A Caenorhabditis elegans assay of seizure-like activity optimised for identifying antiepileptic drugs and their mechanisms of action

Wong, S. Q., Jones, A., Dodd, S., Grimes, D., Barclay, J. W., Marson, A. G., Cunliffe, V. T., Burgoyne, R. D., Sills, G. J. and Morgan, A. (2018) A Caenorhabditis elegans assay of seizure-like activity optimised for identifying antiepileptic drugs and their mechanisms of action. Journal of Neuroscience Methods, 309, pp. 132-142. (doi: 10.1016/j.jneumeth.2018.09.004) (PMID:30189284)

Abstract

Background: Epilepsy affects around 1% of people, but existing antiepileptic drugs (AEDs) only offer symptomatic relief and are ineffective in approximately 30% of patients. Hence, new AEDs are sorely needed. However, a major bottleneck is the low-throughput nature of early-stage AED screens in conventional rodent models. This process could potentially be expedited by using simpler invertebrate systems, such as the nematode Caenorhabditis elegans. New method: Head-bobbing convulsions were previously reported to be inducible by pentylenetetrazol (PTZ) in C. elegans with loss-of-function mutations in unc-49, which encodes a GABAA receptor. Given that epilepsy-linked mutations in human GABAA receptors are well documented, this could represent a clinically-relevant system for early-stage AED screens. However, the original agar plate-based assay is unsuited to large-scale screening and has not been validated for identifying AEDs. Therefore, we established an alternative streamlined, higher-throughput approach whereby mutants were treated with PTZ and AEDs via liquid-based incubation. Results: Convulsions induced within minutes of PTZ exposure in unc-49 mutants were strongly inhibited by the established AED ethosuximide. This protective activity was independent of ethosuximide’s suggested target, the T-type calcium channel, as a null mutation in the worm cca-1 ortholog did not affect ethosuximide’s anticonvulsant action. Comparison with existing method Our streamlined assay is AED-validated, feasible for higher throughput compound screens, and can facilitate insights into AED mechanisms of action. Conclusions: Based on an epilepsy-associated genetic background, this C. elegans unc-49 model of seizure-like activity presents an ethical, higher throughput alternative to conventional rodent seizure models for initial AED screens.

• Item Type: Articles
• Additional Information: This work was supported by a Wellcome Trust PhD studentship forSW awarded to AM/RDB (grant number 102378/Z/13); and an MRCDiMeN PhD studentship for AJ awarded to AM/GJS/AGM/VTC. Strainsused in this work were provided by the Caenorhabditis Genetics Center,which is funded by the NIH National Center for Research Resources(NCRR).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Sills, Dr Graeme
• Authors: Wong, S. Q., Jones, A., Dodd, S., Grimes, D., Barclay, J. W., Marson, A. G., Cunliffe, V. T., Burgoyne, R. D., Sills, G. J., and Morgan, A.
• College/School: College of Medical Veterinary and Life Sciences > School of Life Sciences
• Journal Name: Journal of Neuroscience Methods
• Publisher: Elsevier
• ISSN: 0165-0270
• ISSN (Online): 1872-678X
• Published Online: 03 September 2018
• Copyright Holders: Copyright © 2018 The Authors
• First Published: First published in Journal of Neuroscience Methods 309:132-142
• Publisher Policy: Reproduced under a Creative Commons License