A Drosophila systems model of pentylenetetrazole induced locomotor plasticity responsive to antiepileptic drugs

Isometamidium chloride alters redox status, down-regulates p53 and PARP1 genes while modulating at proteomic level in Drosophila melanogaster

As trypanocide, several side effects have been reported in the use of Isometamidium chloride. This study was therefore, designed to evaluate its ability to induce oxidative stress and DNA damage using D. melanogaster as a model organism. The LC50 of the drug was determined by exposing the flies (1-3 days old of both genders) to six different concentrations (1 mg, 10 mg, 20 mg, 40 mg, 50 mg and 100 mg per 10 g of diet) of the drug for a period of seven days. The effect of the drug on survival (28 days), climbing behavior, redox status, oxidative DNA lesion, expression of p53 and PARP1 (Poly-ADP-Ribose Polymerase-1) genes after five days exposure of flies to 4.49 mg, 8.97 mg, 17.94 mg and 35.88 mg per 10 g diet was evaluated. The interaction of the drug in silico with p53 and PARP1 proteins was also evaluated. The result showed the LC50 of isometamidium chloride to be 35.88 mg per 10 g diet for seven days. Twenty-eight (28) days of exposure to isometamidium chloride showed a decreased percentage survival in a time and concentration-dependent manner. Isometamidium chloride significantly (p < 0.05) reduced climbing ability, total thiol level, Glutathione-S-transferase, and Catalase activity. The level of H2O2 was significantly (p < 0.05) increased. The result also showed significant (p < 0.05) reduction in the relative mRNA levels of p53 and PARP1 genes. The in silico molecular docking of isometamidium with p53 and PARP1 proteins showed high binding energy of -9.4 Kcal/mol and -9.2 Kcal/mol respectively. The results suggest that isometamidium chloride could be cytotoxic and a potential inhibitor of p53 and PARP1 proteins.

Neuronal mechanisms regulating locomotion in adult Drosophila

The coordinated action of multiple leg joints and muscles is required even for the simplest movements. Understanding the neuronal circuits and mechanisms that generate precise movements is essential for comprehending the neuronal basis of the locomotion and to infer the neuronal mechanisms underlying several locomotor-related diseases. Drosophila melanogaster provides an excellent model system for investigating the neuronal circuits underlying motor behaviors due to its simple nervous system and genetic accessibility. This review discusses current genetic methods for studying locomotor circuits and their function in adult Drosophila. We highlight recently identified neuronal pathways that modulate distinct forward and backward locomotion and describe the underlying neuronal control of leg swing and stance phases in freely moving flies. We also report various automated leg tracking methods to measure leg motion parameters and define inter-leg coordination, gait and locomotor speed of freely moving adult flies. Finally, we emphasize the role of leg proprioceptive signals to central motor circuits in leg coordination. Together, this review highlights the utility of adult Drosophila as a model to uncover underlying motor circuitry and the functional organization of the leg motor system that governs correct movement.

Teratogenic impacts of Antiepileptic drugs on development, behavior and reproduction in Drosophila melanogaster

Clobazam (CLB) and Vigabatrin (VGB) are the two widely used Antiepileptic drugs, which may have teratogenic potentiality and it has been evaluated in the fruit fly Drosophila melanogaster. These different concentrations of CLB (0.156, 0.25, and 0.312 μg/ml) and VGB (17.6, 22, and 44 μg/ml) were used to evaluate the life-history parameters, developmental, and behavioral abnormalities. The results revealed that life-history parameters (fecundity, fertility, larval and pupal mortality) were significantly affected along with varied developmental duration, and pupal and adult deformities in flies on exposure of CLB and VGB in concentration dependent manner. The present study demonstrated that the prenatal treatment of CLB and VGB has displayed clear teratogenic potentiality with various deformities in the fruit fly. The findings could be correlated with the various abnormalities in human caused by the use of AEDs.

Taste and pheromonal inputs govern the regulation of time investment for mating by sexual experience in male Drosophila melanogaster

Males have finite resources to spend on reproduction. Thus, males rely on a 'time investment strategy' to maximize their reproductive success. For example, male Drosophila melanogaster extends their mating duration when surrounded by conditions enriched with rivals. Here we report a different form of behavioral plasticity whereby male fruit flies exhibit a shortened duration of mating when they are sexually experienced; we refer to this plasticity as 'shorter-mating-duration (SMD)'. SMD is a plastic behavior and requires sexually dimorphic taste neurons. We identified several neurons in the male foreleg and midleg that express specific sugar and pheromone receptors. Using a cost-benefit model and behavioral experiments, we further show that SMD behavior exhibits adaptive behavioral plasticity in male flies. Thus, our study delineates the molecular and cellular basis of the sensory inputs required for SMD; this represents a plastic interval timing behavior that could serve as a model system to study how multisensory inputs converge to modify interval timing behavior for improved adaptation.

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.

A comparative study of the efficiency of Withania somnifera and carbamazepine on lifespan, reproduction and epileptic phenotype - A study in Drosophila paralytic mutant

Background

Seizure disorders are considered a serious health issue because of the vast number of people affected globally and the limited treatment options. Approximately 15 million epileptic patients worldwide do not respond to any of the currently available medications. Carbamazepine (CBZ) is one of the most widely used antiepileptic drugs (AEDs) for the treatment of epilepsy, which is discontinued in less than 5% of epileptic patients due to its side effects. In traditional medicine, to establish the foundation of health care, plant extracts are utilized to a great extent to treat different pathologies. Withania somnifera (W. somnifera) is an herbal component with anticonvulsant properties.

Objectives

To compare the medicinal effects of W. somnifera on lifespan, fecundity, fertility and epileptic phenotype in Drosophila paralytic mutant (para^bss1) model system with CBZ, a commonly used AED.

Material and methods

Flies were exposed to three different doses of W. somnifera or CBZ in standard wheat flour-agar media for six days. Drosophila Oregon-R strain was used as a control.

Results

Results indicate that a high dose of W. somnifera increased the lifespan in Drosophila para^bss1 while remaining safe for fecundity and fertility. CBZ decreased the lifespan of para^bss1 mutant at higher dose (40 μg/ml), as expected, and also reduced the fecundity and fertility of the flies. Our findings indicate that W. somnifera was more effective than CBZ to control epileptic phenotype.

Conclusion

W. somnifera is an effective medication with no side effects for treating epilepsy in Drosophila paralytic mutant.

The gut-microbiota-brain axis in autism: what Drosophila models can offer?

The idea that alterations in gut-microbiome-brain axis (GUMBA)-mediated communication play a crucial role in human brain disorders like autism remains a topic of intensive research in various labs. Gastrointestinal issues are a common comorbidity in patients with autism spectrum disorder (ASD). Although gut microbiome and microbial metabolites have been implicated in the etiology of ASD, the underlying molecular mechanism remains largely unknown. In this review, we have summarized recent findings in human and animal models highlighting the role of the gut-brain axis in ASD. We have discussed genetic and neurobehavioral characteristics of Drosophila as an animal model to study the role of GUMBA in ASD. The utility of Drosophila fruit flies as an amenable genetic tool, combined with axenic and gnotobiotic approaches, and availability of transgenic flies may reveal mechanistic insight into gut-microbiota-brain interactions and the impact of its alteration on behaviors relevant to neurological disorders like ASD.

Changes in Locomotor Activity and Oxidative Stress-Related Factors after the Administration of an Amino Acid Mixture by Generation and Age

Amino acids, as nutrients, are expected to improve sleep disorders. This study aimed to evaluate the generation- and age-dependent sleep-improving effects of γ-aminobutyric acid (GABA) and 5-hydroxytryptophan (5-HTP) coadministration. The differentially expressed genes and generation-related behavior after the administration of a GABA/5-HTP mixture were measured in a Drosophila model, while age-related changes in gene expression and oxidative stress-related parameters were measured in a mouse model. The GABA/5-HTP-treated group showed significant behavioral changes compared to the other groups. Sequencing revealed that the GABA/5-HTP mixture influenced changes in nervous system-related genes, including those involved in the regulation of the expression of behavioral and synaptic genes. Additionally, total sleep time increased with age, and nighttime sleep time in the first- and third-generation flies was significantly different from that of the control groups. The GABA/5-HTP mixture induced significant changes in the expression of sleep-related receptors in both models. Furthermore, the GABA/5-HTP mixture reduced levels of ROS and ROS reaction products in an age-dependent manner. Therefore, the increase in behavioral changes caused by GABA/5-HTP mixture administration was effective in eliminating ROS activity across generations and ages.

Altered Swimming Behaviors in Zebrafish Larvae Lacking Cannabinoid Receptor 2

Background and Objectives: The cannabinoid receptor 2 (CB2) was previously implicated in brain functions, including complex behaviors. Here, we assessed the role of CB2 in selected swimming behaviors in zebrafish larvae and developed an in vivo upscalable whole-organism approach for CB2 ligand screening.

Experimental Approach: Using CRISPR-Cas9 technology, we generated a novel null allele (cnr2^upr1) and a stable homozygote-viable loss-of-function (CB2-KO) line. We measured in untreated wild-type and cnr2^upr1/upr1 larvae, photo-dependent (swimming) responses (PDR) and center occupancy (CO) to establish quantifiable anxiety-like parameters. Next, we measured PDR alteration and CO variation while exposing wild-type and mutant animals to an anxiolytic drug (valproic acid [VPA]) or to an anxiogenic drug (pentylenetetrazol [PTZ]). Finally, we treated wild-type and mutant larvae with two CB2-specific agonists (JWH-133 and HU-308) and two CB2-specific antagonists, inverse agonists (AM-630 and SR-144528).

Results: Untreated CB2-KO showed a different PDR than wild-type larvae as well as a decreased CO. VPA treatments diminished swimming activity in all animals but to a lesser extend in mutants. CO was strongly diminished and even more in mutants. PTZ-induced inverted PDR was significantly stronger in light and weaker in dark periods and the CO lower in PTZ-treated mutants. Finally, two of four tested CB2 ligands had a detectable activity in the assay.

Conclusions: We showed that larvae lacking CB2 behave differently in complex behaviors that can be assimilated to anxiety-like behaviors. Mutant larvae responded differently to VPA and PTZ treatments, providing in vivo evidence of CB2 modulating complex behaviors. We also established an upscalable combined genetic/behavioral approach in a whole organism that could be further developed for high-throughput drug discovery platforms.

A Systematic Review on Non-mammalian Models in Epilepsy Research

Epilepsy is a common neurological disorder characterized by seizures which result in distinctive neurobiological and behavioral impairments. Not much is known about the causes of epilepsy, making it difficult to devise an effective cure for epilepsy. Moreover, clinical studies involving epileptogenesis and ictogenesis cannot be conducted in humans due to ethical reasons. As a result, animal models play a crucial role in the replication of epileptic seizures. In recent years, non-mammalian models have been given a primary focus in epilepsy research due to their advantages. This systematic review aims to summarize the importance of non-mammalian models in epilepsy research, such as in the screening of anti-convulsive compounds. The reason for this review is to integrate currently available information on the use and importance of non-mammalian models in epilepsy testing to aid in the planning of future studies as well as to provide an overview of the current state of this field. A PRISMA model was utilized and PubMed, Springer, ScienceDirect and SCOPUS were searched for articles published between January 2007 and November 2017. Fifty-one articles were finalized based on the inclusion/exclusion criteria and were discussed in this review. The results of this review demonstrated the current use of non-mammalian models in epilepsy research and reaffirmed their potential to supplement the typical rodent models of epilepsy in future research into both epileptogenesis and the treatment of epilepsy. This review also revealed a preference for zebrafish and fruit flies in lieu of other non-mammalian models, which is a shortcoming that should be corrected in future studies due to the great potential of these underutilized animal models.

Functional analysis of the glycogen binding subunit CG9238/Gbs-70E of protein phosphatase 1 in Drosophila melanogaster

The product of the CG9238 gene that we termed glycogen binding subunit 70E (Gbs-70E) was characterized by biochemical and molecular genetics methods. The interaction between Gbs-70E and all catalytic subunits of protein phosphatase 1 (Pp1-87B, Pp1-9C, Pp1-96A and Pp1-13C) of Drosophila melanogaster was confirmed by pairwise yeast two-hybrid tests, co-immunoprecipitation and pull down experiments. The binding of Gbs-70E to glycogen was demonstrated by sedimentation analysis. With RT-PCR we found that the mRNAs coding for the longer Gbs-70E PB/PC protein were expressed in all developmental stages of the fruit flies while the mRNA for the shorter Gbs-70E PA was restricted to the eggs and the ovaries of the adult females. The development specific expression of the shorter splice variant was not conserved in different Drosophila species. The expression level of the gene was manipulated by P-element insertions and gene deletion to analyze the functions of the gene product. A small or moderate reduction in the gene expression resulted in no significant changes, however, a deletion mutant expressing very low level of the transcript lived shorter and exhibited reduced glycogen content in the imagos. In addition, the gene deletion decreased the fertility of the fruit flies. Our results prove that Gbs-70E functions as the glycogen binding subunit of protein phosphatase 1 that regulates glycogen content and plays a role in the development of eggs in D. melanogaster.

Transcriptomic analysis in a Drosophila model identifies previously implicated and novel pathways in the therapeutic mechanism in neuropsychiatric disorders

We have taken advantage of a newly described Drosophila model to gain insights into the potential mechanism of antiepileptic drugs (AEDs), a group of drugs that are widely used in the treatment of several neurological and psychiatric conditions besides epilepsy. In the recently described Drosophila model that is inspired by pentylenetetrazole (PTZ) induced kindling epileptogenesis in rodents, chronic PTZ treatment for 7 days causes a decreased climbing speed and an altered CNS transcriptome, with the latter mimicking gene expression alterations reported in epileptogenesis. In the model, an increased climbing speed is further observed 7 days after withdrawal from chronic PTZ. We used this post-PTZ withdrawal regime to identify potential AED mechanism. In this regime, treatment with each of the five AEDs tested, namely, ethosuximide, gabapentin, vigabatrin, sodium valproate, and levetiracetam, resulted in rescuing of the altered climbing behavior. The AEDs also normalized PTZ withdrawal induced transcriptomic perturbation in fly heads; whereas AED untreated flies showed a large number of up- and down-regulated genes which were enriched in several processes including gene expression and cell communication, the AED treated flies showed differential expression of only a small number of genes that did not enrich gene expression and cell communication processes. Gene expression and cell communication related upregulated genes in AED untreated flies overrepresented several pathways – spliceosome, RNA degradation, and ribosome in the former category, and inositol phosphate metabolism, phosphatidylinositol signaling, endocytosis, and hedgehog signaling in the latter. Transcriptome remodeling effect of AEDs was overall confirmed by microarray clustering that clearly separated the profiles of AED treated and untreated flies. Besides being consistent with previously implicated pathways, our results provide evidence for a role of other pathways in psychiatric drug mechanism. Overall, we provide an amenable model to understand neuropsychiatric mechanism in cellular and molecular terms.

Transcriptome bioinformatic analysis identifies potential therapeutic mechanism of pentylenetetrazole in down syndrome

Background

Pentylenetetrazole (PTZ) has recently been found to ameliorate cognitive impairment in rodent models of Down syndrome (DS). The mechanism underlying PTZ's therapeutic effect in DS is however not clear. Microarray profiling has previously reported differential expression, both up- and down-regulation, of genes in DS. Given this, transcriptomic data related to PTZ treatment, if available, could be used to understand the drug's therapeutic mechanism in DS. No such mammalian data however exists. Nevertheless, a Drosophila model inspired by PTZ induced kindling plasticity in rodents has recently been described. Microarray profiling has shown PTZ's downregulatory effect on gene expression in the fly heads.

Methods

In a comparative transcriptomics approach, I have analyzed the available microarray data in order to identify potential therapeutic mechanism of PTZ in DS. In the analysis, summary data of up- and down-regulated genes reported in human DS studies and of down-regulated genes reported in the Drosophila model has been used.

Results

I find that transcriptomic correlate of chronic PTZ in Drosophila counteracts that of DS. Genes downregulated by PTZ significantly over-represent genes upregulated in DS and under-represent genes downregulated in DS. Further, the genes which are common in the downregulated and upregulated DS set show enrichment for MAP kinase pathway.

Conclusion

My analysis suggests that downregulation of MAP kinase pathway may mediate therapeutic effect of PTZ in DS. Existing evidence implicating MAP kinase pathway in DS supports this observation.

Digital candidate gene approach (DigiCGA) for identification of cancer genes

The candidate gene approach is one of the most commonly used methods for identifying genes underlying disease traits. Advances in genomics have greatly contributed to the development of this approach in the past decade. More recently, with the explosion of genomic resources accessible via the public Web, digital candidate gene approach (DigiCGA) has emerged as a new development in this field. DigiCGA, an approach still in its infancy, has already achieved some primary success in cancer gene discovery. However, a detailed discussion concerning the applications of DigiCGA in cancer gene identification has not been addressed. This chapter will focus on discussing DigiCGA in a generalized sense and its applications to the identification of cancer genes, including the cancer gene resources, application status, platform and tools, challenges, and prospects.

Detection of transgenerational spermatogenic inheritance of adult male acquired CNS gene expression characteristics using a Drosophila systems model

Available instances of inheritance of epigenetic transgenerational phenotype are limited to environmental exposures during embryonic and adult gonadal development. Adult exposures can also affect gametogenesis and thereby potentially result in reprogramming of the germline. Although examples of epigenetic effects on gametogenesis exist, it is notable that transgenerational inheritance of environment-induced adult phenotype has not yet been reported. Epigenetic codes are considered to be critical in neural plasticity. A Drosophila systems model of pentylenetetrazole (PTZ) induced long-term brain plasticity has recently been described. In this model, chronic PTZ treatment of adult males causes alterations in CNS transcriptome. Here, we describe our search for transgenerational spermatogenic inheritance of PTZ induced gene expression phenotype acquired by adult Drosophila males. We generated CNS transcriptomic profiles of F₁ adults after treating F₀ adult males with PTZ and of F₂ adults resulting from a cross between F₁ males and normal females. Surprisingly, microarray clustering showed F₁ male profile as closest to F₁ female and F₀ male profile closest to F₂ male. Differentially expressed genes in F₁ males, F₁ females and F₂ males showed significant overlap with those caused by PTZ. Interestingly, microarray evidence also led to the identification of upregulated rRNA in F₂ males. Next, we generated microarray expression profiles of adult testis from F₀ and F₁ males. Further surprising, clustering of CNS and testis profiles and matching of differentially expressed genes in them provided evidence of a spermatogenic mechanism in the transgenerational effect observed. To our knowledge, we report for the first time detection of transgenerational spermatogenic inheritance of adult acquired somatic gene expression characteristic. The Drosophila systems model offers an excellent opportunity to understand the epigenetic mechanisms underlying the phenomenon. The finding that adult acquired transcriptomic alteration in soma is spermatogenically inherited across generations has potential implications in human health and evolution.