1
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Abiusi E, Costa-Roger M, Bertini ES, Tiziano FD, Tizzano EF, Abiusi E, Baranello G, Bertini E, Boemer F, Burghes A, Codina-Solà M, Costa-Roger M, Dangouloff T, Groen E, Gos M, Jędrzejowska M, Kirschner J, Lemmink HH, Müller-Felber W, Ouillade MC, Quijano-Roy S, Rucinski K, Saugier-Veber P, Tiziano FD, Tizzano EF, Wirth B. 270th ENMC International Workshop: Consensus for SMN2 genetic analysis in SMA patients 10-12 March, 2023, Hoofddorp, the Netherlands. Neuromuscul Disord 2024; 34:114-122. [PMID: 38183850 DOI: 10.1016/j.nmd.2023.12.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2024]
Abstract
The 270th ENMC workshop aimed to develop a common procedure to optimize the reliability of SMN2 gene copy number determination and to reinforce collaborative networks between molecular scientists and clinicians. The workshop involved neuromuscular and clinical experts and representatives of patient advocacy groups and industry. SMN2 copy number is currently one of the main determinants for therapeutic decision in SMA patients: participants discussed the issues that laboratories may encounter in this molecular test and the cruciality of the accurate determination, due the implications as prognostic factor in symptomatic patients and in individuals identified through newborn screening programmes. At the end of the workshop, the attendees defined a set of recommendations divided into four topics: SMA molecular prognosis assessment, newborn screening for SMA, SMN2 copies and treatments, and modifiers and biomarkers. Moreover, the group draw up a series of recommendations for the companies manufacturing laboratory kits, that will help to minimize the risk of errors, regardless of the laboratories' expertise.
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Affiliation(s)
- Emanuela Abiusi
- Section of Genomic Medicine, Department of Public Health and Life Sciences, Università Cattolica del Sacro Cuore, Roma, Italy
| | - Mar Costa-Roger
- Clinical and Molecular Genetics Area, Vall d'Hebron Hospital; Medicine Genetics Group, Vall d'Hebron Research Institute (VHIR), Barcelona, Spain
| | - Enrico Silvio Bertini
- Research Unit of Neuromuscular Disease, Bambino Gesu’ Children's Hospital, IRCCS, Roma, Italy
| | - Francesco Danilo Tiziano
- Section of Genomic Medicine, Department of Public Health and Life Sciences, Università Cattolica del Sacro Cuore, Roma, Italy
- Complex Unit of Medical Genetics, Fondazione Policlinico Universitario IRCCS “A. Gemelli”, Roma, Italy
| | - Eduardo F Tizzano
- Clinical and Molecular Genetics Area, Vall d'Hebron Hospital; Medicine Genetics Group, Vall d'Hebron Research Institute (VHIR), Barcelona, Spain
| | - Emanuela Abiusi
- Section of Genomic Medicine, Dept. of Life Sciences and Public Health, Catholic University of the Sacred Heart, Roma, Italy
| | - Giovanni Baranello
- The Dubowitz Neuromuscular Centre, Developmental Neuroscience Research and Teaching Department, UCL Great Ormond Street Institute of Child Health, NIHR Great Ormond Street Hospital Biomedical Research Centre & Great Ormond Street Hospital NHS Foundation Trust, 30 Guilford Street, London WC1N 1EH, UK
| | - Enrico Bertini
- Italy, Research Unit of Neuromuscular Disease, Bambino Gesù Children's Hospital, IRCCS, Roma, Italy
| | - François Boemer
- Biochemical Genetics Lab, Department of Human Genetics, University Hospital, University of Liège, 4000 Liège, Belgium
| | - Arthur Burghes
- Department of Neurology, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Marta Codina-Solà
- Neuromuscular Reference Center, Department of Paediatrics, University Hospital Liege & University of Liege, Belgium
| | - Mar Costa-Roger
- Department of Neurology & Neurosurgery, UMC Utrecht Brain Center, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Tamara Dangouloff
- Department of Medical Genetics, Institute of Mother and Child, Warsaw, Poland
| | - Ewout Groen
- Department of Neurology, Medical University of Warsaw, Warsaw, Poland
| | - Monika Gos
- Department of Neuropediatrics and Muscle Disorders, Medical Center University of Freiburg, Faculty of Medicine, Freiburg, Germany
| | - Maria Jędrzejowska
- Department of Genetics, University of Groningen, University Medical Center Groningen, 9700 RB Groningen, The Netherlands
| | - Janbernd Kirschner
- Centre for Neuromuscular Disorders, Center for Translational Neuro and Behavioral Sciences, Department of Pediatric Neurology, University Duisburg-Essen, 45147 Essen, Germany
| | - Henny H Lemmink
- AFM Téléthon, Évry, France; SMA Europe; European Alliance for Newborn Screening in Spinal Muscular Atrophy
| | - Wolfgang Müller-Felber
- Pediatric Neuromuscular Unit (NEIDF Reference Center at FILNEMUS & Euro-NMD), Child Neurology Department, Raymond Poincaré Hospital (UVSQ), APHP Université Paris Saclay, Garches France
| | - Marie-Christine Ouillade
- Fundacja SMA, Warsaw, Poland; SMA Europe; European Alliance for Newborn Screening in Spinal Muscular Atrophy
| | - Susana Quijano-Roy
- Univ Rouen Normandie, Inserm U1245, Normandie Univ and CHU Rouen, Department of Genetics and Nord/Est/Ile de France Neuromuscular Reference Center, F-76000 Rouen, France
| | - Kacper Rucinski
- Institute of Medical Genomics, Dept. of Life Sciences and Public Health, Catholic University of the Sacred Heart, and Complex Unit of Medical Genetics, Fondazione Policlinico Universitario IRCCS “A. Gemelli”, Roma, Italy
| | - Pascale Saugier-Veber
- Institute of Human Genetics, University Hospital of Cologne, Center for Molecular Medicine, University of Cologne and Center for Rare Diseases Cologne, University Hopsital of Cologne, Cologne, Germany
| | - Francesco Danilo Tiziano
- Institute of Medical Genomics, Dept. of Life Sciences and Public Health, Catholic University of the Sacred Heart, and Complex Unit of Medical Genetics, Fondazione Policlinico Universitario IRCCS “A. Gemelli”, Roma, Italy
| | - Eduardo Fidel Tizzano
- Clinical and Molecular Genetics Area, Vall d'Hebron Hospital; Medicine Genetics Group, Vall d'Hebron Research Institute (VHIR), Barcelona, Spain
| | - Brunhilde Wirth
- Institute of Human Genetics, University Hospital of Cologne, Center for Molecular Medicine, University of Cologne and Center for Rare Diseases Cologne, University Hopsital of Cologne, Cologne, Germany
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Zhuri D, Gurkan H, Eker D, Karal Y, Yalcintepe S, Atli E, Demir S, Atli EI. Investigation on the Effects of Modifying Genes on the Spinal Muscular Atrophy Phenotype. Glob Med Genet 2022; 9:226-236. [PMID: 36071912 PMCID: PMC9444347 DOI: 10.1055/s-0042-1751302] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Introduction
Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder caused by the degeneration of motor neurons, muscle weakness, and atrophy that leads to infant's death. The duplication of exon 7/8 in the
SMN2
gene reduces the clinical severity of disease, and it is defined as modifying effect. In this study, we aim to investigate the expression of modifying genes related to the prognosis of SMA like
PLS3
,
PFN2
,
ZPR1
,
CORO1C
,
GTF2H2
,
NRN1
,
SERF1A
,
NCALD
,
NAIP
, and
TIA1. Methods
Seventeen patients, who came to Trakya University, Faculty of Medicine, Medical Genetics Department, with a preliminary diagnosis of SMA disease, and eight healthy controls were included in this study after multiplex ligation-dependent probe amplification analysis. Gene expression levels were determined by real-time reverse transcription polymerase chain reaction and delta–delta CT method by the isolation of RNA from peripheral blood of patients and controls.
Results
SERF1A
and
NAIP
genes compared between A group and B + C + D groups, and A group of healthy controls, showed statistically significant differences (
p
= 0.037,
p
= 0.001).
Discussion
PLS3, NAIP
, and
NRN1
gene expressions related to SMA disease have been reported before in the literature. In our study, the expression levels of
SERF1A
,
GTF2H2
,
NCALD
,
ZPR1
,
TIA1
,
PFN2
, and
CORO1C
genes have been studied for the first time in SMA patients.
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Affiliation(s)
- Drenushe Zhuri
- Department of Medical Genetics, Trakya University Faculty of Medicine, Edirne, Turkey
| | - Hakan Gurkan
- Department of Medical Genetics, Trakya University Faculty of Medicine, Edirne, Turkey
| | - Damla Eker
- Department of Medical Genetics, Trakya University Faculty of Medicine, Edirne, Turkey
| | - Yasemin Karal
- Department of Pediatric Neurology, Trakya University Faculty of Medicine, Edirne, Turkey
| | - Sinem Yalcintepe
- Department of Medical Genetics, Trakya University Faculty of Medicine, Edirne, Turkey
| | - Engin Atli
- Department of Medical Genetics, Trakya University Faculty of Medicine, Edirne, Turkey
| | - Selma Demir
- Department of Medical Genetics, Trakya University Faculty of Medicine, Edirne, Turkey
| | - Emine Ikbal Atli
- Department of Medical Genetics, Trakya University Faculty of Medicine, Edirne, Turkey
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3
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Neurological assessment of newborns with spinal muscular atrophy identified through neonatal screening. Eur J Pediatr 2022; 181:2821-2829. [PMID: 35522315 PMCID: PMC9192449 DOI: 10.1007/s00431-022-04470-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 03/31/2022] [Accepted: 04/05/2022] [Indexed: 11/03/2022]
Abstract
UNLABELLED The possibility to identify patients with spinal muscular atrophy through neonatal screenings has highlighted the need for clinical assessments that may systematically evaluate the possible presence of early neurological signs. The aim of this study was to use the Hammersmith Neonatal Neurological Examination (HNNE) and a module specifically designed for floppy infants to assess the possible variability of neurological findings in infants identified through neonatal screening. The infants included in this study were identified as part of a pilot study exploring neonatal screening in two Italian regions. A neurological examination was performed using the HNNE and an additional module developed for the assessment of floppy infants. Seventeen infants were identified through the screening. One patient had 1 SMN2 copy, 9 had 2 copies, 3 had 3, and 4 had more than 3 copies. Nine of the 17 infants (53%) had completely normal results on both scales, 3 had minimal signs, and the other 5 had more obvious clinical signs. The number of SMN2 copies was related to the presence of abnormal neurological signs (p = 0.036) but two SMN2 copies were associated with variable clinical signs as they were found in some infants with respectively normal examination or obvious severe early signs. CONCLUSIONS Our results suggest that the combination of both scales increases the possibility to detect neonatal neurological signs and to define different early patterns of involvement also identifying paucisymptomatic patients. WHAT IS KNOWN • The use of new therapeutic options in presymptomatic SMA patients leads to a dramatic reduction of the onset and severity of the diesease. • The already existing tools commonly used in Type I SMA (HINE and CHOP-intend) may not be suitable to identify minor neurological signs in the neonatal period. WHAT IS NEW • Combining the HNNE and the floppy infant module, we were able to identify early neurological signs in SMA infants identified through newborn screening and may help to predict the individual therapeutic outcome of these patients. • Iinfants with 2 SMN2 copies identified through the screening had a more variable neonatal examination compared to those with three or more copies, in agreement with similar findings in older infants.
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4
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Blatnik AJ, McGovern VL, Burghes AHM. What Genetics Has Told Us and How It Can Inform Future Experiments for Spinal Muscular Atrophy, a Perspective. Int J Mol Sci 2021; 22:8494. [PMID: 34445199 PMCID: PMC8395208 DOI: 10.3390/ijms22168494] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 07/28/2021] [Accepted: 08/04/2021] [Indexed: 02/06/2023] Open
Abstract
Proximal spinal muscular atrophy (SMA) is an autosomal recessive neurodegenerative disorder characterized by motor neuron loss and subsequent atrophy of skeletal muscle. SMA is caused by deficiency of the essential survival motor neuron (SMN) protein, canonically responsible for the assembly of the spliceosomal small nuclear ribonucleoproteins (snRNPs). Therapeutics aimed at increasing SMN protein levels are efficacious in treating SMA. However, it remains unknown how deficiency of SMN results in motor neuron loss, resulting in many reported cellular functions of SMN and pathways affected in SMA. Herein is a perspective detailing what genetics and biochemistry have told us about SMA and SMN, from identifying the SMA determinant region of the genome, to the development of therapeutics. Furthermore, we will discuss how genetics and biochemistry have been used to understand SMN function and how we can determine which of these are critical to SMA moving forward.
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Affiliation(s)
| | | | - Arthur H. M. Burghes
- Department of Biological Chemistry & Pharmacology, The Ohio State University Wexner Medical Center, Rightmire Hall, Room 168, 1060 Carmack Road, Columbus, OH 43210, USA; (A.J.B.III); (V.L.M.)
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5
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In Search of a Cure: The Development of Therapeutics to Alter the Progression of Spinal Muscular Atrophy. Brain Sci 2021; 11:brainsci11020194. [PMID: 33562482 PMCID: PMC7915832 DOI: 10.3390/brainsci11020194] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 01/29/2021] [Accepted: 02/01/2021] [Indexed: 12/19/2022] Open
Abstract
Until the recent development of disease-modifying therapeutics, spinal muscular atrophy (SMA) was considered a devastating neuromuscular disease with a poor prognosis for most affected individuals. Symptoms generally present during early childhood and manifest as muscle weakness and progressive paralysis, severely compromising the affected individual’s quality of life, independence, and lifespan. SMA is most commonly caused by the inheritance of homozygously deleted SMN1 alleles with retention of one or more copies of a paralog gene, SMN2, which inversely correlates with disease severity. The recent advent and use of genetically targeted therapies have transformed SMA into a prototype for monogenic disease treatment in the era of genetic medicine. Many SMA-affected individuals receiving these therapies achieve traditionally unobtainable motor milestones and survival rates as medicines drastically alter the natural progression of this disease. This review discusses historical SMA progression and underlying disease mechanisms, highlights advances made in therapeutic research, clinical trials, and FDA-approved medicines, and discusses possible second-generation and complementary medicines as well as optimal temporal intervention windows in order to optimize motor function and improve quality of life for all SMA-affected individuals.
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6
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Keinath MC, Prior DE, Prior TW. Spinal Muscular Atrophy: Mutations, Testing, and Clinical Relevance. APPLICATION OF CLINICAL GENETICS 2021; 14:11-25. [PMID: 33531827 PMCID: PMC7846873 DOI: 10.2147/tacg.s239603] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Accepted: 01/15/2021] [Indexed: 12/12/2022]
Abstract
Spinal muscular atrophy (SMA) is a heritable neuromuscular disorder that causes degeneration of the alpha motor neurons from anterior horn cells in the spinal cord, which causes severe progressive hypotonia and muscular weakness. With a carrier frequency of 1 in 40–50 and an estimated incidence of 1 in 10,000 live births, SMA is the second most common autosomal recessive disorder. Affected individuals with SMA have a homozygous loss of function of the survival motor neuron gene SMN1 on 5q13 but keep the modifying SMN2 gene. The most common mutation causing SMA is a homozygous deletion of the SMN1 exon 7, which can be readily detected and used as a sensitive diagnostic test. Because SMN2 produces a reduced number of full-length transcripts, the number of SMN2 copies can modify the clinical phenotype and as such, becomes an essential predictive factor. Population-based SMA carrier screening identifies carrier couples that may pass on this genetic disorder to their offspring and allows the carriers to make informed reproductive choices or prepare for immediate treatment for an affected child. Three treatments have recently been approved by the Food and Drug Administration (FDA). Nusinersen increases the expression levels of the SMN protein using an antisense oligonucleotide to alter splicing of the SMN2 transcript. Onasemnogene abeparvovec is a gene therapy that utilizes an adeno-associated virus serotype 9 vector to increase low functional SMN protein levels. Risdiplam is a small molecule that alters SMN2 splicing in order to increase functional SMN protein. Newborn screening for SMA has been shown to be successful in allowing infants to be treated before the loss of motor neurons and has resulted in improved clinical outcomes. Several of the recommendations and guidelines in the review are based on studies performed in the United States.
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Affiliation(s)
- Melissa C Keinath
- Pathology, University Hospitals Center for Human Genetics, Cleveland, OH, USA
| | - Devin E Prior
- Neurology, Mount Auburn Hospital, Cambridge, MA, USA
| | - Thomas W Prior
- Pathology, University Hospitals Center for Human Genetics, Cleveland, OH, USA
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7
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Spinal muscular atrophy: Broad disease spectrum and sex-specific phenotypes. Biochim Biophys Acta Mol Basis Dis 2021; 1867:166063. [PMID: 33412266 DOI: 10.1016/j.bbadis.2020.166063] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 12/14/2020] [Accepted: 12/21/2020] [Indexed: 12/17/2022]
Abstract
Spinal muscular atrophy (SMA) is one of the major genetic disorders associated with infant mortality. More than 90% of cases of SMA result from deletions of or mutations in the Survival Motor Neuron 1 (SMN1) gene. SMN2, a nearly identical copy of SMN1, does not compensate for the loss of SMN1 due to predominant skipping of exon 7. The spectrum of SMA is broad, ranging from prenatal death to infant mortality to survival into adulthood. All tissues, including brain, spinal cord, bone, skeletal muscle, heart, lung, liver, pancreas, gastrointestinal tract, kidney, spleen, ovary and testis, are directly and/or indirectly affected in SMA. Accumulating evidence on impaired mitochondrial biogenesis and defects in X chromosome-linked modifying factors, coupled with the sexual dimorphic nature of many tissues, point to sex-specific vulnerabilities in SMA. Here we review the role of sex in the pathogenesis of SMA.
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8
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Spinal muscular atrophy - insights and challenges in the treatment era. Nat Rev Neurol 2020; 16:706-715. [PMID: 33057172 DOI: 10.1038/s41582-020-00413-4] [Citation(s) in RCA: 110] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/07/2020] [Indexed: 01/05/2023]
Abstract
Spinal muscular atrophy (SMA) is an autosomal recessive motor neuron disease caused by deletion or mutation of SMN1. Four subtypes exist, characterized by different clinical severities. New therapeutic approaches have become available in the past few years, dramatically changing the natural history of all SMA subtypes, including substantial clinical improvement with the severe and advanced SMA type 1 variant. Trials have now demonstrated that phenotypic rescue is even more dramatic when pre-symptomatic patients are treated, and emerging real-world data are demonstrating the benefits of intervention even in the chronic phase of the condition. Here, we critically review how the field is rapidly evolving in response to the new therapies and questions that the new treatments have posed, including the effects of treatment at different ages and stages of disease, new phenotypes and long-term outcomes in patients who would not have survived without treatment, and decisions of who to treat and when. We also discuss how the outcomes associated with different timing of therapeutic intervention are contributing to our understanding of the biology and pathogenesis of SMA.
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9
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Tan CA, Westbrook MJ, Truty R, Kvitek DJ, Kennemer M, Winder TL, Shieh PB. Incorporating Spinal Muscular Atrophy Analysis by Next-Generation Sequencing into a Comprehensive Multigene Panel for Neuromuscular Disorders. Genet Test Mol Biomarkers 2020; 24:616-624. [PMID: 32721234 DOI: 10.1089/gtmb.2019.0282] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Background: Spinal muscular atrophy (SMA) is traditionally molecularly diagnosed by multiplex ligation-dependent probe amplification or quantitative polymerase chain reaction (qPCR). SMA analyses are not routinely incorporated into gene panel analyses for individuals with suspected SMA or broader neuromuscular indications. Aim: We sought to determine whether a next-generation sequencing (NGS) approach that integrates SMA analyses into a multigene neuromuscular disorders panel could detect undiagnosed SMA. Materials and Methods: Sequence and copy number variants of the SMN1/SMN2 genes were simultaneously analyzed in samples from 5304 unselected individuals referred for testing using an NGS-based 122-gene neuromuscular panel. This diagnostic approach was validated using DNA from 68 individuals who had been previously diagnosed with SMA via quantitative PCR for SMN1/SMN2. Results: Homozygous loss of SMN1 was detected in 47 unselected individuals. Heterozygous loss of SMN1 was detected in 118 individuals; 8 had an indeterminate variant in "SMN1 or SMN2" that supported an SMA diagnosis but required additional disambiguation. Of the remaining SMA carriers, 44 had pathogenic variants in other genes. Concordance rates between NGS and qPCR were 100% and 93% for SMN1 and SMN2 copy numbers, respectively. Where there was disagreement, phenotypes were more consistent with the SMN2 results from NGS. Conclusion: Integrating NGS-based SMA testing into a multigene neuromuscular panel allows a single assay to diagnose SMA while comprehensively assessing the spectrum of variants that can occur in individuals with broad differential diagnoses or nonspecific/overlapping neuromuscular features.
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Affiliation(s)
| | | | | | | | | | | | - Perry B Shieh
- Department of Neurology, University of California, Los Angeles, Los Angeles, California, USA
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10
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Ruhno C, McGovern VL, Avenarius MR, Snyder PJ, Prior TW, Nery FC, Muhtaseb A, Roggenbuck JS, Kissel JT, Sansone VA, Siranosian JJ, Johnstone AJ, Nwe PH, Zhang RZ, Swoboda KJ, Burghes AHM. Complete sequencing of the SMN2 gene in SMA patients detects SMN gene deletion junctions and variants in SMN2 that modify the SMA phenotype. Hum Genet 2019; 138:241-256. [PMID: 30788592 PMCID: PMC6503527 DOI: 10.1007/s00439-019-01983-0] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Accepted: 02/14/2019] [Indexed: 12/11/2022]
Abstract
Spinal muscular atrophy (SMA) is a progressive motor neuron disease caused by loss or mutation of the survival motor neuron 1 (SMN1) gene and retention of SMN2. We performed targeted capture and sequencing of the SMN2, CFTR, and PLS3 genes in 217 SMA patients. We identified a 6.3 kilobase deletion that occurred in both SMN1 and SMN2 (SMN1/2) and removed exons 7 and 8. The deletion junction was flanked by a 21 bp repeat that occurred 15 times in the SMN1/2 gene. We screened for its presence in 466 individuals with the known SMN1 and SMN2 copy numbers. In individuals with 1 SMN1 and 0 SMN2 copies, the deletion occurred in 63% of cases. We modeled the deletion junction frequency and determined that the deletion occurred in both SMN1 and SMN2. We have identified the first deletion junction where the deletion removes exons 7 and 8 of SMN1/2. As it occurred in SMN1, it is a pathogenic mutation. We called variants in the PLS3 and SMN2 genes, and tested for association with mild or severe exception patients. The variants A-44G, A-549G, and C-1897T in intron 6 of SMN2 were significantly associated with mild exception patients, but no PLS3 variants correlated with severity. The variants occurred in 14 out of 58 of our mild exception patients, indicating that mild exception patients with an intact SMN2 gene and without modifying variants occur. This sample set can be used in the association analysis of candidate genes outside of SMN2 that modify the SMA phenotype.
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Affiliation(s)
- Corey Ruhno
- Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, OH, USA
| | - Vicki L McGovern
- Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, OH, USA
| | | | - Pamela J Snyder
- Department of Pathology, The Ohio State University, Columbus, OH, USA
| | - Thomas W Prior
- Department of Pathology, Case Western Reserve Medical Center, Cleveland, OH, USA
| | - Flavia C Nery
- Department of Neurology, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
| | - Abdurrahman Muhtaseb
- Department of Neurology, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
| | | | - John T Kissel
- Department of Neurology, The Ohio State University, Columbus, OH, USA
| | | | - Jennifer J Siranosian
- Department of Neurology, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
| | - Alec J Johnstone
- Department of Neurology, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
| | - Pann H Nwe
- Department of Neurology, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
| | - Ren Z Zhang
- Department of Neurology, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
| | - Kathryn J Swoboda
- Department of Neurology, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
| | - Arthur H M Burghes
- Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, OH, USA.
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