Abstract
In this paper, we report a novel microfluidic method to conduct a Caenorhabditis elegans electrotaxis movement assay and neuronal imaging on up to 16 worms in parallel. C. elegans is a model organism for neurodegenerative disease and movement disorders such as Parkinson’s disease (PD), and for screening chemicals that alleviate protein aggregation, neuronal death, and movement impairment in PD. Electrotaxis of C. elegans in microfluidic channels has led to the development of neurobehavioral screening platforms, but enhancing the throughput of the electrotactic behavioral assay has remained a challenge. Our device consisted of a hierarchy of tree-like channels for worm loading into 16 parallel electrotaxis screening channels with equivalent electric fields. Tapered channels at the ends of electrotaxis channels were used for worm immobilization and fluorescent imaging of neurons. Parallel electrotaxis of worms was first validated against established single-worm electrotaxis phenotypes. Then, mutant screening was demonstrated using the NL5901 strain, carrying human -synuclein in the muscle cells, by showing the associated electrotaxis defects in the average speed, body bend frequency (BBF), and electrotaxis time index (ETI). Moreover, chemical screening of a PD worm model was shown by exposing the BZ555 strain, expressing green fluorescence protein (GFP) in the dopaminergic neurons (DNs), to 6-hydroxydopamine neurotoxin. The neurotoxin-treated worms exhibited a reduction in electrotaxis swimming speed, BBF, ETI, and DNs fluorescence intensity. We envision our technique to be used widely in C. elegans-based movement disorder assays to accelerate behavioral and cellular phenotypic investigations.
Highlights
High-throughput screening (HTS) is a crucial drug discovery process that aims to test large compound libraries on a specific target in a sensitive, fast, and cost-effective manner [1]
C. elegans continues to be of importance in drug discovery due to a fully sequenced genome, genetic tractability, and many other experimental advantages [8,9]
We showed the applicability of our device for genetic, chemical, and neuronal screening after validating it against the single-worm electrotaxis assay
Summary
High-throughput screening (HTS) is a crucial drug discovery process that aims to test large compound libraries on a specific target in a sensitive, fast, and cost-effective manner [1]. The positive hits are tested on whole-animal mammalian models to evaluate the chemical potency and toxicity before preliminary clinical trials [2] Very commonly, these compounds are found to be impractical on whole animals due to the drug toxicity, metabolism complications, or poor target engagement, thereby rendering the process expensive and tedious [2]. These compounds are found to be impractical on whole animals due to the drug toxicity, metabolism complications, or poor target engagement, thereby rendering the process expensive and tedious [2] Model organisms such as Caenorhabditis elegans (C. elegans) [1,3,4], Drosophila melanogaster [5,6], and Danio rerio [7] have shown promising outcomes to fill the gap between in-vitro cell-based and in-vivo whole-animal studies. Various mutants have been created to help reveal the causes underpinning these NDs and to identify novel neuroprotective compounds [19]
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