scholarly journals A Drosophila melanogaster model of spinal muscular atrophy reveals a function for SMN in striated muscle

2007 ◽  
Vol 176 (6) ◽  
pp. 831-841 ◽  
Author(s):  
T.K. Rajendra ◽  
Graydon B. Gonsalvez ◽  
Michael P. Walker ◽  
Karl B. Shpargel ◽  
Helen K. Salz ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Spinal Muscular Atrophy ◽  
Motor Neurons ◽  
Striated Muscle ◽  
Flight Muscle ◽  
Muscular Atrophy ◽  
Survival Motor Neurons ◽  
Protein Levels

Mutations in human survival motor neurons 1 (SMN1) cause spinal muscular atrophy (SMA) and are associated with defects in assembly of small nuclear ribonucleoproteins (snRNPs) in vitro. However, the etiological link between snRNPs and SMA is unclear. We have developed a Drosophila melanogaster system to model SMA in vivo. Larval-lethal Smn-null mutations show no detectable snRNP reduction, making it unlikely that these animals die from global snRNP deprivation. Hypomorphic mutations in Smn reduce dSMN protein levels in the adult thorax, causing flightlessness and acute muscular atrophy. Mutant flight muscle motoneurons display pronounced axon routing and arborization defects. Moreover, Smn mutant myofibers fail to form thin filaments and phenocopy null mutations in Act88F, which is the flight muscle–specific actin isoform. In wild-type muscles, dSMN colocalizes with sarcomeric actin and forms a complex with α-actinin, the thin filament crosslinker. The sarcomeric localization of Smn is conserved in mouse myofibrils. These observations suggest a muscle-specific function for SMN and underline the importance of this tissue in modulating SMA severity.

scholarly journals Electrophysiological Properties of Motor Neurons in a Mouse Model of Severe Spinal Muscular Atrophy: In Vitro versus In Vivo Development

PLoS ONE ◽  
2010 ◽  
Vol 5 (7) ◽  
pp. e11696 ◽  
Author(s):  
Hongmei Zhang ◽  
Natallia Robinson ◽  
Chiayen Wu ◽  
Wenlan Wang ◽  
Melissa A. Harrington
Keyword(s):  
Mouse Model ◽  
Spinal Muscular Atrophy ◽  
Motor Neurons ◽  
Muscular Atrophy ◽  
Electrophysiological Properties

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 Chondrolectin affects cell survival and neuronal outgrowth in in vitro and in vivo models of spinal muscular atrophy

2013 ◽  
Vol 23 (4) ◽  
pp. 855-869 ◽  
Author(s):  
James N. Sleigh ◽  
Antón Barreiro-Iglesias ◽  
Peter L. Oliver ◽  
Angeliki Biba ◽  
Thomas Becker ◽  
...  
Keyword(s):  
Spinal Muscular Atrophy ◽  
Cell Survival ◽  
Muscular Atrophy ◽  
In Vivo Models ◽  
Neuronal Outgrowth

scholarly journals Synthesis and Characterization of Pseudocantharidins, Novel Phosphatase Modulators That Promote the Inclusion of Exon 7 into the SMN (Survival of Motoneuron) pre-mRNA

2011 ◽  
Vol 286 (12) ◽  
pp. 10126-10136 ◽  
Author(s):  
Zhaiyi Zhang ◽  
Olga Kelemen ◽  
Maria A. van Santen ◽  
Sharon M. Yelton ◽  
Alison E. Wendlandt ◽  
...  
Keyword(s):  
Spinal Muscular Atrophy ◽  
Muscular Atrophy ◽  
Central Element ◽  
Detectable Effect ◽  
Splice Site Selection ◽  
Eukaryotic Gene ◽  
Constitutive Splicing ◽  
New Compounds

Alternative pre-mRNA splicing is a central element of eukaryotic gene expression. Its deregulation can lead to disease, and methods to change splice site selection are developed as potential therapies. Spinal muscular atrophy is caused by the loss of the SMN1 (survival of motoneuron 1) gene. A therapeutic avenue for spinal muscular atrophy treatment is to promote exon 7 inclusion of the almost identical SMN2 (survival of motoneuron 2) gene. The splicing factor tra2-beta1 promotes inclusion of this exon and is antagonized by protein phosphatase (PP) 1. To identify new compounds that promote exon 7 inclusion, we synthesized analogs of cantharidin, an inhibitor of PP1, and PP2A. Three classes of compounds emerged from these studies. The first class blocks PP1 and PP2A activity, blocks constitutive splicing in vitro, and promotes exon 7 inclusion in vivo. The second class has no measurable effect on PP1 activity but activates PP2A. This class represents the first compounds described with these properties. These compounds cause a dephosphorylation of Thr-33 of tra2-beta1, which promotes exon 7 inclusion. The third class had no detectable effect on phosphatase activity and could promote exon 7 via allosteric effects. Our data show that subtle changes in similar compounds can turn a phosphatase inhibitor into an activator. These chemically related compounds influence alternative splicing by distinct mechanisms.

scholarly journals Functional characterizations of rare UBA1 variants in X-linked Spinal Muscular Atrophy

F1000Research ◽  
2017 ◽  
Vol 6 ◽  
pp. 1636 ◽  
Author(s):  
Chris D. Balak ◽  
Jesse M. Hunter ◽  
Mary E. Ahearn ◽  
David Wiley ◽  
Gennaro D'urso ◽  
...  
Keyword(s):  
Spinal Muscular Atrophy ◽  
Muscular Atrophy ◽  
Diagnostic Assays ◽  
Missense Variants ◽  
Thioester Bond ◽  
In The Wild ◽  
Ubiquitin Proteasome ◽  
Proteasome Pathway

Background: X-linked spinal muscular atrophy (XL-SMA) results from mutations in the Ubiquitin-Like Modifier Activating Enzyme 1 (UBA1). Previously, four novel closely clustered mutations have been shown to cause this fatal infantile disorder affecting only males. These mutations, three missense and one synonymous, all lie within Exon15 of the UBA1 gene, which contains the active adenylation domain (AAD). Methods: In this study, our group characterized the three known missense variants in vitro. Using a novel Uba1 assay and other methods, we investigated Uba1 adenylation, thioester, and transthioesterification reactions in vitro to determine possible biochemical effects of the missense variants. Results: Our data revealed that only one of the three XL-SMA missense variants impairs the Ubiquitin-adenylating ability of Uba1. Additionally, these missense variants retained Ubiquitin thioester bond formation and transthioesterification rates equal to that found in the wild type. Conclusions: Our results demonstrate a surprising shift from the likelihood of these XL-SMA mutations playing a damaging role in Uba1’s enzymatic activity with Ubiquitin, to other roles such as altering UBA1 mRNA splicing via the disruption of splicing factor binding sites, similar to a mechanism in traditional SMA, or disrupting binding to other important in vivo binding partners.  These findings help to narrow the search for the areas of possible dysfunction in the Ubiquitin-proteasome pathway that ultimately result in XL-SMA. Moreover, this investigation provides additional critical understanding of the mutations’ biochemical mechanisms, vital for the development of future effective diagnostic assays and therapeutics.

scholarly journals SAM68 is a physiological regulator of SMN2 splicing in spinal muscular atrophy

2015 ◽  
Vol 211 (1) ◽  
pp. 77-90 ◽  
Author(s):  
Vittoria Pagliarini ◽  
Laura Pelosi ◽  
Maria Blaire Bustamante ◽  
Annalisa Nobili ◽  
Maria Grazia Berardinelli ◽  
...  
Keyword(s):  
Spinal Muscular Atrophy ◽  
Motor Neurons ◽  
Messenger Rna ◽  
Muscular Atrophy ◽  
Splicing Factors ◽  
Hnrnp A1 ◽  
Smn1 Gene ◽  
Smn2 Gene ◽  
Physiological Regulator

Spinal muscular atrophy (SMA) is a neurodegenerative disease caused by loss of motor neurons in patients with null mutations in the SMN1 gene. The almost identical SMN2 gene is unable to compensate for this deficiency because of the skipping of exon 7 during pre–messenger RNA (mRNA) processing. Although several splicing factors can modulate SMN2 splicing in vitro, the physiological regulators of this disease-causing event are unknown. We found that knockout of the splicing factor SAM68 partially rescued body weight and viability of SMAΔ7 mice. Ablation of SAM68 function promoted SMN2 splicing and expression in SMAΔ7 mice, correlating with amelioration of SMA-related defects in motor neurons and skeletal muscles. Mechanistically, SAM68 binds to SMN2 pre-mRNA, favoring recruitment of the splicing repressor hnRNP A1 and interfering with that of U2AF65 at the 3′ splice site of exon 7. These findings identify SAM68 as the first physiological regulator of SMN2 splicing in an SMA mouse model.

scholarly journals MARP Protein Family: A Possible Role in Molecular Mechanisms of Tumorigenesis

2010 ◽  
Vol 29 (3) ◽  
pp. 157-164 ◽  
Author(s):  
Snežana Kojić
Keyword(s):  
Molecular Mechanisms ◽  
Striated Muscle ◽  
Muscular Atrophy ◽  
Protein Family ◽  
Renal Oncocytoma ◽  
Cardiac Muscle Cells ◽  
Altered Expression ◽  
Duchene Muscular Dystrophy

MARP Protein Family: A Possible Role in Molecular Mechanisms of TumorigenesisThe MARP (muscle ankyrin repeat protein) family comprises three structurally similar proteins: CARP/Ankrd1, Ankrd2/Arpp and DARP/Ankrd23. They share four conserved copies of 33-residue ankyrin repeats and contain a nuclear localization signal, allowing the sorting of MARPs to the nucleus. They are found both in the nucleus and in the cytoplasm of skeletal and cardiac muscle cells, suggesting that MARPs shuttle within the cell enabling them to play a role in signal transduction in striated muscle. Expression of MARPs is altered under different pathological conditions. In skeletal muscle, CARP/Ankrd1 and Ankrd2/Arpp are up-regulated in muscle in patients suffering from Duchene muscular dystrophy, congenital myopathy and spinal muscular atrophy. Mutations inAnkrd1gene (coding CARP/Ankrd1) were identified in dilated and hypertrophic cardiomyopathies. Altered expression of MARPs is also observed in rhabdomyosarcoma, renal oncocytoma and ovarian cancer. In order to functionally characterize MARP family members CARP/Ankrd1 and Ankrd2/Arpp, we have found that both proteins interact with the tumor suppressor p53 bothin vivoandin vitroand that p53 up-regulates their expression. Our results implicate the potential role of MARPs in molecular mechanisms relevant to tumor response and progression.

scholarly journals Utilizing gene therapy methods to probe the genetic requirements to prevent spinal muscular atrophy.

2016 ◽  
Author(s):  
◽  
Madeline R. Miller
Keyword(s):  
Neuromuscular Junction ◽  
Spinal Muscular Atrophy ◽  
Motor Neuron ◽  
Motor Neurons ◽  
Muscular Atrophy ◽  
Survival Motor Neuron ◽  
Downstream Effects ◽  
Smn Protein ◽  
Progressive Weakness

Spinal Muscular Atrophy is clinically recognized as a progressive weakness within the trunk and proximal limbs that will lead to breathing failure and death within infants. As a neurodegenerative genetic disease, SMA is caused by loss of motor neurons, which in turn is caused by low levels of the Survival Motor Neuron (SMN) protein. The mechanism by which a ubiquitously expressed protein such as SMN is able to cause the specific death of motor neurons is highly debated and of great interest. Work presented here focuses on understanding the biological requirements of SMN and its downstream effects on the neuromuscular junction. To this end we utilize viral based gene delivery as a powerful tool to assess the effects of genes of interest in vivo. Our findings contribute to the conversation regarding whether SMA is truly a "motor neuron" disease, suggesting that astrocytes play a meaningful role in staving off SMA. Further, we investigate the domains within SMN needed to maintain its function in a mammalian system. We take a novel and challenging approach to identify a minimal domain capable of maintaining function. Finally, we demonstrate the practical use of morophological analysis of the neuromuscular junction as a means to characterize SMA pathology.

scholarly journals Calpain system is altered in survival motor neuron-reduced cells from in vitro and in vivo spinal muscular atrophy models

2020 ◽  
Vol 11 (6) ◽  
Author(s):  
Sandra de la Fuente ◽  
Alba Sansa ◽  
Iván Hidalgo ◽  
Nuria Vivancos ◽  
Ricardo Romero-Guevara ◽  
...  
Keyword(s):  
Spinal Muscular Atrophy ◽  
Motor Neuron ◽  
Muscular Atrophy ◽  
Survival Motor Neuron ◽  
Calpain System
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