a-low-cost-method-for-analyzing-seizure-like-activity-movement

A Low-cost Method for Analyzing Seizure-like Activity and Movement in <em>Drosophila</em>

Video tracking systems have been used widely to analyze Drosophila melanogaster movement and detect various abnormalities in locomotive behavior. While ...

Franciscan University of Steubenville

We report here the characterization of slamdance (sda), a Drosophila melanogaster "bang-sensitive" (BS) paralytic mutant. This mutant exhibits hyperactive behavior and paralysis following a mechanical "bang" or electrical shock. Electrophysiological analyses have shown that this mutant is much more prone to seizure episodes than normal flies because it has a drastically lowered seizure threshold. Through genetic mapping, molecular cloning, and RNA interference, we have demonstrated that the sda phenotype can be attributed to a mutation in the Drosophila homolog of the human aminopeptidase N (APN) gene. Furthermore, using mRNA in situ hybridization and LacZ staining, we have found that the sda gene is expressed specifically in the central nervous system at particular developmental stages. Together, these results suggest that the bang sensitivity in sda mutants is caused by a defective APN gene that somehow increases seizure susceptibility. Finally, by using the sda mutation as a sensitized background, we have been able to identify a rich variety of sda enhancers and other independent BS mutations.

The Drosophila slamdance gene: a mutation in an aminopeptidase can cause seizure, paralysis and neuronal failure.

Despite the frequency of seizure disorders in the human population, the genetic basis for these defects remains largely unclear. Currently, only a fraction of the epilepsies can be linked conclusively to a genetic determinant. In addition, a significant number of epileptics do not respond to the current anticonvulsant therapies. We have turned to Drosophila as a model to address these problems and have identified genetic mutants that are more sensitive to seizures, bang-sensitive (BS) mutants, such as slamdance (sda), bangsenseless (bss) and easily shocked (eas), as well as mutants that are resistant to seizures, such as paralytic, maleless(napts), shaking-B(2) and Shaker. Here, we have developed a new method for evaluating compounds with anticonvulsant activity. The methodology uses Drosophila BS mutants to assay the ability of compounds to suppress the seizure susceptible phenotype normally seen in the BS mutants. To test the effectiveness of this method, two BS mutant strains were administered the anticonvulsant valproate and in both cases the drug was able to suppress seizures. The Drosophila system provides a potentially powerful way of developing and testing new drugs with anticonvulsant properties.

Anticonvulsant valproate reduces seizure-susceptibility in mutant Drosophila.

Human seizure disorders represent a heterogeneous collection of neuropathies, many of which are poorly understood. To investigate the etiology of seizure disorders, we have used a group of Drosophila mutants known as the bang-sensitive (BS) paralytics. The BS mutants exhibit seizure-like activity (SLA) following a wide variety of insults including mechanical shock, electrical shock, high frequency light and cold temperatures. In this study, we show that two novel insults, hypoxia and hypercapnia (elevated CO(2) levels) are potent triggers of SLA in a number of the BS mutants. We also show that both of these insults, hypoxia and hypercapnia, can trigger SLA in wild-type flies as well. However, we find that the BS mutants are more susceptible than wild-type flies to these insults as they exhibit more SLA following these insults and, in the case of hypercapnia, they exhibit SLA at a lower threshold. In addition, we demonstrate that the BS mutants are more susceptible to the anesthetizing effects of CO(2) as compared to wild-type flies. The increased sensitivity to both hypoxia and hypercapnia in these BS mutants suggests possible physiological defects that may underlie seizure susceptibility.

Sensitivity to seizure-like activity in Drosophila following acute hypoxia and hypercapnia.

There is increasing evidence that alterations in metabolism can affect seizure susceptibility in a wide range of organisms. In order to investigate the link between metabolism and seizures, we took advantage of a group of Drosophila mutants, the Bang-sensitive (BS) paralytics, which are 3-10 times more susceptible to seizure-like activity (SLA) than wild type flies following a variety of stimuli including mechanical shock. To alter metabolism, we introduced the atsugari (atu) mutation into three of the BS mutants, easily shocked (eas), bang senseless (bss), and technical knockout (tko). The atu mutants, which exhibit reduced expression of the Drosophila ortholog of dystroglycan gene, have previously been shown to have a higher metabolic rate than wild type flies. Following mechanical shock, all three BS;atu double mutants displayed a reduction in SLA and the eas;atu and tko;atu double mutants recovered from the shock quicker than the respective single mutant BS flies. In addition, the eas;atu and tko;atu flies displayed higher levels of metabolism as compared to the single mutant BS flies. To further study the correlation between metabolism and seizure susceptibility, the three BS strains were fed a sulfonylurea drug (tolbutamide) known to both increase heamolymph glucose concentrations and stimulate lipid metabolism in flies. Following mechanical shock, the eas and tko mutants fed tolbutamide displayed less SLA and recovered quicker than unfed flies. While the bss mutants fed tolbutamide did not display a reduction in SLA, they did recover quicker than unfed controls. These data indicate that the upregulation of metabolism can have a protective effect against seizure susceptibility, a result that suggests new avenues for possible drug development.

Daniel Kuebler

Department of Biology

Franciscan University of Steubenville

A Low-cost Method for Analyzing Seizure-like Activity and Movement in Drosophila