Prerpints.org logo
Preprint
Review

Caenorhabditis elegans Models Count

Altmetrics

Downloads

119

Views

45

Comments

0

A peer-reviewed article of this preprint also exists.

This version is not peer-reviewed

Submitted:

06 November 2023

Posted:

07 November 2023

You are already at the latest version

Alerts
Abstract
Amyotrophic Lateral Sclerosis (ALS) stands as a debilitating neurodegenerative condition characterized by the progressive degeneration of motor neurons. Despite extensive research in various model animals, the cellular signal mechanisms of ALS remain elusive, impeding the development of efficacious treatments. Among these models, a well-characterized and diminutive organism, Caenorhabditis elegans (C. elegans), has arisen as a potent tool for investigating the molecular and cellular dimensions of ALS pathogenesis. This review summarizes the contributions of C. elegans models to our comprehension of ALS, emphasizing pivotal findings pertaining to genetics, protein aggregation, cellular pathways, and potential therapeutic strategies. We analyze both the merits and constraints of C. elegans system in the realm of ALS research, and point towards future investigations that could bridge the chasm between C. elegans foundational discoveries and clinical applications.
Keywords: 
Subject: Biology and Life Sciences  -   Neuroscience and Neurology

1. Brief introduction of Amyotrophic Lateral Sclerosis

Motor neuron disease (MND) encompasses a group of disorders, including but not limited to amyotrophic lateral sclerosis (ALS), progressive spinal muscular atrophy, primary lateral sclerosis, and progressive bulbar palsy These disorders share a common feature, the damage to upper and lower motor neurons, leading to the loss of essential motor function [1,2]. Typically, individuals diagnosed with MND display symptoms such as muscle wasting and limb weakness. Beyond motor impairments, they may also experience language and swallowing difficulties [3]. As MND advances, most patients succumb to complications like pneumonia or respiratory failure [4]. This review zeroes in on the intricate mechanisms underlying ALS, the most prevalent adult-onset neurodegenerative form of MND, insights from studies conducted with the small model animal Caenorhabditis elegans (C. elegans).
ALS is also referred to as Charcot’s disease or Lou Gehrig’s disease. Like most MNDs, ALS targets both upper and lower motor neurons within the central nervous system, which regulate voluntary muscle movement. Clinically, ALS is typified by muscle rigidity and the progressive weakening of limbs and bulbar muscles, leading to varying degrees of difficulty in speech, swallowing, and respiration [4,5]. It is worth noting that functions like bladder control, bowel movements, and eye movements are typically preserved until the advanced stages of the disease [6]. Beyond muscle dysfunction, 30-50% of ALS patients also exhibit cognitive and other nervous system deficits. Common cognitive symptoms in ALS patients encompass challenges in social cognition, verbal memory, language, and executive function [7]. In about 15% of cases where cognitive impairment is observed, there is visible atrophy in the frontal and/or temporal lobes, which results in behavioral changes or language impairment meeting the criteria for frontotemporal dementia (FTD) [8]. These observations suggest that ALS is a complex and progressive diseases involving functional deficits in multiple tissues.
The onset of ALS generally occurs between the ages of 40 and 70, although instances in younger patients have been documented. Patients with ALS typically succumb to the disease within 2-5 years after diagnosis [9,10]. The estimated incidence rate of ALS varies from 0.3 to 2.5 cases per 100,000 individuals [11]. While ALS might be perceived as relatively rare in the public’s perception, it exerts substantial impact on patients’ quality of life.

2. ALS Associated Genetic Mutations Modeled in C. elegans

In the pursuit of understanding the pivotal genetic factors underlying various forms of ALS the development of in vivo models has proven indispensable. Two overarching strategies have been employed for generating these models. The first method involves the overexpression of human wild-type or mutated proteins in model organisms, allowing researchers to scrutinize the functional and structural consequences of these proteins in specific tissues. This approach unveils the underlying pathological mechanisms of human ALS-associated molecules in animal models. The second approach revolves around the creation of loss-of-function or gain-of-function mutants through the manipulation of homologous genes in model organisms. This will help to introduce the intrinsic functions of the key molecules involved in ALS and to compare the similarities in the pathogenic mechanisms of the different species.
The C. elegans has emerged as a powerful tool for probing the mechanisms underpinning neurodegenerative diseases [12,13,14,15]. This is primarily due to its ease of genetic manipulation, rapid cultivation, and its capacity to serve as a whole-animal system amenable to a plethora of molecular and biochemical techniques [16]. Furthermore, C. elegans shares functional conservation with many critical pathogenic genes associated with ALS, reinforcing the notion that models established in this organism possess biological relevance [17,18]. Indeed, C. elegans has gained widespread recognition as an animal model for investigating the fundamental causal genes of ALS [19,20,21,22,23]. Approximately 42% of human disease-associated genes have identifiable nematode orthologs, rendering this worm an apt model for delving into the molecular mechanisms and cellular processes that drive disease onset and progression [16,24]. In Table 1 below, we provide an overview of the nematode ALS models employed in different studies.

3. Mechanisms Investigation of Protein Aggregation, Propagation in C. elegans

The misfolding and aggregation of frequently encountered proteins, such as SOD1, TDP-43, FUS, C9orf72, optineurin (OPTN), and others, occur in over 90% of ALS patients [34].
SOD-1, a ubiquitously expressed cytosolic protein, functions in the conversion of toxic superoxide anions to hydrogen peroxide, serving as a cellular defense against oxidative stress [35]. While initially associated with a loss of dismutase activity, it is now acknowledged that mutations in SOD1 primarily induce toxicity through a gain-of-function mechanism, although the precise toxic mechanisms remain to be fully elucidated [36]. Mutations in the SOD1 gene induce alterations in the enzyme’s folding and stability, ultimately leading to aggregation within motor neurons and subsequent paralysis [14].
TDP-43, a protein encoded by the TARDBP gene on human chromosome I, is expressed ubiquitously and predominantly localized within neuronal nuclei [37]. TDP-43 serves as a multifunctional RNA-binding protein involved in RNA processing, including the regulation of alternative mRNA splicing and mRNA stability [38]. Notably, TDP-43 represents a key constituent of ubiquitin-positive aggregates within the motor neurons of ALS patients. These aggregates comprise C-terminally truncated and hyperphosphorylated TDP-43 [37]. Over 40 mutations linked to ALS have been identified, with G298S, A315T, M337V, G348C, and A382T being the most frequently associated mutations [39].
FUS, a DNA and RNA-binding protein that plays a role in regulating transcription and mRNA processing in neurons, experiences mutations that result in aggregated proteins, inducing motor impairment and altering synaptic functions through overexpression [40,41]. At the molecular level, mutations in FUS provoke dysregulation in RNA processes, encompassing splicing, transcription, and stabilization, ultimately leading to neuronal dysfunction [42,43].
C9ORF72, the most common genetic cause of ALS is the expansion of the hexanucleotide GGGGCC repeat in the first intron of the C9ORF72 gene [44]. The exact mechanism of this expansion remains elusive, one interpretation is that AUG individual translation of GGGGCC may lead to the formation of dipeptide repeats [45].
Optineurin (OPTN) is a highly conserved hexameric protein weighing 64 kDa, composed of 577 amino acids (aa). OPTN interacts with a multitude of proteins involved in processes such as inflammation, vesicle-based protein trafficking, and signal transduction, including the nuclear factor kappa B (NF-κB) pathway [46,47]. Linked to neurodegenerative diseases like ALS, OPTN comprises several coiled-coil domains, a ubiquitin-binding domain (UBD), a leucine-zipper kinase, and an LC3-binding domain [48]. Specific mutations in OPTN, including exon 5 deletion, Q398 nonsense, and E478G missense mutations, have been identified in ALS patients [49,50].
Several transgenic C. elegans strains, expressing human SOD-1 variants, have been developed to investigate the functions of mutant SOD-1 [13]. Initially, an ALS C. elegans model was established by employing the hsp16.2 or mec-3 promoter to introduce human wild-type SOD-1 and various family ALS (FALS)-related mutants (A4V, G37R, and G93A) of SOD-1. However, these transgenic nematodes did not exhibit any discernible phenotypes [26]. Another transgenic C. elegans model was then developed to explore differences in the aggregation and toxicity tendencies of wild-type and mutant SOD-1. This was achieved by introducing YFP-tagged wild-type or mutant (G85R and G93A) SOD-1 proteins into the body wall muscle cells under the regulation of the unc-54 promoter [29]. Transgenic C. elegans with pan-neuronal expression of SOD-1(G85R) exhibited severe locomotor defects and presynaptic dysfunction, which were correlated with the insoluble aggregation of SOD-1 in neurons under the control of synaptobrevin (snb-1) gene promoter [51]. When mutant SOD-1(G93A) was expressed in GABAergic motor neurons, it led to age-dependent motor impairments, axon guidance failures, and significant SOD-1 accumulation [23]. The C. elegans sod-1 gene shares functional similarities with its human counterpart. Expressing SOD-1loss of function mutants increased the levels of superoxide anions in worms, resulting in a shorter lifespan and heightened susceptibility to certain environmental stresses [52]. Conversely, over-activation of C. elegans sod-1, as a by-product of the catalase reaction, elevated hydrogen peroxide levels and extended lifespan [21].
TDP-1, the C. elegans ortholog of TDP-43, played a pioneering role in modeling TDP-43-related ALS. Initially, this model was established by inducing pan-neuronal expression of human TDP-43 under the snb-1 promoter’s control. This resulted in a notable presentation of harmonious, slow movement and defasciculation of the GABAergic motor neurons [53]. Recent developments in transgenic C. elegans models have included the introduction of pan-neuronal expression of both human wild-type and mutant TDP-43 variants, including G290A, A315T, and M337V. These studies have revealed that wild-type TDP-43 induces moderate motor defects, while the mutant TDP-43 variants lead to severe motor dysfunction [54]. Intriguingly, similar phenotypes to those observed with the overactivation of wild-type TDP-43 were observed when the C-terminal fragment of human TDP-43 was pan-neuronally expressed [33].
Numerous transgenic C. elegans models have been generated to investigate the effects of mutated and overexpressed FUS genes. FUST-1 serves as the C. elegans ortholog of the human FUS gene, and studies in C. elegans have revealed that FUS and TDP-43 share common functions and exhibit similar outcomes when mutated variants associated with ALS are expressed [55]. Moreover, specific ALS-related mutations, R524S and P525L, in the FUS gene have been used to establish transgenic C. elegans models. These models exhibit impaired neuromuscular function and locomotion, mirroring characteristics of ALS [20]. Recent advancements in genetic manipulation have enabled the creation of a single-copy FUS mutant transgenic strain of C. elegans, which displays ALS-like phenotypes, including GABAergic neurodegeneration and progressive paralysis [56]. Furthermore, it has been demonstrated that reducing dnc-1 (dynactin 1) levels can enhance autophagosome transport and promote motor neuron degeneration. Building on this insight, Ikenaka and their team have developed a novel C. elegans transgenic model with dnc-1 knockdown [57]. Notably, this behavior-based model has been employed to identify and assess potential neuroprotective drugs against motor neuron diseases, opening up new avenues for drug discovery [58].
Alfa-1, an ortholog of the ALS/FTD-associated gene C9ORF72 in C. elegans, offers a valuable model to investigate their association with ALS [22]. The development of a transgenic model inducing motor deficits in C. elegans began with a mutation in the alfa-1 ortholog. This model revealed a synergistic toxic effect when combined with a TDP-43 mutation [19]. C. elegans with loss-of-function mutations in the alfa-1 gene exhibit age-dependent motility impairments, ultimately leading to paralysis and GABAergic stress-dependent neurodegeneration [12,19]. Notably, alfa-1 mutants display endocytosis defects, which can be partially rescued by the expression of the human wild-type C9ORF72 protein, underscoring a degree of functional conservation [59]. However, it’s worth noting that transgenic nematode models are predominantly employed to investigate human C9ORF72 toxicity, as alfa-1 does not harbor hexanucleotide repeat expansions [12]. Comparative studies using models with different repeat lengths have revealed that transgenes containing 29 GGGGCC repeats result in early-onset paralysis and increased lethality, albeit with less severe impacts than their counterparts with nine repeats [60,61].
Gene mutations encoding optineurin have been identified in ALS patients. Three distinct types of OPTN mutations—a homozygous deletion of exon 5, a homozygous Q398X nonsense mutation, and a heterozygous E478G missense mutation within its ubiquitin-binding domain—are linked to ALS pathogenesis in C. elegans [50]. Notably, the nonsense and missense mutations in OPTN led to the reversal of the inhibition of NF-kB activation, as evidenced through cell transfection analyses. Moreover, these mutations demonstrated that the E478G mutation resulted in a distinct cytoplasmic distribution, differing from the wild type or a primary open-angle glaucoma (POAG) mutation [49]. Hence, OPTN plays a significant role in the pathogenesis of ALS, and targeting NF-kB with inhibitors could potentially be a therapeutic approach for ALS treatment.
We summarize the ALS pathogenic mechanisms in Table 2.

4. Cell Signaling Pathways Implicated in C. elegans Based ALS

A range of pathology-related signaling pathways has been explored in ALS nematode models. Data from clinical studies show that multiple genetic mutations linked to ALS (eg, mutations in SOD1, TARDBP, and C9orf72) enhance neuroinflammation, which provides compelling evidence for immune dysregulation in the pathogenesis of ALS [50,79]. Therefore, an improved understanding of the biological processes that induce this immune dysregulation will help to identify therapeutic strategies that circumvent or ameliorate the pathogenesis of ALS. Notably, mutant ALS proteins have been found to activate an innate immune response of C. elegans [80,81,82]. In C. elegans strains expressing mutant TDP-43 or FUS in their motor neurons, age-dependent motility defects culminate in paralysis and motor neuron degeneration at a rate significantly higher than that observed in wild-type TDP-43 or FUS control strains. By examining the expression of immune response proteins, including NLP-29 (an antimicrobial, neuropeptide-like protein expressed in hypodermal and intestinal tissue) [83,84], it’s evident that the expression of mutant proteins linked to ALS in C. elegans motor neurons triggers an innate immune response through TIR-1/Sarm1. Loss-of-function mutations in tir-1, downstream kinases, and the transcription factor atf-7 collectively serve to suppress motor neuron degeneration. Furthermore, the neurosecretory proteins UNC-13 and UNC-31 play a vital role in response and the subsequent degeneration of motor neurons. Notably, the human orthologue of UNC-13, UNC13A, has been identified as a genetic modifier of survival in ALS [80]. Cell-based strategies that enhance the anti-inflammatory reactivity and reverse immune dysregulation offer the potential of slowing disease progression and improving quality of life of patients with ALS.
It is well known that the dysregulation of autophagy in motor neurons is a pivotal event in ALS [85,86]. Particularly, intensified immunoreactivity for microtubule-associated protein 1 light chain 3 (LC3), which is a marker of autophagosome, is often observed in the spinal motor neurons of ALS patients [87,88]. The expression of DNC-1, the homolog of dynactin 1, is specifically knocked down in motor neurons in C. elegans. This model exhibited severe motor defects together with axonal and neuronal degeneration and also observed impaired movement and increased number of autophagosomes in the degenerated neurons [57]. It can be seen that transport of autophagosomes is a novel and substantial therapeutic target for motor neuron degeneration. In addition, defective autophagy likely contributes to neuronal dysfunction in ALS diseases, as demonstrated in autophagy-related genes SQSTM1/p62, UBQLN2, VCP, OPTN and TBK1 [50,89,90,91,92,93]. Autophagy adaptor protein SQSTM1 accumulates in ALS patient motor neurons [94], which may indicate autophagy dysfunction. Consistent with this, LC3-positive autophagy vesicles are elevated in ALS FUS patient motor neurons [95]. Unlike animals lacking the endogenous FUS ortholog, ALS FUS animals exhibit impaired neuronal autophagy and an increased accumulation of SQST-1 in motor neurons. The loss of sqst-1, the C. elegans ortholog for the ALS-linked autophagy adaptor protein SQSTM1/p62, suppresses both neuromuscular and stress-induced locomotion defects in ALS FUS animals. However, it’s important to note that it does not suppress neuronal autophagy defects. Consequently, it is evident that autophagy dysfunction is upstream of SQSTM1 function in ALS FUS pathogenesis, and not dependent on it. The highly conserved autophagy pathway plays a crucial role in preventing and countering pathogenic insults that can lead to neurodegeneration [96,97]
Protein homeostasis, often referred to as proteostasis, is carefully maintained through an intricately regulated and interconnected network of biological pathways. This network serves the crucial function of preventing the accumulation and aggregation of damaged or misfolded proteins. Therefore, the integrity of the proteostasis network is paramount in ensuring the longevity and overall health of an organism [98]. Conversely, when proteostasis falters, it contributes to the development of diseases like ALS, which involve the problematic aggregation of proteins [99]. Transgenic C. elegans models that express human TDP-43 variants in the nervous system developed severe locomotor defects associated with the aggregation of TDP-43 in neurons. The neurotoxicity and the protein aggregation of TDP-43 were regulated by environmental temperature and heat shock transcriptional factor 1 (HSF-1). Furthermore, the neurotoxicity and the protein aggregation of TDP-43 can be significantly attenuated by a deficiency in the insulin/insulin-like growth factor 1 (IGF-1) signaling in C. elegans and mammalian cells [33]. In addition, protein misfolding associated with TDP-43 underlies the aging-dependent neurodegeneration. One extensively studied mechanism for regulating longevity revolves around phosphorylation’s control of the insulin/IGF-1 signaling pathway [100,101]. The downstream receptor of insulin molecules in C. elegans, daf-2, demonstrates the capacity to mitigate the shortened lifespan associated with FUS overexpression as well as well as a significant reduction in aggregates in the insoluble pellets of extracted worm homogenates [33,102]. The identification and harnessing of biological networks and molecular targets that govern aging and longevity have, therefore, become central to research, with the ultimate goal of translating these findings into therapeutic strategies.

5. Advances in Therapeutic Application of C. elegans ALS Models

C. elegans has provided a valuable platform for investigating potential therapeutic strategies for ALS. Researchers have delved into the use of small molecules to modulate disease pathways, RNA-based therapies targeting specific genes, and genetic modifiers to gain deeper insights into disease mechanisms. These studies not only enhance our comprehension of ALS but also offer insights into potential treatments that may eventually progress to clinical trials for human patients. However, it is imperative to acknowledge that findings in C. elegans require validation in more complex models and, ultimately, in clinical trials to ensure their relevance to human ALS. In Table 3, we present a summary of the advances in therapeutic approaches in C. elegans ALS models.

6. Limitations of C. elegans as ALS Models and Future Directions

ALS is a multifactorial disease, and a growing body of literature underscores the influence of comorbid processes on its pathological progression [5,120,121]. A significant challenge in the quest for effective disease-modifying therapies lies in our limited comprehension of the multifaceted pathways contributing to the development of the disease. While mammalian disease models provide valuable in vivo opportunities and share considerable similarities with the human brain, they come with their complexities. However, the relatively straightforward architecture of C. elegans, a microscopic nematode, also brings its own set of constraints. Notably, various tissue and organ systems crucially implicated in neurodegenerative diseases, particularly the central nervous system (CNS) and brain, are notably absent or been greatly simplified in these worms, rendering them less suitable for investigating the systemic pathogenesis of ALS. Consequently, C. elegans often serves as a complementary model to gain insights into the pathogenesis and therapeutic approaches for ALS. Nevertheless, it is essential to underscore that the findings derived from C. elegans research demand validation in mammalian models and clinical settings to ascertain their clinical relevance.
One potential approach to develop C. elegans ALS models involves functionally annotating human genome variants to identify factors contributing to susceptibility and resilience. The continuous growth of databases containing human gene sequence information has led to an overwhelming volume of variants with uncertain significance. Functional gene analysis in C. elegans can be directed towards the functional attributes of mutation data, significantly enhancing our comprehension of pathogenic mechanisms and treatment possibilities [122].
Nematodes hold great potential for expediting the development of neuroprotective drugs due to their simple genetic properties and suitability for high-throughput compound screening [58]. Both target-driven and phenotypic screening approaches can be readily implemented in these organisms, rendering C. elegans an ideal screening target. Unlike rodent models, worm models offer a rapid and cost-effective means to test numerous drug combinations. Additionally, the advent of technologies such as CRISPR provides the potential to swiftly generate new and more precise nematode models of ALS [123,124]. This is achieved by precisely delivering a single copy of the mutated gene identified from the patient to the desired location in the worm’s genome. In the future, the amalgamation of a more accurate genetic C. elegans model with a high-throughput automated drug screening platform presents a potentially highly effective strategy for drug discovery in the treatment of ALS.
In summary, C. elegans models have made remarkable contributions in facilitating the transition from experimental research to clinical applications. The manifold advantages of C. elegans offer an appealing and ethically sound alternative to costlier and time-consuming in vitro or mammalian models. With a growing track record of translational outcomes arising from C. elegans research, this microscopic organism is poised to illuminate the remaining obscurities surrounding ALS. Indeed, ALS, as a global neurodegenerative ailment, imposes a substantial burden on tens of millions of individuals daily. Injecting urgency and innovative strategies into model systems research is imperative to expedite discoveries and advancements.

Author Contributions

S.G. and L.C. conceived the project, S.Z. and S.L. contributed to the manuscript. S.G. and L.C. wrote the manuscript.

Funding

This review was supported by the Major International (Regional) Joint Research Project (32020103007), the National Key Research and Development Program of China (2022YFA1206001), the National Natural Science Foundation of China (32371189, 32300984).

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Arora, R.D.; Khan, Y.S. Motor Neuron Disease. In StatPearls; Treasure Island (FL) ineligible companies. Disclosure: Yusuf Khan declares no relevant financial relationships with ineligible companies, 2023. [Google Scholar]
  2. Dugger, B.N.; Dickson, D.W. Pathology of Neurodegenerative Diseases. Cold Spring Harb Perspect Biol 2017, 9. [Google Scholar] [CrossRef]
  3. Chen, S.; Sayana, P.; Zhang, X.; Le, W. Genetics of amyotrophic lateral sclerosis: an update. Mol Neurodegener 2013, 8, 28. [Google Scholar] [CrossRef]
  4. Wijesekera, L.C.; Leigh, P.N. Amyotrophic lateral sclerosis. Orphanet J Rare Dis 2009, 4, 3. [Google Scholar] [CrossRef]
  5. Zarei, S.; Carr, K.; Reiley, L.; Diaz, K.; Guerra, O.; Altamirano, P.F.; Pagani, W.; Lodin, D.; Orozco, G.; Chinea, A. A comprehensive review of amyotrophic lateral sclerosis. Surg Neurol Int 2015, 6, 171. [Google Scholar] [CrossRef]
  6. Hobson, E.V.; McDermott, C.J. Supportive and symptomatic management of amyotrophic lateral sclerosis. Nat Rev Neurol 2016, 12, 526–538. [Google Scholar] [CrossRef]
  7. Beeldman, E.; Raaphorst, J.; Klein Twennaar, M.; de Visser, M.; Schmand, B.A.; de Haan, R.J. The cognitive profile of ALS: a systematic review and meta-analysis update. J Neurol Neurosurg Psychiatry 2016, 87, 611–619. [Google Scholar] [CrossRef]
  8. Ringholz, G.M.; Appel, S.H.; Bradshaw, M.; Cooke, N.A.; Mosnik, D.M.; Schulz, P.E. Prevalence and patterns of cognitive impairment in sporadic ALS. Neurology 2005, 65, 586–590. [Google Scholar] [CrossRef]
  9. Broussalis, E.; Grinzinger, S.; Kunz, A.B.; Killer-Oberpfalzer, M.; Haschke-Becher, E.; Hartung, H.P.; Kraus, J. Late age onset of amyotrophic lateral sclerosis is often not considered in elderly people. Acta Neurol Scand 2018, 137, 329–334. [Google Scholar] [CrossRef]
  10. Karceski, S. Understanding the different types of ALS. Neurology 2020, 94, e880–e883. [Google Scholar] [CrossRef]
  11. Sathasivam, S. Motor neurone disease: clinical features, diagnosis, diagnostic pitfalls and prognostic markers. Singapore Med J 2010, 51, 367–372. [Google Scholar]
  12. Roussos, A.; Kitopoulou, K.; Borbolis, F.; Palikaras, K. Caenorhabditis elegans as a Model System to Study Human Neurodegenerative Disorders. Biomolecules 2023, 13. [Google Scholar] [CrossRef]
  13. Van Pelt, K.M.; Truttmann, M.C. Caenorhabditis elegans as a model system for studying aging-associated neurodegenerative diseases. Transl Med Aging 2020, 4, 60–72. [Google Scholar] [CrossRef]
  14. Caldwell, K.A.; Willicott, C.W.; Caldwell, G.A. Modeling neurodegeneration in Caenorhabditiselegans. Dis Model Mech 2020, 13. [Google Scholar] [CrossRef]
  15. Li, J.; Le, W. Modeling neurodegenerative diseases in Caenorhabditis elegans. Exp Neurol 2013, 250, 94–103. [Google Scholar] [CrossRef]
  16. Brenner, S. The genetics of Caenorhabditis elegans. Genetics 1974, 77, 71–94. [Google Scholar] [CrossRef]
  17. Kaletta, T.; Hengartner, M.O. Finding function in novel targets: C. elegans as a model organism. Nat Rev Drug Discov 2006, 5, 387–398. [Google Scholar] [CrossRef]
  18. Shaye, D.D.; Greenwald, I. OrthoList: a compendium of C. elegans genes with human orthologs. PLoS One 2011, 6, e20085. [Google Scholar] [CrossRef]
  19. Therrien, M.; Rouleau, G.A.; Dion, P.A.; Parker, J.A. Deletion of C9ORF72 results in motor neuron degeneration and stress sensitivity in C. elegans. PLoS One 2013, 8, e83450. [Google Scholar] [CrossRef]
  20. Baskoylu, S.N.; Chapkis, N.; Unsal, B.; Lins, J.; Schuch, K.; Simon, J.; Hart, A.C. Disrupted autophagy and neuronal dysfunction in C. elegans knockin models of FUS amyotrophic lateral sclerosis. Cell Rep 2022, 38, 110195. [Google Scholar] [CrossRef]
  21. Cabreiro, F.; Ackerman, D.; Doonan, R.; Araiz, C.; Back, P.; Papp, D.; Braeckman, B.P.; Gems, D. Increased life span from overexpression of superoxide dismutase in Caenorhabditis elegans is not caused by decreased oxidative damage. Free Radic Biol Med 2011, 51, 1575–1582. [Google Scholar] [CrossRef]
  22. Rudich, P.; Snoznik, C.; Watkins, S.C.; Monaghan, J.; Pandey, U.B.; Lamitina, S.T. Nuclear localized C9orf72-associated arginine-containing dipeptides exhibit age-dependent toxicity in C. elegans. Hum Mol Genet 2017, 26, 4916–4928. [Google Scholar] [CrossRef]
  23. Li, J.; Huang, K.X.; Le, W.D. Establishing a novel C. elegans model to investigate the role of autophagy in amyotrophic lateral sclerosis. Acta Pharmacol Sin 2013, 34, 644–650. [Google Scholar] [CrossRef] [PubMed]
  24. Wheelan, S.J.; Boguski, M.S.; Duret, L.; Makalowski, W. Human and nematode orthologs--lessons from the analysis of 1800 human genes and the proteome of Caenorhabditis elegans. Gene 1999, 238, 163–170. [Google Scholar] [CrossRef] [PubMed]
  25. Fatouros, C.; Pir, G.J.; Biernat, J.; Koushika, S.P.; Mandelkow, E.; Mandelkow, E.M.; Schmidt, E.; Baumeister, R. Inhibition of tau aggregation in a novel Caenorhabditis elegans model of tauopathy mitigates proteotoxicity. Hum Mol Genet 2012, 21, 3587–3603. [Google Scholar] [CrossRef] [PubMed]
  26. Oeda, T.; Shimohama, S.; Kitagawa, N.; Kohno, R.; Imura, T.; Shibasaki, H.; Ishii, N. Oxidative stress causes abnormal accumulation of familial amyotrophic lateral sclerosis-related mutant SOD1 in transgenic Caenorhabditis elegans. Hum Mol Genet 2001, 10, 2013–2023. [Google Scholar] [CrossRef]
  27. Wang, X.; Su, B.; Lee, H.G.; Li, X.; Perry, G.; Smith, M.A.; Zhu, X. Impaired balance of mitochondrial fission and fusion in Alzheimer’s disease. J Neurosci 2009, 29, 9090–9103. [Google Scholar] [CrossRef] [PubMed]
  28. Witan, H.; Kern, A.; Koziollek-Drechsler, I.; Wade, R.; Behl, C.; Clement, A.M. Heterodimer formation of wild-type and amyotrophic lateral sclerosis-causing mutant Cu/Zn-superoxide dismutase induces toxicity independent of protein aggregation. Hum Mol Genet 2008, 17, 1373–1385. [Google Scholar] [CrossRef] [PubMed]
  29. Gidalevitz, T.; Krupinski, T.; Garcia, S.; Morimoto, R.I. Destabilizing protein polymorphisms in the genetic background direct phenotypic expression of mutant SOD1 toxicity. PLoS Genet 2009, 5, e1000399. [Google Scholar] [CrossRef]
  30. Yao, X.L.; Ye, C.H.; Liu, Q.; Wan, J.B.; Zhen, J.; Xiang, A.P.; Li, W.Q.; Wang, Y.; Su, H.; Lu, X.L. Motoneuron differentiation of induced pluripotent stem cells from SOD1G93A mice. PLoS One 2013, 8, e64720. [Google Scholar] [CrossRef]
  31. Murakami, A.; Kojima, K.; Ohya, K.; Imamura, K.; Takasaki, Y. A new conformational epitope generated by the binding of recombinant 70-kd protein and U1 RNA to anti-U1 RNP autoantibodies in sera from patients with mixed connective tissue disease. Arthritis Rheum 2002, 46, 3273–3282. [Google Scholar] [CrossRef]
  32. Vaccaro, A.; Patten, S.A.; Ciura, S.; Maios, C.; Therrien, M.; Drapeau, P.; Kabashi, E.; Parker, J.A. Methylene blue protects against TDP-43 and FUS neuronal toxicity in C. elegans and D. rerio. PLoS One 2012, 7, e42117. [Google Scholar] [CrossRef]
  33. Zhang, T.; Mullane, P.C.; Periz, G.; Wang, J. TDP-43 neurotoxicity and protein aggregation modulated by heat shock factor and insulin/IGF-1 signaling. Hum Mol Genet 2011, 20, 1952–1965. [Google Scholar] [CrossRef]
  34. Corcia, P.; Lunetta, C.; Vourc’h, P.; Pradat, P.F.; Blasco, H. Time for optimism in amyotrophic lateral sclerosis. Eur J Neurol 2023, 30, 1459–1464. [Google Scholar] [CrossRef]
  35. Levefaudes, M.; Patin, D.; de Sousa-d’Auria, C.; Chami, M.; Blanot, D.; Herve, M.; Arthur, M.; Houssin, C.; Mengin-Lecreulx, D. Diaminopimelic Acid Amidation in Corynebacteriales: NEW INSIGHTS INTO THE ROLE OF LtsA IN PEPTIDOGLYCAN MODIFICATION. J Biol Chem 2015, 290, 13079–13094. [Google Scholar] [CrossRef]
  36. Saccon, R.A.; Bunton-Stasyshyn, R.K.; Fisher, E.M.; Fratta, P. Is SOD1 loss of function involved in amyotrophic lateral sclerosis? Brain 2013, 136, 2342–2358. [Google Scholar] [CrossRef]
  37. Neumann, M.; Sampathu, D.M.; Kwong, L.K.; Truax, A.C.; Micsenyi, M.C.; Chou, T.T.; Bruce, J.; Schuck, T.; Grossman, M.; Clark, C.M.; et al. Ubiquitinated TDP-43 in frontotemporal lobar degeneration and amyotrophic lateral sclerosis. Science 2006, 314, 130–133. [Google Scholar] [CrossRef]
  38. Ratti, A.; Buratti, E. Physiological functions and pathobiology of TDP-43 and FUS/TLS proteins. J Neurochem 2016, 138 Suppl 1, 95–111. [Google Scholar] [CrossRef]
  39. Corcia, P.; Valdmanis, P.; Millecamps, S.; Lionnet, C.; Blasco, H.; Mouzat, K.; Daoud, H.; Belzil, V.; Morales, R.; Pageot, N.; et al. Phenotype and genotype analysis in amyotrophic lateral sclerosis with TARDBP gene mutations. Neurology 2012, 78, 1519–1526. [Google Scholar] [CrossRef]
  40. Wang, X.; Schwartz, J.C.; Cech, T.R. Nucleic acid-binding specificity of human FUS protein. Nucleic Acids Res 2015, 43, 7535–7543. [Google Scholar] [CrossRef]
  41. Ling, S.C.; Dastidar, S.G.; Tokunaga, S.; Ho, W.Y.; Lim, K.; Ilieva, H.; Parone, P.A.; Tyan, S.H.; Tse, T.M.; Chang, J.C.; et al. Overriding FUS autoregulation in mice triggers gain-of-toxic dysfunctions in RNA metabolism and autophagy-lysosome axis. Elife 2019, 8. [Google Scholar] [CrossRef]
  42. Yang, L.; Gal, J.; Chen, J.; Zhu, H. Self-assembled FUS binds active chromatin and regulates gene transcription. Proc Natl Acad Sci U S A 2014, 111, 17809–17814. [Google Scholar] [CrossRef]
  43. Schwartz, J.C.; Ebmeier, C.C.; Podell, E.R.; Heimiller, J.; Taatjes, D.J.; Cech, T.R. FUS binds the CTD of RNA polymerase II and regulates its phosphorylation at Ser2. Genes Dev 2012, 26, 2690–2695. [Google Scholar] [CrossRef]
  44. Smeyers, J.; Banchi, E.G.; Latouche, M. C9ORF72: What It Is, What It Does, and Why It Matters. Front Cell Neurosci 2021, 15, 661447. [Google Scholar] [CrossRef]
  45. Cleary, J.D.; Ranum, L.P. New developments in RAN translation: insights from multiple diseases. Curr Opin Genet Dev 2017, 44, 125–134. [Google Scholar] [CrossRef]
  46. Sundaramoorthy, V.; Walker, A.K.; Tan, V.; Fifita, J.A.; McCann, E.P.; Williams, K.L.; Blair, I.P.; Guillemin, G.J.; Farg, M.A.; Atkin, J.D. Defects in optineurin- and myosin VI-mediated cellular trafficking in amyotrophic lateral sclerosis. Hum Mol Genet 2015, 24, 3830–3846. [Google Scholar] [CrossRef]
  47. Akizuki, M.; Yamashita, H.; Uemura, K.; Maruyama, H.; Kawakami, H.; Ito, H.; Takahashi, R. Optineurin suppression causes neuronal cell death via NF-kappaB pathway. J Neurochem 2013, 126, 699–704. [Google Scholar] [CrossRef]
  48. Ryan, T.A.; Tumbarello, D.A. Optineurin: A Coordinator of Membrane-Associated Cargo Trafficking and Autophagy. Front Immunol 2018, 9, 1024. [Google Scholar] [CrossRef]
  49. Tak, Y.J.; Park, J.H.; Rhim, H.; Kang, S. ALS-Related Mutant SOD1 Aggregates Interfere with Mitophagy by Sequestering the Autophagy Receptor Optineurin. Int J Mol Sci 2020, 21. [Google Scholar] [CrossRef]
  50. Maruyama, H.; Morino, H.; Ito, H.; Izumi, Y.; Kato, H.; Watanabe, Y.; Kinoshita, Y.; Kamada, M.; Nodera, H.; Suzuki, H.; et al. Mutations of optineurin in amyotrophic lateral sclerosis. Nature 2010, 465, 223–226. [Google Scholar] [CrossRef]
  51. Wang, J.; Farr, G.W.; Hall, D.H.; Li, F.; Furtak, K.; Dreier, L.; Horwich, A.L. An ALS-linked mutant SOD1 produces a locomotor defect associated with aggregation and synaptic dysfunction when expressed in neurons of Caenorhabditis elegans. PLoS Genet 2009, 5, e1000350. [Google Scholar] [CrossRef]
  52. Yanase, S.; Onodera, A.; Tedesco, P.; Johnson, T.E.; Ishii, N. SOD-1 deletions in Caenorhabditis elegans alter the localization of intracellular reactive oxygen species and show molecular compensation. J Gerontol A Biol Sci Med Sci 2009, 64, 530–539. [Google Scholar] [CrossRef] [PubMed]
  53. Ash, P.E.; Zhang, Y.J.; Roberts, C.M.; Saldi, T.; Hutter, H.; Buratti, E.; Petrucelli, L.; Link, C.D. Neurotoxic effects of TDP-43 overexpression in C. elegans. Hum Mol Genet 2010, 19, 3206–3218. [Google Scholar] [CrossRef] [PubMed]
  54. Liachko, N.F.; Guthrie, C.R.; Kraemer, B.C. Phosphorylation promotes neurotoxicity in a Caenorhabditis elegans model of TDP-43 proteinopathy. J Neurosci 2010, 30, 16208–16219. [Google Scholar] [CrossRef] [PubMed]
  55. Murakami, T.; Yang, S.P.; Xie, L.; Kawano, T.; Fu, D.; Mukai, A.; Bohm, C.; Chen, F.; Robertson, J.; Suzuki, H.; et al. ALS mutations in FUS cause neuronal dysfunction and death in Caenorhabditis elegans by a dominant gain-of-function mechanism. Hum Mol Genet 2012, 21, 1–9. [Google Scholar] [CrossRef] [PubMed]
  56. Labarre, A.; Tossing, G.; Maios, C.; Doyle, J.J.; Parker, J.A. A single copy transgenic mutant FUS strain reproduces age-dependent ALS phenotypes in C. elegans. MicroPubl Biol 2021, 2021. [Google Scholar] [CrossRef]
  57. Ikenaka, K.; Kawai, K.; Katsuno, M.; Huang, Z.; Jiang, Y.M.; Iguchi, Y.; Kobayashi, K.; Kimata, T.; Waza, M.; Tanaka, F.; et al. dnc-1/dynactin 1 knockdown disrupts transport of autophagosomes and induces motor neuron degeneration. PLoS One 2013, 8, e54511. [Google Scholar] [CrossRef] [PubMed]
  58. Ikenaka, K.; Tsukada, Y.; Giles, A.C.; Arai, T.; Nakadera, Y.; Nakano, S.; Kawai, K.; Mochizuki, H.; Katsuno, M.; Sobue, G.; et al. A behavior-based drug screening system using a Caenorhabditis elegans model of motor neuron disease. Sci Rep 2019, 9, 10104. [Google Scholar] [CrossRef] [PubMed]
  59. Corrionero, A.; Horvitz, H.R. A C9orf72 ALS/FTD Ortholog Acts in Endolysosomal Degradation and Lysosomal Homeostasis. Curr Biol 2018, 28, 1522–1535 e1525. [Google Scholar] [CrossRef]
  60. Wang, X.; Hao, L.; Saur, T.; Joyal, K.; Zhao, Y.; Zhai, D.; Li, J.; Pribadi, M.; Coppola, G.; Cohen, B.M.; et al. Forward Genetic Screen in Caenorhabditis elegans Suggests F57A10.2 and acp-4 As Suppressors of C9ORF72 Related Phenotypes. Front Mol Neurosci 2016, 9, 113. [Google Scholar] [CrossRef]
  61. DeJesus-Hernandez, M.; Mackenzie, I.R.; Boeve, B.F.; Boxer, A.L.; Baker, M.; Rutherford, N.J.; Nicholson, A.M.; Finch, N.A.; Flynn, H.; Adamson, J.; et al. Expanded GGGGCC hexanucleotide repeat in noncoding region of C9ORF72 causes chromosome 9p-linked FTD and ALS. Neuron 2011, 72, 245–256. [Google Scholar] [CrossRef]
  62. Kumar Ghosh, D.; Nanaji Shrikondawar, A.; Ranjan, A. Local structural unfolding at the edge-strands of beta sheets is the molecular basis for instability and aggregation of G85R and G93A mutants of superoxide dismutase 1. J Biomol Struct Dyn 2020, 38, 647–659. [Google Scholar] [CrossRef]
  63. Zhang, T.; Hwang, H.Y.; Hao, H.; Talbot, C., Jr.; Wang, J. Caenorhabditis elegans RNA-processing protein TDP-1 regulates protein homeostasis and life span. J Biol Chem 2012, 287, 8371–8382. [Google Scholar] [CrossRef] [PubMed]
  64. Bunton-Stasyshyn, R.K.; Saccon, R.A.; Fratta, P.; Fisher, E.M. SOD1 Function and Its Implications for Amyotrophic Lateral Sclerosis Pathology: New and Renascent Themes. Neuroscientist 2015, 21, 519–529. [Google Scholar] [CrossRef] [PubMed]
  65. Liu, E.Y.; Cali, C.P.; Lee, E.B. RNA metabolism in neurodegenerative disease. Dis Model Mech 2017, 10, 509–518. [Google Scholar] [CrossRef] [PubMed]
  66. Van Damme, P.; Robberecht, W.; Van Den Bosch, L. Modelling amyotrophic lateral sclerosis: progress and possibilities. Dis Model Mech 2017, 10, 537–549. [Google Scholar] [CrossRef]
  67. Arai, T.; Hasegawa, M.; Akiyama, H.; Ikeda, K.; Nonaka, T.; Mori, H.; Mann, D.; Tsuchiya, K.; Yoshida, M.; Hashizume, Y.; et al. TDP-43 is a component of ubiquitin-positive tau-negative inclusions in frontotemporal lobar degeneration and amyotrophic lateral sclerosis. Biochem Biophys Res Commun 2006, 351, 602–611. [Google Scholar] [CrossRef] [PubMed]
  68. Zhang, T.; Wu, Y.C.; Mullane, P.; Ji, Y.J.; Liu, H.; He, L.; Arora, A.; Hwang, H.Y.; Alessi, A.F.; Niaki, A.G.; et al. FUS Regulates Activity of MicroRNA-Mediated Gene Silencing. Mol Cell 2018, 69, 787–801 e788. [Google Scholar] [CrossRef] [PubMed]
  69. Freischmidt, A.; Muller, K.; Ludolph, A.C.; Weishaupt, J.H.; Andersen, P.M. Association of Mutations in TBK1 With Sporadic and Familial Amyotrophic Lateral Sclerosis and Frontotemporal Dementia. JAMA Neurol 2017, 74, 110–113. [Google Scholar] [CrossRef]
  70. Rhinn, H.; Tatton, N.; McCaughey, S.; Kurnellas, M.; Rosenthal, A. Progranulin as a therapeutic target in neurodegenerative diseases. Trends Pharmacol Sci 2022, 43, 641–652. [Google Scholar] [CrossRef]
  71. Vaccaro, A.; Tauffenberger, A.; Aggad, D.; Rouleau, G.; Drapeau, P.; Parker, J.A. Mutant TDP-43 and FUS cause age-dependent paralysis and neurodegeneration in C. elegans. PLoS One 2012, 7, e31321. [Google Scholar] [CrossRef]
  72. Forsberg, K.; Jonsson, P.A.; Andersen, P.M.; Bergemalm, D.; Graffmo, K.S.; Hultdin, M.; Jacobsson, J.; Rosquist, R.; Marklund, S.L.; Brannstrom, T. Novel antibodies reveal inclusions containing non-native SOD1 in sporadic ALS patients. PLoS One 2010, 5, e11552. [Google Scholar] [CrossRef]
  73. Butler, V.J.; Gao, F.; Corrales, C.I.; Cortopassi, W.A.; Caballero, B.; Vohra, M.; Ashrafi, K.; Cuervo, A.M.; Jacobson, M.P.; Coppola, G.; et al. Age- and stress-associated C. elegans granulins impair lysosomal function and induce a compensatory HLH-30/TFEB transcriptional response. PLoS Genet 2019, 15, e1008295. [Google Scholar] [CrossRef]
  74. Lagier-Tourenne, C.; Polymenidou, M.; Hutt, K.R.; Vu, A.Q.; Baughn, M.; Huelga, S.C.; Clutario, K.M.; Ling, S.C.; Liang, T.Y.; Mazur, C.; et al. Divergent roles of ALS-linked proteins FUS/TLS and TDP-43 intersect in processing long pre-mRNAs. Nat Neurosci 2012, 15, 1488–1497. [Google Scholar] [CrossRef]
  75. Tan, A.Y.; Manley, J.L. TLS inhibits RNA polymerase III transcription. Mol Cell Biol 2010, 30, 186–196. [Google Scholar] [CrossRef]
  76. Zondler, L.; Muller, K.; Khalaji, S.; Bliederhauser, C.; Ruf, W.P.; Grozdanov, V.; Thiemann, M.; Fundel-Clemes, K.; Freischmidt, A.; Holzmann, K.; et al. Peripheral monocytes are functionally altered and invade the CNS in ALS patients. Acta Neuropathol 2016, 132, 391–411. [Google Scholar] [CrossRef]
  77. Higelin, J.; Catanese, A.; Semelink-Sedlacek, L.L.; Oeztuerk, S.; Lutz, A.K.; Bausinger, J.; Barbi, G.; Speit, G.; Andersen, P.M.; Ludolph, A.C.; et al. NEK1 loss-of-function mutation induces DNA damage accumulation in ALS patient-derived motoneurons. Stem Cell Res 2018, 30, 150–162. [Google Scholar] [CrossRef]
  78. Pelegrini, A.L.; Moura, D.J.; Brenner, B.L.; Ledur, P.F.; Maques, G.P.; Henriques, J.A.; Saffi, J.; Lenz, G. Nek1 silencing slows down DNA repair and blocks DNA damage-induced cell cycle arrest. Mutagenesis 2010, 25, 447–454. [Google Scholar] [CrossRef]
  79. Ravits, J.; Appel, S.; Baloh, R.H.; Barohn, R.; Brooks, B.R.; Elman, L.; Floeter, M.K.; Henderson, C.; Lomen-Hoerth, C.; Macklis, J.D.; et al. Deciphering amyotrophic lateral sclerosis: what phenotype, neuropathology and genetics are telling us about pathogenesis. Amyotroph Lateral Scler Frontotemporal Degener 2013, 14 Suppl 1, 5–18. [Google Scholar] [CrossRef]
  80. Veriepe, J.; Fossouo, L.; Parker, J.A. Neurodegeneration in C. elegans models of ALS requires TIR-1/Sarm1 immune pathway activation in neurons. Nat Commun 2015, 6, 7319. [Google Scholar] [CrossRef] [PubMed]
  81. Beers, D.R.; Appel, S.H. Immune dysregulation in amyotrophic lateral sclerosis: mechanisms and emerging therapies. Lancet Neurol 2019, 18, 211–220. [Google Scholar] [CrossRef] [PubMed]
  82. Heneka, M.T.; Kummer, M.P.; Latz, E. Innate immune activation in neurodegenerative disease. Nat Rev Immunol 2014, 14, 463–477. [Google Scholar] [CrossRef]
  83. Pujol, N.; Zugasti, O.; Wong, D.; Couillault, C.; Kurz, C.L.; Schulenburg, H.; Ewbank, J.J. Anti-fungal innate immunity in C. elegans is enhanced by evolutionary diversification of antimicrobial peptides. PLoS Pathog 2008, 4, e1000105. [Google Scholar] [CrossRef]
  84. Couillault, C.; Pujol, N.; Reboul, J.; Sabatier, L.; Guichou, J.F.; Kohara, Y.; Ewbank, J.J. TLR-independent control of innate immunity in Caenorhabditis elegans by the TIR domain adaptor protein TIR-1, an ortholog of human SARM. Nat Immunol 2004, 5, 488–494. [Google Scholar] [CrossRef]
  85. Ravikumar, B.; Acevedo-Arozena, A.; Imarisio, S.; Berger, Z.; Vacher, C.; O’Kane, C.J.; Brown, S.D.; Rubinsztein, D.C. Dynein mutations impair autophagic clearance of aggregate-prone proteins. Nat Genet 2005, 37, 771–776. [Google Scholar] [CrossRef]
  86. Komatsu, M.; Wang, Q.J.; Holstein, G.R.; Friedrich, V.L., Jr.; Iwata, J.; Kominami, E.; Chait, B.T.; Tanaka, K.; Yue, Z. Essential role for autophagy protein Atg7 in the maintenance of axonal homeostasis and the prevention of axonal degeneration. Proc Natl Acad Sci U S A 2007, 104, 14489–14494. [Google Scholar] [CrossRef]
  87. Sasaki, S. Autophagy in spinal cord motor neurons in sporadic amyotrophic lateral sclerosis. J Neuropathol Exp Neurol 2011, 70, 349–359. [Google Scholar] [CrossRef]
  88. Li, L.; Zhang, X.; Le, W. Altered macroautophagy in the spinal cord of SOD1 mutant mice. Autophagy 2008, 4, 290–293. [Google Scholar] [CrossRef]
  89. Fecto, F.; Yan, J.; Vemula, S.P.; Liu, E.; Yang, Y.; Chen, W.; Zheng, J.G.; Shi, Y.; Siddique, N.; Arrat, H.; et al. SQSTM1 mutations in familial and sporadic amyotrophic lateral sclerosis. Arch Neurol 2011, 68, 1440–1446. [Google Scholar] [CrossRef]
  90. Deng, H.X.; Chen, W.; Hong, S.T.; Boycott, K.M.; Gorrie, G.H.; Siddique, N.; Yang, Y.; Fecto, F.; Shi, Y.; Zhai, H.; et al. Mutations in UBQLN2 cause dominant X-linked juvenile and adult-onset ALS and ALS/dementia. Nature 2011, 477, 211–215. [Google Scholar] [CrossRef]
  91. Buchan, J.R.; Kolaitis, R.M.; Taylor, J.P.; Parker, R. Eukaryotic stress granules are cleared by autophagy and Cdc48/VCP function. Cell 2013, 153, 1461–1474. [Google Scholar] [CrossRef]
  92. Wong, Y.C.; Holzbaur, E.L. Optineurin is an autophagy receptor for damaged mitochondria in parkin-mediated mitophagy that is disrupted by an ALS-linked mutation. Proc Natl Acad Sci U S A 2014, 111, E4439–4448. [Google Scholar] [CrossRef] [PubMed]
  93. Freischmidt, A.; Wieland, T.; Richter, B.; Ruf, W.; Schaeffer, V.; Muller, K.; Marroquin, N.; Nordin, F.; Hubers, A.; Weydt, P.; et al. Haploinsufficiency of TBK1 causes familial ALS and fronto-temporal dementia. Nat Neurosci 2015, 18, 631–636. [Google Scholar] [CrossRef]
  94. Blokhuis, A.M.; Groen, E.J.; Koppers, M.; van den Berg, L.H.; Pasterkamp, R.J. Protein aggregation in amyotrophic lateral sclerosis. Acta Neuropathol 2013, 125, 777–794. [Google Scholar] [CrossRef] [PubMed]
  95. Soo, K.Y.; Sultana, J.; King, A.E.; Atkinson, R.; Warraich, S.T.; Sundaramoorthy, V.; Blair, I.; Farg, M.A.; Atkin, J.D. ALS-associated mutant FUS inhibits macroautophagy which is restored by overexpression of Rab1. Cell Death Discov 2015, 1, 15030. [Google Scholar] [CrossRef] [PubMed]
  96. Gomez-Virgilio, L.; Silva-Lucero, M.D.; Flores-Morelos, D.S.; Gallardo-Nieto, J.; Lopez-Toledo, G.; Abarca-Fernandez, A.M.; Zacapala-Gomez, A.E.; Luna-Munoz, J.; Montiel-Sosa, F.; Soto-Rojas, L.O.; et al. Autophagy: A Key Regulator of Homeostasis and Disease: An Overview of Molecular Mechanisms and Modulators. Cells 2022, 11. [Google Scholar] [CrossRef] [PubMed]
  97. Chua, J.P.; De Calbiac, H.; Kabashi, E.; Barmada, S.J. Autophagy and ALS: mechanistic insights and therapeutic implications. Autophagy 2022, 18, 254–282. [Google Scholar] [CrossRef] [PubMed]
  98. Noormohammadi, A.; Calculli, G.; Gutierrez-Garcia, R.; Khodakarami, A.; Koyuncu, S.; Vilchez, D. Mechanisms of protein homeostasis (proteostasis) maintain stem cell identity in mammalian pluripotent stem cells. Cell Mol Life Sci 2018, 75, 275–290. [Google Scholar] [CrossRef] [PubMed]
  99. Hohn, A.; Tramutola, A.; Cascella, R. Proteostasis Failure in Neurodegenerative Diseases: Focus on Oxidative Stress. Oxid Med Cell Longev 2020, 2020, 5497046. [Google Scholar] [CrossRef] [PubMed]
  100. Halaschek-Wiener, J.; Khattra, J.S.; McKay, S.; Pouzyrev, A.; Stott, J.M.; Yang, G.S.; Holt, R.A.; Jones, S.J.; Marra, M.A.; Brooks-Wilson, A.R.; et al. Analysis of long-lived C. elegans daf-2 mutants using serial analysis of gene expression. Genome Res 2005, 15, 603–615. [Google Scholar] [CrossRef]
  101. Chistyakova, O.V.; Bondareva, V.M.; Shipilov, V.N.; Sukhov, I.B.; Shpakov, A.O. Intranasal administration of insulin eliminates the deficit of long-term spatial memory in rats with neonatal diabetes mellitus. Dokl Biochem Biophys 2011, 440, 216–218. [Google Scholar] [CrossRef]
  102. Boccitto, M.; Lamitina, T.; Kalb, R.G. Daf-2 signaling modifies mutant SOD1 toxicity in C. elegans. PLoS One 2012, 7, e33494. [Google Scholar] [CrossRef] [PubMed]
  103. Wokke, J.H. [Riluzole treatment in amyotrophic lateral sclerosis]. Ned Tijdschr Geneeskd 1996, 140, 2265–2268. [Google Scholar] [PubMed]
  104. Saitoh, Y.; Takahashi, Y. Riluzole for the treatment of amyotrophic lateral sclerosis. Neurodegener Dis Manag 2020, 10, 343–355. [Google Scholar] [CrossRef] [PubMed]
  105. Khalifeh, M.; Barreto, G.E.; Sahebkar, A. Therapeutic potential of trehalose in neurodegenerative diseases: the knowns and unknowns. Neural Regen Res 2021, 16, 2026–2027. [Google Scholar] [CrossRef] [PubMed]
  106. Dong, H.; Xu, L.; Wu, L.; Wang, X.; Duan, W.; Li, H.; Li, C. Curcumin abolishes mutant TDP-43 induced excitability in a motoneuron-like cellular model of ALS. Neuroscience 2014, 272, 141–153. [Google Scholar] [CrossRef] [PubMed]
  107. Dibaj, P.; Zschuntzsch, J.; Steffens, H.; Scheffel, J.; Goricke, B.; Weishaupt, J.H.; Le Meur, K.; Kirchhoff, F.; Hanisch, U.K.; Schomburg, E.D.; et al. Influence of methylene blue on microglia-induced inflammation and motor neuron degeneration in the SOD1(G93A) model for ALS. PLoS One 2012, 7, e43963. [Google Scholar] [CrossRef] [PubMed]
  108. Musteikyte, G.; Ziaunys, M.; Smirnovas, V. Methylene blue inhibits nucleation and elongation of SOD1 amyloid fibrils. PeerJ 2020, 8, e9719. [Google Scholar] [CrossRef]
  109. Mauvezin, C.; Neufeld, T.P. Bafilomycin A1 disrupts autophagic flux by inhibiting both V-ATPase-dependent acidification and Ca-P60A/SERCA-dependent autophagosome-lysosome fusion. Autophagy 2015, 11, 1437–1438. [Google Scholar] [CrossRef]
  110. Rivera, V.M.; Breitbach, W.B.; Swanke, L. Letter: Dantrolene in amyotrophic lateral sclerosis. JAMA 1975, 233, 863–864. [Google Scholar] [CrossRef]
  111. Shi, Y.; Wang, Y.; Wei, H. Dantrolene: From Malignant Hyperthermia to Alzheimer’s Disease. CNS Neurol Disord Drug Targets 2019, 18, 668–676. [Google Scholar] [CrossRef]
  112. Lam, V.; Clarnette, R.; Francis, R.; Bynevelt, M.; Watts, G.; Flicker, L.; Orr, C.F.; Loh, P.; Lautenschlager, N.; Reid, C.M.; et al. Efficacy of probucol on cognitive function in Alzheimer’s disease: study protocol for a double-blind, placebo-controlled, randomised phase II trial (PIA study). BMJ Open 2022, 12, e058826. [Google Scholar] [CrossRef] [PubMed]
  113. Sawda, C.; Moussa, C.; Turner, R.S. Resveratrol for Alzheimer’s disease. Ann N Y Acad Sci 2017, 1403, 142–149. [Google Scholar] [CrossRef] [PubMed]
  114. Ahmed, T.; Javed, S.; Javed, S.; Tariq, A.; Samec, D.; Tejada, S.; Nabavi, S.F.; Braidy, N.; Nabavi, S.M. Resveratrol and Alzheimer’s Disease: Mechanistic Insights. Mol Neurobiol 2017, 54, 2622–2635. [Google Scholar] [CrossRef] [PubMed]
  115. Rizvanov, A.A.; Gulluoglu, S.; Yalvac, M.E.; Palotas, A.; Islamov, R.R. RNA interference and amyotrophic lateral sclerosis. Curr Drug Metab 2011, 12, 679–683. [Google Scholar] [CrossRef] [PubMed]
  116. Xia, X.G.; Zhou, H.; Zhou, S.; Yu, Y.; Wu, R.; Xu, Z. An RNAi strategy for treatment of amyotrophic lateral sclerosis caused by mutant Cu,Zn superoxide dismutase. J Neurochem 2005, 92, 362–367. [Google Scholar] [CrossRef] [PubMed]
  117. Wang, H.; Yang, B.; Qiu, L.; Yang, C.; Kramer, J.; Su, Q.; Guo, Y.; Brown, R.H., Jr.; Gao, G.; Xu, Z. Widespread spinal cord transduction by intrathecal injection of rAAV delivers efficacious RNAi therapy for amyotrophic lateral sclerosis. Hum Mol Genet 2014, 23, 668–681. [Google Scholar] [CrossRef]
  118. Fang, T.; Je, G.; Pacut, P.; Keyhanian, K.; Gao, J.; Ghasemi, M. Gene Therapy in Amyotrophic Lateral Sclerosis. Cells 2022, 11. [Google Scholar] [CrossRef] [PubMed]
  119. Amado, D.A.; Davidson, B.L. Gene therapy for ALS: A review. Mol Ther 2021, 29, 3345–3358. [Google Scholar] [CrossRef] [PubMed]
  120. Eisen, A. Amyotrophic lateral sclerosis is a multifactorial disease. Muscle Nerve 1995, 18, 741–752. [Google Scholar] [CrossRef]
  121. Mejzini, R.; Flynn, L.L.; Pitout, I.L.; Fletcher, S.; Wilton, S.D.; Akkari, P.A. ALS Genetics, Mechanisms, and Therapeutics: Where Are We Now? Front Neurosci 2019, 13, 1310. [Google Scholar] [CrossRef]
  122. Cook, S.J.; Jarrell, T.A.; Brittin, C.A.; Wang, Y.; Bloniarz, A.E.; Yakovlev, M.A.; Nguyen, K.C.Q.; Tang, L.T.; Bayer, E.A.; Duerr, J.S.; et al. Whole-animal connectomes of both Caenorhabditis elegans sexes. Nature 2019, 571, 63–71. [Google Scholar] [CrossRef] [PubMed]
  123. Kim, H.; Ishidate, T.; Ghanta, K.S.; Seth, M.; Conte, D., Jr.; Shirayama, M.; Mello, C.C. A co-CRISPR strategy for efficient genome editing in Caenorhabditis elegans. Genetics 2014, 197, 1069–1080. [Google Scholar] [CrossRef] [PubMed]
  124. Wang, H.; Park, H.; Liu, J.; Sternberg, P.W. An Efficient Genome Editing Strategy To Generate Putative Null Mutants in Caenorhabditis elegans Using CRISPR/Cas9. G3 (Bethesda) 2018, 8, 3607–3616. [Google Scholar] [CrossRef] [PubMed]
Table 1. A list of published C. elegans models of ALS.
Table 1. A list of published C. elegans models of ALS.
Model Strain/Transgene name/Plasmid Expression in C. elegans Phenotypes
Pro-aggregant lines: Is[Prab-3::F3ΔK280 + Pmyo-2::mCherry] BR5270, 5485, 5706, 5944 Constitutive pan neuronal Severe locomotive impairment of adulthood at day 1; accelerating aggregate formation; severe developmental deficiency in nervous system; injury in presynaptic transmission [25]
Anti-aggregant lines: Is[Prab-3::F3ΔK280(I277P)(I308P) + Pmyo-2::mCherry] BR5271, 5486, 6427, 6516 Constitutive pan-neuronal No overt locomotive impairment; minimum influence on neurodevelopment [25]
Is[Phsp-16.2::sod-1 (WT, A4V, G37R,G93A) + Pmyo-3::sod-1(WT, A4V)::gfp + rol-6(su1006)] n.a. Heat-shock inducible muscles Oxidative stress-induced aggregate formation [26]
iwIs8[Psnb-1::sod-1(WT, G85R)::yfp] n.a. Constitutive pan-neuronal Severe motor dysfunction accompanied by both soluble oligomers and insoluble aggregate deposits [27]
Is[Psng-1::sod-1(WT, A4V, G37R, G93C)::gfp] n.a. Constitutive pan-neuronal Compared to heterodimers, mutant homodimers demonstrate increased aggregate formation but G85R heterodimers are more toxic in functional assays [28]
Is[Punc-54::sod-1(WT, G85R, G93A,G127insTGGGstop)::yfp] AM263, 265 Constitutive muscle SOD-1 mutants demonstrate morphologically heterogenous aggregates with variety biophysical properties and mild motility defects [29]
ngIs36[Punc-25::sod-1(G93A)::gfp] n.a. GABAergic motor neurons G93A SOD-1 animals demonstrate progressive motor dysfunction, aggregate formation, and axonal guidance defects [30]
lin-15(n765ts); [Prgef-1::FUS (WT, R514G, R521G, R522G, R524S, P525L) + Ppab-1:: mCherry; lin-15(+)] PJH897 Constitutive pan-neuronal Form of cytoplasmic FUS aggregates: R522G, P525L, FUS513 and FUS501 demonstrate a significantly shorter lifespan; P525L, FUS513 and FUS501 demonstrate a partially or completely paralyses, severely shrunken by 8 days of age [31]
unc-119(ed3); Is[Punc-47::TDP-43-(WT, A315T) + unc-119(+)]
unc-119(ed3); Is[Punc-47::FUS-(WT, S57Δ) + unc-119(+)]		 xqIs132, xqIs133,
xqIs173, xqIs98 		GABAergic motor neurons Having normal lifespan, but displayed adult-onset, age-dependent damage of motility, progressive paralysis, neuronal degeneration, accumulation of highly insoluble TDP-43 and FUS proteins [32]
iwIs26 [Psnb-1::TDP-43-YFP WT],
iwIs22[Psnb-1::TDP-C25-YFP],
iwEx20[Psnb-1::TDP-43-YFP Q331 K],
iwEx28[Psnb-1::TDP-43-YFP M337 V)], iwIs27[Psnb-1::SOD1-YFP WT],
iwIs8[Psnb-1::SOD1-YFP G85R]		 IW63, IW33, IW20, IW46, IW31, IW8 Constitutive pan-neuronal Transgenic models developed robust locomotion defects and protein aggregation [33]
Table 2. ALS pathogenic mechanisms.
Table 2. ALS pathogenic mechanisms.
Pathogenic Molecule Normal Functions Pathogenic Mechanism C. elegans Model Phonotype
C9orf72-SMCR8 complex subunit (C9orf72) [66] Guanine nucleotide exchange factor (GEF) activity and regulating autophagy [45] A hexanucleotide repeat (GGGGCC) within the first intron of C9orf72 undergoes expansion with AUG independent producing five separate dipeptide-containing proteins [19] alfa-1 Motor neuron degeneration and a motility defect [59]
Superoxide dismutase (SOD1) [66] A cytosolic enzyme, catalyzes the detoxification of superoxide [64] Mutant alleles of SOD1 generating toxic increase of function in motor neurons; misfold and then eventually aggregate in motor neurons until in vitro; ER stress [62] a: Pan-neuronal expression of human G85R SOD1;
b: Motor neuron overexpression of a human G93A SOD1 [51]		 a: Locomotor deficiency, growth of aggregates and axonal abnormalities;
b: Age-dependent paralysis result in the consequence of axonal guidance defects [23]
Transactive response (TAR) DNA-binding protein 43 (TDP-43) [67] Participate in various steps of RNA metabolism, including mRNA splicing, RNA transport, translation, and microRNA biogenesis [65] a: Deficiency of normal function in the nucleus;
b: A toxic GOF by form of cytoplasmic aggregates [63]		 a: Pan-neuronal expression of humanTDP-43;
b: C. elegans homologous gene, TDP-1 [53]		 a: Within the GABAergic neurons, occur to slowed and uncoordinated movement, as well as defasciculation of the motor neurons; b: Deficiency of tdp-1 result in lower fertility, slower growth, and a locomotor deficit [55]
Progranulin (PGRN) Participate in a diversity of physiologic and pathological processes, consist of cell proliferation, wound healing, and modulation of inflammation Decreasing PGRN levels result in the hexanucleotide repeat expansion in the C9orf72 gene Stress and aging produces PGRN impairing the expression and activity of lysosomal proteases [73] PGRN deficiency resulted in abnormal expression of multiple lysosomal, immune-related, and lipid metabolic genes lysosomal dysfunction, defects in autophagy, and neuroinflammation [70]
RNA-binding protein FUS/TLS (FUS) DNA repair and several aspects of RNA metabolism involving in transcription alternative splicing mRNA transport, mRNA stability, and microRNA biogenesis [75] Disturb the nuclear localization signal resulting in mis-localization of FUS to the cytoplasm with protein aggregates [74] a: Expressing a FUS variant prone to aggregate in GABAergic neurons by the unc-47 promoter;
b: Expressing panneuronlly in FUS mutants under control of the rgef-1 promoter;
c: C. elegans homologous gene, fust-1 [55,71]		 a: Neurodegeneration, synaptic dysfunction, paralysis and aggregation;
b: Motor dysfunction;
c: Achieve maximum microRNA (miRNA)-mediated gene silencing [68]
TANK-binding kinase 1 (TBK1)/optineurin gene (OPTN) TBK1conducts to inflammatory pathways via conducting downstream of proteins that sense bacterial lipopolysaccharides and viral RNA/DNA; OPTN involves in ubiquitinated proteins and produces its role as an autophagy adaptor [76] Malfunctions of the autophagic pathway a: Loss of function Variants;
b: In-Frame Deletions of Single Amino Acids;
c: Missense Variants [69]		 Neuronal protein aggregates results in malfunctions of the autophagic pathway [72]
NIMA-related serine/threonine kinase protein family (NEK), NEK1 [67] Controlling cell cycle, DNA damage repair, and ciliogenesis
splicing, RNA transport, translation, and microRNA biogenesis [65,78]		 Increasing DNA damage and a compromised DNA damage response [77] Acting on DDR signaling downstream of ATM/ATR [78] DNA damage response and repair as well as mitochondrial function [77]
Table 3. Advances in Therapeutic Strategies.
Table 3. Advances in Therapeutic Strategies.
Therapeutic Strategies Functions Mechanisms of Treatment
Small molecules Riluzole [103,104] Decreasing glutamate release for neuroprotective Decreasing glutamate release for neuroprotective
Trehalose [105] Autophagy-enhancing properties contributing to clear protein aggregates in ALS Improving motor function and increasing the lifespan of C. elegans models of ALS
Curcumin [106] Decreasing oxidative stress and slowing disease progression Prospective neuroprotective effects
Methylene blue [107,108] An aggregation inhibitor of the phenothiazine class Protects against oxidative stress
Bafilomycin [109] Blocking autophagosome-lysosome fusion and inhibiting acidification and protein degradation in cell lysosomes to produce the effect of inducing apoptosis Decreasing neurodegeneration via inhibiting autophagic vesicle maturation
Dantrolene [110,111] A muscle relaxant for noncompetitively inhibiting human erythrocyte glutathione reductase Decreasing neurodegeneration by inhibition of intracellular calcium free in the ER
Probucol [112] Regulating blood lipid and anti-lipid peroxidation Attenuating neurodegeneration by its antioxidant properties
Resveratrol [113,114] Antioxidant and anti-inflammatory properties Mitigating ALS-like symptoms via activating cellular protective mechanisms
RNA-based therapies RNAi (RNA Interference) [115,116,117,118] A gene therapy for ALS and FTD because of reduction in toxicity induced by the repeat-containing C9orf72 transcripts Aiming and knocking down genes associated with ALS-related proteins by RNAi
Antisense Oligonucleotides (ASOs) [118,119] Reducing, restoring, or modifying RNA and protein expression Modulating the expression of ALS-associated genes and potentially reducing toxic protein production
Genetic modifiers Cell division cycle kinase 7 (CDC7) Decreasing the transactive response DNA binding protein of 43 KDa (TDP-43) phosphorylation in vitro and vivo Decreasing phosphorylation of TDP-43 and the consequent neurodegeneration
UNC-13A [80] Regulates the release of neurotransmitters UNC-13 is required for induction of the degeneration of motor neurons
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.
Copyright: This open access article is published under a Creative Commons CC BY 4.0 license, which permit the free download, distribution, and reuse, provided that the author and preprint are cited in any reuse.
Prerpints.org logo

Preprints.org is a free preprint server supported by MDPI in Basel, Switzerland.

facebook logotwitter logolinkedin logo
MDPI Initiatives
Important Links
Subscribe

Disclaimer

Terms of Use

Privacy Policy

© 2024 MDPI (Basel, Switzerland) unless otherwise stated