RNAi screening in Drosophila cells and in vivo

An image-based RNAi screen identifies the EGFR signaling pathway as a regulator of Imp RNP granules

Biomolecular condensates have recently retained much attention given that they provide a fundamental mechanism of cellular organization. Among those, cytoplasmic ribonucleoprotein (RNP) granules selectively and reversibly concentrate RNA molecules and regulatory proteins, thus contributing to the spatiotemporal regulation of associated RNAs. Extensive in vitro work has unraveled the molecular and chemical bases of RNP granule assembly. The signaling pathways controlling this process in a cellular context are, however, still largely unknown. Here, we aimed at identifying regulators of cytoplasmic RNP granules characterized by the presence of the evolutionarily conserved Imp RNA-binding protein (a homolog of IGF2BP proteins). We performed a high-content image-based RNAi screen targeting all Drosophila genes encoding RNA-binding proteins, phosphatases and kinases. This led to the identification of dozens of genes regulating the number of Imp-positive RNP granules in S2R+ cells, among which were components of the MAPK pathway. Combining functional approaches, phospho-mapping and generation of phospho-variants, we further showed that EGFR signaling inhibits Imp-positive RNP granule assembly through activation of the MAPK-ERK pathway and downstream phosphorylation of Imp at the S15 residue. This work illustrates how signaling pathways can regulate cellular condensate assembly by post-translational modifications of specific components.

Truffle protein and its derived peptides exhibit sleep-promoting effects via regulation of lysosomal autophagy, neurological activity, tyrosine metabolism, and fatty acid elongation

Black truffle (Tuber sinense) is a famous luxurious mushroom with abundant protein resources. Nevertheless, until now, no single study has explored the potential function of black truffle protein in any animal models. Thus, this study investigated the sleep-promoting effects of truffle albumin (TA) and its hydrolysate (TAH). Then, two novel sleep-enhancing peptides were explored from TAH. Our results showed that TA and TAH significantly prolonged the total sleep time and improved sleep quality of insomnia Drosophila. Additionally, two novel peptides YLDLAPL and YLRPEGDW with strong sleep-enhancing activity were explored by virtual screening and Drosophila with transgenic RNA interference (RNAi) technology. Finally, the transcriptomics analysis investigated potential mechanisms of sleep-enhancing effects in Drosophila: (1) regulation of the autophagic activity by altering the lysosomal protein; (2) up-regulation the genes in the pathway of neuroactive ligand-receptor interaction and promotion the function of neurons; (3) promotion the conversion of tyrosine into neurotransmitters; (4) regulation substrate feeding into the tricarboxylic acid (TCA) cycle and promotion free radical scavenging in neuronal cells; (5) promotion the fatty acid elongation and preservation neuronal cells avoid from oxidation.

Chlorella pyrenoidosa polysaccharides supplementation increases Drosophila melanogaster longevity at high temperature

Chlorella pyrenoidos polysaccharides (CPPs) are the main active components of Chlorella pyrenoidos. They possess beneficial health properties, such as antioxidant, anti-inflammatory, and immune-enhancing. This study aims to investigate the protective function and mechanism of CPPs against high-temperature stress injury. Results showed that supplementation with 20 mg/mL CPPs significantly extended the lifespan of Drosophila melanogaster under high-temperature stress, improved its motility, and enhanced its resistance to starvation and oxidative stress. These effects were mainly attributed to the activation of Nrf2 signaling and enhanced antioxidant capacity. Additionally, it has been discovered that CPPs supplementation enhanced Drosophila resilience by preventing the disruption of the intestinal barrier and accumulation of reactive oxygen species caused by heat stress. Overall, these studies suggest that CPPs could be a useful natural therapy for preventing heat stress-induced injury.

Nematode infection and antinematode immunity in Drosophila

The entomopathogenic nematodes Heterorhabditis and Steinernema form mutualistic complexes with Gram-negative bacteria. These insect parasites have emerged as excellent research tools for studying nematode pathogenicity and elucidating the features that allow them to persist and multiply within the host. A better understanding of the molecular mechanisms of nematode infection and host antinematode processes will lead to the development of novel means for parasitic nematode control. Recent work has demonstrated the power of using the Drosophila infection model to identify novel parasitic nematode infection factors and elucidate the genetic and functional bases of host antinematode defense. Here, we aim to highlight the recent advances and address their contribution to the development of novel means for parasitic nematode control.

Serum-free adapted Drosophila S2R+ line is amenable to RNA interference

We have previously adapted a select number of Drosophila cell lines to grow in serum-free media supplemented with fly extract. This condition is arguably more representative of a native growth environment. Here, we validated that the fly extract adapted line, S2R+ (FEx 2.5%) is amenable to RNAi. RNAi against Rho1 in both S2R+ and S2R+ (FEx 2.5%) produced phenotypes similar to ones previously described in Drosophila S2 cells.

Drosophila melanogaster as a powerful tool for studying insect toxicology

Insecticides are valuable and widely used tools for the control of pest insects. Despite the use of synthetic insecticides for >50 years, we continue to have a limited understanding of the genes that influence the key steps of the poisoning process. Major barriers for improving our understanding of insecticide toxicity have included a narrow range of tools and/or a large number of candidate genes that could be involved in the poisoning process. Herein, we discuss the numerous tools and resources available in Drosophila melanogaster that could be brought to bear to improve our understanding of the processes determining insecticide toxicity. These include unbiased approaches such as forward genetic screens, population genetic methods and candidate gene approaches. Examples are provided to showcase how D. melanogaster has been successfully used for insecticide toxicology studies in the past, and ideas for future studies using this valuable insect are discussed.

Daywake, an Anti-siesta Gene Linked to a Splicing-Based Thermostat from an Adjoining Clock Gene

Sleep is fundamental to animal survival but is a vulnerable state that also limits how much time can be devoted to critical wake-dependent activities [1]. Although many animals are day-active and sleep at night, they exhibit a midday nap, or "siesta," that can vary in intensity and is usually more prominent on warm days. In humans, the balance between maintaining the wake state or sleeping during the day has important health implications [2], but the mechanisms underlying this dynamic regulation are poorly understood. Using the well-established Drosophila melanogaster animal model to study sleep [3], we identify a new wake-sleep regulator that we term daywake (dyw). dyw encodes a juvenile hormone-binding protein [4] that functions in neurons as a day-specific anti-siesta gene, with little effect on sleep levels during the nighttime or in the absence of light. Remarkably, dyw expression is stimulated in trans via cold-enhanced splicing of the dmpi8 intron [5] from the reverse-oriented but slightly overlapping period (per) clock gene [6]. The functionally integrated dmpi8-dyw genetic unit operates as a "behavioral temperate acclimator" by increasingly counterbalancing siesta-promoting pathways as daily temperatures become cooler and carry reduced risks from daytime heat exposure. While daily patterns of when animals are awake and when they sleep are largely scheduled by the circadian timing system, dyw implicates a less recognized class of modulatory wake-sleep regulators that primarily function to enhance flexibility in wake-sleep preference, a behavioral plasticity that is commonly observed in animals during the midday, raising the possibility of shared mechanisms.

Generating and working with Drosophila cell cultures: Current challenges and opportunities

The use of Drosophila cell cultures has positively impacted both fundamental and biomedical research. The most widely used cell lines: Schneider, Kc, the CNS and imaginal disc lines continue to be the choice for many applications. Drosophila cell lines provide a homogenous source of cells suitable for biochemical experimentations, transcriptomics, functional genomics, and biomedical applications. They are amenable to RNA interference and serve as a platform for high-throughput screens to identify relevant candidate genes or drugs for any biological process. Currently, CRISPR-based functional genomics are also being developed for Drosophila cell lines. Even though many uniquely derived cell lines exist, cell genetic techniques such the transgenic UAS-GAL4-based Ras^V12 oncogene expression, CRISPR-Cas9 editing and recombination mediated cassette exchange are likely to drive the establishment of many more lines from specific tissues, cells, or genotypes. However, the pace of creating new lines is hindered by several factors inherent to working with Drosophila cell cultures: single cell cloning, optimal media formulations and culture conditions capable of supporting lines from novel tissue sources or genotypes. Moreover, even though many Drosophila cell lines are morphologically and transcriptionally distinct it may be necessary to implement a standard for Drosophila cell line authentication, ensuring the identity and purity of each cell line. Altogether, recent advances and a standardized authentication effort should improve the utility of Drosophila cell cultures as a relevant model for fundamental and biomedical research. This article is categorized under: Technologies > Analysis of Cell, Tissue, and Animal Phenotypes.

Newly Identified Electrically Coupled Neurons Support Development of the Drosophila Giant Fiber Model Circuit

The Drosophila giant fiber (GF) escape circuit is an extensively studied model for neuron connectivity and function. Researchers have long taken advantage of the simple linear neuronal pathway, which begins at peripheral sensory modalities, travels through the central GF interneuron (GFI) to motor neurons, and terminates on wing/leg muscles. This circuit is more complex than it seems, however, as there exists a complex web of coupled neurons connected to the GFI that widely innervates the thoracic ganglion. Here, we define four new neuron clusters dye coupled to the central GFI, which we name GF coupled (GFC) 1-4. We identify new transgenic Gal4 drivers that express specifically in these neurons, and map both neuronal architecture and synaptic polarity. GFC1-4 share a central site of GFI connectivity, the inframedial bridge, where the neurons each form electrical synapses. Targeted apoptotic ablation of GFC1 reveals a key role for the proper development of the GF circuit, including the maintenance of GFI connectivity with upstream and downstream synaptic partners. GFC1 ablation frequently results in the loss of one GFI, which is always compensated for by contralateral innervation from a branch of the persisting GFI axon. Overall, this work reveals extensively coupled interconnectivity within the GF circuit, and the requirement of coupled neurons for circuit development. Identification of this large population of electrically coupled neurons in this classic model, and the ability to genetically manipulate these electrically synapsed neurons, expands the GF system capabilities for the nuanced, sophisticated circuit dissection necessary for deeper investigations into brain formation.

Defense Mechanisms against Viral Infection in Drosophila: RNAi and Non-RNAi

RNAi is considered a major antiviral defense mechanism in insects, but its relative importance as compared to other antiviral pathways has not been evaluated comprehensively. Here, it is attempted to give an overview of the antiviral defense mechanisms in Drosophila that involve both RNAi and non-RNAi. While RNAi is considered important in most viral infections, many other pathways can exist that confer antiviral resistance. It is noted that very few direct recognition mechanisms of virus infections have been identified in Drosophila and that the activation of immune pathways may be accomplished indirectly through cell damage incurred by viral replication. In several cases, protection against viral infection can be obtained in RNAi mutants by non-RNAi mechanisms, confirming the variability of the RNAi defense mechanism according to the type of infection and the physiological status of the host. This analysis is aimed at more systematically investigating the relative contribution of RNAi in the antiviral response and more specifically, to ask whether RNAi efficiency is affected when other defense mechanisms predominate. While Drosophila can function as a useful model, this issue may be more critical for economically important insects that are either controlled (agricultural pests and vectors of diseases) or protected from parasite infection (beneficial insects as bees) by RNAi products.

Epigallocatechin-3-Gallate Protects and Prevents Paraquat-Induced Oxidative Stress and Neurodegeneration in Knockdown dj-1-β Drosophila melanogaster

Epigallocatechin-3-gallate (EGCG) is a polyhydroxyphenol constituent of green tea (e.g., Camellia sinensis) with known antioxidant properties. Due to these properties, others have proposed it as a potential therapeutic agent for the treatment of Parkinson's disease (PD). Previously, we demonstrated that EGCG prolonged the lifespan and locomotor activity in wild-type Canton-S flies exposed to the neurotoxicant paraquat (PQ), suggesting neuroprotective properties. Both gene mutations and environmental neurotoxicants (e.g., PQ) are factors involved in the development of PD. Thus, the first aim of this study was to create a suitable animal model of PD, which encompasses both of these factors. To create the model, we knocked down dj-1-β function specifically in the dopaminergic neurons to generate TH > dj-1-β-RNAi/+ Drosophila melanogaster flies. Next, we induced neurotoxicity in the transgenic flies with PQ. The second aim of this study was to validate the model by comparing the effects of vehicle, EGCG, and chemicals with known antioxidant and neuroprotective properties in vivo (e.g., propyl gallate and minocycline) on life-span, locomotor activity, lipid peroxidation, and neurodegeneration. The EGCG treatment provided protection and prevention from the PQ-induced reduction in the life-span and locomotor activity and from the PQ-induced increase in lipid peroxidation and neurodegeneration. These effects were augmented in the EGCG-treated flies when compared to the flies treated with either PG or MC. Altogether, these results suggest that the transgenic TH > dj-1-β-RNAi/+ flies treated with PQ serve as a suitable PD model for screening of potential therapeutic agents.

RNA Interference (RNAi) Screening in Drosophila

In the last decade, RNA interference (RNAi), a cellular mechanism that uses RNA-guided degradation of messenger RNA transcripts, has had an important impact on identifying and characterizing gene function. First discovered in Caenorhabditis elegans, RNAi can be used to silence the expression of genes through introduction of exogenous double-stranded RNA into cells. In Drosophila, RNAi has been applied in cultured cells or in vivo to perturb the function of single genes or to systematically probe gene function on a genome-wide scale. In this review, we will describe the use of RNAi to study gene function in Drosophila with a particular focus on high-throughput screening methods applied in cultured cells. We will discuss available reagent libraries and cell lines, methodological approaches for cell-based assays, and computational methods for the analysis of high-throughput screens. Furthermore, we will review the generation and use of genome-scale RNAi libraries for tissue-specific knockdown analysis in vivo and discuss the differences and similarities with the use of genome-engineering methods such as CRISPR/Cas9 for functional analysis.

Optimized strategy for in vivo Cas9-activation in Drosophila

While several large-scale resources are available for in vivo loss-of-function studies in Drosophila, an analogous resource for overexpressing genes from their endogenous loci does not exist. We describe a strategy for generating such a resource using Cas9 transcriptional activators (CRISPRa). First, we compare a panel of CRISPRa approaches and demonstrate that, for in vivo studies, dCas9-VPR is the most optimal activator. Next, we demonstrate that this approach is scalable and has a high success rate, as >75% of the lines tested activate their target gene. We show that CRISPRa leads to physiologically relevant levels of target gene expression capable of generating strong gain-of-function (GOF) phenotypes in multiple tissues and thus serves as a useful platform for genetic screening. Based on the success of this CRISRPa approach, we are generating a genome-wide collection of flies expressing single-guide RNAs (sgRNAs) for CRISPRa. We also present a collection of more than 30 Gal4 > UAS:dCas9-VPR lines to aid in using these sgRNA lines for GOF studies in vivo.

RNAi-Mediated Reverse Genetic Screen Identified Drosophila Chaperones Regulating Eye and Neuromuscular Junction Morphology

Accumulation of toxic proteins in neurons has been linked with the onset of neurodegenerative diseases, which in many cases are characterized by altered neuronal function and synapse loss. Molecular chaperones help protein folding and the resolubilization of unfolded proteins, thereby reducing the protein aggregation stress. While most of the chaperones are expressed in neurons, their functional relevance remains largely unknown. Here, using bioinformatics analysis, we identified 95 Drosophila chaperones and classified them into seven different classes. Ubiquitous actin5C-Gal4-mediated RNAi knockdown revealed that ∼50% of the chaperones are essential in Drosophila Knocking down these genes in eyes revealed that ∼30% of the essential chaperones are crucial for eye development. Using neuron-specific knockdown, immunocytochemistry, and robust behavioral assays, we identified a new set of chaperones that play critical roles in the regulation of Drosophila NMJ structural organization. Together, our data present the first classification and comprehensive analysis of Drosophila chaperones. Our screen identified a new set of chaperones that regulate eye and NMJ morphogenesis. The outcome of the screen reported here provides a useful resource for further elucidating the role of individual chaperones in Drosophila eye morphogenesis and synaptic development.

Phenotypic screening with primary neurons to identify drug targets for regeneration and degeneration

High-throughput, target-based screening techniques have been utilized extensively for drug discovery in the past several decades. However, the need for more predictive in vitro models of in vivo disease states has generated a shift in strategy towards phenotype-based screens. Phenotype based screens are particularly valuable in studying complex conditions such as CNS injury and degenerative disease, as many factors can contribute to a specific cellular response. In this review, we will discuss different screening frameworks and their relative utility in examining mechanisms of neurodegeneration and axon regrowth, particularly in cell-based in vitro disease models.

The immunomodulatory protein RH36 is relating to blood-feeding success and oviposition in hard ticks

An immunomodulatory protein designated RH36 was identified in the tick Rhipicephalus haemaphysaloides. The cDNA sequence of RH36 has 844bp and encodes a deduced protein with a predicted molecular weight of 24kDa. Bioinformatics analysis indicated that RH36 presented a degree of similarity of 34.36% with the immunomodulatory protein p36 from the tick Dermacentor andersoni. The recombinant RH36 (rRH36) expressed in Sf9 insect cells suppressed the T-lymphocyte mitogen-driven in vitro proliferation of splenocytes and the expression of several cytokines such as IL-2, IL-12, and TNF-α. Furthermore, the proliferation of splenocytes isolated from rRH36-inoculated mice was significantly lower than that in control mice, suggesting that rRH36 could directly suppress immune responses in vivo. In addition, microarray analysis of splenocytes indicated that the expression of several immunomodulatory genes was downregulated by rRH36. The silencing of the RH36 gene by RNAi led to a 37.5% decrease in the tick attachment rate 24h after placement into the rabbit ears, whereas vaccination with RH36 caused a 53.06% decrease in the tick engorgement rate. Unexpectedly, RNAi induced a significant decrease in the oviposition rate, ovary weight at day 12 after engorgement, and egg-hatching rate. The effects of RH36 on blood feeding and oviposition were further confirmed by vaccination tests using the recombinant protein. These results indicate that RH36 is a novel member of immunosuppressant proteins and affects tick blood feeding and oviposition.

Minocycline protects, rescues and prevents knockdown transgenic parkin Drosophila against paraquat/iron toxicity: Implications for autosomic recessive juvenile parkinsonism

Autosomal recessive Juvenile Parkinsonism (AR-JP) is a chronic, progressive neurodegenerative disorder caused by mutation in the PARKIN gene, and invariably associated with dopaminergic (DAergic) neuronal loss and brain iron accumulation. Since current medical therapy is symptomatic and lacks significant disease-modifying effects, other treatment approaches are urgently needed it. In the present work, we investigate the role of minocycline (MC) in paraquat (PQ)/iron-induced neurotoxicity in the Drosophila TH>parkin-RNAi/+ (w[*]; UAS-parkin-RNAi; TH-GAL4) fly and have shown the following: (i) MC increased life span and restored the locomotor activity of knockdown (KD) transgenic parkin flies in comparison with the control (vehicle) group; (ii) MC at low (0.1 and 0.3mM) and middle (0.5mM) concentrations protected, rescued and prevented KD parkin Drosophila against PQ toxicity. However, MC at high (1mM) concentration aggravated the toxic effect of PQ; (iii) MC protected and rescued DAergic neurons against the PQ toxic effect according to tyrosine hydroxylase (TH)>green-fluorescent protein (GFP) reporter protein microscopy and anti-TH Western blotting analysis; (iv) MC protected DAergic neurons against PQ/iron toxicity; (v) MC significantly abridged lipid peroxidation (LPO) in the protection, rescue and prevention treatment in TH>parkin-RNAi/+ flies against PQ or iron alone or combined (PQ/iron)-induced neuronal oxidative stress (OS). Our results suggest that MC exerts neuroprotection against PQ/iron-induced OS in DAergic neurons most probably by the scavenging activity of reactive oxygen species (ROS), and by chelating iron. Therefore, MC might be a potential therapeutic drug to delay, revert, or prevent AR-JP.

DNA Repair in Drosophila: Mutagens, Models, and Missing Genes

The numerous processes that damage DNA are counterbalanced by a complex network of repair pathways that, collectively, can mend diverse types of damage. Insights into these pathways have come from studies in many different organisms, including Drosophila melanogaster Indeed, the first ideas about chromosome and gene repair grew out of Drosophila research on the properties of mutations produced by ionizing radiation and mustard gas. Numerous methods have been developed to take advantage of Drosophila genetic tools to elucidate repair processes in whole animals, organs, tissues, and cells. These studies have led to the discovery of key DNA repair pathways, including synthesis-dependent strand annealing, and DNA polymerase theta-mediated end joining. Drosophila appear to utilize other major repair pathways as well, such as base excision repair, nucleotide excision repair, mismatch repair, and interstrand crosslink repair. In a surprising number of cases, however, DNA repair genes whose products play important roles in these pathways in other organisms are missing from the Drosophila genome, raising interesting questions for continued investigations.

RNAi-Based Techniques for the Analysis of Gene Function in Drosophila Germline Stem Cells

Elucidating the full repertoire of molecular mechanisms that promote stem cell maintenance requires sophisticated techniques for identifying and characterizing gene function in stem cells in their native environment. Ovarian germline stem cells in the fruit fly, Drosophila melanogaster, are an ideal model to study the complex molecular mechanisms driving stem cell function in vivo. A variety of new genetic tools make RNAi a useful complement to traditional genetic mutants for the investigation of the molecular mechanisms guiding ovarian germline stem cell function. Here, we provide a detailed guide for using targeted RNAi knockdown for the discovery of gene function in ovarian germline stem cells and their progeny.

Knockdown transgenic Lrrk Drosophila resists paraquat-induced locomotor impairment and neurodegeneration: A therapeutic strategy for Parkinson's disease

Leucine-rich repeat kinase 2 (LRRK2) has been linked to familial and sporadic Parkinson's disease. However, it is still unresolved whether LRRK2 in dopaminergic (DAergic) neurons may or may not aggravate the phenotype. We demonstrate that knocking down (KD) the Lrrk gene by RNAi in DAergic neurons untreated or treated with paraquat (PQ) neither affected the number of DAergic clusters, tyrosine hydroxylase (TH) protein levels, lifespan nor locomotor activity when compared to control (i.e. TH/+) flies. KD transgenic Lrrk flies dramatically increased locomotor activity in presence of TH enzyme inhibitor alpha-methyl-para-tyrosine (aMT), whereas no effect on lifespan was observed in both fly lines. Most importantly, KD Lrrk flies had reduced lipid peroxidation (LPO) index alone or in presence of PQ and the antioxidant minocycline (MC, 0.5mM). Taken together, these findings suggest that Lrrk appears unessential for the viability of DAergic neurons in D. melanogaster. Moreover, Lrrk might negatively regulate homeostatic levels of dopamine, thereby dramatically increasing locomotor activity, extending lifespan, and reducing oxidative stress (OS). Our data also indicate that reduced expression of Lrrk in the DAergic neurons of transgenic TH>Lrrk-RNAi/+ flies conferred PQ resistance and absence of neurodegeneration. The present findings support the notion that reduced/suppressed LRRK2 expression might delay or prevent motor symptoms and/or frank Parkinsonism in individuals at risk to suffer autosomal dominant Parkinsonism (AD-P) by blocking OS-induced neurodegenerative processes in the DAergic neurons.

Drosophila tools and assays for the study of human diseases

Many of the internal organ systems of Drosophila melanogaster are functionally analogous to those in vertebrates, including humans. Although humans and flies differ greatly in terms of their gross morphological and cellular features, many of the molecular mechanisms that govern development and drive cellular and physiological processes are conserved between both organisms. The morphological differences are deceiving and have led researchers to undervalue the study of invertebrate organs in unraveling pathogenic mechanisms of diseases. In this review and accompanying poster, we highlight the physiological and molecular parallels between fly and human organs that validate the use of Drosophila to study the molecular pathogenesis underlying human diseases. We discuss assays that have been developed in flies to study the function of specific genes in the central nervous system, heart, liver and kidney, and provide examples of the use of these assays to address questions related to human diseases. These assays provide us with simple yet powerful tools to study the pathogenic mechanisms associated with human disease-causing genes.

Editors' choice - Drosophila Collection: In this review and accompanying poster, we highlight the physiological and molecular parallels between fly and human organs that validate the use of Drosophila to study the molecular pathogenesis underlying human diseases.

Loss-of-function genetic tools for animal models: cross-species and cross-platform differences

Our understanding of the genetic mechanisms that underlie biological processes has relied extensively on loss-of-function (LOF) analyses. LOF methods target DNA, RNA or protein to reduce or to ablate gene function. By analysing the phenotypes that are caused by these perturbations the wild-type function of genes can be elucidated. Although all LOF methods reduce gene activity, the choice of approach (for example, mutagenesis, CRISPR-based gene editing, RNA interference, morpholinos or pharmacological inhibition) can have a major effect on phenotypic outcomes. Interpretation of the LOF phenotype must take into account the biological process that is targeted by each method. The practicality and efficiency of LOF methods also vary considerably between model systems. We describe parameters for choosing the optimal combination of method and system, and for interpreting phenotypes within the constraints of each method.

A simple and effective method for ultrastructural analysis of mitosis in Drosophila S2 cells

The Drosophila S2 tissue culture cells are a widely used system for studies on mitosis. S2 cells are particularly sensitive to gene silencing by RNA interference (RNAi), allowing targeted inactivation of mitotic genes. S2 cells are also well suited for high-resolution light microscopy analysis of mitosis in fixed cells, and can be easily immunostained to detect mitotic components. In addition, S2 cells are amenable to transformation with plasmid encoding fluorescently tagged mitotic proteins, allowing in vivo analysis of their behavior throughout cell division. However, S2 cells have not been widely used for transmission electron microscopy (TEM) analysis, which provides ultrastructural details on the morphology of the mitotic apparatus that cannot be obtained with high-resolution confocal microscopy. Here, we describe a simple method for the ultrastructural analysis of mitosis in Drosophila S2 cells. •Our method, which involves fixation and sectioning of a cell pellet, provides excellent preservation of mitotic structures and allows analysis of a higher number of mitotic divisions per sample, compared to correlative light-electron microscopy.•Dividing cells are randomly oriented within the pellet and are sectioned along different planes, providing all-around information on the structure of the mitotic apparatus.

Regionalization of surface lipids in insects

Cuticular hydrocarbons (CHCs) play a critical role in the establishment of the waterproof barrier that prevents dehydration and wetting in insects. While rich data are available on CHC composition in different species, we know little about their distribution and organization. Here, we report on our studies of the surface barrier of the fruit fly Drosophila melanogaster applying a newly developed Eosin Y staining method. The inert Eosin Y penetrates different regions of the adult body at distinct temperatures. By contrast, the larval body takes up the dye rather uniformly and gradually with increasing temperature. Cooling down specimens to 25°C after incubation at higher temperatures restores impermeability. Eosin Y penetration is also sensitive to lipid solvents such as chloroform indicating that permeability depends on CHCs. As in D. melanogaster adult flies, Eosin Y penetration is regionalized in Tenebrio molitor larvae, whereas it is not in Locusta migratoria nymphs. Regionalization of the fly surface implies tissue-specific variation of the genetic or biochemical programmes of CHC production and deposition. The Eosin Y-based map of CHC distribution may serve to identify the respective factors that are activated to accommodate ecological needs.

Reagent and Data Resources for Investigation of RNA Binding Protein Functions in Drosophila melanogaster Cultured Cells

RNA binding proteins (RBPs) are involved in many cellular functions. To facilitate functional characterization of RBPs, we generated an RNA interference (RNAi) library for Drosophila cell-based screens comprising reagents targeting known or putative RBPs. To test the quality of the library and provide a baseline analysis of the effects of the RNAi reagents on viability, we screened the library using a total ATP assay and high-throughput imaging in Drosophila S2R+ cultured cells. The results are consistent with production of a high-quality library that will be useful for functional genomics studies using other assays. Altogether, we provide resources in the form of an initial curated list of Drosophila RBPs; an RNAi screening library we expect to be used with additional assays that address more specific biological questions; and total ATP and image data useful for comparison of those additional assay results with fundamental information such as effects of a given reagent in the library on cell viability. Importantly, we make the baseline data, including more than 200,000 images, easily accessible online.

The locus of sexual selection: moving sexual selection studies into the post-genomics era

Sexual selection drives fundamental evolutionary processes such as trait elaboration and speciation. Despite this importance, there are surprisingly few examples of genes unequivocally responsible for variation in sexually selected phenotypes. This lack of information inhibits our ability to predict phenotypic change due to universal behaviours, such as fighting over mates and mate choice. Here, we discuss reasons for this apparent gap and provide recommendations for how it can be overcome by adopting contemporary genomic methods, exploiting underutilized taxa that may be ideal for detecting the effects of sexual selection and adopting appropriate experimental paradigms. Identifying genes that determine variation in sexually selected traits has the potential to improve theoretical models and reveal whether the genetic changes underlying phenotypic novelty utilize common or unique molecular mechanisms. Such a genomic approach to sexual selection will help answer questions in the evolution of sexually selected phenotypes that were first asked by Darwin and can furthermore serve as a model for the application of genomics in all areas of evolutionary biology.

A drosophila genetic resource of mutants to study mechanisms underlying human genetic diseases

Invertebrate model systems are powerful tools for studying human disease owing to their genetic tractability and ease of screening. We conducted a mosaic genetic screen of lethal mutations on the Drosophila X chromosome to identify genes required for the development, function, and maintenance of the nervous system. We identified 165 genes, most of whose function has not been studied in vivo. In parallel, we investigated rare variant alleles in 1,929 human exomes from families with unsolved Mendelian disease. Genes that are essential in flies and have multiple human homologs were found to be likely to be associated with human diseases. Merging the human data sets with the fly genes allowed us to identify disease-associated mutations in six families and to provide insights into microcephaly associated with brain dysgenesis. This bidirectional synergism between fly genetics and human genomics facilitates the functional annotation of evolutionarily conserved genes involved in human health.

Chemical mutagens, transposons, and transgenes to interrogate gene function in Drosophila melanogaster

The study of genetics, genes, and chromosomal inheritance was initiated by Thomas Morgan in 1910, when the first visible mutations were identified in fruit flies. The field expanded upon the work initiated by Herman Muller in 1926 when he used X-rays to develop the first balancer chromosomes. Today, balancers are still invaluable to maintain mutations and transgenes but the arsenal of tools has expanded vastly and numerous new methods have been developed, many relying on the availability of the genome sequence and transposable elements. Forward genetic screens based on chemical mutagenesis or transposable elements have resulted in the unbiased identification of many novel players involved in processes probed by specific phenotypic assays. Reverse genetic approaches have relied on the availability of a carefully selected set of transposon insertions spread throughout the genome to allow the manipulation of the region in the vicinity of each insertion. Lastly, the ability to transform Drosophila with single copy transgenes using transposons or site-specific integration using the ΦC31 integrase has allowed numerous manipulations, including the ability to create and integrate genomic rescue constructs, generate duplications, RNAi knock-out technology, binary expression systems like the GAL4/UAS system as well as other methods. Here, we will discuss the most useful methodologies to interrogate the fruit fly genome in vivo focusing on chemical mutagenesis, transposons and transgenes. Genome engineering approaches based on nucleases and RNAi technology are discussed in following chapters.