SMN2 splicing modifiers improve motor function and longevity in mice with spinal muscular atrophy

Science ◽  
2014 ◽  
Vol 345 (6197) ◽  
pp. 688-693 ◽  
Author(s):  
Nikolai A. Naryshkin ◽  
Marla Weetall ◽  
Amal Dakka ◽  
Jana Narasimhan ◽  
Xin Zhao ◽  
...  
Keyword(s):  
Spinal Muscular Atrophy ◽  
Motor Function ◽  
Messenger Rna ◽  
High Selectivity ◽  
Therapeutic Potential ◽  
Muscular Atrophy ◽  
Chemical Screening ◽  
Protein Levels ◽  
Smn Protein ◽  
Survival Of Motor Neuron

Spinal muscular atrophy (SMA) is a genetic disease caused by mutation or deletion of the survival of motor neuron 1 (SMN1) gene. A paralogous gene in humans, SMN2, produces low, insufficient levels of functional SMN protein due to alternative splicing that truncates the transcript. The decreased levels of SMN protein lead to progressive neuromuscular degeneration and high rates of mortality. Through chemical screening and optimization, we identified orally available small molecules that shift the balance of SMN2 splicing toward the production of full-length SMN2 messenger RNA with high selectivity. Administration of these compounds to Δ7 mice, a model of severe SMA, led to an increase in SMN protein levels, improvement of motor function, and protection of the neuromuscular circuit. These compounds also extended the life span of the mice. Selective SMN2 splicing modifiers may have therapeutic potential for patients with SMA.

scholarly journals The E3 ubiquitin ligase mind bomb 1 ubiquitinates and promotes the degradation of survival of motor neuron protein

2013 ◽  
Vol 24 (12) ◽  
pp. 1863-1871 ◽  
Author(s):  
Deborah Y. Kwon ◽  
Maria Dimitriadi ◽  
Barbara Terzic ◽  
Casey Cable ◽  
Anne C. Hart ◽  
...  
Keyword(s):  
Spinal Muscular Atrophy ◽  
Motor Neuron ◽  
Ubiquitin Ligase ◽  
Cultured Cells ◽  
Muscular Atrophy ◽  
E3 Ubiquitin Ligase ◽  
Proteasome Inhibition ◽  
Protein Levels ◽  
Smn Protein ◽  
Survival Of Motor Neuron

Spinal muscular atrophy is an inherited motor neuron disease that results from a deficiency of the survival of motor neuron (SMN) protein. SMN is ubiquitinated and degraded through the ubiquitin proteasome system (UPS). We have previously shown that proteasome inhibition increases SMN protein levels, improves motor function, and reduces spinal cord, muscle, and neuromuscular junction pathology of spinal muscular atrophy (SMA) mice. Specific targets in the UPS may be more efficacious and less toxic. In this study, we show that the E3 ubiquitin ligase, mind bomb 1 (Mib1), interacts with and ubiquitinates SMN and facilitates its degradation. Knocking down Mib1 levels increases SMN protein levels in cultured cells. Also, knocking down the Mib1 orthologue improves neuromuscular function in Caenorhabditis elegans deficient in SMN. These findings demonstrate that Mib1 ubiquitinates and catalyzes the degradation of SMN, and thus represents a novel therapeutic target for SMA.

Effect of Discontinuation of Nusinersen Treatment in Long-Standing SMA3

2021 ◽  
pp. 1-6
Author(s):  
Miriam Hiebeler ◽  
Angela Abicht ◽  
Peter Reilich ◽  
Maggie C. Walter
Keyword(s):  
Spinal Muscular Atrophy ◽  
Motor Function ◽  
Rna Splicing ◽  
Rating Scale ◽  
Muscular Atrophy ◽  
Spinal Muscular Atrophy Type ◽  
Protein Levels ◽  
Discontinuation Of Treatment ◽  
Smn Protein ◽  
Treatment Onset

Background: Spinal muscular atrophy is an autosomal recessive neuromuscular disease leading to ongoing degeneration of anterior horn cells in the spinal cord. Nusinersen is the first approved treatment for the condition, an intrathecally administered antisense oligonucleotide. It modulates pre-RNA splicing of the SMN2 gene and increases full-length SMN protein expression, thereby increasing SMN protein levels. The benefit of Nusinersen for patients with spinal muscular atrophy type 3 (SMA3) has recently been shown in several real-world cohorts. Objective: We aim to elucidate not only the effect of therapy with Nusinersen, but the development of the disease course after discontinuation of treatment. To our knowledge, there are so far no reports on the effects of Nusinersen discontinuation. Methods: We report on a 45-year-old female patient with genetically confirmed SMA3 and a disease duration of 40 years prior to treatment onset. Results: The patient was non-ambulantory, best motor function at treatment onset was holding arms with support, reflected in MRC of 3/5 in upper limbs. After having received Nusinersen for 11 months without complications, the patient showed improvement in motor functions, as measured by hand grip measurement (HGS), Hammersmith Functional Rating Scale Expanded (HFMSE), and Revised Upper Limb Module (RULM). Due to worsening of a pre-existing anxiety disorder, treatment was discontinued after six injections. Sixteen months later, progression of the disease became evident with worsening of HFMSE and RULM scores, while hand strength remained stable. Conclusion: Treatment with Nusinersen in SMA3 improves motor function in longstanding disease even in clinically advanced stages; however, after discontinuation of treatment, further progression mirroring the natural history of the disease is anticipated.

SMN mRNA and protein levels in peripheral blood

Neurology ◽  
2006 ◽  
Vol 66 (7) ◽  
pp. 1067-1073 ◽  
Author(s):  
C. J. Sumner ◽  
S. J. Kolb ◽  
G. G. Harmison ◽  
N. O. Jeffries ◽  
K. Schadt ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Spinal Muscular Atrophy ◽  
Disease Severity ◽  
Peripheral Blood ◽  
Muscular Atrophy ◽  
Gene Copy ◽  
Blood Levels ◽  
Type I ◽  
Protein Levels ◽  
Smn Protein

Background: Clinical trials of drugs that increase SMN protein levels in vitro are currently under way in patients with spinal muscular atrophy.Objective: To develop and validate measures of SMN mRNA and protein in peripheral blood and to establish baseline SMN levels in a cohort of controls, carriers, and patients of known genotype, which could be used to follow response to treatment.Methods: SMN1 and SMN2 gene copy numbers were determined in blood samples collected from 86 subjects. Quantitative reverse transcription PCR was used to measure blood levels of SMN mRNA with and without exon 7. A cell immunoassay was used to measure blood levels of SMN protein.Results: Blood levels of SMN mRNA and protein were measured with high reliability. There was little variation in SMN levels in individual subjects over a 5-week period. Levels of exon 7-containing SMN mRNA and SMN protein correlated with SMN1 and SMN2 gene copy number. With the exception of type I SMA, there was no correlation between SMN levels and disease severity.Conclusion: SMN mRNA and protein levels can be reliably measured in the peripheral blood and used during clinical trials in spinal muscular atrophy, but these levels do not necessarily predict disease severity.

scholarly journals Temporal and tissue-specific variability of SMN protein levels in mouse models of spinal muscular atrophy

2018 ◽  
Vol 27 (16) ◽  
pp. 2851-2862 ◽  
Author(s):  
Ewout J N Groen ◽  
Elena Perenthaler ◽  
Natalie L Courtney ◽  
Crispin Y Jordan ◽  
Hannah K Shorrock ◽  
...  
Keyword(s):  
Spinal Muscular Atrophy ◽  
Mouse Models ◽  
Muscular Atrophy ◽  
Tissue Specific ◽  
Protein Levels ◽  
Smn Protein

scholarly journals P.064 FIREFISH Part 1: 1-year results on motor function in infants with Type 1 spinal muscular atrophy (SMA) receiving risdiplam (RG7916)

2019 ◽  
Vol 46 (s1) ◽  
pp. S31 ◽  
Author(s):  
TJ Seabrook ◽  
G Baranello ◽  
L Servais ◽  
JW Day ◽  
N Deconinck ◽  
...  
Keyword(s):  
Motor Function ◽  
Muscular Atrophy ◽  
Protein A ◽  
Analysis Data ◽  
Open Label ◽  
Protein Levels ◽  
Gene Copies ◽  
Patient Withdrawal ◽  
Smn Protein

Background: SMA is characterized by reduced levels of survival of motor neuron (SMN) protein from deletions and/or mutations of the SMN1 gene. While SMN1 produces full-length SMN protein, a second gene, SMN2, produces low levels of functional SMN protein. Risdiplam (RG7916/RO7034067) is an investigational, orally administered, centrally and peripherally distributed small molecule that modulates pre-mRNA splicing of SMN2 to increase SMN protein levels. Methods: FIREFISH (NCT02913482) is an ongoing, multicenter, open-label operationally seamless study of risdiplam in infants aged 1–7 months with Type 1 SMA and two SMN2 gene copies. Exploratory Part 1 (n=21) assesses the safety, tolerability, pharmacokinetics and pharmacodynamics of different risdiplam dose levels. Confirmatory Part 2 (n=40) is assessing the safety and efficacy of risdiplam. Results: In a Part 1 interim analysis (data-cut 09/07/18), 93% (13/14) of babies had ≥4-point improvement in CHOP-INTEND total score from baseline at Day 245, with a median change of 16 points. The number of infants meeting HINE-2 motor milestones (baseline to Day 245) increased. To date (data-cut 09/07/18), no drug-related safety findings have led to patient withdrawal. No significant ophthalmological findings have been observed. Conclusions: In FIREFISH Part 1, risdiplam improved motor function in infants with Type 1 SMA.

scholarly journals The Survival of Motor Neurons Protein Determines the Capacity for snRNP Assembly: Biochemical Deficiency in Spinal Muscular Atrophy

2005 ◽  
Vol 25 (13) ◽  
pp. 5543-5551 ◽  
Author(s):  
Lili Wan ◽  
Daniel J. Battle ◽  
Jeongsik Yong ◽  
Amelie K. Gubitz ◽  
Stephen J. Kolb ◽  
...  
Keyword(s):  
Spinal Muscular Atrophy ◽  
Motor Neurons ◽  
Muscular Atrophy ◽  
Protein Levels ◽  
Small Nuclear Ribonucleoprotein ◽  
Cell Extracts ◽  
Smn Complex ◽  
Survival Of Motor Neurons ◽  
Smn Protein ◽  
Nuclear Ribonucleoprotein

ABSTRACT Reduction of the survival of motor neurons (SMN) protein levels causes the motor neuron degenerative disease spinal muscular atrophy, the severity of which correlates with the extent of reduction in SMN. SMN, together with Gemins 2 to 7, forms a complex that functions in the assembly of small nuclear ribonucleoprotein particles (snRNPs). Complete depletion of the SMN complex from cell extracts abolishes snRNP assembly, the formation of heptameric Sm cores on snRNAs. However, what effect, if any, reduction of SMN protein levels, as occurs in spinal muscular atrophy patients, has on the capacity of cells to produce snRNPs is not known. To address this, we developed a sensitive and quantitative assay for snRNP assembly, the formation of high-salt- and heparin-resistant stable Sm cores, that is strictly dependent on the SMN complex. We show that the extent of Sm core assembly is directly proportional to the amount of SMN protein in cell extracts. Consistent with this, pulse-labeling experiments demonstrate a significant reduction in the rate of snRNP biogenesis in low-SMN cells. Furthermore, extracts of cells from spinal muscular atrophy patients have a lower capacity for snRNP assembly that corresponds directly to the reduced amount of SMN. Thus, SMN determines the capacity for snRNP biogenesis, and our findings provide evidence for a measurable deficiency in a biochemical activity in cells from patients with spinal muscular atrophy.

scholarly journals Self-oligomerization regulates stability of survival motor neuron protein isoforms by sequestering an SCFSlmb degron

2018 ◽  
Vol 29 (2) ◽  
pp. 96-110 ◽  
Author(s):  
Kelsey M. Gray ◽  
Kevin A. Kaifer ◽  
David Baillat ◽  
Ying Wen ◽  
Thomas R. Bonacci ◽  
...  
Keyword(s):  
Spinal Muscular Atrophy ◽  
Motor Neuron ◽  
Muscular Atrophy ◽  
Survival Motor Neuron ◽  
Protein Isoforms ◽  
Survival Motor Neuron Protein ◽  
Protein Levels ◽  
Motor Neuron Protein ◽  
Smn Protein ◽  
Oligomerization Domain

SMN protein levels inversely correlate with the severity of spinal muscular atrophy. The SCFSlmbE3 ligase complex interacts with a degron embedded within the C-terminal self-oligomerization domain of SMN. The findings elucidate a model whereby accessibility of the SMN degron is regulated by self-multimerization.

scholarly journals Identification of Novel Compounds That Increase SMN Protein Levels Using an Improved SMN2 Reporter Cell Assay

2012 ◽  
Vol 17 (4) ◽  
pp. 481-495 ◽  
Author(s):  
Jonathan J. Cherry ◽  
Matthew C. Evans ◽  
Jake Ni ◽  
Gregory D. Cuny ◽  
Marcie A. Glicksman ◽  
...  
Keyword(s):  
Motor Neuron ◽  
Neurodegenerative Disorder ◽  
Muscular Atrophy ◽  
Full Length ◽  
Reporter Cell ◽  
Protein Levels ◽  
Smn2 Gene ◽  
Smn Protein ◽  
Neuron Function ◽  
Survival Of Motor Neuron

Spinal muscular atrophy (SMA) is a neurodegenerative disorder that is characterized by progressive loss of motor neuron function. It is caused by the homozygous loss of the SMN1 ( survival of motor neuron 1) gene and a decrease in full-length SMN protein. SMN2 is a nearly identical homolog of SMN1 that, due to alternative splicing, expresses predominantly truncated SMN protein. SMN2 represents an enticing therapeutic target. Increasing expression of full-length SMN from the SMN2 gene might represent a treatment for SMA. We describe a newly designed cell-based reporter assay that faithfully and reproducibly measures full-length SMN expression from the SMN2 gene. This reporter can detect increases of SMN protein by an array of compounds previously shown to regulate SMN2 expression and by the overexpression of proteins that modulate SMN2 splicing. It also can be used to evaluate changes at both the transcriptional and splicing level. This assay can be a valuable tool for the identification of novel compounds that increase SMN2 protein levels and the optimization of compounds already known to modulate SMN2 expression. We present here preliminary data from a high-throughput screen using this assay to identify novel compounds that increase expression of SMN2.

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