Conserved Genes Act as Modifiers of Invertebrate SMN Loss of Function Defects

Dimitriadi, Maria; Sleigh, James N.; Walker, Alec J.; Chang, Howard C.; Sen, Anindya; Kalloo, Geetika; Harris, Jevede; Barsby, Tom; Walsh, Melissa B.; Satterlee, John S.; Li, Chris; Vactor, David Van; Artavanis‐Tsakonas, Spyros; Hart, Anne C.

doi:10.1371/journal.pgen.1001172

Cited by 97 publications

(126 citation statements)

References 153 publications

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“…The pumping rates of smn-1 loss-of-function animals [smn-1(ok355)] are significantly reduced (P = 3e-12; Fig. 1B) (31,32). To confirm that the defects described here are caused by smn-1 loss, we generated a new smn-1 allele, smn-1(rt248), using CRISPR/Cas9-targeted mutagenesis (34,35).…”

Section: Significancementioning

confidence: 84%

“…elegans Behavioral Assays. Pharyngeal pumping assays were performed in the last larval stage as previously described (32). Grinder movement in any axis was scored as a pumping event.…”

Section: Methodsmentioning

confidence: 99%

“…Animals with a wildtype copy of the endogenous smn-1 gene are referred to herein as smn-1(+) and are used as controls. Diminished smn-1 function causes slow growth and larval lethality and impairs neuromuscular function in pharyngeal pumping during feeding (31,32) (Fig. 1A).…”

Section: Significancementioning

confidence: 99%

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Decreased function of survival motor neuron protein impairs endocytic pathways

Dimitriadi

Derdowski

Kalloo

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Spinal muscular atrophy (SMA) is caused by depletion of the ubiquitously expressed survival motor neuron (SMN) protein, with 1 in 40 Caucasians being heterozygous for a disease allele. SMN is critical for the assembly of numerous ribonucleoprotein complexes, yet it is still unclear how reduced SMN levels affect motor neuron function. Here, we examined the impact of SMN depletion in Caenorhabditis elegans and found that decreased function of the SMN ortholog SMN-1 perturbed endocytic pathways at motor neuron synapses and in other tissues. Diminished SMN-1 levels caused defects in C. elegans neuromuscular function, and smn-1 genetic interactions were consistent with an endocytic defect. Changes were observed in synaptic endocytic proteins when SMN-1 levels decreased. At the ultrastructural level, defects were observed in endosomal compartments, including significantly fewer docked synaptic vesicles. Finally, endocytosis-dependent infection by JC polyomavirus (JCPyV) was reduced in human cells with decreased SMN levels. Collectively, these results demonstrate for the first time, to our knowledge, that SMN depletion causes defects in endosomal trafficking that impair synaptic function, even in the absence of motor neuron cell death.endocytic trafficking | survival motor neuron | spinal muscular atrophy | C. elegans | infection S pinal muscular atrophy (SMA) is one of the most severe neuromuscular diseases of childhood, with an incidence of 1 in 10,000 live births and a high carrier frequency of roughly 1 in 40 Caucasians (1-3). SMA is caused by reduced levels of the ubiquitously expressed survival of motor neuron (SMN) protein and results in degeneration of α-spinal cord motor neurons, muscle weakness, and/or death. Two human genes encode the SMN protein, SMN1 and SMN2. SMA alleles arise at relatively high frequency due to small intrachromosomal de novo rearrangements including the SMN1 locus (4). Patients often carry homozygous SMN1 deletions, although missense and nonsense alleles exist (5). Multiple copies of SMN2 rarely compensate for loss of SMN1 due to a C > T nucleotide change in SMN2 exon 7 that perturbs pre-mRNA splicing and results in a truncated protein of diminished function and stability (SMNΔ7) (5-9).SMN has numerous roles and interacts with various proteins, yet it remains unclear which interactions are most pertinent to SMA pathogenesis. As a component of the Gemin complex, SMN is required for biogenesis of small nuclear ribonucleoprotein (snRNP) particles critical for pre-mRNA splicing (10-12). Furthermore, SMN is needed for stress granule formation (13,14), is found in RNP granules moving through neuronal processes, and is part of RNP complexes implicated in synaptic local translation (15)(16)(17)(18)(19)(20). Additional roles for SMN, in transcription (21), in the PTEN-mediated protein synthesis pathway (22), in translational control (23), and in cell proliferation/differentiation (24), have been described. Importantly, no consensus has been reached regarding the cellular and molecular pathways wh...

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Section: Significancementioning

confidence: 84%

“…elegans Behavioral Assays. Pharyngeal pumping assays were performed in the last larval stage as previously described (32). Grinder movement in any axis was scored as a pumping event.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Decreased function of survival motor neuron protein impairs endocytic pathways

Dimitriadi

Derdowski

Kalloo

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

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“…Large-scale RNAi-based phenotypic screens in lower organisms have successfully identified genes involved in the rescue of neuronal degenerations (46)(47)(48). Parallel screens using primary vertebrate neurons, however, have been more difficult because of the challenges in working with and transfecting primary neuronal cell cultures.…”

Section: Discussionmentioning

confidence: 99%

Functional genomic screening identifies dual leucine zipper kinase as a key mediator of retinal ganglion cell death

Welsbie

Yang

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

229

307

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Glaucoma, a major cause of blindness worldwide, is a neurodegenerative optic neuropathy in which vision loss is caused by loss of retinal ganglion cells (RGCs). To better define the pathways mediating RGC death and identify targets for the development of neuroprotective drugs, we developed a high-throughput RNA interference screen with primary RGCs and used it to screen the full mouse kinome. The screen identified dual leucine zipper kinase (DLK) as a key neuroprotective target in RGCs. In cultured RGCs, DLK signaling is both necessary and sufficient for cell death. DLK undergoes robust posttranscriptional up-regulation in response to axonal injury in vitro and in vivo. Using a conditional knockout approach, we confirmed that DLK is required for RGC JNK activation and cell death in a rodent model of optic neuropathy. In addition, tozasertib, a small molecule protein kinase inhibitor with activity against DLK, protects RGCs from cell death in rodent glaucoma and traumatic optic neuropathy models. Together, our results establish a previously undescribed drug/drug target combination in glaucoma, identify an early marker of RGC injury, and provide a starting point for the development of more specific neuroprotective DLK inhibitors for the treatment of glaucoma, nonglaucomatous forms of optic neuropathy, and perhaps other CNS neurodegenerations.G laucoma is the leading cause of irreversible blindness worldwide (1). It is a neurodegenerative disease in which vision loss is caused by the axonal injury and death of retinal ganglion cells (RGCs) (2), the projection neurons that process and transmit vision from the retina to the brain. Current therapies (i.e., surgery, laser, and eye drops) all act by lowering intraocular pressure (IOP). However, pressure reduction can be difficult to achieve, and even with significant pressure lowering, RGC loss can continue. Efforts have therefore been made to develop neuroprotective agents that would complement IOP-lowering therapies by directly inhibiting the RGC cell death process (3, 4). However, no neuroprotective agent has yet been approved for clinical use.Protein kinases provide attractive targets for the development of neuroprotective agents. A number of kinases, including cyclindependent kinases, death-associated protein kinases, JNK1-3, MAPKs, and glycogen synthase kinase-3β, are involved in neuronal cell death (5-12). An additional attraction is that protein kinases are readily druggable. The pharmacology and medicinal chemistry of kinase inhibitors are well-developed, with kinases now being the most important class of drug targets after G protein-coupled receptors (13). Although the primary clinical use of kinase inhibitors continues to be as antineoplastic agents, increasing attention is being paid to their use in other areas (14,15).To identify, in a comprehensive and unbiased manner, kinases that could serve as targets for neuroprotective glaucoma therapy, we screened the entire mouse kinome for kinases whose inhibition promotes RGC survival. For this screen, we develope...

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“…In addition, it is highly amenable to genetic manipulation. Unbiased forward genetic screens can be used to identify phenotype-215 modifying mutations and reverse screening using RNA interference (RNAi) can reduce target gene function, allowing the development of disease models and their subsequent genetic dissection [6]. Pivotal to its use as a genetic model, conservative estimates suggest that approximately 60% of human genes posses a C. elegans homologue [7,8,9].…”

Section: Introductionmentioning

confidence: 99%

C. elegans models of neuromuscular diseases expedite translational research

Sleigh

Sattelle²

2010

Translational Neuroscience

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The nematode Caenorhabditis elegans is a genetic model organism and the only animal with a complete nervous system wiring diagram. With only 302 neurons and 95 striated muscle cells, a rich array of mutants with defective locomotion and the facility for individual targeted gene knockdown by RNA interference, it lends itself to the exploration of gene function at nerve muscle junctions. With approximately 60% of human disease genes having a C. elegans homologue, there is growing interest in the deployment of lowcost, high-throughput, drug screens of nematode transgenic and mutant strains mimicking aspects of the pathology of devastating human neuromuscular disorders. Here we explore the contributions already made by C. elegans to our understanding of muscular dystrophies (Duchenne and Becker), spinal muscular atrophy, amyotrophic lateral sclerosis, Friedreich’s ataxia, inclusion body myositis and the prospects for contributions to other neuromuscular disorders. A bottleneck to low-cost, in vivo, large-scale chemical library screening for new candidate therapies has been rapid, automated, behavioural phenotyping. Recent progress in quantifying simple swimming (thrashing) movements is making such screening possible and is expediting the translation of drug candidates towards the clinic.

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Conserved Genes Act as Modifiers of Invertebrate SMN Loss of Function Defects

Cited by 97 publications

References 153 publications

Decreased function of survival motor neuron protein impairs endocytic pathways

Decreased function of survival motor neuron protein impairs endocytic pathways

Functional genomic screening identifies dual leucine zipper kinase as a key mediator of retinal ganglion cell death

C. elegans models of neuromuscular diseases expedite translational research

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