Abstract
The study of mechanisms that govern feeding behaviour and its related disorders is a matter of global health interest. The roundworm Caenorhabditis elegans is becoming a model organism of choice to study these conserved pathways. C. elegans feeding depends on the contraction of the pharynx (pumping). Thanks to the worm transparency, pumping can be directly observed under a stereoscope. Therefore, C. elegans feeding has been historically investigated by counting pharyngeal pumping or by other indirect approaches. However, those methods are short-term, time-consuming and unsuitable for independent measurements of sizable numbers of individuals. Although some particular devices and long-term methods have been lately reported, they fail in the automated, scalable and/or continuous aspects. Here we present an automated bioluminescence-based method for the analysis and continuous monitoring of worm feeding in a multi-well format. We validate the method using genetic, environmental and pharmacological modulators of pharyngeal pumping. This flexible methodology allows studying food intake at specific time-points or during longer periods of time, in single worms or in populations at any developmental stage. Additionally, changes in feeding rates in response to differential metabolic status or external environmental cues can be monitored in real time, allowing accurate kinetic measurements.
Highlights
The regulation of food intake is a critical mechanism with major physiological impacts
The decrease in the signal is due to the specific depletion of ingested luciferin during the quiescent periods, what led us to hypothesise that the bioluminescence signal could report for food intake behaviours
Luminescence assay for the analysis of food intake behaviour in C. elegans
Summary
Luminescence assay for the analysis of food intake behaviour in C. elegans. We measured luminescence from single animals that constitutively and ubiquitously express the luciferase protein fused to GFP (Psur-5::luc+::gfp)[23,24], in 96-well plates. We concluded that the reduction in the luminescence signal emitted by eat-2 mutants results from a specific reduction of the ingested luciferin and reflects reduced food intake We tested whether this method can be useful to monitor feeding behaviour in small populations of worms. When animals are fed after a period of fasting, the signal increases to reach a similar level to that of fed worms (Supplementary Fig. S3) This assay can be used to study the modulation of food intake in response to changes in food quality or other environmental cues. The assay we describe here allows the automatic and continuous analysis of food intake in a multi-well format This method permits the scrutiny of feeding behaviours at specific time-points, during long periods of time and in real time, being suitable for both, populations and single worms at any developmental. The method described here adds an invaluable tool to investigate how internal and external cues modulate feeding behaviours
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