Methods to assay Drosophila behavior

Development and testing of a sedation protocol for Neocaridina davidi

Neocaridina davidi, a small freshwater shrimp native to Asia, specifically China, Japan, Korea, and Vietnam, possesses remarkable resistance to poor water quality and offers various advantages over other invertebrate species to examine crucial issues in neuroscience and other related areas. These advantages include robustness, ease of maintenance, and transparency, making them useful for in vivo studies with optical imaging techniques. Despite its suitability for research purposes, particularly in the fields of imaging and fluorescent techniques, the lack of attention given to this species has resulted in the absence of a robust and replicable sedation protocol for immobilization and safe manipulation. Consequently, researchers face challenges in performing experimental procedures while minimizing harm to this specimen. In this study, we have developed and evaluated a simple sedation protocol specifically designed for Neocaridina davidi, assessing its effectiveness using light microscopy and image processing.

Alleviation of arsenic-induced neurobehavioral defects with selenium in the larvae of Zaprionus indianus

Selenium is an essential antioxidative micronutrient. This study was conducted to characterize the arsenic toxicity induced on the African fig fly, Zaprionus indianus, and its possible amelioration by selenium. We used computational tools and in vivo experiments to elucidate the mechanism of action of arsenic and selenium on Z. indianus larvae. We conducted experiments to study neurobehavioral parameters including learning and memory ability test and crawling and contraction assays. Our in silico study revealed twelve primary targets of arsenic trioxide. The gene ontology annotation of primary and secondary targets of arsenic trioxide revealed selenocysteine metabolic processes as one of the most reliable targets. To validate our in silico data, we analyzed the effect of arsenic trioxide on larvae of Z. indianus and tested the possible amelioration by sodium selenite supplementation. Our data demonstrated that the arsenic trioxide deteriorated the learning and memory ability of 2nd instar larvae of Z. indianus and such effect was reversed by sodium selenite supplementation. Furthermore, crawling and contraction assay done on 3rd instar larvae showed that there was reduction in both parameters upon arsenic trioxide exposure, which was restored with sodium selenite supplementation. Altogether, our computational and in vivo results strongly indicated that the neurobehavioral defects induced by arsenic trioxide on the larvae of Z. indianus can be successfully alleviated in the presence of sodium selenite.

Glucose Challenge Uncovers Temporal Fungibility of Metabolic Homeostasis Throughout the Day

Rhythmicity is a central feature of behavioral and biological processes including metabolism, however, the mechanisms of metabolite cycling are poorly understood. A robust oscillation in a network of key metabolite pathways downstream of glucose is described in humans, then these pathways mechanistically probed through purpose-built 13C6-glucose isotope tracing in Drosophila every 4h. A temporal peak in biosynthesis was noted by broad labelling of pathways downstream of glucose in wild-type flies shortly following lights on. Krebs cycle labelling was generally increased in a hyperactive mutant (fumin) along with glycolysis labelling primarily observed at dawn. Surprisingly, neither underlying feeding rhythms nor the presence of food explains the rhythmicity of glucose processing across genotypes. These results are consistent with clinical data demonstrating detrimental effects of mis-timed energy intake. This approach provides a window into the dynamic range of metabolic processing ability through the day and mechanistic basis for exploring circadian metabolic homeostasis in disease states.

Serratia marcescens in the intestine of housefly larvae inhibits host growth by interfering with gut microbiota

BACKGROUND

The structure of gut microbiota is highly complex. Insects have ubiquitous associations with intestinal symbiotic bacteria, which play essential roles. Thus, understanding how changes in the abundance of a single bacterium interfere with bacterial interactions in the insect's gut is important.

METHODS

Here, we analyzed the effects of Serratia marcescens on the growth and development of housefly larvae using phage technology. We used 16S rRNA gene sequencing technology to explore dynamic diversity and variation in gut bacterial communities and performed plate confrontation assays to study the interaction between S. marcescens and intestinal microorganisms. Furthermore, we performed phenoloxidase activity assay, crawling assay, and trypan blue staining to explore the negative effects of S. marcescens on housefly larvae's humoral immunity, motility, and intestinal organization.

RESULTS

The growth and development of housefly larvae were inhibited after feeding on S. marcescens, and their intestinal bacterial composition changed with increasing abundance of Providencia and decreasing abundance of Enterobacter and Klebsiella. Meanwhile, the depletion of S. marcescens by phages promoted the reproduction of beneficial bacteria.

CONCLUSIONS

In our study, using phage as a tool to regulate the abundance of S. marcescens, we highlighted the mechanism by which S. marcescens inhibits the growth and development of housefly larvae and illustrated the importance of intestinal flora for larval development. Furthermore, by studying the dynamic diversity and variation in gut bacterial communities, we improved our understanding of the possible relationship between the gut microbiome and housefly larvae when houseflies are invaded by exogenous pathogenic bacteria.

Novel EAAT2 activators improve motor and cognitive impairment in a transgenic model of Huntington's disease

Introduction

Glutamate excitotoxicity is causal in striatal neurodegeneration underlying motor dysfunction and cognitive deficits in Huntington's disease (HD). Excitatory amino acid transporter 2 (EAAT2), the predominant glutamate transporter accounting for >90% of glutamate transport, plays a key role in preventing excitotoxicity by clearing excess glutamate from the intrasynaptic cleft. Accordingly, EAAT2 has emerged as a promising therapeutic target for prevention of neuronal excitotoxicity underlying HD and other neurodegenerative diseases.

Methods

We have previously designed novel EAAT2 positive allosteric modulator GT951, GTS467, and GTS551, with low nanomolar efficacy in glutamate uptake and favorable pharmacokinetic properties. In this study, we test the neuroprotective abilities of these novel EAAT2 activators in vivo using the robust Drosophila HD transgenic model expressing human huntingtin gene with expanded repeats (Htt128Q).

Results

All three compounds significantly restored motor function impaired under HD pathology over a wide dose range. Additionally, treatment with all three compounds significantly improved HD-associated olfactory associative learning and short-term memory defects, while GT951 and GTS551 also improved middle-term memory in low-performing group. Similarly, treatment with GT951 and GTS551 partially protected against early mortality observed in our HD model. Further, treatment with all three EAAT2 activators induced epigenetic expression of EAAT2 Drosophila homolog and several cognition-associated genes.

Conclusion

Together, these results highlight the efficacy of GT951, GTS467 and GTS551 in treating motor and cognitive impairments under HD pathology and support their development for treatment of HD.

Stochastic RNA editing of the Complexin C-terminus within single neurons regulates neurotransmitter release

Neurotransmitter release requires assembly of the SNARE complex fusion machinery, with multiple SNARE-binding proteins regulating this process to control when and where synaptic vesicle fusion occurs. Complexin (Cpx) controls spontaneous and evoked neurotransmitter release by modulating SNARE complex zippering. Although the central SNARE-binding helix is essential, post-translational modifications to Cpx's C-terminal membrane-binding amphipathic helix modulate its activity. Here we demonstrate that RNA editing of the Cpx C-terminus regulates its ability to clamp SNARE-mediated fusion and alters presynaptic output. RNA editing of Cpx within single neurons is stochastic, generating up to eight edit variants that fine-tune neurotransmitter release by changing the subcellular localization and clamping properties of the protein. Similar editing rules for other synaptic genes were observed, indicating stochastic editing at single adenosines and across multiple mRNAs can generate unique synaptic proteomes within the same population of neurons to fine-tune presynaptic output.

Drosophila melanogaster as a versatile model organism to study genetic epilepsies: An overview

Epilepsy is one of the most prevalent neurological disorders, affecting more than 45 million people worldwide. Recent advances in genetic techniques, such as next-generation sequencing, have driven genetic discovery and increased our understanding of the molecular and cellular mechanisms behind many epilepsy syndromes. These insights prompt the development of personalized therapies tailored to the genetic characteristics of an individual patient. However, the surging number of novel genetic variants renders the interpretation of pathogenetic consequences and of potential therapeutic implications ever more challenging. Model organisms can help explore these aspects in vivo. In the last decades, rodent models have significantly contributed to our understanding of genetic epilepsies but their establishment is laborious, expensive, and time-consuming. Additional model organisms to investigate disease variants on a large scale would be desirable. The fruit fly Drosophila melanogaster has been used as a model organism in epilepsy research since the discovery of "bang-sensitive" mutants more than half a century ago. These flies respond to mechanical stimulation, such as a brief vortex, with stereotypic seizures and paralysis. Furthermore, the identification of seizure-suppressor mutations allows to pinpoint novel therapeutic targets. Gene editing techniques, such as CRISPR/Cas9, are a convenient way to generate flies carrying disease-associated variants. These flies can be screened for phenotypic and behavioral abnormalities, shifting of seizure thresholds, and response to anti-seizure medications and other substances. Moreover, modification of neuronal activity and seizure induction can be achieved using optogenetic tools. In combination with calcium and fluorescent imaging, functional alterations caused by mutations in epilepsy genes can be traced. Here, we review Drosophila as a versatile model organism to study genetic epilepsies, especially as 81% of human epilepsy genes have an orthologous gene in Drosophila. Furthermore, we discuss newly established analysis techniques that might be used to further unravel the pathophysiological aspects of genetic epilepsies.

WiFi Related Radiofrequency Electromagnetic Fields Promote Transposable Element Dysregulation and Genomic Instability in Drosophila melanogaster

Exposure to artificial radio frequency electromagnetic fields (RF-EMFs) has greatly increased in recent years, thus promoting a growing scientific and social interest in deepening the biological impact of EMFs on living organisms. The current legislation governing the exposure to RF-EMFs is based exclusively on their thermal effects, without considering the possible non-thermal adverse health effects from long term exposure to EMFs. In this study we investigated the biological non-thermal effects of low-level indoor exposure to RF-EMFs produced by WiFi wireless technologies, using Drosophila melanogaster as the model system. Flies were exposed to 2.4 GHz radiofrequency in a Transverse Electromagnetic (TEM) cell device to ensure homogenous controlled fields. Signals were continuously monitored during the experiments and regulated at non thermal levels. The results of this study demonstrate that WiFi electromagnetic radiation causes extensive heterochromatin decondensation and thus a general loss of transposable elements epigenetic silencing in both germinal and neural tissues. Moreover, our findings provide evidence that WiFi related radiofrequency electromagnetic fields can induce reactive oxygen species (ROS) accumulation, genomic instability, and behavioural abnormalities. Finally, we demonstrate that WiFi radiation can synergize with Ras^V12 to drive tumor progression and invasion. All together, these data indicate that radiofrequency radiation emitted from WiFi devices could exert genotoxic effects in Drosophila and set the stage to further explore the biological effects of WiFi electromagnetic radiation on living organisms.

Effects of plant growth retardant daminozide (Alar) on neuromuscular co-ordination behavior in Drosophila melanogaster

Daminozide (alar), a plant growth retardant, is used in different fruit orchard to make fruits attractive and reduce pre-harvest losses. Previously data demonstrated that acute daminozide exposure affected reproductive fitness and produced neurodegeneration in Drosophila melanogaster. The goal of this study was to determine whether continuous exposure to daminozide affects neuromuscular co-ordination in D. melanogaster as manifested in various behavioral responses. Fruit flies were exposed to 200 or 400 mg/L concentration of daminozide for two successive generations. Treated D. melanogaster were examined for the behaviors indicative of neuromuscular coordination and cognitive abilities, that include climbing, social interaction, adult grooming, migration, flight, male aggression, and adult courtship. Aberrant behavioral responses were noted among treated D. melanogaster of both sexes as evidenced by the following parameters: reduction in flight duration, abnormal social interaction, altered copulatory acts, and over-aggressiveness. Data suggest that daminozide produces impairment in neuromuscular coordination and cognitive ability in Drosophila, which was reflected as altered behavioral patterns. As Drosophila is considered as a reliable in vivo model utilized in toxicity testing, our findings may help us to anticipate and monitor potential daminozide-induced toxicity in animals and humans.

Evaluation of Mitochondrial Turnover Using Fluorescence Microscopy in Drosophila

Mitochondrial dysfunction is associated with perturbations in the cellular oxidative status, changes in energy production and metabolic rate, and the onset of pathological processes. Classic methods of assessing mitochondrial dysfunction rely on indirect measures, such as evaluating mitochondrial DNA copy numbers, or direct but more costly and skilled techniques, such as electron microscopy. The protocol presented here was recently implemented to evaluate mitochondrial dysfunction in response to insecticide exposure in Drosophila melanogaster larvae, and it relies on the use of a previously established MitoTimer mutant strain. MitoTimer is a genetically engineered mitochondrial protein that shows green fluorescence when newly synthetized, irreversibly turning into red as mitochondria age. The protocol described here allows for the easy and direct assessment of shifts in mitochondrial turnover, with tissue-specific accuracy. This protocol can be adapted to assess changes in mitochondrial turnover in response to drugs, rearing conditions, and/or mutations in larva, pupa, or adult fruit flies.

Systemic lipolysis promotes physiological fitness in Drosophila melanogaster

Since interventions such as caloric restriction or fasting robustly promote lipid catabolism and improve aging-related phenotypical markers, we investigated the direct effect of increased lipid catabolism via overexpression of bmm (brummer, FBgn0036449), the major triglyceride hydrolase in Drosophila, on lifespan and physiological fitness. Comprehensive characterization was carried out using RNA-seq, lipidomics and metabolomics analysis. Global overexpression of bmm strongly promoted numerous markers of physiological fitness, including increased female fecundity, fertility maintenance, preserved locomotion activity, increased mitochondrial biogenesis and oxidative metabolism. Increased bmm robustly upregulated the heat shock protein 70 (Hsp70) family of proteins, which equipped the flies with higher resistance to heat, cold, and ER stress via improved proteostasis. Despite improved physiological fitness, bmm overexpression did not extend lifespan. Taken together, these data show that bmm overexpression has broad beneficial effects on physiological fitness, but these effects did not impact lifespan.

ALS-linked KIF5A ΔExon27 mutant causes neuronal toxicity through gain-of-function

Mutations in the human kinesin family member 5A (KIF5A) gene were recently identified as a genetic cause of amyotrophic lateral sclerosis (ALS). Several KIF5A ALS variants cause exon 27 skipping and are predicted to produce motor proteins with an altered C-terminal tail (referred to as ΔExon27). However, the underlying pathogenic mechanism is still unknown. Here, we confirm the expression of KIF5A mutant proteins in patient iPSC-derived motor neurons. We perform a comprehensive analysis of ΔExon27 at the single-molecule, cellular, and organism levels. Our results show that ΔExon27 is prone to form cytoplasmic aggregates and is neurotoxic. The mutation relieves motor autoinhibition and increases motor self-association, leading to drastically enhanced processivity on microtubules. Finally, ectopic expression of ΔExon27 in Drosophila melanogaster causes wing defects, motor impairment, paralysis, and premature death. Our results suggest gain-of-function as an underlying disease mechanism in KIF5A-associated ALS.

Crucial Roles of Ubiquitin Carboxy-Terminal Hydrolase L1 in Motor Neuronal Health by Drosophila Model

Aims: Ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1) plays an important role in the ubiquitin-proteasome system and is distributed mostly in the brain. Previous studies have shown that mutated forms or reduction of UCH-L1 are related to neurodegenerative disorders, but the mechanisms of pathogenesis are still not well understood. To study its roles in motor neuronal health, we utilized the Drosophila model in which dUCH, a homolog of human UCH-L1, was specifically knocked down in motor neurons. Results: The reduction of Drosophila ubiquitin carboxyl-terminal hydrolase (dUCH) in motor neurons induced excessive reactive oxygen species production and multiple aging-like phenotypes, including locomotive defects, muscle degeneration, enhanced apoptosis, and shortened longevity. In addition, there is a decrease in the density of the synaptic active zone and glutamate receptor area at the neuromuscular junction. Interestingly, all these defects were rescued by vitamin C treatment, suggesting a close association with oxidative stress. Strikingly, the knockdown of dUCH at motor neurons exhibited aberrant morphology and function of mitochondria, such as mitochondrial DNA (mtDNA) depletion, an increase in mitochondrial size, and overexpression of antioxidant enzymes. Innovation: This research indicates a new, possible pathogenesis of dUCH deficiency in the ventral nerve cord and peripheral nervous systems, which starts with abnormal mitochondria, leading to oxidative stress and accumulation aging-like defects in general. Conclusion: Taken together, by using the Drosophila model, our findings strongly emphasize how the UCH-L1 shortage affects motor neurons and further demonstrate the crucial roles of UCH-L1 in neuronal health. Antioxid. Redox Signal. 37, 257-273.

Treating the Onset of Diabetes Using Probiotics Along with Prebiotic from Pachyrhizus erosus in High-Fat Diet Fed Drosophila melanogaster

The increasing mortality due to hypertension and hypercholesterolemia is directly linked with type-2 diabetes. This shows the lethality of the disease. Reports suggest that the prebiotics along with probiotics help in lowering the effects of type-2 diabetes. Prebiotic like inulin is best known for its anti-diabetic effect. The current study utilizes jicama extract as prebiotic source of inulin along with the bacterial strains with probiotic properties (Lactiplantibacillus plantarum and Enterococcus faecium) for treating type-2 diabetes in high-fat diet-induced Drosophila melanogaster model. The high-fat diet-induced Drosophila showed deposition of lipid droplets and formation of micronuclei in the gut. The larva and adult treated with probiotics and synbiotic (probiotic + prebiotic- inulin) comparatively reduced the lipid deposition and micronuclei number in the gut. The increased amount of triglyceride in the whole body of the fatty larva and adult indicated the onset of diabetes. The overexpression of insulin-like genes (Dilp 2) and (Dilp 5) confirmed the insulin resistance, whereas the expression was reduced in the larva and adult supplemented with probiotics and synbiotic. The reactive oxygen species level was reduced with the supplementation of probiotics. The weight, larva size, crawling speed and climbing were also altered in high-fat diet-induced Drosophila melanogaster. The study confirmed the effects of probiotics and synbiotic in successfully lowering diabetes in Drosophila. The study also proved the anti-diabetic potential of the probiotics. Further, it was also confirmed that the probiotics work better in the presence of prebiotic.

Controlled decoration of nanoceria on the surface of MoS2nanoflowers to improve the biodegradability and biocompatibility inDrosophila melanogastermodel

In recent years, nanozymes based on two-dimensional (2D) nanomaterials have been receiving great interest for cancer photothermal therapy. 2D materials decorated with nanoparticles (NPs) on their surface are advantageous over conventional NPs and 2D material based systems because of their ability to synergistically improve the unique properties of both NPs and 2D materials. In this work, we report a nanozyme based on flower-like MoS₂nanoflakes (NFs) by decorating their flower petals with NCeO₂using polyethylenimine (PEI) as a linker molecule. A detailed investigation on toxicity, biocompatibility and degradation behavior of fabricated nanozymes in wild-typeDrosophila melanogastermodel revealed that there were no significant effects on the larval size, morphology, larval length, breadth and no time delay in changing larvae to the third instar stage at 7-10 d for MoS₂NFs before and after NCeO₂decoration. The muscle contraction and locomotion behavior of third instar larvae exhibited high distance coverage for NCeO₂decorated MoS₂NFs when compared to bare MoS₂NFs and control groups. Notably, the MoS₂and NCeO₂-PEI-MoS₂NFs treated groups at 100μg ml^-1covered a distance of 38.2 mm (19.4% increase when compared with control) and 49.88 mm (no change when compared with control), respectively. High-resolution transmission electron microscopy investigations on the new born fly gut showed that the NCeO₂decoration improved the degradation rate of MoS₂NFs. Hence, nanozymes reported here have huge potential in various fields ranging from biosensing, cancer therapy and theranostics to tissue engineering and the treatment of Alzheimer's disease and retinal therapy.

Phenotyping of Drosophila melanogaster—A Nutritional Perspective

The model organism Drosophila melanogaster was increasingly applied in nutrition research in recent years. A range of methods are available for the phenotyping of D. melanogaster, which are outlined in the first part of this review. The methods include determinations of body weight, body composition, food intake, lifespan, locomotor activity, reproductive capacity and stress tolerance. In the second part, the practical application of the phenotyping of flies is demonstrated via a discussion of obese phenotypes in response to high-sugar diet (HSD) and high-fat diet (HFD) feeding. HSD feeding and HFD feeding are dietary interventions that lead to an increase in fat storage and affect carbohydrate-insulin homeostasis, lifespan, locomotor activity, reproductive capacity and stress tolerance. Furthermore, studies regarding the impacts of HSD and HFD on the transcriptome and metabolome of D. melanogaster are important for relating phenotypic changes to underlying molecular mechanisms. Overall, D. melanogaster was demonstrated to be a valuable model organism with which to examine the pathogeneses and underlying molecular mechanisms of common chronic metabolic diseases in a nutritional context.

Glial immune-related pathways mediate effects of closed head traumatic brain injury on behavior and lethality in Drosophila

In traumatic brain injury (TBI), the initial injury phase is followed by a secondary phase that contributes to neurodegeneration, yet the mechanisms leading to neuropathology in vivo remain to be elucidated. To address this question, we developed a Drosophila head-specific model for TBI termed Drosophila Closed Head Injury (dCHI), where well-controlled, nonpenetrating strikes are delivered to the head of unanesthetized flies. This assay recapitulates many TBI phenotypes, including increased mortality, impaired motor control, fragmented sleep, and increased neuronal cell death. TBI results in significant changes in the transcriptome, including up-regulation of genes encoding antimicrobial peptides (AMPs). To test the in vivo functional role of these changes, we examined TBI-dependent behavior and lethality in mutants of the master immune regulator NF-κB, important for AMP induction, and found that while sleep and motor function effects were reduced, lethality effects were enhanced. Similarly, loss of most AMP classes also renders flies susceptible to lethal TBI effects. These studies validate a new Drosophila TBI model and identify immune pathways as in vivo mediators of TBI effects.

Traumatic brain injury in Drosophila causes sleep and motor impairments, as well as a strong activation of the innate immune response that is crucial for survival. This study leverages Drosophila as a model organism to reveal neuroprotective and neurotoxic injury mechanisms more quickly using high throughout approaches.

Roles of Drosophila Hox Genes in the Assembly of Neuromuscular Networks and Behavior

Hox genes have been known for specifying the anterior-posterior axis (AP) in bilaterian body plans. Studies in vertebrates have shown their importance in developing region-specific neural circuitry and diversifying motor neuron pools. In Drosophila, they are instrumental for segment-specific neurogenesis and myogenesis early in development. Their robust expression in differentiated neurons implied their role in assembling region-specific neuromuscular networks. In the last decade, studies in Drosophila have unequivocally established that Hox genes go beyond their conventional functions of generating cellular diversity along the AP axis of the developing central nervous system. These roles range from establishing and maintaining the neuromuscular networks to controlling their function by regulating the motor neuron morphology and neurophysiology, thereby directly impacting the behavior. Here we summarize the limited knowledge on the role of Drosophila Hox genes in the assembly of region-specific neuromuscular networks and their effect on associated behavior.

Rbfox1 is required for myofibril development and maintaining fiber type-specific isoform expression in Drosophila muscles

Protein isoform transitions confer muscle fibers with distinct properties and are regulated by differential transcription and alternative splicing. RNA-binding Fox protein 1 (Rbfox1) can affect both transcript levels and splicing, and is known to contribute to normal muscle development and physiology in vertebrates, although the detailed mechanisms remain obscure. In this study, we report that Rbfox1 contributes to the generation of adult muscle diversity in Drosophila Rbfox1 is differentially expressed among muscle fiber types, and RNAi knockdown causes a hypercontraction phenotype that leads to behavioral and eclosion defects. Misregulation of fiber type-specific gene and splice isoform expression, notably loss of an indirect flight muscle-specific isoform of Troponin-I that is critical for regulating myosin activity, leads to structural defects. We further show that Rbfox1 directly binds the 3'-UTR of target transcripts, regulates the expression level of myogenic transcription factors myocyte enhancer factor 2 and Salm, and both modulates expression of and genetically interacts with the CELF family RNA-binding protein Bruno1 (Bru1). Rbfox1 and Bru1 co-regulate fiber type-specific alternative splicing of structural genes, indicating that regulatory interactions between FOX and CELF family RNA-binding proteins are conserved in fly muscle. Rbfox1 thus affects muscle development by regulating fiber type-specific splicing and expression dynamics of identity genes and structural proteins.

Using Drosophila to uncover molecular and physiological functions of circRNAs

Circular RNAs (circRNAs) are a class of covalently closed RNA molecules generated by backsplicing. circRNAs are expressed in a tissue-specific manner, accumulate with age in neural tissues, and are highly stable. In many cases, circRNAs are generated at the expense of a linear transcript as back-splicing competes with linear splicing. Some circRNAs regulate gene expression in cis, and some circRNAs can be translated into protein. The advent of deep sequencing and new bioinformatic tools has allowed detection of thousands of circRNAs in eukaryotes. Studying the functions of circRNAs is done using a combination of molecular and genetic methods. The unique genetic tools that can be used in studies of Drosophila melanogaster are ideal for deciphering the functions of circRNAs in vivo. These tools include the GAL4-UAS system, which can be used to manipulate the levels of circRNAs with exquisite temporal and spatial control, and genetic interaction screening, which could be used to identify pathways regulated by circRNAs. Research performed in Drosophila has revealed circRNAs production mechanisms, details of their translation, and their physiological functions. Due to their short lifecycle and the existence of excellent neurodegeneration models, Drosophila can also be used to study the role of circRNAs in aging and age-related disorders. Here, we review molecular and genetic tools and methods for detecting, manipulating, and studying circRNAs in Drosophila.

Aza-Flavanone Diminishes Parkinsonism in the Drosophila melanogaster Parkin Mutant

Parkinson's disease is a chronic and progressive neurodegenerative disease, induced by slow and progressive death of the dopaminergic (DA) neurons from the midbrain region called substantia nigra (SNc) leading to difficulty in locomotion. At present, very few potential therapeutic drugs are available for treatment, necessitating an urgent need for development. In the current study, the parkin transgenic Drosophila melanogaster model that induces selective loss in dopaminergic neurons and impairment of locomotory functions has been used to see the effect of the aza-flavanone molecule. D. melanogaster serves as an amazing in vivo model making valuable contribution in the development of promising treatment strategies. Our in-silico study showed spontaneous binding of this molecule to the D2 receptor making it a potential dopamine agonist. PARKIN protein is well conserved, and it has been reported that Drosophila PARKIN is 42% identical to human PARKIN. Interestingly, this molecule enhances the motor coordination and survivability rate of the transgenic flies along with an increase in expression of the master regulator of Dopamine synthesis, that is, tyrosine hydroxylase (TH), in the substantia nigra region of the fly brain. Moreover, it plays a significant effect on mitochondrial health and biogenesis via modulation of a conserved mitochondrial protein PHB2. Therefore, this molecule could lead to the development of an effective therapeutic approach for the treatment of PD.

Two oppositely-charged sf3b1 mutations cause defective development, impaired immune response, and aberrant selection of intronic branch sites in Drosophila

SF3B1 mutations occur in many cancers, and the highly conserved His662 residue is one of the hotspot mutation sites. To address effects on splicing and development, we constructed strains carrying point mutations at the corresponding residue His698 in Drosophila using the CRISPR-Cas9 technique. Two mutations, H698D and H698R, were selected due to their frequent presence in patients and notable opposite charges. Both the sf3b1-H698D and–H698R mutant flies exhibit developmental defects, including less egg-laying, decreased hatching rates, delayed morphogenesis and shorter lifespans. Interestingly, the H698D mutant has decreased resistance to fungal infection, while the H698R mutant shows impaired climbing ability. Consistent with these phenotypes, further analysis of RNA-seq data finds altered expression of immune response genes and changed alternative splicing of muscle and neural-related genes in the two mutants, respectively. Expression of Mef2-RB, an isoform of Mef2 gene that was downregulated due to splicing changes caused by H698R, partly rescues the climbing defects of the sf3b1-H698R mutant. Lariat sequencing reveals that the two sf3b1-H698 mutations cause aberrant selection of multiple intronic branch sites, with the H698R mutant using far upstream branch sites in the changed alternative splicing events. This study provides in vivo evidence from Drosophila that elucidates how these SF3B1 hotspot mutations alter splicing and their consequences in development and in the immune system.

In the past decade, one of the important findings in the RNA splicing field has been that somatic SF3B1 mutations widely occur in many cancers. Including R625, H662, K666, K700 and E902, there are five hotspot mutation sites in the highly conserved HEAT repeats of SF3B1. Several kinds of H662 mutations have been found widely in MDS, AML, CLL and breast cancers; however, it remains unclear how these H662 mutations alter splicing and whether they have in vivo effects on development. To address these questions, in this manuscript, we first summarized the H662 mutations in human diseases and constructed two corresponding Drosophila mutant strains, sf3b1-H698D and -H698R using CRISPR-Cas9. Analyses of these two fly strains find that the two oppositely charged Sf3b1-H698 mutants are defective in development. In addition, one mutant has decreased climbing ability, whereas the other mutant has impaired immune response. Further RNA-seq allows us to find responsible genes in each mutant strain, and lariat sequencing reveals that both mutations cause aberrant selection of the intronic branch sites. Our findings provide the first in vivo evidence that Sf3b1 mutations result in defective development, and also reveal a molecular mechanism of these hotspot histidine mutations that enhance the use of cryptic branch sites to alter splicing. Importantly, we demonstrate that the H698R mutant prefers to use far upstream branch sites.

Enhancing mask activity in dopaminergic neurons extends lifespan in flies

Dopaminergic neurons (DANs) are essential modulators for brain functions involving memory formation, reward processing, and decision‐making. Here I demonstrate a novel and important function of the DANs in regulating aging and longevity. Overexpressing the putative scaffolding protein Mask in two small groups of DANs in flies can significantly extend the lifespan in flies and sustain adult locomotor and fecundity at old ages. This Mask‐induced beneficial effect requires dopaminergic transmission but cannot be recapitulated by elevating dopamine production alone in the DANs. Independent activation of Gα_s in the same two groups of DANs via the drug‐inducible DREADD system also extends fly lifespan, further indicating the connection of specific DANs to aging control. The Mask‐induced lifespan extension appears to depend on the function of Mask to regulate microtubule (MT) stability. A structure–function analysis demonstrated that the ankyrin repeats domain in the Mask protein is both necessary for regulating MT stability (when expressed in muscles and motor neurons) and sufficient to prolong longevity (when expressed in the two groups of DANs). Furthermore, DAN‐specific overexpression of Unc‐104 or knockdown of p150^Glued, two independent interventions previously shown to impact MT dynamics, also extends lifespan in flies. Together, these data demonstrated a novel DANs‐dependent mechanism that, upon the tuning of their MT dynamics, modulates systemic aging and longevity in flies.

The function of Scox in glial cells is essential for locomotive ability in Drosophila

Synthesis of cytochrome c oxidase (Scox) is a Drosophila homolog of human SCO2 encoding a metallochaperone that transports copper to cytochrome c, and is an essential protein for the assembly of cytochrome c oxidase in the mitochondrial respiratory chain complex. SCO2 is highly conserved in a wide variety of species across prokaryotes and eukaryotes, and mutations in SCO2 are known to cause mitochondrial diseases such as fatal infantile cardioencephalomyopathy, Leigh syndrome, and Charcot-Marie-Tooth disease, a neurodegenerative disorder. These diseases have a common symptom of locomotive dysfunction. However, the mechanisms of their pathogenesis remain unknown, and no fundamental medications or therapies have been established for these diseases. In this study, we demonstrated that the glial cell-specific knockdown of Scox perturbs the mitochondrial morphology and function, and locomotive behavior in Drosophila. In addition, the morphology and function of synapses were impaired in the glial cell-specific Scox knockdown. Furthermore, Scox knockdown in ensheathing glia, one type of glial cell in Drosophila, resulted in larval and adult locomotive dysfunction. This study suggests that the impairment of Scox in glial cells in the Drosophila CNS mimics the pathological phenotypes observed by mutations in the SCO2 gene in humans.

DDX17 is involved in DNA damage repair and modifies FUS toxicity in an RGG-domain dependent manner

Mutations in the RNA binding protein, Fused in Sarcoma (FUS), lead to amyotrophic lateral sclerosis (ALS), the most frequent form of motor neuron disease. Cytoplasmic aggregation and defective DNA repair machinery are etiologically linked to mutant FUS-associated ALS. Although FUS is involved in numerous aspects of RNA processing, little is understood about the pathophysiological mechanisms of mutant FUS. Here, we employed RNA-sequencing technology in Drosophila brains expressing FUS to identify significantly altered genes and pathways involved in FUS-mediated neurodegeneration. We observed the expression levels of DEAD-Box Helicase 17 (DDX17) to be significantly downregulated in response to mutant FUS in Drosophila and human cell lines. Mutant FUS recruits nuclear DDX17 into cytoplasmic stress granules and physically interacts with DDX17 through the RGG1 domain of FUS. Ectopic expression of DDX17 reduces cytoplasmic mislocalization and sequestration of mutant FUS into cytoplasmic stress granules. We identified DDX17 as a novel regulator of the DNA damage response pathway whose upregulation repairs defective DNA damage repair machinery caused by mutant neuronal FUS ALS. In addition, we show DDX17 is a novel modifier of FUS-mediated neurodegeneration in vivo. Our findings indicate DDX17 is downregulated in response to mutant FUS, and restoration of DDX17 levels suppresses FUS-mediated neuropathogenesis and toxicity in vivo.

Methods to Assay the Behavior of Drosophila melanogaster for Toxicity Study

Drosophila melanogaster, the fruit fly, has been widely used in biological investigation as an invertebrate alternative to mammals for its various advantages compared to other model organisms, which include short life cycle, easy handling, high prolificacy, and great availability of substantial genetic information. The behavior of Drosophila melanogaster is closely related to its growth, which can reflect the physiological conditions of Drosophila. We have optimized simple and robust behavioral assays for determining the larvae survival, adult climbing ability (mobility assay), reproductive behavior, and lifespan of Drosophila. In this chapter, we present the step-by-step detailed method for studying Drosophila behavior.

In vivo Evaluation of a Newly Synthesized Acetylcholinesterase Inhibitor in a Transgenic Drosophila Model of Alzheimer's Disease

Alzheimer's disease is a neurodegenerative disease characterized by disrupted memory, learning functions, reduced life expectancy, and locomotor dysfunction, as a result of the accumulation and aggregation of amyloid peptides that cause neuronal damage in neuronal circuits. In the current study, we exploited a transgenic Drosophila melanogaster line, expressing amyloid-β peptides to investigate the efficacy of a newly synthesized acetylcholinesterase inhibitor, named XJP-1, as a potential AD therapy. Behavioral assays and confocal microscopy were used to characterize the drug effect on AD symptomatology and amyloid peptide deposition. The symptomatology induced in this particular transgenic model recapitulates the scenario observed in human AD patients, showing a shortened lifespan and reduced locomotor functions, along with a significant accumulation of amyloid plaques in the brain. XJP-1 treatment resulted in a significant improvement of AD symptoms and a reduction of amyloid plaques by diminishing the amyloid aggregation rate. In comparison with clinically effective AD drugs, our results demonstrated that XJP-1 has similar effects on AD symptomatology, but at 10 times lower drug concentration than donepezil. It also showed an earlier beneficial effect on the reduction of amyloid plaques at 10 days after drug treatment, as observed for donepezil at 20 days, while the other drugs tested have no such effect. As a novel and potent AChE inhibitor, our study demonstrates that inhibition of the enzyme AChE by XJP-1 treatment improves the amyloid-induced symptomatology in Drosophila, by reducing the number of amyloid plaques within the fruit fly CNS. Thus, compound XJP-1 has the therapeutic potential to be further investigated for the treatment of AD.

Secreted C-type lectin regulation of neuromuscular junction synaptic vesicle dynamics modulates coordinated movement

The synaptic cleft manifests enriched glycosylation, with structured glycans coordinating signaling between presynaptic and postsynaptic cells. Glycosylated signaling ligands orchestrating communication are tightly regulated by secreted glycan-binding lectins. Using the Drosophila neuromuscular junction (NMJ) as a model glutamatergic synapse, we identify a new Ca2+-binding (C-type) lectin, Lectin-galC1 (LGC1), which modulates presynaptic function and neurotransmission strength. We find that LGC1 is enriched in motoneuron presynaptic boutons and secreted into the NMJ extracellular synaptomatrix. We show that LGC1 limits locomotor peristalsis and coordinated movement speed, with a specific requirement for synaptic function, but not NMJ architecture. LGC1 controls neurotransmission strength by limiting presynaptic active zone (AZ) and postsynaptic glutamate receptor (GluR) aligned synapse number, reducing both spontaneous and stimulation-evoked synaptic vesicle (SV) release, and capping SV cycling rate. During high-frequency stimulation (HFS), mutants have faster synaptic depression and impaired recovery while replenishing depleted SV pools. Although LGC1 removal increases the number of glutamatergic synapses, we find that LGC1-null mutants exhibit decreased SV density within presynaptic boutons, particularly SV pools at presynaptic active zones. Thus, LGC1 regulates NMJ neurotransmission to modulate coordinated movement.

Loss of function mutations in GEMIN5 cause a neurodevelopmental disorder

GEMIN5, an RNA-binding protein is essential for assembly of the survival motor neuron (SMN) protein complex and facilitates the formation of small nuclear ribonucleoproteins (snRNPs), the building blocks of spliceosomes. Here, we have identified 30 affected individuals from 22 unrelated families presenting with developmental delay, hypotonia, and cerebellar ataxia harboring biallelic variants in the GEMIN5 gene. Mutations in GEMIN5 perturb the subcellular distribution, stability, and expression of GEMIN5 protein and its interacting partners in patient iPSC-derived neurons, suggesting a potential loss-of-function mechanism. GEMIN5 mutations result in disruption of snRNP complex assembly formation in patient iPSC neurons. Furthermore, knock down of rigor mortis, the fly homolog of human GEMIN5, leads to developmental defects, motor dysfunction, and a reduced lifespan. Interestingly, we observed that GEMIN5 variants disrupt a distinct set of transcripts and pathways as compared to SMA patient neurons, suggesting different molecular pathomechanisms. These findings collectively provide evidence that pathogenic variants in GEMIN5 perturb physiological functions and result in a neurodevelopmental delay and ataxia syndrome.

Acteoside exerts neuroprotection effects in the model of Parkinson's disease via inducing autophagy: Network pharmacology and experimental study

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease. At present, the incidence rate of PD is increasing worldwide, there is no effective cure available so far, and currently using drugs are still limited in efficacy due to serious side effects. Acteoside (ACT) is an active ingredient of many valuable medicinal plants, possesses potential therapeutic effects on many pathological conditions. In this study, we dissected the neuroprotection effects of ACT on PD and its potential molecular mechanism in our PD model pathology based on network pharmacology prediction and experimental assays. Network pharmacology and bioinformatics analysis demonstrated that ACT has 381 potential targets; among them 78 putative targets associated with PD were closely related to cellular autophagy and apoptotic processes. Our experimental results showed that ACT exerted significant neuroprotection effects on Rotenone (ROT) -induced injury of neuronal cells and Drosophila melanogaster (D. melanogaster). Meanwhile, ACT treatment induced autophagy in both neuronal cell lines and fat bodies of D. melanogaster. Furthermore, ACT treatment decreased ROT induced apoptotic rate and reactive oxygen species production, increased mitochondrial membrane potentials in neuronal cells, and promoted clearance of α-synuclein (SNCA) aggregations in SNCA overexpressed cell model through the autophagy-lysosome pathway. Interestingly, ACT treatment significantly enhanced mitophagy and protected cell injury in neuronal cells. Taken together, ACT may represent a potent stimulator of mitophagy pathway, thereby exerts preventive and therapeutic effects against neurodegenerative diseases such as PD by clearing pathogenic proteins and impaired cellular organelles like damaged mitochondria in neurons.

Potential of Pueraria tuberosa (Willd.) DC. to rescue cognitive decline associated with BACE1 protein of Alzheimer's disease on Drosophila model: An integrated molecular modeling and in vivo approach

The indispensable role of Beta-site amyloid precursor protein cleaving enzyme-1 (BACE1) in Amyloid beta (Aβ) plaques generation and Aβ-mediated synaptic dysfunctions makes it a crucial target for therapeutic intervention in Alzheimer's disease (AD). In order to find out the potential inhibitors of BACE1, the present study focused on five phytochemicals from Pueraria tuberosa, namely, daidzin, genistin, mangiferin, puerarin, and tuberosin. A molecular docking study showed that all five phytochemicals presented the strongest BACE1 inhibition. Integrated molecular dynamics simulations and free energy calculations demonstrated that all five natural compounds have stable and favorable energies causing strong binding with the pocket site of BACE1 on 50 ns. All these molecules also passed Lipinski's rule of five. To validate the molecular modeling based findings, we primarily targeted the cognitive decline associated with BACE1 expression in AD flies with P. tuberosa. Significant improvement in cognitive decline was observed in AD flies in different behavioral assays such as Larval crawling assay (16.38%), Larval light preference assay (26.39%), Climbing assay (32.97%), Cold sensitivity assay (43.6%), and Thermal sensitivity assay (44.42%). The present findings suggest that P. tuberosa may be considered as a promising dietary supplement that can significantly ameliorate cognitive decline caused by BACE1 in Alzheimer's disease (AD).

Drosophila model of anti-retroviral therapy induced peripheral neuropathy and nociceptive hypersensitivity

The success of antiretroviral therapy (ART) has improved the survival of HIV-infected patients significantly. However, significant numbers of patients on ART whose HIV disease is well controlled show peripheral sensory neuropathy (PSN), suggesting that ART may cause PSN. Although the nucleoside reverse transcriptase inhibitors (NRTIs), one of the vital components of ART, are thought to contribute to PSN, the mechanisms underlying the PSN induced by NRTIs are unclear. In this study, we developed a Drosophila model of NRTI-induced PSN that recapitulates the salient features observed in patients undergoing ART: PSN and nociceptive hypersensitivity. Furthermore, our data demonstrate that pathways known to suppress PSN induced by chemotherapeutic drugs are ineffective in suppressing the PSN or nociception induced by NRTIs. Instead, we found that increased dynamics of a peripheral sensory neuron may possibly underlie NRTI-induced PSN and nociception. Our model provides a solid platform in which to investigate further mechanisms of ART-induced PSN and nociceptive hypersensitivity.

This article has an associated First Person interview with the first author of the paper.

Summary: Nucleoside reverse transcriptase inhibitors (NRTIs) that are important components of anti-retroviral therapies also cause peripheral sensory neuropathies (PSN). This article investigates ways in which NRTIs may cause PSN and outlines ways to better understand the mechanisms underlying it.

Impaired muscle morphology in a Drosophila model of myosin storage myopathy was supressed by overexpression of an E3 ubiquitin ligase

Myosin is vital for body movement and heart contractility. Mutations in MYH7, encoding slow/β-cardiac myosin heavy chain, are an important cause of hypertrophic and dilated cardiomyopathy, as well as skeletal muscle disease. A dominant missense mutation (R1845W) in MYH7 has been reported in several unrelated cases of myosin storage myopathy. We have developed a Drosophila model for a myosin storage myopathy in order to investigate the dose-dependent mechanisms underlying the pathological roles of the R1845W mutation. This study shows that a higher expression level of the mutated allele is concomitant with severe impairment of muscle function and progressively disrupted muscle morphology. The impaired muscle morphology associated with the mutant allele was suppressed by expression of Thin (herein referred to as Abba), an E3 ubiquitin ligase. This Drosophila model recapitulates pathological features seen in myopathy patients with the R1845W mutation and severe ultrastructural abnormalities, including extensive loss of thick filaments with selective A-band loss, and preservation of I-band and Z-disks were observed in indirect flight muscles of flies with exclusive expression of mutant myosin. Furthermore, the impaired muscle morphology associated with the mutant allele was suppressed by expression of Abba. These findings suggest that modification of the ubiquitin proteasome system may be beneficial in myosin storage myopathy by reducing the impact of MYH7 mutation in patients.

Exposure to bisphenol A differentially impacts neurodevelopment and behavior in Drosophila melanogaster from distinct genetic backgrounds

Bisphenol A (BPA) is a ubiquitous environmental chemical that has been linked to behavioral differences in children and shown to impact critical neurodevelopmental processes in animal models. Though data is emerging, we still have an incomplete picture of how BPA disrupts neurodevelopment; in particular, how its impacts may vary across different genetic backgrounds. Given the genetic tractability of Drosophila melanogaster, they present a valuable model to address this question. Fruit flies are increasingly being used for assessment of neurotoxicants because of their relatively simple brain structure and variety of measurable behaviors. Here we investigated the neurodevelopmental impacts of BPA across two genetic strains of Drosophila-w¹¹¹⁸ (control) and the Fragile X Syndrome (FXS) model-by examining both behavioral and neuronal phenotypes. We show that BPA induces hyperactivity in larvae, increases repetitive grooming behavior in adults, reduces courtship behavior, impairs axon guidance in the mushroom body, and disrupts neural stem cell development in the w¹¹¹⁸ genetic strain. Remarkably, for every behavioral and neuronal phenotype examined, the impact of BPA in FXS flies was either insignificant or contrasted with the phenotypes observed in the w¹¹¹⁸ strain. This data indicates that the neurodevelopmental impacts of BPA can vary widely depending on genetic background and suggests BPA may elicit a gene-environment interaction with Drosophila fragile X mental retardation 1 (dFmr1)-the ortholog of human FMR1, which causes Fragile X Syndrome and is associated with autism spectrum disorder.

An insight on Drosophila myogenesis and its assessment techniques

Movement assisted by muscles forms the basis of various behavioural traits seen in Drosophila. Myogenesis involves developmental processes like cellular specification, differentiation, migration, fusion, adherence to tendons and neuronal innervation in a series of coordinated event well defined in body space and time. Gene regulatory networks are switched on-off, fine tuning at the right developmental stage to assist each cellular event. Drosophila is a holometabolous organism that undergoes myogenesis waves at two developmental stages, and is ideal for comparative analysis of the role of genes and genetic pathways conserved across phyla. In this review we have summarized myogenic events from the embryo to adult focussing on the somatic muscle development during the early embryonic stage and then on indirect flight muscles (IFM) formation required for adult life, emphasizing on recent trends of analysing muscle mutants and advances in Drosophila muscle biology.

Identification of Caffeic Acid Phenethyl Ester (CAPE) as a Potent Neurodifferentiating Natural Compound That Improves Cognitive and Physiological Functions in Animal Models of Neurodegenerative Diseases

Cell-based screening of bioactive compounds has served as an important gateway in drug discovery. In the present report, using human neuroblastoma cells and enrolling an extensive three-step screening of 57 phytochemicals, we have identified caffeic acid phenethyl ester (CAPE) as a potent neurodifferentiating natural compound. Analyses of control and CAPE-induced neurodifferentiated cells revealed: (i) modulation of several key proteins (NF200, MAP-2, NeuN, PSD95, Tuj1, GAP43, and GFAP) involved in neurodifferentiation process; and (ii) attenuation of neuronal stemness (HOXD13, WNT3, and Msh-2) and proliferation-promoting (CDC-20, CDK-7, and BubR1) proteins. We anticipated that the neurodifferentiation potential of CAPE may be beneficial for the treatment of neurodegenerative diseases and tested it using the Drosophila model of Alzheimer’s disease (AD) and mice model of amnesia/loss of memory. In both models, CAPE exhibited improved disease symptoms and activation of physiological functions. Remarkably, CAPE-treated mice showed increased levels of neurotrophin-BDNF, neural progenitor marker-Nestin, and differentiation marker-NeuN, both in the cerebral cortex and hippocampus. Taken together, we demonstrate the differentiation-inducing and therapeutic potential of CAPE for neurodegenerative diseases.

RNA dependent suppression of C9orf72 ALS/FTD associated neurodegeneration by Matrin-3

The most common genetic cause of amyotrophic lateral sclerosis (ALS) is a GGGGCC (G4C2) hexanucleotide repeat expansions in first intron of the C9orf72 gene. The accumulation of repetitive RNA sequences can mediate toxicity potentially through the formation of intranuclear RNA foci that sequester key RNA-binding proteins (RBPs), and non-ATG mediated translation into toxic dipeptide protein repeats. However, the contribution of RBP sequestration to the mechanisms underlying RNA-mediated toxicity remain unknown. Here we show that the ALS-associated RNA-binding protein, Matrin-3 (MATR3), colocalizes with G4C2 RNA foci in patient tissues as well as iPSC-derived motor neurons harboring the C9orf72 mutation. Hyperexpansion of C9 repeats perturbed subcellular distribution and levels of endogenous MATR3 in C9-ALS patient-derived motor neurons. Interestingly, we observed that ectopic expression of human MATR3 strongly mitigates G4C2-mediated neurodegeneration in vivo. MATR3-mediated suppression of C9 toxicity was dependent on the RNA-binding domain of MATR3. Importantly, we found that expression of MATR3 reduced the levels of RAN-translation products in mammalian cells in an RNA-dependent manner. Finally, we have shown that knocking down endogenous MATR3 in C9-ALS patient-derived iPSC neurons decreased the presence of G4C2 RNA foci in the nucleus. Overall, these studies suggest that MATR3 genetically modifies the neuropathological and the pathobiology of C9orf72 ALS through modulating the RNA foci and RAN translation.

Recent Advances in Drosophila Models of Charcot-Marie-Tooth Disease

Charcot-Marie-Tooth disease (CMT) is one of the most common inherited peripheral neuropathies. CMT patients typically show slowly progressive muscle weakness and sensory loss in a distal dominant pattern in childhood. The diagnosis of CMT is based on clinical symptoms, electrophysiological examinations, and genetic testing. Advances in genetic testing technology have revealed the genetic heterogeneity of CMT; more than 100 genes containing the disease causative mutations have been identified. Because a single genetic alteration in CMT leads to progressive neurodegeneration, studies of CMT patients and their respective models revealed the genotype-phenotype relationships of targeted genes. Conventionally, rodents and cell lines have often been used to study the pathogenesis of CMT. Recently, Drosophila has also attracted attention as a CMT model. In this review, we outline the clinical characteristics of CMT, describe the advantages and disadvantages of using Drosophila in CMT studies, and introduce recent advances in CMT research that successfully applied the use of Drosophila, in areas such as molecules associated with mitochondria, endosomes/lysosomes, transfer RNA, axonal transport, and glucose metabolism.

The Pathopharmacological Interplay between Vanadium and Iron in Parkinson's Disease Models

Parkinson's disease (PD) pathology is characterised by distinct types of cellular defects, notably associated with oxidative damage and mitochondria dysfunction, leading to the selective loss of dopaminergic neurons in the brain's substantia nigra pars compacta (SNpc). Exposure to some environmental toxicants and heavy metals has been associated with PD pathogenesis. Raised iron levels have also been consistently observed in the nigrostriatal pathway of PD cases. This study explored, for the first time, the effects of an exogenous environmental heavy metal (vanadium) and its interaction with iron, focusing on the subtoxic effects of these metals on PD-like oxidative stress phenotypes in Catecholaminergic a-differentiated (CAD) cells and PTEN-induced kinase 1 (PINK-1)B9Drosophila melanogaster models of PD. We found that undifferentiated CAD cells were more susceptible to vanadium exposure than differentiated cells, and this susceptibility was modulated by iron. In PINK-1 flies, the exposure to chronic low doses of vanadium exacerbated the existing motor deficits, reduced survival, and increased the production of reactive oxygen species (ROS). Both Aloysia citrodora Paláu, a natural iron chelator, and Deferoxamine Mesylate (DFO), a synthetic iron chelator, significantly protected against the PD-like phenotypes in both models. These results favour the case for iron-chelation therapy as a viable option for the symptomatic treatment of PD.

Oxalate-Degrading Bacillus subtilis Mitigates Urolithiasis in a Drosophila melanogaster Model

Kidney stone disease is a morbid condition that is increasing in prevalence, with few nonsurgical treatment options. The majority of stones are composed of calcium oxalate. Unlike humans, some microbes can break down oxalate, suggesting that microbial therapeutics may provide a novel treatment for kidney stone patients. This study demonstrated that Bacillus subtilis 168 (BS168) decreased stone burden, improved health, and complemented the microbiota in a Drosophila melanogaster urolithiasis model, while not exacerbating calcium oxalate aggregation or adhesion to renal cells in vitro. These results identify this bacterium as a candidate for ameliorating stone formation; given that other strains of B. subtilis are components of fermented foods and are used as probiotics for digestive health, strain 168 warrants testing in humans. With the severe burden that recurrent kidney stone disease imposes on patients and the health care system, this microbial therapeutic approach could provide an inexpensive therapeutic adjunct.

Kidney stones affect nearly 10% of the population in North America and are associated with high morbidity and recurrence, yet novel prevention strategies are lacking. Recent evidence suggests that the human gut microbiota can influence the development of nephrolithiasis, although clinical trials have been limited and inconclusive in determining the potential for microbially based interventions. Here, we used an established Drosophila melanogaster model of urolithiasis as a high-throughput screening platform for evaluation of the therapeutic potential of oxalate-degrading bacteria in calcium oxalate (CaOx) nephrolithiasis. The results demonstrated that Bacillus subtilis 168 (BS168) is a promising candidate based on its preferential growth in high oxalate concentrations, its ability to stably colonize the D. melanogaster intestinal tract for as long as 5 days, and its prevention of oxalate-induced microbiota dysbiosis. Single-dose BS168 supplementation exerted beneficial effects on D. melanogaster for as long as 14 days, decreasing stone burden in dissected Malpighian tubules and fecal excreta while increasing survival and behavioral markers of health over those of nonsupplemented lithogenic controls. These findings were complemented by in vitro experiments using the established MDCK renal cell line, which demonstrated that BS168 pretreatment prevented increased CaOx crystal adhesion and aggregation. Taking our results together, this study supports the notion that BS168 can functionally reduce CaOx stone burden in vivo through its capacity for oxalate degradation. Given the favorable safety profile of many B. subtilis strains already used as digestive aids and in fermented foods, these findings suggest that BS168 could represent a novel therapeutic adjunct to reduce the incidence of recurrent CaOx nephrolithiasis in high-risk patients.

IMPORTANCE Kidney stone disease is a morbid condition that is increasing in prevalence, with few nonsurgical treatment options. The majority of stones are composed of calcium oxalate. Unlike humans, some microbes can break down oxalate, suggesting that microbial therapeutics may provide a novel treatment for kidney stone patients. This study demonstrated that Bacillus subtilis 168 (BS168) decreased stone burden, improved health, and complemented the microbiota in a Drosophila melanogaster urolithiasis model, while not exacerbating calcium oxalate aggregation or adhesion to renal cells in vitro. These results identify this bacterium as a candidate for ameliorating stone formation; given that other strains of B. subtilis are components of fermented foods and are used as probiotics for digestive health, strain 168 warrants testing in humans. With the severe burden that recurrent kidney stone disease imposes on patients and the health care system, this microbial therapeutic approach could provide an inexpensive therapeutic adjunct.

Miro, a Rho GTPase genetically interacts with Alzheimer's disease-associated genes (Tau, Aβ42 and Appl) in Drosophila melanogaster

Miro (mitochondrial Rho GTPases), a mitochondrial outer membrane protein, facilitates mitochondrial axonal transport along the microtubules to facilitate neuronal function. It plays an important role in regulating mitochondrial dynamics (fusion and fission) and cellular energy generation. Thus, Miro might be associated with the key pathologies of several neurodegenerative diseases (NDs) including Alzheimer's disease (AD). In the present manuscript, we have demonstrated the possible genetic interaction between Miro and AD-related genes such as Tau, Aβ42 and Appl in Drosophila melanogaster Ectopic expression of Tau, Aβ42 and Appl induced a rough eye phenotype, defects in phototaxis and climbing activity, and shortened lifespan in the flies. In our study, we have observed that overexpression of Miro improves the rough eye phenotype, behavioral activities (climbing and phototaxis) and ATP level in AD model flies. Further, the improvement examined in AD-related phenotypes was correlated with decreased oxidative stress, cell death and neurodegeneration in Miro overexpressing AD model flies. Thus, the obtained results suggested that Miro genetically interacts with AD-related genes in Drosophila and has the potential to be used as a therapeutic target for the design of therapeutic strategies for NDs.This article has an associated First Person interview with the first author of the paper.

Environmental cue affects the hearing-related behaviors of Drosophila melanogaster by targeting the redox pathways

Environmental cues like noise, pressure, and circadian rhythm can affect the hearing ability of human beings. Nevertheless, the complex physiology of the human being does not allow us to understand how these factors can affect hearing and hearing-related behaviors. Conversely, these effects can be easily checked using the hearing organ of Drosophila melanogaster, the Johnston organ. In the current study, the Drosophila was exposed to challenging environments like noise, low pressure, and altered circadian rhythm. The hearing organ of larvae, as well as adults, was analyzed for hearing-related defects. In the third instar larva, the cell deaths were detected in the antenna imaginal disc, the precursor of Johnston's organ. Elevated levels of reactive oxygen species and antioxidant enzymes were also detected in the adult antennae of environmentally challenged flies. The ultrastructure of the antennae suggests the presence of abundant mitochondria in the scolopidia of control. Fewer amounts of mitochondria are found in the environmentally challenged adult antennae. In adults, various hearing-related behaviors were analyzed as a readout of functionality of the hearing organ. Analysis of climbing, aggressive, and courtship behaviors suggests abnormal behavior in environmentally challenged flies than the control. The current study suggests that the environmental cues can alter hearing-related behaviors in Drosophila. The methods used in this study can be used to monitor the environmental pollution or to study the effect of alteration of noise, pressure, and circadian rhythm on hearing-related behaviors taking Drosophila melanogaster as a model organism. Graphical abstract.

The carboxyl termini of RAN translated GGGGCC nucleotide repeat expansions modulate toxicity in models of ALS/FTD

An intronic hexanucleotide repeat expansion in C9ORF72 causes familial and sporadic amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). This repeat is thought to elicit toxicity through RNA mediated protein sequestration and repeat-associated non-AUG (RAN) translation of dipeptide repeat proteins (DPRs). We generated a series of transgenic Drosophila models expressing GGGGCC (G₄C₂) repeats either inside of an artificial intron within a GFP reporter or within the 5' untranslated region (UTR) of GFP placed in different downstream reading frames. Expression of 484 intronic repeats elicited minimal alterations in eye morphology, viability, longevity, or larval crawling but did trigger RNA foci formation, consistent with prior reports. In contrast, insertion of repeats into the 5' UTR elicited differential toxicity that was dependent on the reading frame of GFP relative to the repeat. Greater toxicity correlated with a short and unstructured carboxyl terminus (C-terminus) in the glycine-arginine (GR) RAN protein reading frame. This change in C-terminal sequence triggered nuclear accumulation of all three RAN DPRs. A similar differential toxicity and dependence on the GR C-terminus was observed when repeats were expressed in rodent neurons. The presence of the native C-termini across all three reading frames was partly protective. Taken together, these findings suggest that C-terminal sequences outside of the repeat region may alter the behavior and toxicity of dipeptide repeat proteins derived from GGGGCC repeats.

Developmental and behavioural toxicity induced by acrylamide exposure and amelioration using phytochemicals in Drosophila melanogaster

Acrylamide, an environmental pollutant, is known to occur in food substances cooked at high temperatures. Studies on various models indicate acrylamide to cause several physiological conditions such as neuro- and reproductive toxicity, and carcinogenesis. In our study, exposure of Drosophila melanogaster (Oregon K strain) to acrylamide via their diet resulted in a concentration and time-dependent mortality, while the surviving flies exhibited significant locomotor deficits, most likely due to oxidative stress-induced neuronal damage. Also, Drosophila embryos exhibited signs of developmental toxicity as evidenced by the alteration in the migration of border cells and cluster cells during the developmental stages, concomitant to modulation in expression of gurken and oskar genes. Curcumin, a known antioxidant has been widely studied for its neuroprotective effects against acrylamide; however; very few studies focus on thymoquinone for its role against food toxicant. Our research focuses on the toxicity elicited by acrylamide and the ability of the antioxidants: thymoquinone, curcumin and combination of thereof, in reversing the same.

Using Drosophila Motor Mutants to Teach Neurodevelopment in an Undergraduate Neurobiology Lab

Most undergraduate neuroscience courses include a neurodevelopment component. Typically, the focus is on development of the mammalian central nervous system, including the concepts of neurulation, patterning of the neural tube, and differentiation of the various cells required to build a functional nervous system. However, it can be challenging to design an affordable undergraduate laboratory exercise to reinforce these concepts for students outside of lecture. Here we describe a laboratory exercise that takes advantage of the high level of conservation in neurodevelopmental pathways using Drosophila as a model organism to illuminate the connection between cell differentiation and nervous system function. Following a lesson discussing spinal cord development, students use Drosophila larvae to assess the effects of mutations in highly conserved motor neuron differentiation genes on motor behaviors such as crawling. As outcomes of this laboratory, students are able to master important neurodevelopmental concepts, connect neurodevelopment to nervous system function, and gain experience with experimental design and data analysis.

Loss of highwire Protects Against the Deleterious Effects of Traumatic Brain Injury in Drosophila Melanogaster

Traumatic brain injury is a major global cause of death and disability. Axonal injury is a major underlying mechanism of TBI and could represent a major therapeutic target. We provide evidence that targeting the axonal death pathway known as Wallerian degeneration improves outcome in a Drosophila Melanogaster model of high impact trauma. This cell-autonomous neurodegenerative pathway is initiated following axon injury, and in Drosophila, involves activity of the E3 ubiquitin ligase highwire. We demonstrate that a loss-of-function mutation in the highwire gene rescues deleterious effects of a traumatic injury, including-improved functional outcomes, lifespan, survival of dopaminergic neurons, and retention of synaptic proteins. This data suggests that highwire represents a potential therapeutic target in traumatic injury.

Bi-allelic Loss-of-Function Variants in NUP188 Cause a Recognizable Syndrome Characterized by Neurologic, Ocular, and Cardiac Abnormalities

Nucleoporins (NUPs) are an essential component of the nuclear-pore complex, which regulates nucleocytoplasmic transport of macromolecules. Pathogenic variants in NUP genes have been linked to several inherited human diseases, including a number with progressive neurological degeneration. We present six affected individuals with bi-allelic truncating variants in NUP188 and strikingly similar phenotypes and clinical courses, representing a recognizable genetic syndrome; the individuals are from four unrelated families. Key clinical features include congenital cataracts, hypotonia, prenatal-onset ventriculomegaly, white-matter abnormalities, hypoplastic corpus callosum, congenital heart defects, and central hypoventilation. Characteristic dysmorphic features include small palpebral fissures, a wide nasal bridge and nose, micrognathia, and digital anomalies. All affected individuals died as a result of respiratory failure, and five of them died within the first year of life. Nuclear import of proteins was decreased in affected individuals' fibroblasts, supporting a possible disease mechanism. CRISPR-mediated knockout of NUP188 in Drosophila revealed motor deficits and seizure susceptibility, partially recapitulating the neurological phenotype seen in affected individuals. Removal of NUP188 also resulted in aberrant dendrite tiling, suggesting a potential role of NUP188 in dendritic development. Two of the NUP188 pathogenic variants are enriched in the Ashkenazi Jewish population in gnomAD, a finding we confirmed with a separate targeted population screen of an international sampling of 3,225 healthy Ashkenazi Jewish individuals. Taken together, our results implicate bi-allelic loss-of-function NUP188 variants in a recessive syndrome characterized by a distinct neurologic, ophthalmologic, and facial phenotype.

Condensin I subunit Cap-G is essential for proper gene expression during the maturation of post-mitotic neurons

Condensin complexes are essential for mitotic chromosome assembly and segregation during cell divisions, however, little is known about their functions in post-mitotic cells. Here we report a role for the condensin I subunit Cap-G in Drosophila neurons. We show that, despite not requiring condensin for mitotic chromosome compaction, post-mitotic neurons express Cap-G. Knockdown of Cap-G specifically in neurons (from their birth onwards) results in developmental arrest, behavioural defects, and dramatic gene expression changes, including reduced expression of a subset of neuronal genes and aberrant expression of genes that are not normally expressed in the developing brain. Knockdown of Cap-G in mature neurons results in similar phenotypes but to a lesser degree. Furthermore, we see dynamic binding of Cap-G at distinct loci in progenitor cells and differentiated neurons. Therefore, Cap-G is essential for proper gene expression in neurons and plays an important role during the early stages of neuronal development.

PARIS induced defects in mitochondrial biogenesis drive dopamine neuron loss under conditions of parkin or PINK1 deficiency

BACKGROUND

Mutations in PINK1 and parkin cause autosomal recessive Parkinson's disease (PD). Evidence placing PINK1 and parkin in common pathways regulating multiple aspects of mitochondrial quality control is burgeoning. However, compelling evidence to causatively link specific PINK1/parkin dependent mitochondrial pathways to dopamine neuron degeneration in PD is lacking. Although PINK1 and parkin are known to regulate mitophagy, emerging data suggest that defects in mitophagy are unlikely to be of pathological relevance. Mitochondrial functions of PINK1 and parkin are also tied to their proteasomal regulation of specific substrates. In this study, we examined how PINK1/parkin mediated regulation of the pathogenic substrate PARIS impacts dopaminergic mitochondrial network homeostasis and neuronal survival in Drosophila.

METHODS

The UAS-Gal4 system was employed for cell-type specific expression of the various transgenes. Effects on dopamine neuronal survival and function were assessed by anti-TH immunostaining and negative geotaxis assays. Mitochondrial effects were probed by quantitative analysis of mito-GFP labeled dopaminergic mitochondria, assessment of mitochondrial abundance in dopamine neurons isolated by Fluorescence Activated Cell Sorting (FACS) and qRT-PCR analysis of dopaminergic factors that promote mitochondrial biogenesis. Statistical analyses employed two-tailed Student's T-test, one-way or two-way ANOVA as required and data considered significant when P < 0.05.

RESULTS

We show that defects in mitochondrial biogenesis drive adult onset progressive loss of dopamine neurons and motor deficits in Drosophila models of PINK1 or parkin insufficiency. Such defects result from PARIS dependent repression of dopaminergic PGC-1α and its downstream transcription factors NRF1 and TFAM that cooperatively promote mitochondrial biogenesis. Dopaminergic accumulation of human or Drosophila PARIS recapitulates these neurodegenerative phenotypes that are effectively reversed by PINK1, parkin or PGC-1α overexpression in vivo. To our knowledge, PARIS is the only co-substrate of PINK1 and parkin to specifically accumulate in the DA neurons and cause neurodegeneration and locomotor defects stemming from disrupted dopamine signaling.

CONCLUSIONS

Our findings identify a highly conserved role for PINK1 and parkin in regulating mitochondrial biogenesis and promoting mitochondrial health via the PARIS/ PGC-1α axis. The Drosophila models described here effectively recapitulate the cardinal PD phenotypes and thus will facilitate identification of novel regulators of mitochondrial biogenesis for physiologically relevant therapeutic interventions.