted understanding. However, creative solutions are needed to manage the sudden and overwhelming burden of expectation for laboratories and clinicians to assay and interpret these complex genomic variations as awareness permeates medical practice. Challenges remain for understanding the relationship between genomic changes and the phenotypes that might be predicted and prevented by such knowledge.
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Riessland M, Ackermann B, Förster A, Jakubik M, Hauke J, Garbes L, Fritzsche I, Mende Y, Blumcke I, Hahnen E, Wirth B. SAHA ameliorates the SMA phenotype in two mouse models for spinal muscular atrophy. Hum Mol Genet 2010; 19:1492-506. [PMID: 20097677 DOI: 10.1093/hmg/ddq023] [Citation(s) in RCA: 174] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Proximal spinal muscular atrophy (SMA) is a common autosomal recessively inherited neuromuscular disorder determined by functional impairment of alpha-motor neurons within the spinal cord. SMA is caused by functional loss of the survival motor neuron gene 1 (SMN1), whereas disease severity is mainly influenced by the number of SMN2 copies. SMN2, which produces only low levels of full-length mRNA/protein, can be modulated by small molecules and drugs, thus offering a unique possibility for SMA therapy. Here, we analysed suberoylanilide hydroxamic acid (SAHA), a FDA-approved histone deacetylase inhibitor, as potential drug in two severe SMA mouse models each carrying two SMN2 transgenes: US-SMA mice with one SMN2 per allele (Smn(-/-);SMN2(tg/tg)) and Taiwanese-SMA mice with two SMN2 per allele (Smn(-/-);SMN2(tg/wt)), both on pure FVB/N background. The US-SMA mice were embryonically lethal with heterozygous males showing significantly reduced fertility. SAHA treatment of pregnant mothers rescued the embryonic lethality giving rise to SMA offspring. By using a novel breeding strategy for the Taiwanese model (Smn(-/-);SMN2(tg/tg) x Smn(-/+) mice), we obtained 50% SMA offspring that survive approximately 10 days and 50% control carriers in each litter. Treatment with 25 mg/kg twice daily SAHA increased lifespan of SMA mice by 30%, significantly improved motor function abilities, reduced degeneration of motor neurons within the spinal cord and increased the size of neuromuscular junctions and muscle fibers compared with vehicle-treated SMA mice. SMN RNA and protein levels were significantly elevated in various tissues including spinal cord and muscle. Hence, SAHA, which lessens the progression of SMA, might be suitable for SMA therapy.
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Affiliation(s)
- Markus Riessland
- Institute of Human Genetics, University of Cologne, Cologne, Germany
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Burghes AHM, Beattie CE. Spinal muscular atrophy: why do low levels of survival motor neuron protein make motor neurons sick? Nat Rev Neurosci 2009; 10:597-609. [PMID: 19584893 DOI: 10.1038/nrn2670] [Citation(s) in RCA: 537] [Impact Index Per Article: 35.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Many neurogenetic disorders are caused by the mutation of ubiquitously expressed genes. One such disorder, spinal muscular atrophy, is caused by loss or mutation of the survival motor neuron1 gene (SMN1), leading to reduced SMN protein levels and a selective dysfunction of motor neurons. SMN, together with partner proteins, functions in the assembly of small nuclear ribonucleoproteins (snRNPs), which are important for pre-mRNA splicing. It has also been suggested that SMN might function in the assembly of other ribonucleoprotein complexes. Two hypotheses have been proposed to explain the molecular dysfunction that gives rise to spinal muscular atrophy (SMA) and its specificity to a particular group of neurons. The first hypothesis states that the loss of SMN's well-known function in snRNP assembly causes an alteration in the splicing of a specific gene (or genes). The second hypothesis proposes that SMN is crucial for the transport of mRNA in neurons and that disruption of this function results in SMA.
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Affiliation(s)
- Arthur H M Burghes
- Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA.
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Workman E, Saieva L, Carrel TL, Crawford TO, Liu D, Lutz C, Beattie CE, Pellizzoni L, Burghes AH. A SMN missense mutation complements SMN2 restoring snRNPs and rescuing SMA mice. Hum Mol Genet 2009; 18:2215-29. [PMID: 19329542 PMCID: PMC2685758 DOI: 10.1093/hmg/ddp157] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2009] [Accepted: 03/25/2009] [Indexed: 11/13/2022] Open
Abstract
Spinal muscular atrophy (SMA) is an autosomal recessive neurodegenerative disease. Loss of the survival motor neuron (SMN1) gene, in the presence of the SMN2 gene causes SMA. SMN functions in snRNP assembly in all cell types, however, it is unclear how this function results in specifically motor neuron cell death. Lack of endogenous mouse SMN (Smn) in mice results in embryonic lethality. Introduction of two copies of human SMN2 results in a mouse with severe SMA, while one copy of SMN2 is insufficient to overcome embryonic lethality. We show that SMN(A111G), an allele capable of snRNP assembly, can rescue mice that lack Smn and contain either one or two copies of SMN2 (SMA mice). The correction of SMA in these animals was directly correlated with snRNP assembly activity in spinal cord, as was correction of snRNA levels. These data support snRNP assembly as being the critical function affected in SMA and suggests that the levels of snRNPs are critical to motor neurons. Furthermore, SMN(A111G) cannot rescue Smn-/- mice without SMN2 suggesting that both SMN(A111G) and SMN from SMN2 undergo intragenic complementation in vivo to function in heteromeric complexes that have greater function than either allele alone. The oligomer composed of limiting full-length SMN and SMN(A111G) has substantial snRNP assembly activity. Also, the SMN(A2G) and SMN(A111G) alleles in vivo did not complement each other leading to the possibility that these mutations could affect the same function.
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MESH Headings
- Animals
- Cells, Cultured
- Disease Models, Animal
- Female
- Humans
- Male
- Mice
- Mice, Knockout
- Mice, Transgenic
- Motor Neurons/metabolism
- Muscular Atrophy, Spinal/genetics
- Muscular Atrophy, Spinal/metabolism
- Muscular Atrophy, Spinal/mortality
- Muscular Atrophy, Spinal/physiopathology
- Mutation, Missense
- Ribonucleoproteins, Small Nuclear/genetics
- Ribonucleoproteins, Small Nuclear/metabolism
- Spinal Cord/metabolism
- Spinal Cord/physiopathology
- Survival of Motor Neuron 1 Protein/genetics
- Survival of Motor Neuron 1 Protein/metabolism
- Survival of Motor Neuron 2 Protein/genetics
- Survival of Motor Neuron 2 Protein/metabolism
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Affiliation(s)
| | - Luciano Saieva
- Center for Motor Neuron Biology and Disease, Department of Pathology and Cell Biology, Columbia University Medical Center, New York, NY 10032, USA
| | - Tessa L. Carrel
- Department of Neuroscience and Center for Molecular Neurobiology, The Ohio State University, Columbus, OH 43210, USA
| | - Thomas O. Crawford
- Department of Neurology
- Department of Pediatrics, The Johns Hopkins Hospital, Baltimore, MD 21287, USA
| | - Don Liu
- The Jackson Laboratory, 600 Main Street, Bar Harbor, ME 04609, USA
| | - Cathleen Lutz
- The Jackson Laboratory, 600 Main Street, Bar Harbor, ME 04609, USA
| | - Christine E. Beattie
- Department of Neuroscience and Center for Molecular Neurobiology, The Ohio State University, Columbus, OH 43210, USA
| | - Livio Pellizzoni
- Center for Motor Neuron Biology and Disease, Department of Pathology and Cell Biology, Columbia University Medical Center, New York, NY 10032, USA
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Rossoll W, Bassell GJ. Spinal muscular atrophy and a model for survival of motor neuron protein function in axonal ribonucleoprotein complexes. Results Probl Cell Differ 2009; 48:289-326. [PMID: 19343312 PMCID: PMC3718852 DOI: 10.1007/400_2009_4] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Spinal muscular atrophy (SMA) is a neurodegenerative disease that results from loss of function of the SMN1 gene, encoding the ubiquitously expressed survival of motor neuron (SMN) protein, a protein best known for its housekeeping role in the SMN-Gemin multiprotein complex involved in spliceosomal small nuclear ribonucleoprotein (snRNP) assembly. However, numerous studies reveal that SMN has many interaction partners, including mRNA binding proteins and actin regulators, suggesting its diverse role as a molecular chaperone involved in mRNA metabolism. This review focuses on studies suggesting an important role of SMN in regulating the assembly, localization, or stability of axonal messenger ribonucleoprotein (mRNP) complexes. Various animal models for SMA are discussed, and phenotypes described that indicate a predominant function for SMN in neuronal development and synapse formation. These models have begun to be used to test different therapeutic strategies that have the potential to restore SMN function. Further work to elucidate SMN mechanisms within motor neurons and other cell types involved in neuromuscular circuitry hold promise for the potential treatment of SMA.
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Affiliation(s)
- Wilfried Rossoll
- Departments of Cell Biology and Neurology, Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, GA 30322, USA.
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