The aim of this study was to analyze the copy numbers and gene structures of sma related genes in chinese sma patients and unrelated healthy controls. Approximately 95%98% of individuals with sma are homozygous for a deletion or gene conversion of smn1 to smn2 and about 2%5% are compound heterozygotes for an smn1 deletion or conversion mutation and an smn1 pathogenic sequence variant. Spinal muscular atrophy sma is a recessive disorder characterized by loss of motor neurons in the spinal cord. Being the major modifier gene of spinal muscular atrophy sma. Of extraordinary interest, the structural analysis highlights three smn residues. Spinal muscular atrophy sma is an autosomal recessive neuromuscular disease with dysfunctional. Alterations within an almost identical copy gene, the centromeric survival motor neuron 2 smn2 gene. These mutations included 2 frameshift mutations 800ins11 and 542delgt and 3. Mutation surveyor software, quantitative analysis, sanger dna. Methods paper molecular analysis of smn1, smn2, naip, gtf2h2, and h4f5 genes in 157 chinese patients with spinal muscular atrophy. Sma identified tests look at whether any of your smn1 genes are missing or varied, and the sma. The general functions of the main smn1 protein product, fulllength smn flsmn, do not explain the selective motoneuronal loss of sma. Original article survival motor neuron 1 smn1 gene acts. If a child inherits only 1 mutated smn1 gene, they are considered a carrier, but usually do not have symptoms of spinal muscular atrophy.
Please note, for carriertargeted variant tests the approval status depends on whether the gene is in an approved genedx singlegene or multigene test. Spinal muscular atrophy sma is one of the most prevalent genetic disorders in caucasians. This copy number analysis does not detect individuals who are carriers of sma as a result of either two or very rarely three copies of the smn1 gene on one chromosome and the absence of the smn1 gene on the other chromosome. Mutation spectrum of the survival of motor neuron 1 and.
Molecular analysis of survival motor neuron gene in 338 suspicious children patients with spinal muscular atrophy. Spinal muscular atrophy sma is a common autosomal recessive disorder in humans, caused by homozygous absence of the survival motor neuron gene 1 smn1. Smn2, a copy gene, influences the severity of sma and may be used in somatic gene. Spinal muscular atrophy is an autosomal recessive disease, which means that for a individual to be at risk, he or she must inherit 1 mutated smn1 gene from each parent.
Spinal muscular atrophy smn1 gene analysis test show filters. Genetic testing for spinal muscular atrophy sma requires prior authorization for all product lines. Genetic testing options for spinal muscular atrophy. In any case of spinal muscular atrophy, smn2 gene copy number is less predictive of prognosis than age of onset and the achievement of functional abilities 10. Types ii and iii are the next most common and types 0 and iv are rare. Sma occurs when an individual inherits two mutated smn1 genes and the smn2 gene cannot produce sufficient smn protein to maintain motor neuron function. Spinal muscular atrophy sma is the most common neurodegenerative disorder and the leading genetic cause of infant mortality. An autosomal recessive form of spinal muscular atrophy, a neuromuscular disorder characterized by degeneration of the anterior horn cells of the spinal cord, leading to symmetrical muscle weakness and atrophy. Smn2, a copy gene, influences the severity of sma and may be used in somatic gene therapy of patients with sma in the future. Arg288met mutation causing smn1 transcript exclusion of exon7 qu yujin 0 du juan 0 li er. Spinal muscular atrophy sma is an inherited neurodegenerative disorder characterized by progressive muscle weakening and wasting due to the gradual loss of motor neurons, or nerve cells, that control muscles. The quantitative analysis and clinical implications of smn1 gene dosage are somewhat complicated by the presence of a highly homologous gene.
Smn1dosage analysis in spinal muscular atrophy from india. Spinal muscular atrophy and the difficult smn1 gene. In spinal muscular atrophy, homozygous mutations or deletions of smn1 produce a shortage of smn protein, which causes degeneration of motor neurons in the spinal cord. As a result, little or no smn protein is produced by this gene. Proximal spinal muscular atrophy sma is a common fatal autosomal recessive disorder caused by deletion or mutation of the survival of motor neuron 1 smn1. Exon 7 from both the smn1 and smn2 genes was amplified by the. Frontiers newborn screening for spinal muscular atrophy. Gene dosage was performed in 202 parents of patients with sma with homozygous deletion of smn1 exon 7, and in 375 people from the general population as described by gerard et al. It is caused by mutations in the telomeric survival motor neuron 1 smn1 gene. Many mutations in the smn1 gene have been found to cause spinal muscular atrophy. How do smalinked mutations of smn1 lead to structuralfunctional. The smn1 gene has been recognised to be responsible for sma because of homozygous deletions, sequence conversions, or intragenic mutations in smn1 result in childhood onset of sma. Depending on the type of sma, the age of onset and severity of the disorder can vary. Gene expression analysis of lasermicrodissected motorneurons in spinal muscular atrophy sma spinal muscular atrophy sma is an autosomal recessive motor.
We identified axonalsmn asmn, an alternatively spliced smn form, preferentially encoded by the smn1 gene. Paramount applies coding edits to all medical claims through coding logic software. Jin he a,1, qijie zhang a,1, qifang lin a, yafang chen a, xiaozhen lin a, minting lin a. Yes are approved or conditionally approved by new york state and do not require an nys npl exemption.
We present a new, fast, and highly reliable quantitative test, based on realtime lightcycler pcr that amplifies. Pcr analysis relative to an internal standard reference gene. A new method for smn1 and hybrid smn gene analysis in spinal muscular. Subtle mutations in the smn1 gene in chinese patients with. Use this ddpcr smn1 copy number determination kit to determine the copy number of the smn1 gene, one of two highly similar genes that play a pivotal role in spinal muscular atrophy. Quantitative analysis of smn1 and smn2 gene based on dhplc. Smn1 copy number analysis is an important parameter for identification of couples at risk for having a child affected with sma and reduces unwarranted prenatal diagnosis for sma. Detection of intragenic smn1 mutations in spinal muscular. Highly homologous genes complicate genetic analysis. The dosage analysis does not test for smn point mutations which occur in about 5% of affected individuals. Due to the near identical sequences of smn1 and smn2, analysis of this region is. Direct analysis of smn1 gene deletion is valuable in both sma molecular diagnosis and carrier screening 14, 20.
In 23 sma compound heterozygotes sma patients with absence of exon 7 of the smn1 gene on 1 allele only, parsons et al. Patients with sma lack the smn1 gene and rely on a closely related gene called. A sma silentcarrier contains 2 copies of the smn1 gene in cis on one chromosome. Sma is characterized by progressive, symmetric proximal muscle weakness and respiratory failure. We demonstrate that this assay is able to accurately distinguish 2 gene copies from 4 gene copies and it can identify sma carriers and normal populations by the accurate determination of smn copy number. Omim 253300 is an autosomal recessive disorder caused by mutations in the smn1 gene omim 600354. Approximately 95% of sma patients have a homozygous deletion of the survival motor neuron 1 smn1 gene, whereas 5% harbor compound heterozygous mutations such as an smn1 deletion allele and an intragenic mutation in the other smn1 allele.
Spinal muscular atrophy sma is a group of neuromuscular disorders characterized by degeneration of. The copy numbers and gene structures of smarelated genes were. Sma, smn1 gene, gene conversion, molecular analysis. Lastly, sequence analysis of the smn1 gene may also be of importance for patients with an sma phenotype, two copies of the smn1 gene, and are born to consanguineous parents or originate from genetic isolates.
The biogensponsored sma identified program, offered through invitae, facilitates access to genetic testing at. Wo2017156290a1 a novel algorithm for smn1 and smn2 copy. In the case of smn2, the smn2 copy number of affected patients was related to the phenotype data not shown. About 95% of sma cases are caused by the homozygous absence of smn1due to gene. The sasa values were calculated by the dssp program 32, 33 for all. Spinal muscular atrophy sma is caused by homozygous deletion or compound heterozygous mutation of survival motor neuron gene 1 smn1, which is the key to. Compound heterozygous patients account for approximately 4% of spinal. We further quantified exons 7 and 8 in smn1 and smn2. The smn complex plays a catalyst role in the assemble of small nuclear ribonucleoproteins, the building blocks of the spliceosome. Detection of spinal muscular atrophy genotypes in a highly. The telomeric and centromeric copies of this gene are nearly identical and encode the same protein survival motor neuron protein. Sma affects children with varying severity, ranging from the severe and usually fatal sma type 1 werdnighoffman disease to milder forms that are associated with longer survival but significant morbidity. Acog recommends that screening for spinal muscular atrophy sma be offered to all women who are considering or who are currently pregnant. Accurate diagnosis of spinal muscular atrophy and 22q11.
Sma is characterized by the loss of motor neurons, nerve cells in the spinal cord. Due to the high carrier frequency, the burden of this genetic disorder is very heavy in developing countries like india. Sma patients are classified as type iiv based on severity of symptoms and age of onset. These sequences represent the protein coding region of the. The frequency of smn gene variants lacking exon 7 and 8 is highly. For carrier screening, when two copies of smn1 are detected, allelic discrimination qpcr targeting c. Spinal muscular atrophy testing via smn1 smn2 copy number. Smn1 is fully functional but smn2 is only partially functional.
The survival motor neuron gene 1 smn1 encodes the fulllength, and functional. False positive or false negative results may occur for reasons that include genetic variants, blood transfusions, bone marrow transplantation. Sep 12, 2005 the assay uses the xlinked cybb gene and krit1 gene as standards to determine the relative gene dosage of smn1 and smn2 genes. Spinal muscular atrophy sma is the most common autosomal recessive disorder in humans after cystic fibrosis. Spinal muscular atrophy smn1 gene analysis test cost. Analysis of smn1 gene partial deletion of spinal muscular atrophy based on mlpa. Research article open access smn1 dosage analysis in. Although smn1 was identified as the sma diseasedetermining gene, modifier genes mapped to 5q were affirmed to play. This duplicated region contains at least four genes and repetitive elements which make it prone to rearrangements and deletions. The study was to establish and evaluate a new diagnostic method for sma. Sep 15, 2011 the survival motor neuron 1 smn1 gene is an sma determining gene and smn2 represents an sma modifying gene. Data analyses were done with the proprietary axiom analysis suite software to obtain smn1 and smn2 gene. Although smn1 was identified as the sma diseasedetermining gene.
Spinal muscular atrophy baylor college of medicine. A new method for smn1 and hybrid smn gene analysis in. Data were analyzed with the genemapper software v3. Graduate school of medicine and global center of excellence coe program, tokyo. About 95% of sma cases are caused by the homozygous absence of smn1due to gene deletion or conversion into smn2. How do smalinked mutations of smn1 lead to structural. Smn1 dosage analysis in spinal muscular atrophy from india. The ddpcr smn1 copy number determination kit is designed to determine the copy number of the smn1 gene only, one of two highly similar genes that play a pivotal role in spinal muscular. The most common form of sma types 14 is caused by a defect mutation in the smn1 gene on chromosome 5. Spinal muscular atrophy genetics home reference nih. Spinal muscular atrophy sma represents the second most common fatal autosomal recessive disorder after cystic fibrosis.
Sma identified program spinal muscular atrophy genetic testing. Pdf quantitative analyses of smn1 and smn2 based on real. Sma causesinheritance muscular dystrophy association. Dec 20, 2018 spinal muscular atrophy sma is caused by homozygous deletion or compound heterozygous mutation of survival motor neuron gene 1 smn1, which is the key to diagnose sma. Typically a person who is not a carrier of sma will have two copies of the smn1 gene, one on each chromosome. Molecular analysis of the smn1 and naip genes in iranian. The smn2 gene copy number is related to, but not predictive of, disease severity, and care decisions should not be made based on copy number alone.
Molecular characterization and copy number of smn1, smn2. Bmc medical genetics subtle mutations in the smn1 gene in chinese patients with sma. Sequencing data were analyzed using sequencing analysis software v. This study describes smn1 deletion frequency, carrier studies, and the effect of the modifying smn2 gene on the spinal muscular atrophy sma phenotype. If no smn1 deletion is detected in a patient with suspected sma, smn1 copy number analysis and intragenic mutation. The sma identified program facilitates access to genetic testing to help in the. Here, we report the results of carrier screening in parents of patients with sma.
Molecular analysis of the smn1 and naip genes in iranian patients with spinal muscular atrophy. Analysis of smn1 gene partial deletion of spinal muscular atrophy. Jan 21, 2020 spinal muscular atrophy sma is the most common autosomal recessive disorder in humans after cystic fibrosis. It is classified into five clinical grades based on age of onset and severity of the disease. The following smn1 gene cdna orf clone sequences were retrieved from the ncbi reference sequence database refseq. Molecular analysis of smn1, smn2, naip, gtf2h2, and h4f5. Some carriers will have both of their copies of the smn1 gene on the same chromosome and a deletion on the other chromosome and will go undetected with our current level of testing. Spinal muscular atrophy smn1 gene analysis test archives. Smn1 and smn2 are part of a 500 kb inverted duplication on chromosome 5q. In patients with one copy of smn1 in whom there is a high suspicion of sma, smn1 sequencing should be considered to look for a small variant or deletion. Here, we applied capillary electrophoresis to quantify the smn gene dosage in 163 normal individuals, 94 sma patients and 8 of their parents. With its streamlined pcrce workflow, rapid turnaround time, and automated results reporting software.
Spinal muscular atrophy type i is the most common type, accounting for about half of all cases. Smn1 is the telomeric copy of the gene encoding the smn protein. Spinal muscular atrophy sma is an autosomal recessive inherited disorder caused by alterations in the survival motor neuron i smn1 gene. Prevalence of smn1 deletion and duplication in carrier and. Spinal muscular atrophy sma is caused by smn1 dysfunction, and the copy number of smn2 and naip can modify the phenotype of sma. Genetic pattern of smn1, smn2, and naip genes in prognosis. May 23, 2005 spinal muscular atrophy sma represents the second most common fatal autosomal recessive disorder after cystic fibrosis. A new method for smn1 and hybrid smn gene analysis in spinal. As there is no cure or effective treatment, genetic counseling becomes very important in disease management. Molecular analysis of smn1, smn2, naip, gtf2h2, and h4f5 genes in 157 chinese. Spinal muscular atrophy sma is an autosomal recessive.
Smn1 and smn2 gene mutations spinal muscular atrophy. Spinal muscular atrophy sma is a common inherited and fatal neuromuscular disease caused by deletions andor mutations that lead to altered. This condition is characterized by a loss of motor neurons that leads to weakness and wasting atrophy in muscles used for movement skeletal muscles that worsens with age. Genetic pattern of smn1, smn2, and naip genes in prognosis of. Although smn1 was identified as the sma diseasedetermining gene, modifier genes mapped to 5q were affirmed to play a crucial role in determination of disease severity and used as a target. Smn1 gene cdna orf clone, homo sapienshuman genscript. The methods determine whether or not an individual is a carrier of an autosomal recessive gene mutation using a determination of copy number of two genes, in specific embodiments.
To understand the science of sma, it is important to understand the flow of genetic information. Smn2 can modify the phenotype in individuals with smn1 related sma. Spinal muscular atrophy affects 1 per 8,000 to 10,000 people worldwide. It should be noted that, like all other previously. Identification of bidirectional gene conversion between smn1. Results generated by the new method was confirmed by pcrrflp and by dna sequencing when required. Then the data were analyzed by the software coffalyser. The amplidex pcrce smn1 kit provides a rapid, robust, and reliable method for the quantification of smn1 exon 7 copy number from whole blood and buccal samples. Multiplex ligationdependent probe amplification mlpa for genetic testing of sma was based. Lastly, sequence analysis of the smn1 gene may also be of importance for patients with an sma phenotype, two copies of the smn1 gene. A single nucleotide difference that alters splicing patterns distinguishes the sma gene smn1 from. Molecular characterization and copy number of smn1, smn2 and. Spinal muscular atrophy sma is caused by homozygous deletion or compound heterozygous mutation of survival motor neuron gene 1 smn1, which is the key to diagnose. An animation shows how the change in the smn2 gene produces a.
Onset is in adulthood, disease progression is slow, and patients can stand and walk. Out of these, only a single patient had one copy of smn1 gene, and the remaining four cases had two copies of smn1 gene. Us20190066842a1 a novel algorithm for smn1 and smn2 copy. Spinal muscular atrophy sma is caused by homozygous deletion or compound.
The next generation of populationbased spinal muscular atrophy. The majority of mutations responsible for sma are either deletions or gene conversions. Lastly, although dna testing is highly accurate, diagnostic errors can occur. The smn1 gene is associated with autosomal recessive spinal muscular atrophy sma medgen uid. Multiethnic smn1 copynumber analysis for sma carrier population. Quantitative analyses of smn1 and smn2 based on realtime. In conclusion, a protocol based on realtime pcr was shown to be effective and specific for molecular analysis of sma patients. The aim of this study was to analyze the copy numbers and gene. Spinal muscular atrophy is an autosomal recessive disease, which means that for a child to be at risk, he or she must inherit 1 mutated smn1 gene from each parent. Homozygous deletions in the smn1 have been reported in more than 90% of spinal muscular atrophy cases. Spinal muscular atrophy is caused by a mutation in the survival motor neuron smn gene on chromosome 5. To characterise the molecular mechanism of smn1 deletion in these families, we used two.
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