Assay in fly eye contributes to study related to ALS & FTD

J Biol Chem. 2022 Aug;298(8):102191. doi: 10.1016/j.jbc.2022.102191. 

Casein kinase 1δ/ε phosphorylates fused in sarcoma (FUS) and ameliorates FUS-mediated neurodegeneration

Kishino Y, Matsukawa K, Matsumoto T, Miyazaki R, Wakabayashi T, Nonaka T, Kametani F, Hasegawa M, Hashimoto T, Iwatsubo T

From the abstract:

Aberrant cytoplasmic accumulation of an RNA-binding protein, fused in sarcoma (FUS), characterizes the neuropathology of subtypes of ALS and frontotemporal lobar degeneration ... we show that casein kinase 1δ (CK1δ) phosphorylates FUS at 10 serine/threonine residues in vitro ... We also show that phosphorylation by CK1δ or CK1ε significantly increased the solubility of FUS in human embryonic kidney 293 cells. In transgenic Drosophila that overexpress wt or P525L ALS-mutant human FUS in the retina or in neurons, we found coexpression of human CK1δ or its Drosophila isologue Dco in the photoreceptor neurons significantly ameliorated the observed retinal degeneration, and neuronal coexpression of human CK1δ extended fly life span. .. our data suggest a novel regulatory mechanism of the assembly and toxicity of FUS through CK1δ/CK1ε-mediated phosphorylation, which could represent a potential therapeutic target in FUS proteinopathies.

DOI: 10.1016/j.jbc.2022.102191
PMCID: PMC9293781
PMID: 35753345

New fly models with relevance to Multisystem Proteinopathy, ALS, and other valosin containig protein (VCP)-related diseases

"The power of a genetically tractable model organism coupled with well-established in vivo assays and a relatively short life cycle make Drosophila an attractive system to study VCP disease pathogenesis and novel treatment strategies."

Dis Model Mech. 2021 Jun 23:dmm.048603. doi: 10.1242/dmm.048603.

CRISPR/Cas9-engineered Drosophila knock-in models to study VCP diseases.

Wall JM, Basu A, Zunica ERM, Dubuisson OS, Pergola K, Broussard JP, Kirwan JP, Axelrod CL, Johnson AE

Abstract

"Valosin containing protein (VCP) is a hexameric type II AAA ATPase required for several cellular processes including ER-associated degradation, organelle biogenesis, autophagy and membrane fusion. VCP contains three domains: a regulatory N-terminal domain and two ATPase domains (D1 and D2). Mutations in the N-terminal and D1 domains are associated with several degenerative diseases, including Multisystem Proteinopathy (MSP-1) and ALS. However, patients with VCP mutations vary widely in their pathology and clinical penetrance, making it difficult to devise effective treatment strategies. Having a deeper understanding of how each mutation affects VCP function could enhance the prediction of clinical outcomes and design of personalized treatment options. Over-expressing VCP patient mutations in Drosophila has been shown to mimic many pathologies observed in human patients. The power of a genetically tractable model organism coupled with well-established in vivo assays and a relatively short life cycle make Drosophila an attractive system to study VCP disease pathogenesis and novel treatment strategies. Using CRISPR/Cas9, we have generated individual Drosophila knock-in mutants that include nine hereditary VCP disease mutations. We validate that these models display many hallmarks of VCP-mediated degeneration, including progressive decline in mobility, protein aggregate accumulation and defects in lysosomal and mitochondrial function. We also made some novel and unexpected findings, including laminopathies and sex-specific phenotypic differences in several mutants. Taken together, the Drosophila VCP disease models we have generated in this study will be useful for studying the etiology of individual VCP patient mutations and for testing potential genetic and/or pharmacological therapies."

DOI: 10.1242/dmm.048603
PMID: 34160014

Fly model related to FIG-4 associated neurological disorders uncovers potential link to epigenetic regulation

Neuroreport. 2021 May 5;32(7):562-568. doi: 10.1097/WNR.0000000000001636.

Identification of Rpd3 as a novel epigenetic regulator of Drosophila FIG 4, a
Charcot-Marie-Tooth disease-causing gene.

Muraoka Y, Nikaido A, Kowada R, Kimura H, Yamaguchi M, Yoshida H

Abstract:

Mutations in the factor-induced-gene 4 (FIG 4) gene are associated with multiple disorders, including Charcot-Marie-Tooth disease (CMT), epilepsy with polymicrogyria, Yunis-Varón syndrome and amyotrophic lateral sclerosis. The wide spectrum of disorders associated with FIG 4 may be related to the dysregulated epigenetics. Using Gene Expression Omnibus, we found that HDAC1 binds to the FIG 4 gene locus in the genome of human CD4+ T cells. Rpd3 is a well-known Drosophila homolog of human HDAC1. We previously established Drosophila models targeting Drosophila FIG 4 (dFIG 4) that exhibited defective locomotive ability, abnormal synapse morphology at neuromuscular junctions, enlarged vacuoles in the fat body and aberrant compound eye morphology. Genetic crossing experiments followed by physiological and immunocytochemical analyses revealed that Rpd3 mutations suppressed these defects induced by dFIG 4 knockdown. This demonstrated Rpd3 to be an important epigenetic regulator of dFIG 4, suggesting that the inhibition of HDAC1 represses the pathogenesis of FIG 4-associated disorders, including CMT. Defects in epigenetic regulators, such as HDAC1, may also explain the diverse symptoms of FIG 4-associated disorders.

Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.

DOI: 10.1097/WNR.0000000000001636
PMID: 33850086

Review: Drosophila models of neurological diseases including ALS, CMT and Sotos syndrome

Exp Cell Res. 2021 Mar 31:112584. doi: 10.1016/j.yexcr.2021.112584. Online ahead
of print.

Drosophila models to study causative genes for human rare intractable
neurological diseases

Yamaguchi M, Lee IS, Jantrapirom S, Suda K, Yoshida H

Abstract

Drosophila is emerging as a convenient model for investigating human diseases. Functional homologues of almost 75% of human disease-related genes are found in Drosophila. Amyotrophic lateral sclerosis (ALS) is a severe neurodegenerative disease that causes defects in motoneurons. Charcot-Marie-Tooth disease (CMT) is one of the most commonly found inherited neuropathies affecting both motor and  sensory neurons. No effective therapy has been established for either of these diseases. In this review, after overviewing ALS, Drosophila models targeting several ALS-causing genes, including TDP-43, FUS and Ubiquilin2, are described with their genetic interactants. Then, after overviewing CMT, examples of
Drosophila models targeting several CMT-causing genes, including mitochondria-related genes and FIG 4, are also described with their genetic interactants. In addition, we introduce Sotos syndrome caused by mutations in the epigenetic regulator gene NSD1. Lastly, several genes and pathways that commonly interact with ALS- and/or CMT-causing genes are described. In the case of ALS and CMT that have many causative genes, it may be not practical to perform gene therapy for each of the many disease-causing genes. The possible uses of the common genes and pathways as novel diagnosis markers and effective  therapeutic targets are discussed.

Copyright © 2021. Published by Elsevier Inc.

DOI: 10.1016/j.yexcr.2021.112584
PMID: 33812867

Fly model leads to new model for cellular mechanisms underlying diseases associated with disruption of Valosin-Containing Proteins

Nat Commun. 2021 Jan 21;12(1):513. doi: 10.1038/s41467-020-20796-8.

SVIP is a molecular determinant of lysosomal dynamic stability, neurodegeneration and lifespan.

Johnson AE, Orr BO, Fetter RD, Moughamian AJ, Primeaux LA,
Geier EG, Yokoyama JS, Miller BL, Davis GW
 

From the abstract:

Missense mutations in Valosin-Containing Protein (VCP) are linked to diverse degenerative diseases including IBMPFD, amyotrophic lateral sclerosis (ALS), muscular dystrophy and Parkinson's disease. Here, we characterize a VCP-binding co-factor (SVIP) that specifically recruits VCP to lysosomes. ... We also establish multiple links between SVIP and VCP-dependent disease in our Drosophila model system. ... Finally, we identify a human SVIP mutation and confirm the pathogenicity of this mutation in our Drosophila model. We propose a model for VCP disease based on the differential, co-factor-dependent recruitment of VCP to intracellular organelles.

DOI: 10.1038/s41467-020-20796-8
PMID: 33479240

Wondering what's IBMPFD? Answer: Inclusion body myopathy with early-onset Paget disease and frontotemporal dementia.

PubMedCentral: Fly model used in studies related to ALS and FTLD

Wang P, Deng J, Dong J, Liu J, Bigio EH, Mesulam M, Wang T, Sun L, Wang L, Lee AY, McGee WA, Chen X, Fushimi K, Zhu L, Wu JY. TDP-43 induces mitochondrial damage and activates the mitochondrial unfolded protein response. PLoS Genet. 2019 May 17;15(5):e1007947. PubMed PMID: 31100073; PubMed Central PMCID: PMC6524796.

From the abstract: "Mutations in or dys-regulation of the TDP-43 gene have been associated with TDP-43 proteinopathy, a spectrum of neurodegenerative diseases including Frontotemporal Lobar Degeneration (FTLD) and Amyotrophic Lateral Sclerosis (ALS). The underlying molecular and cellular defects, however, remain unclear. Here, we report a systematic study combining analyses of patient brain samples with cellular and animal models for TDP-43 proteinopathy. ... Our work has not only uncovered a previously unknown role of LonP1 in regulating mitochondrial TDP-43 levels, but also advanced our understanding of the pathogenic mechanisms for TDP-43 proteinopathy. Our study suggests that blocking or reversing mitochondrial damage may provide a potential therapeutic approach to these devastating diseases."

Bogaert E, Boeynaems S, Kato M, Guo L, Caulfield TR, Steyaert J, Scheveneels W, Wilmans N, Haeck W, Hersmus N, Schymkowitz J, Rousseau F, Shorter J, Callaerts P, Robberecht W, Van Damme P, Van Den Bosch L. Molecular Dissection of FUS Points at Synergistic Effect of Low-Complexity Domains in Toxicity. Cell Rep. 2018 Jul 17;24(3):529-537.e4. PubMed PMID: 30021151; PubMed Central PMCID: PMC6077250.

Abstract: "RNA-binding protein aggregation is a pathological hallmark of several neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). To gain better insight into the molecular interactions underlying this process, we investigated FUS, which is mutated and aggregated in both ALS and FTLD. We generated a Drosophila model of FUS toxicity and identified a previously unrecognized synergistic effect between the N-terminal prion-like domain and the C-terminal arginine-rich domain to mediate toxicity. Although the prion-like domain is generally considered to mediate aggregation of FUS, we find that arginine residues in the C-terminal low-complexity domain are also required for maturation of FUS in cellular stress granules. These data highlight an important role for arginine-rich domains in the pathology of RNA-binding proteins."

Fly studies help provide insights into role of nucleocytoplasmic transport in ALS/FTD

Chou CC, Zhang Y, Umoh ME, Vaughan SW, Lorenzini I, Liu F, Sayegh M, Donlin-Asp PG, Chen YH, Duong DM, Seyfried NT, Powers MA, Kukar T, Hales CM, Gearing M, Cairns NJ, Boylan KB, Dickson DW, Rademakers R, Zhang YJ, Petrucelli L, Sattler R, Zarnescu DC, Glass JD, Rossoll W. TDP-43 pathology disrupts nuclear pore complexes and nucleocytoplasmic transport in ALS/FTD. Nat Neurosci. 2018 Feb;21(2):228-239. doi: 10.1038/s41593-017-0047-3. Epub 2018 Jan 8. PubMed PMID: 29311743; PubMed Central PMCID: PMC5800968.

Abstract: "The cytoplasmic mislocalization and aggregation of TAR DNA-binding protein-43 (TDP-43) is a common histopathological hallmark of the amyotrophic lateral sclerosis and frontotemporal dementia disease spectrum (ALS/FTD). However, the composition of aggregates and their contribution to the disease process remain unknown. Here we used proximity-dependent biotin identification (BioID) to interrogate the interactome of detergent-insoluble TDP-43 aggregates and found them enriched for components of the nuclear pore complex and nucleocytoplasmic transport machinery. Aggregated and disease-linked mutant TDP-43 triggered the sequestration and/or mislocalization of nucleoporins and transport factors, and interfered with nuclear protein import and RNA export in mouse primary cortical neurons, human fibroblasts and induced pluripotent stem cell-derived neurons. Nuclear pore pathology is present in brain tissue in cases of sporadic ALS and those involving genetic mutations in TARDBP and C9orf72. Our data strongly implicate TDP-43-mediated nucleocytoplasmic transport defects as a common disease mechanism in ALS/FTD."

See also comment in Nature Neuroscience.

Autophagy, lysosomes, and ALS/FTD

Şentürk M, Mao D, Bellen HJ. Loss of proteins associated with amyotrophic lateral sclerosis affect lysosomal acidification via different routes. Autophagy. 2019 Apr 28:1-3. PubMed
PMID: 31032688.

Abstract: "Abnormal accumulation of proteins is a hallmark of a variety of neurological diseases including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Maintenance of protein homeostasis (proteostasis) in neurons via proteasomal and macroautophagy/autophagy-lysosomal degradation is thought to be central for proper neuronal function and survival. We recently reported evolutionarily conserved roles for two ALS-linked proteins, UBQLN2 (ubiquilin 2) and VAPB, in regulation of lysosomal degradation. Ubiquilins are required for v-ATPase-mediated lysosomal acidification, whereas VAPs are required for the PtdIns4P-mediated endo-lysosomal trafficking pathway."

Review -- Drosophila models for the study of motor neuron diseases

Walters R, Manion J, Neely GG. Dissecting Motor Neuron Disease With Drosophila melanogaster. Front Neurosci. 2019 Apr 12;13:331. doi: 10.3389/fnins.2019.00331. PMID: 31031583; PMCID: PMC6473072.

Abstract: "Motor Neuron Disease (MND) typically affects patients during the later stages of life, and thus, MND is having an increasingly devastating impact on diagnosed individuals, their families and society. The umbrella term MND refers to diseases which cause the progressive loss of upper and/or lower motor neurons and a subsequent decrease in motor ability such as amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA). The study of these diseases is complex and has recently involved the use of genome-wide association studies (GWAS). However, in the case of MND, it has been difficult to identify the complex genetics involved in subtypes, and functional investigation of new candidate disease genes is warranted. Drosophila is a powerful model for addressing these complex diseases. The UAS/Gal4/Gal80 system allows for the upregulation of Drosophila genes, the "knockdown" of genes and the ectopic expression of human genes or mutations in a tissue-specific manner; often resulting in Drosophila models which exhibit typical MND disease pathologies. These can then be further interrogated to identify disease-modifying genes or mutations and disease pathways. This review will discuss two common MNDs and the current Drosophila models which are being used to research their genetic basis and the different pathologies of MND."

Reports related to neurodegenerative and neuromuscular disorders

Bondar VV, Adamski CJ, Onur TS, Tan Q, Wang L, Diaz-Garcia J, Park J, Orr HT, Botas J, Zoghbi HY. PAK1 regulates ATXN1 levels providing an opportunity to modify its toxicity in spinocerebellar ataxia type 1. Hum Mol Genet. 2018 Aug 15;27(16):2863-2873.PMID: 29860311; PMCID: PMC6077814.

From the abstract: "... Loss-of-function of fly Pak3 or Pak1, whose mammalian homologs belong to Group I of PAK proteins, reduces ATXN1 levels, and accordingly, improves disease pathology in a Drosophila model of SCA1. Knockdown of PAK1 potently reduces ATXN1 levels in mammalian cells ... this study identifies PAK signaling as a distinct molecular pathway that regulates ATXN1 levels and presents a promising opportunity to pursue for developing potential therapeutics for SCA1."

Adusumalli S, Ngian ZK, Lin WQ, Benoukraf T, Ong CT. Increased intron retention is a post-transcriptional signature associated with progressive aging and Alzheimer's disease. Aging Cell. 2019 Mar 13:e12928. PMID: 30868713.

From the abstract: "Intron retention (IR) by alternative splicing is a conserved regulatory mechanism that can affect gene expression and protein function during adult development and age-onset diseases. ... By profiling the transcriptome of Drosophila head cells at different ages, we observed a significant increase in IR events for many genes during aging. ... our results suggest that an increased IR is an conserved signature that is associated with aging. ... changes of IR pattern during aging may regulate the transition from healthy to pathological state in late-onset sporadic AD."

Wang TH, Wang SY, Wang XD, Jiang HQ, Yang YQ, Wang Y, Cheng JL, Zhang CT, Liang WW, Feng HL. Fisetin Exerts Antioxidant and Neuroprotective Effects in Multiple Mutant hSOD1 Models of Amyotrophic Lateral Sclerosis by Activating ERK. Neuroscience. 2018 May 21;379:152-166. PMID: 29559385.

From the abstract: "Oxidative stress exhibits a central role in the course of amyotrophic lateral sclerosis (ALS) ... Fisetin, a natural antioxidant, has shown benefits in varied neurodegenerative diseases. ... Three different hSOD1-related mutant models were used ... results indicate that fisetin protects cells from ROS damage and improves the pathological behaviors caused by oxidative stress in disease models related to SOD1 gene mutations ... providing a potential treatment for ALS."

Lakkappa N, Krishnamurthy PT, M D P, Hammock BD, Hwang SH. Soluble epoxide hydrolase inhibitor, APAU, protects dopaminergic neurons against rotenone induced neurotoxicity: Implications for Parkinson's disease. Neurotoxicology. 2019 Jan;70:135-145. PMID: 30472438.

From the abstract: "Epoxyeicosatrienoic acids (EETs), metabolites of arachidonic acid, play a crucial role in cytoprotection by attenuating oxidative stress, inflammation and apoptosis. EETs are rapidly metabolised in vivo by the soluble epoxide hydrolase (sEH). Increasing the half life of EETs by inhibiting the sEH enzyme is a novel strategy for neuroprotection. ... sEH inhibitors APAU was screened in silico and further evaluated for their antiparkinson activity against rotenone (ROT) induced neurodegeneration in N27 dopaminergic cell line and Drosophila melanogaster model of Parkinson disease (PD). ..."

 Krench M, Cho RW, Littleton JT. A Drosophila model of Huntington disease-like 2 exhibits nuclear toxicity and distinct pathogenic mechanisms from Huntington disease. Hum Mol Genet. 2016 Aug 1;25(15):3164-3177. PMID: 27288455; PMCID: PMC5179919.

From the abstract: "Huntington disease-like 2 (HDL2) and Huntington disease (HD) are adult-onset neurodegenerative diseases ... we generated and characterized a Drosophila HDL2 model and compared it with a previously established HD model. We find that neuronal expression of HDL2-Q15 is not toxic, while the expression of an expanded HDL2-Q138 protein is lethal. HDL2-Q138 forms large nuclear aggregates, with only smaller puncta observed in the cytoplasm. This is in contrast to what is observed in a Drosophila model of HD, where polyQ aggregates localize exclusively to the cytoplasm. ... We conclude that while HD and HDL2 have similar clinical profiles, distinct pathogenic mechanisms are likely to drive toxicity in Drosophila models of these disorders."

Poska H, Haslbeck M, Kurudenkandy FR, Hermansson E, Chen G, Kostallas G, Abelein A, Biverstål H, Crux S, Fisahn A, Presto J, Johansson J. Dementia-related Bri2 BRICHOS is a versatile molecular chaperone that efficiently inhibits Aβ42 toxicity in Drosophila. Biochem J. 2016 Oct 15;473(20):3683-3704. PMID: 27514716.

From the abstract: "Formation of fibrils of the amyloid-β peptide (Aβ) is suggested to play a central role in neurodegeneration in Alzheimer's disease (AD), for which no effective treatment exists. The BRICHOS domain is a part of several disease-related proproteins ... we find that transgenic expression of the Bri2 BRICHOS domain in the Drosophila central nervous system (CNS) or eyes efficiently inhibits Aβ42 toxicity. ... These findings suggest that Bri2 BRICHOS can be a physiologically relevant chaperone for Aβ in the CNS ..."

Potential new drug repurposing strategy identified using fly model of ALS

Xu W, Bao P, Jiang X, Wang H, Qin M, Wang R, Wang T, Yang Y, Lorenzini I, Liao L, Sattler R, Xu J. Reactivation of nonsense-mediated mRNA decay protects against C9orf72 dipeptide-repeat neurotoxicity. Brain. 2019 Apr 1. pii: awz070. PMID: 30938419.

From the abstract: "Amyotrophic lateral sclerosis is a deleterious neurodegenerative disease without effective treatment options. Recent studies have indicated the involvement of the dysregulation of RNA metabolism in the pathogenesis of amyotrophic lateral sclerosis. Among the various RNA regulatory machineries, nonsense-mediated mRNA decay (NMD) is a stress responsive cellular surveillance system that degrades selected mRNA substrates to prevent the translation of defective or harmful proteins. ... Here we report the inhibition of NMD by arginine-rich dipeptide repeats derived from C9orf72 hexanucleotide repeat expansion, the most common cause of familial amyotrophic lateral sclerosis. Bioinformatic analysis of multiple transcriptome profiles revealed significant overlap of upregulated genes in NMD-defective cells with those in the brain tissues, micro-dissected motor neurons, or induced pluripotent stem cell-derived motor neurons specifically from amyotrophic lateral sclerosis patients carrying C9orf72 hexanucleotide repeat expansion, suggesting the suppression of NMD pathway in these patients. Using Drosophila as a model, we have validated that the C9orf72 hexanucleotide repeat expansion products could lead to the accumulation of the NMD substrates and identified arginine-rich dipeptide repeats ... Remarkably, expression of UPF1, a core gene in the NMD pathway, efficiently blocked neurotoxicity caused by arginine-rich dipeptide repeats in both cellular and Drosophila models. ... UPF2 also ameliorated the degenerative phenotypes in dipeptide repeat-expressing flies ... Finally, after validating tranilast as an NMD-activating drug, we demonstrated the therapeutic potential of this asthma drug in cellular and Drosophila models of C9orf72 dipeptide repeat neurotoxicity. Therefore, our study has revealed a cellular mechanism whereby arginine-rich C9orf72 dipeptide repeats could inhibit NMD activities by reducing the abundance of processing bodies. Furthermore, our results suggested that activation of the NMD pathway could be a potential therapeutic strategy for amyotrophic lateral sclerosis with defective RNA metabolism."

Study of neuroprotection by urate using fly model of ALS

Zhang C, Yang Y, Liang W, Wang T, Wang S, Wang X, Wang Y, Jiang H, Feng H. Neuroprotection by urate on the Mutant hSOD1-related Cellular and Drosophila Models of Amyotrophic Lateral Sclerosis: Implication for GSH synthesis via Activating Akt/GSK3β/Nrf2/GCLC Pathways. Brain Res Bull. 2019 Jan 25. pii: S0361-9230(18)30605-1. PMID: 30690059.

From the abstract: "Oxidative stress has been considered as a principal mechanism of motor neuron death in amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease which could be caused by dominant mutations in an antioxidant enzyme superoxide dismutase-1 (SOD1). The aim of the present study was to investigate the potential neuroprotective effects and mechanisms of urate, an important endogenous antioxidant and a biomarker of favorable ALS progression rates, in the mutant human SOD1-related cellular and Drosophila models of ALS. Our results showed that urate treatment provided neuroprotective effects as confirmed by enhanced survival, attenuated motor impairments, reduced oxidative damage and increased antioxidant defense in hSOD1-G85R-expressing Drosophila models of ALS. ... Overall, these results suggested that, in addition to its direct scavenging of ROS, urate markedly enhanced GSH expression by activating Akt/GSK3β/Nrf2/GCLC pathway, and thus offering neuroprotective effects on motor neurons against oxidative stress."

Fly model used in drug discovery study related to FTD and ALS (research report now available at PubMed Central)

Simone R, et al. G-quadruplex-binding small molecules ameliorate C9orf72 FTD/ALS pathology in vitro and in vivo. EMBO Mol Med. 2018 Jan;10(1):22-31. doi: 10.15252/emmm.201707850. PubMed PMID: 29113975; PubMed Central PMCID: PMC5760849.

From the abstract: "Intronic GGGGCC repeat expansions in C9orf72 are the most common known cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS), which are characterised by degeneration of cortical and motor neurons, respectively. ... We performed a screen that identified three structurally related small molecules that specifically stabilise GGGGCC repeat G-quadruplex RNA ... Furthermore, they also reduce dipeptide repeat proteins and improve survival in vivo, in GGGGCC repeat-expressing Drosophila ... These data provide proof of principle that targeting GGGGCC repeat G-quadruplexes has therapeutic potential."

Results from a fly genetic screen implicate a long non-coding RNA in Charcot-Marie-Tooth disease

Muraoka Y, Nakamura A, Tanaka R, Suda K, Azuma Y, Kushimura Y, Piccolo LL, Yoshida H, Mizuta I, Tokuda T, Mizuno T, Nakagawa M, Yamaguchi M. Genetic screening of the genes interacting with Drosophila FIG4 identified a novel link between CMT-causing gene and long noncoding RNAs. Exp Neurol. 2018 Aug 27. pii: S0014-4886(18)30377-7. PMID: 30165075.

From the abstract: "Neuron-specific knockdown of the dFIG4 gene, a Drosophila homologue of human FIG4 and one of the causative genes for Charcot-Marie-Tooth disease (CMT), reduces the locomotive abilities of adult flies, as well as causing defects at neuromuscular junctions ... By genetic screening, we detected 9 and 15 chromosomal regions whose deletions either suppressed or enhanced the rough eye phenotype induced by the dFIG4 knockdown. By further genetic screening ... we identified the gene CR18854 that suppressed the rough eye phenotype and the loss-of-cone cell phenotype. The CR18854 gene encodes a long non-coding RNA (lncRNA) consisting of 2566 bases. ... We also obtained data indicating genetic interaction between CR18854 and Cabeza, a Drosophila homologue of human FUS, which is one of the causing genes for amyotrophic lateral sclerosis (ALS). These results suggest that lncRNAs such as CR18854 and hsrω are involved in a common pathway in CMT and ALS pathogenesis."

New fly model of FUS toxicity

Bogaert E, Boeynaems S, Kato M, Guo L, Caulfield TR, Steyaert J, Scheveneels W, Wilmans N, Haeck W, Hersmus N, Schymkowitz J, Rousseau F, Shorter J, Callaerts P, Robberecht W, Van Damme P, Van Den Bosch L. Molecular Dissection of FUS Points at Synergistic Effect of Low-Complexity Domains in Toxicity. Cell Rep. 2018 Jul 17;24(3):529-537.e4. PMID: 30021151.

From the abstract: "RNA-binding protein aggregation is a pathological hallmark of several neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). To gain better insight into the molecular interactions underlying this process, we investigated FUS, which is mutated and aggregated in both ALS and FTLD. We generated a Drosophila model of FUS toxicity ..."

Drosophila used in study related to ALS/FTLD

Mordes DA, Prudencio M, Goodman LD, Klim JR, Moccia R, Limone F, Pietilainen O, Chowdhary K, Dickson DW, Rademakers R, Bonini NM, Petrucelli L, Eggan K. Dipeptide repeat proteins activate a heat shock response found in C9ORF72-ALS/FTLD patients. Acta Neuropathol Commun. 2018 Jul 4;6(1):55. PMID: 29973287.

Abstract: "A hexanucleotide (GGGGCC) repeat expansion in C9ORF72 is the most common genetic contributor to amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). Reduced expression of the C9ORF72 gene product has been proposed as a potential contributor to disease pathogenesis. Additionally, repetitive RNAs and dipeptide repeat proteins (DPRs), such as poly-GR, can be produced by this hexanucleotide expansion that disrupt a number of cellular processes, potentially contributing to neural degeneration. To better discern which of these mechanisms leads to disease-associated changes in patient brains, we analyzed gene expression data generated from the cortex and cerebellum. We found that transcripts encoding heat shock proteins (HSPs) regulated by the HSF1 transcription factor were significantly induced in C9ORF72-ALS/FTLD patients relative to both sporadic ALS/FTLD cases and controls. Treatment of human neurons with chemically synthesized DPRs was sufficient to activate a similar transcriptional response. Expression of GGGGCC repeats and also poly-GR in the brains of Drosophila lead to the upregulation of HSF1 and the same highly-conserved HSPs. Additionally, HSF1 was a modifier of poly-GR toxicity in Drosophila. Our results suggest that the expression of DPRs are associated with upregulation of HSF1 and activation of a heat shock response in C9ORF72-ALS/FTLD."

Review of Drosophila research related to ALS

Zhang K, Coyne AN, Lloyd TE. Drosophila models of amyotrophic lateral sclerosis with defects in RNA metabolism. Brain Res. 2018 May 9. PMID: 29752901.

From the abstract: " ... The conservation of nervous system biology coupled with the rapid life cycle and powerful genetic tools in the fly have enabled the identification of novel therapeutic targets that have been validated in vertebrate model systems and human patients. A recent example is in the study of the devastating motor neuron degenerative disease amyotrophic lateral sclerosis (ALS). ... In this review, we will discuss the utilization of Drosophila models of ALS with defects in RNA metabolism."

Studies "launching from Drosophila models" provide insights into molecular mechanisms of ALS and FTD

Berson A, Sartoris A, Nativio R, Van Deerlin V, Toledo JB, Porta S, Liu S, Chung CY, Garcia BA, Lee VM, Trojanowski JQ, Johnson FB, Berger SL, Bonini NM. TDP-43 Promotes Neurodegeneration by Impairing Chromatin Remodeling. Curr Biol. 2017 Nov 9. pii: S0960-9822(17)31327-1. PMID: 29153328.

The abstract: "Regulation of chromatin structure is critical for brain development and function. However, the involvement of chromatin dynamics in neurodegeneration is less well understood. Here we find, launching from Drosophila models of amyotrophic lateral sclerosis and frontotemporal dementia, that TDP-43 impairs the induction of multiple key stress genes required to protect from disease by reducing the recruitment of the chromatin remodeler Chd1 to chromatin. Chd1 depletion robustly enhances TDP-43-mediated neurodegeneration and promotes the formation of stress granules. Conversely, upregulation of Chd1 restores nucleosomal dynamics, promotes normal induction of protective stress genes, and rescues stress sensitivity of TDP-43-expressing animals. TDP-43-mediated impairments are conserved in mammalian cells, and, importantly, the human ortholog CHD2 physically interacts with TDP-43 and is strikingly reduced in level in temporal cortex of human patient tissue. These findings indicate that TDP-43-mediated neurodegeneration causes impaired chromatin dynamics that prevents appropriate expression of protective genes through compromised function of the chromatin remodeler Chd1/CHD2. Enhancing chromatin dynamics may be a treatment approach to amyotrophic lateral scleorosis (ALS)/frontotemporal dementia (FTD)."

Fly research and neurodegenerative diseases

Research articles related to ALS and Alzheimer's disease

Baldwin KR, Godena VK, Hewitt VL, Whitworth AJ. Axonal transport defects are a common phenotype in Drosophila models of ALS. Hum Mol Genet. 2016 Jun 15;25(12):2378-2392. Epub 2016 Apr 7. PMID: 27056981; PMCID: PMC5181624.

From the abstract: "Amyotrophic lateral sclerosis (ALS) is characterized by the degeneration of motor neurons resulting in a catastrophic loss of motor function. Current therapies are severely limited owing to a poor mechanistic understanding of the pathobiology. Mutations in a large number of genes have now been linked to ALS, including SOD1, TARDBP (TDP-43), FUS and C9orf72. Functional analyses of these genes and their pathogenic mutations have provided great insights into the underlying disease mechanisms. Defective axonal transport is hypothesized to be a key factor in the selective vulnerability of motor nerves ... Here, we assessed the axonal transport of different cargos in multiple Drosophila models of ALS. ... These results further support defects in axonal transport as a common factor in models of ALS that may contribute to the pathogenic process."

Bernstein AI, Lin Y, Street RC, Lin L, Dai Q, Yu L, Bao H, Gearing M, Lah JJ, Nelson PT, He C, Levey AI, Mullé JG, Duan R, Jin P. 5-Hydroxymethylation-associated epigenetic modifiers of Alzheimer's disease modulate Tau-induced neurotoxicity. Hum Mol Genet. 2016 Jun 15;25(12):2437-2450. PMID: 27060332; PMCID: PMC5181627.

From the abstract: "Alzheimer's disease (AD) is a chronic neurodegenerative disorder characterized by progressive deterioration of cognitive function. Pathogenesis of AD is incompletely understood; evidence suggests a role for epigenetic regulation, in particular the cytosine modifications 5-methylcytosine and 5-hydroxymethylcytosine (5hmC). 5hmC is enriched in the nervous system and displays neurodevelopment and age-related changes. To determine the role of 5hmC in AD, we performed genome-wide analyses of 5hmC in DNA from prefrontal cortex of post-mortem AD patients, and RNA-Seq to correlate changes in 5hmC with transcriptional changes. We identified 325 genes containing differentially hydroxymethylated loci (DhMLs) in both discovery and replication datasets. ... Finally, using an existing AD fly model, we showed some of these genes modulate AD-associated toxicity. ..."

And a review related to Parkinson's disease

Voigt A, Berlemann LA, Winklhofer KF. The mitochondrial kinase PINK1: functions beyond mitophagy. J Neurochem. 2016 Oct;139 Suppl 1:232-239. PMID: 27251035.

From the abstract: "Mutations in the genes encoding the mitochondrial kinase PINK1 and the E3 ubiquitin ligase Parkin cause autosomal recessive Parkinson's disease (PD). Pioneering work in Drosophila melanogaster revealed that the loss of PINK1 or Parkin function causes similar phenotypes including dysfunctional mitochondria. Further research showed that PINK1 can act upstream of Parkin in a mitochondrial quality control pathway to induce removal of damaged mitochondria in a process called mitophagy. ... In this review, we summarize and discuss the functional roles of PINK1 in maintaining mitochondrial integrity, eliminating damaged mitochondria, and promoting cell survival. This article is part of a special issue on Parkinson disease."

Genetic modifier screen with a fly model of ALS/FTD

Boeynaems S, Bogaert E, Michiels E, Gijselinck I, Sieben A, Jovičić A, De Baets G, Scheveneels W, Steyaert J, Cuijt I, Verstrepen KJ, Callaerts P, Rousseau F, Schymkowitz J, Cruts M, Van Broeckhoven C, Van Damme P, Gitler AD, Robbenecht W, Van Den Bosch L. Drosophila screen connects nuclear transport genes to DPR pathology in c9ALS/FTD. Sci Rep. 2016 Feb 12;6:20877. PMID: 26869068; PMCID: PMC4751451.

From the abstract: "Hexanucleotide repeat expansions in C9orf72 are the most common cause of amyotrophic lateral sclerosis (ALS) and frontotemporal degeneration (FTD) (c9ALS/FTD). ... We performed a modifier screen in Drosophila and discovered a critical role for importins and exportins, Ran-GTP cycle regulators, nuclear pore components, and arginine methylases in mediating DPR toxicity. These findings provide evidence for an important role for nucleocytoplasmic transport in the pathogenic mechanism of c9ALS/FTD."