Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q16637 (SMA)
 8,107 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Spinal muscular atrophy (SMA) is a motor neuron disease caused by reduced levels of the survival motor neuron (SMN) protein. SMN together with Gemins2-8 and unrip proteins form a macromolecular complex that functions in the assembly of small nuclear ribonucleoproteins (snRNPs) of both the major and the minor splicing pathways. It is not known whether the levels of spliceosomal snRNPs are decreased in SMA. Here we analyzed the consequence of SMN deficiency on snRNP metabolism in the spinal cord of mouse models of SMA with differing phenotypic severities. We demonstrate that the expression of a subset of Gemin proteins and snRNP assembly activity are dramatically reduced in the spinal cord of severe SMA mice. Comparative analysis of different tissues highlights a similar decrease in SMN levels and a strong impairment of snRNP assembly in tissues of severe SMA mice, although the defect appears smaller in kidney than in neural tissue. We further show that the extent of reduction in both Gemin proteins expression and snRNP assembly activity in the spinal cord of SMA mice correlates with disease severity. Remarkably, defective SMN complex function in snRNP assembly causes a significant decrease in the levels of a subset of snRNPs and preferentially affects the accumulation of U11 snRNP--a component of the minor spliceosome--in tissues of severe SMA mice. Thus, impairment of a ubiquitous function of SMN changes the snRNP profile of SMA tissues by unevenly altering the normal proportion of endogenous snRNPs. These findings are consistent with the hypothesis that SMN deficiency affects the splicing machinery and in particular the minor splicing pathway of a rare class of introns in SMA.
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PMID:Ribonucleoprotein assembly defects correlate with spinal muscular atrophy severity and preferentially affect a subset of spliceosomal snRNPs. 1789 63

Progressive spinal muscular atrophy (SMA), the most prevalent hereditary lower motor neuron disease, is caused by mutations in the telomeric copy of the survival of motor neuron (SMN1) gene. Unlike other cells, lower motor neurons cannot tolerate low levels of smn protein. However, it is unclear as to the nature of the cell death involved. There is evidence that lower motor neurons undergo apoptosis in SMA, leading to muscle weakness and wasting. This study investigated whether SMN1 regulation in a motor neuron model affected indices of apoptotic cell death. Decreased smn expression in neuroblastoma hybrid (NSC-34) cell lines by small interfering RNA (siRNA) was demonstrated at the mRNA and protein level. Smn-depleted cells showed elevated caspase-3 activity, decreased cell viability and increased percentage of TUNEL positive cells. Conversely, NSC-34 cell smn overexpression by adenoviral gene transfer decreased staurosporine-induced caspase-3 elevation and mitigated induced cell toxicity as assessed by 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. However, increased smn expression by itself did not increase cell viability. These data suggest not only that decreased smn levels increase apoptosis in an in vitro model of SMA, but also that increased smn can protect against neural injury.
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PMID:Survival motor neuron protein regulates apoptosis in an in vitro model of spinal muscular atrophy. 1836 39

Spinal muscular atrophy is an autosomal recessive motor neuron disease that is caused by mutation of the survival motor neuron gene (SMN1) but all patients retain a nearly identical copy, SMN2. The disease severity correlates inversely with increased SMN2 copy. Currently, the most promising therapeutic strategy for spinal muscular atrophy is induction of SMN2 gene expression by histone deacetylase inhibitors. Polyphenols are known for protection against oxidative stress and degenerative diseases. Among our candidate prodrug library, we found that (E )-resveratrol, which is one of the polyphenolic compounds, inhibited histone deacetylase activity in a concentration-dependent manner and half-maximum inhibition was observed at 650 microM. Molecular docking studies showed that (E )-resveratrol had more favorable free energy of binding (-9.09 kcal/mol) and inhibition constant values (0.219 microM) than known inhibitors. To evaluate the effect of (E )-resveratrol on SMN2 expression, spinal muscular atrophy type I fibroblast cell lines was treated with (E )-resveratrol. The level of full-length SMN2 mRNA and protein showed 1.2- to 1.3-fold increase after treatment with 100 microM (E )-resveratrol in only one cell line. These results indicate that response to (E )-resveratrol treatment is variable among cell lines. This data demonstrate a novel activity of (E )-resveratrol and that it could be a promising candidate for the treatment of spinal muscular atrophy.
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PMID:Histone deacetylase inhibition activity and molecular docking of (e )-resveratrol: its therapeutic potential in spinal muscular atrophy. 1920 72

The motor neuron disease spinal muscular atrophy (SMA) is one of the leading genetic killers of infants worldwide. SMA is caused by mutation of the survival motor neuron 1 (SMN1) gene and deficiency of the survival motor neuron (SMN) protein. All patients retain one or more copies of the SMN2 gene, which (by producing a small amount of the SMN protein) rescues embryonic lethality and modifies disease severity. Rapid progress continues in dissecting the cellular functions of the SMN protein, but the mechanisms linking SMN deficiency with dysfunction and loss of functioning motor units remain poorly defined. Clinically, SMA should to be distinguished from other neuromuscular disorders, and the diagnosis can be readily confirmed with genetic testing. Quality of life and survival of SMA patients are improved with aggressive supportive care including optimized respiratory and nutritional care and management of scoliosis and contractures. Because SMA is caused by inadequate amounts of SMN protein, one aim of current SMA therapeutics development is to increase SMN protein levels in SMA patients by activating SMN2 gene expression and/or increasing levels of full-length SMN2 transcripts. Several potential therapeutic compounds are currently being studied in clinical trials in SMA patients.
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PMID:Emerging treatment options for spinal muscular atrophy. 1921 Sep 11

Spinal muscular atrophy (SMA) is a motor neuron disease caused by the loss of survival motor neuron-1 (SMN1). A nearly identical copy gene, SMN2, is present in all SMA patients, which produces low levels of functional protein. Although the SMN2 coding sequence has the potential to produce normal, full-length SMN, approximately 90% of SMN2-derived transcripts are alternatively spliced and encode a truncated protein lacking the final coding exon (exon 7). SMN2, however, is an excellent therapeutic target. Previously, we developed bifunctional RNAs that bound SMN exon 7 and modulated SMN2 splicing. To optimize the efficiency of the bifunctional RNAs, a different antisense target was required. To this end, we genetically verified the identity of a putative intronic repressor and developed bifunctional RNAs that target this sequence. Consequently, there is a 2-fold mechanism of SMN induction: inhibition of the intronic repressor and recruitment of SR proteins via the SR recruitment sequence of the bifunctional RNA. The bifunctional RNAs effectively increased SMN in human primary SMA fibroblasts. Lead candidates were synthesized as 2'-O-methyl RNAs and were directly injected in the central nervous system of SMA mice. Single-RNA injections were able to illicit a robust induction of SMN protein in the brain and throughout the spinal column of neonatal SMA mice. In a severe model of SMA, mean life span was extended following the delivery of bifunctional RNAs. This technology has direct implications for the development of an SMA therapy, but also lends itself to a multitude of diseases caused by aberrant pre-mRNA splicing.
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PMID:Delivery of bifunctional RNAs that target an intronic repressor and increase SMN levels in an animal model of spinal muscular atrophy. 1922 73

Spinal muscular atrophy (SMA) is a common autosomal-recessive motor neuron disease caused by the homozygous loss of the SMN1 gene. A nearly identical gene, SMN2, has been shown to decrease the severity of SMA in a dose-dependent manner. However SMN2 is not the sole phenotypic modifier, because there are discrepant SMA cases in which the SMN2 copy number does not explain the clinical phenotype. This report describes three unrelated SMA patients who possessed SMN2 copy numbers that did not correlate with the observed mild clinical phenotypes. A single base substitution in SMN2, c.859G>C,, was identified in exon 7 in the patients' DNA. We now show that the change creates a new exonic splicing enhancer element and increases the amount of full-length transcripts, thus resulting in the less severe phenotypes. This demonstrates that the c.859G>C substitution is a positive modifier of the SMA phenotype and that not all SMN2 genes are equivalent. We have shown not only that the SMA phenotype is modified by the number of SMN2 genes but that SMN2 sequence variations can also affect the disease severity.
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PMID:A positive modifier of spinal muscular atrophy in the SMN2 gene. 1971 10

The childhood motor neuron disease spinal muscular atrophy (SMA) results from reduced expression of the survival motor neuron (SMN) gene. Previous studies using in vitro model systems and lower organisms have suggested that low levels of Smn protein disrupt prenatal developmental processes in lower motor neurons, influencing neuronal outgrowth, axon branching and neuromuscular connectivity. The extent to which these developmental pathways contribute to selective vulnerability and pathology in the mammalian neuromuscular system in vivo remains unclear. Here, we have investigated the pre-symptomatic development of neuromuscular connectivity in differentially vulnerable motor neuron populations in Smn(-/-);SMN2 mice, a model of severe SMA. We show that reduced Smn levels have no detectable effect on morphological correlates of pre-symptomatic development in either vulnerable or stable motor units, indicating that abnormal pre-symptomatic developmental processes are unlikely to be a prerequisite for subsequent pathological changes to occur in vivo. Microarray analyses of spinal cord from two different severe SMA mouse models demonstrated that only minimal changes in gene expression were present in pre-symptomatic mice. In stark contrast, microarray analysis of late-symptomatic spinal cord revealed widespread changes in gene expression, implicating extracellular matrix integrity, growth factor signalling and myelination pathways in SMA pathogenesis. Taken together, these data suggest that reduced Smn levels induce SMA pathology by instigating rapidly progressive neurodegenerative pathways in lower motor neurons around the time of disease onset rather than by modulating pre-symptomatic neurodevelopmental pathways.
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PMID:Pre-symptomatic development of lower motor neuron connectivity in a mouse model of severe spinal muscular atrophy. 1988 70

Translation elongation factor eEF1A (eukaryotic elongation factor 1A) exists as two individually encoded variants in mammals, which are 98% similar and 92% identical at the amino acid level. One variant, eEF1A1, is almost ubiquitously expressed, the other variant, eEF1A2, shows a very restricted pattern of expression. A spontaneous mutation was described in 1972, which gives rise to the wasted phenotype: homozygous wst/wst mice develop normally until shortly after weaning, but then lose muscle bulk, acquire tremors and gait abnormalities and die by 4 weeks. This mutation has been shown to be a deletion of 15 kb that removes the promoter and first exon of the gene encoding eEF1A2. The reciprocal pattern of expression of eEF1A1 and eEF1A2 in muscle fits well with the timing of onset of the phenotype of wasted mice: eEF1A1 declines after birth until it is undetectable by 3 weeks, whereas eEF1A2 expression increases over this time. No other gene is present in the wasted deletion, and transgenic studies have shown that the phenotype is due to loss of eEF1A2. We have shown that eEF1A2, but not eEF1A1, is also expressed at high levels in motor neurons in the spinal cord. Wasted mice develop many pathological features of motor neuron degeneration and may represent a good model for early onset of motor neuron disease. Molecular modelling of the eEF1A1 and eEF1A2 protein structures highlights differences between the two variants that may be critical for functional differences. Interactions between eEF1A2 and ZPR1 (zinc-finger protein 1), which interacts with the SMN (survival motor neuron) protein, may be important in motor neuron biology.
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PMID:eEF1A2 and neuronal degeneration. 1990 65

Spinal muscular atrophy is a severe motor neuron disease caused by inactivating mutations in the SMN1 gene leading to reduced levels of full-length functional SMN protein. SMN is a critical mediator of spliceosomal protein assembly, and complete loss or drastic reduction in protein leads to loss of cell viability. However, the reason for selective motor neuron degeneration when SMN is reduced to levels which are tolerated by all other cell types is not currently understood. Widespread splicing abnormalities have recently been reported at end-stage in a mouse model of SMA, leading to the proposition that disruption of efficient splicing is the primary mechanism of motor neuron death. However, it remains unclear whether splicing abnormalities are present during early stages of the disease, which would be a requirement for a direct role in disease pathogenesis. We performed exon-array analysis of RNA from SMN deficient mouse spinal cord at 3 time points, pre-symptomatic (P1), early symptomatic (P7), and late-symptomatic (P13). Compared to littermate control mice, SMA mice showed a time-dependent increase in the number of exons showing differential expression, with minimal differences between genotypes at P1 and P7, but substantial variation in late-symptomatic (P13) mice. Gene ontology analysis revealed differences in pathways associated with neuronal development as well as cellular injury. Validation of selected targets by RT-PCR confirmed the array findings and was in keeping with a shift between physiologically occurring mRNA isoforms. We conclude that the majority of splicing changes occur late in SMA and may represent a secondary effect of cell injury, though we cannot rule out significant early changes in a small number of transcripts crucial to motor neuron survival.
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PMID:Alternative splicing events are a late feature of pathology in a mouse model of spinal muscular atrophy. 2001 2

Proximal spinal muscular atrophy (SMA) is caused by homozygous loss or mutation of the SMN1 gene on human chromosome 5. Depending on the levels of SMN protein produced from a second SMN gene (SMN2), different forms of the disease are distinguished. In patients with milder forms of the disease, type III or type IV SMA that normally reach adulthood, enlargement of motor units is regularly observed. However, the underlying mechanisms are not understood. Smn(+/-) mice, a mouse model of type III/IV SMA, reveal progressive loss of motor neurons and denervation of motor endplates starting at 4 weeks of age. Loss of spinal motor neurons between 1 month and 12 months reaches 40%, whereas muscle strength is not reduced. In these animals, amplitude of single motor unit action potentials in the gastrocnemic muscle is increased more than 2-fold. Confocal analysis reveals pronounced sprouting of innervating motor axons. As ciliary neurotrophic factor (CNTF) is highly expressed in Schwann cells, we investigated its role for a compensatory sprouting response and maintenance of muscle strength in this mouse model. Genetic ablation of CNTF results in reduced sprouting and decline of muscle strength in Smn(+/-) mice. These findings indicate that CNTF is necessary for a sprouting response and thus enhances the size of motor units in skeletal muscles of Smn(+/-) mice. This compensatory mechanism could guide the way to new therapies for this motor neuron disease.
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PMID:Ciliary neurotrophic factor-induced sprouting preserves motor function in a mouse model of mild spinal muscular atrophy. 2002 87


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