Effects of valproate on seizure-like activity in Drosophila melanogaster with a knockdown of Ube3a in different neuronal populations as a model of Angelman Syndrome

Abstract

Angelman Syndrome is a rare, genetically induced neurodevelopmental disorder. This disorder stems from a mutation or deletion of the maternal UBE3A gene. Characteristics of this disease include developmental delay, recurring seizures, and severe intellectual disabilities. We studied seizure activity in male Drosophila melanogaster with a knockdown of Ube3a in different neuronal populations (GABAergic, glutamatergic, mushroom body, and all neurons) and investigated the effects of the antiseizure medication (ASM) on seizure-like activity. Epileptiform activity was monitored in individual fruit flies using imaging chambers and mechanically induced seizures using a vortex assay. A positive control was also used: eas (easily shocked seizure phenotype). Seizure activity was analyzed for sums of seizure durations, number of seizures, and total time to return to normal activity. Ube3a knockdowns in GABAergic neurons elicited more seizure-like episodes than knockdowns in glutamatergic neurons and were on par with the positive control group and those with knockdowns in the mushroom bodies. We have established a method whereby valproate could be administered through food rather than through injections to effectively treat epileptiform activity. We demonstrated that if Ube3a is not knocked down pan-neuronally, Angelman Syndrome seizure-like activity can be studied using Drosophila melanogaster and therefore allows for high-throughput drug discovery.

Keywords: Angelman Syndrome; Drosophila melanogaster; Seizure-like activity; Valproate.

Fig. 1

Characterization of seizure-like activity. Each of the GAL4 lines were crossed with UAS-Ube3a (RNAi) lines and the male progeny were the test subjects shown above. a) Average number of seizure-like episodes per testing session of all male flies studied are shown by genetic lines of flies and includes both flies raised in regular food (solid bars) vs. food with valproate (bars with diagonal lines). b) Total elapsed times before resuming normal activity are shown for male flies that exhibited seizure-like episodes; excludes flies that didn’t have seizure-like episodes. Includes both male flies raised in regular food (solid bars) vs. food with valproate (bars with diagonal lines). Means are shown +/- SEM. A Dunnett’s multiple comparison test was used to test for differences of each group compared to the control group (ns: p > 0.05, *: p < 0.05, **: p < 0.01, ****: p < 0.0001). Sample numbers are indicated above each bar.