Name: comparative analysis of experimental methods to quantify animal activity in caenorhabditis elegans models of mitochondrial disease
Uploaded: 2021-04-04T14:00:00
Description: Watch this Scientific Journal Video about Comparative Analysis of Experimental Methods to Quantify Animal Activity in Caenorhabditis elegans Models of Mitochondrial Disease at JoVE.com

We are grateful to Anthony Rosner, PhD., with his organizational support for the early preparation of this project, and to Erin Haus for contributing to protocol analysis. This work was funded by the Juliet&#39;s Cure FBXL4 Mitochondrial Disease Research Fund, the Jaxson Flynt C12ORF65 Research Fund, and the National Institutes of Health (R01-GM120762, R01-GM120762-08S1, R35-GM134863, and T32-NS007413). The content is solely the responsibility of the authors and does not necessarily represent the official views of the funders or the National Institutes of Health.

1. Worm locomotor activity analysis in liquid media on glass slides using ZebraLab software
<ol>
	<li>Nematode growth and handling
	<ol>
		<li>Grow C. elegans on Petri plates containing nematode growth media (NGM) and spread with Escherichia coli OP50 as food source. Maintain worm culture at 20 &#176;C, as previously described8.</li>
		<li>Synchronize worms performing a timed egg lay52 and study worms at the desired stage. In this protocol, L4 stage worm...

Here, the study summarized detailed information and rationales for studying C. elegans neuromuscular activity at the level of diverse outcomes, including worm thrashing, locomotion, pharyngeal pumping, and chemotaxis. The comparison of 16 different activity analysis methodologies was performed in terms of the relative throughput, advantages, and limitations of quantify nematode activities in a single worm or worm populations at different ages and experimental durations. Among these, two novel adaptations and&#16...

Caenorhabiditis elegans is widely recognized as an outstanding model in neuroscience based on it having 302 neurons that coordinate all worm behaviors, including mating, feeding, egg-laying, defecation, swimming, and locomotion on solid media1. These hermaphroditic nematodes are also widely used to understand a wide array of human disease mechanisms, made possible by its well-characterized genome and high homology of ~80% genes between C. elegans and humans2,3,4. C. elegans have long been used to interrogate human mitochondrial disease5,6,7,8,9,10, which is a highly genetically and phenotypically heterogeneous group of inherited metabolic disorders that share impaired capacity to generate cellular energy and often clinically present with substantially impaired neuromuscular function, exercise intolerance, and fatigue11,12,13,14.To this end, the use of C. elegans models enable preclinical modeling of quantitative aspects of animal activity and neuromuscular function in different genetic subtypes of mitochondrial disease, as well as their response to candidate therapies that may improve their neuromuscular function and overall activity.
Neuromuscular activity in C. elegans is objectively measurable by a range of experimental methodologies, including both manual and semi-automated approaches that allow functional analyses in either solid or liquid media (Table 1)1,15. Accurate quantitation of C. elegans activity has proven important to enable discoveries related to function and development of the muscular and nervous system16,17,18. This study summarizes and compares experimental requirements, advantages, and limitations of 17 different assays that can be performed in research laboratories to evaluate neuromuscular function and activity on four key outcomes in C. elegans diseases models, both at the baseline at a range of developmental stages and ages as well as in response to candidate therapies (Table 1). Indeed, the study provides a detailed overview of the range of available experimental approaches to characterize rates of C. elegans thrashing (body bends per minute), locomotor activity, pharyngeal pumping, and chemotaxis-in each case specifying the experimental and analytic methodology used, the advantages and limitations of each method, the equipment and software needed to perform and analyze each assay, and the throughput capacity of each method to support its use for high-throughput genetic or drug screening purposes. The throughput capacity of each assay is described as low, medium, or high based on the experimental protocol complexity, including worm maintenance, processing time, the use of single or multi-well plates, and/or experimenter time needed to complete the experimental setting and data analyses.
Manual analyses of thrashing19, locomotor activity20, pharyngeal pumping17,21, and chemotaxis22,23 are well-established methodologies to evaluate worm activity that require a stereomicroscope24. While measuring thrashing activity of worms requires analysis in liquid media to determine the frequency of body bends per minute, worm locomotor activity may be measured either on solid media or in liquid media. However, manual analyses of individual worm activity are inherently time-consuming and involves unavoidable user-generated bias. Automation of worm activity analyses minimizes user-generated bias and can greatly increase experimental throughput25. Video recordings of worm thrashing activity in liquid media can be analyzed using wrMTrck, an ImageJ plugin26. However, the original experimental settings that were developed for wrMTrck limited its utility, since too many worms in a single liquid drop led to overlapping of worms that made accurate tracking difficult. While this experimental limitation has been resolved27, the wrMTrck method is not able to support high-throughput screening.
A range of methods exist to quantify worm locomotor activity&#160;at baseline and in response to candidate therapies in C. elegans mitochondrial disease models. These include ZebraLab (ViewPoint Life Sciences), Tierpsy Tracker28, wide field-of-view nematode tracking platform (WF-NTP)29, WormMotel, WormWatcher30, WormLab31, Infinity Chip32, and WMicrotracker One33 (Table 1). These methods enable concurrent analysis of locomotion in multiple worm strains or conditions, typically on multi-well plates, thereby supporting higher-throughput drug screening applications. Some of these methods have unique considerations that may limit or enhance their general utility, such as the need for expensive equipment versus open-access software, and varying ease of performing experimental protocols. Overall, no single experimental system or protocol is ideally suited to all C. elegans locomotor activity experiments. Rather, it is important to carefully choose which method is best suited to the specific investigator&#39;s experimental goals and requirements.
Pharyngeal pumping represents another important outcome to assess neuromuscular activity in C. elegans. The C. elegans pharynx is composed of 20 muscle cells, 20 neurons, and 20 other cells that enable ingestion of Escherichia coli (E. coli) at the anterior end of the worm&#39;s alimentary tract34,35,36. Several manual methods have been established to determine pharyngeal pumping rates17,21,37,38. Most methods are based on the use of a stereomicroscope and camera to visualize and record pharyngeal pumping frequency with direct counting by the experimental observer21. Automated pharyngeal pumping rate analysis is possible by performing an extracellular recording termed electropharyngeogram (EPG), which provides additional information on the duration of each pump39. Pharyngeal pumping rate analysis is also possible in a microfluidic system, WormSpa, where individual worms are confined in chambers40,41. A commercial method available to facilitate analysis of the pharyngeal pump rate is the ScreenChip System (InVivo Biosystems), which measures, visualizes, and analyzes the neuromuscular aspects of feeding behavior in a single worm that is immobilized in a custom chip. This pharyngeal pumping quantitation approach can be used to assess both neuronal and physiological responses to drugs, aging, and other factors42,43,44,45.
Chemotaxis describes the movement of C. elegans in response to an odorant placed away from the worms in a defined area of the nematode growth media (NGM) plate. Assessing the chemotaxis response provides an integrated measure of worm neuronal and neuromuscular activity that is quantifiable by observing and measuring the physical distance traveled by worms toward the odorant in a defined time period46. The Multi-Worm Tracker is an automatic method that can be used to improve the experimental efficiency of quantifying the distance traveled by worms toward an attractant or from a repellant47.
Here, the detailed protocol for two novel, semi-automated methods established for quantifying worm activity is described. The first approach utilizes ZebraLab a commercial software that was originally developed to study swimming activity of Danio rerio (zebrafish), for a novel medium-throughput application to quantify overall locomotor activity in liquid media of C. elegans based on pixel changes during movement (Table 1, Figure 1). Data output is quickly obtained from a large number of concurrent conditions and samples analyzed on a glass slide, although this method is not suitable to a multi-well plate format. The second approach is a novel adaptation of the WormScan methodology48,49 (Figure 2), which uses a flatbed scanner to create a differential image of two sequential scans that can variably be used with open-source software to enable semi-automated quantitative analysis of integrated physiologic outcomes such as fecundity and survival. Here, a novel high-throughput adaptation of the WormScan methodology to quantify worm locomotor activity in liquid media in populations of fifteen larval-stage 4 (L4) worms per well of a 96-well, flat-bottom plate was developed. This semi-automated and low-cost WormScan methodology can be readily adapted to high-throughput drug screens, as well as to analyses of various animal stages and ages48,49.
Here, the protocol and efficacy of analyzing C. elegans locomotor activity using both ZebraLab and WormScan semi-automated methods is demonstrated in a well-established C. elegans model for mitochondrial complex I disease, gas-1(fc21). gas-1 (K09A9.5 gene) is an ortholog of human NDUFS2 (NADH: ubiquinone oxidoreductase core (iron-sulfur protein) subunit 2) (Figure 3). The C. elegans gas-1(fc21) mutant strain carries a homozygous p.R290K missense mutation in the human ortholog of NDUFS250, causing significantly decreased fecundity and lifespan, impaired respiratory chain oxidative phosphorylation (OXPHOS) capacity51, as well as decreased mitochondrial mass and membrane potential with increased oxidative stress5,8. Despite its well-established use over the past two decades to study mitochondrial disease, locomotor activity of gas-1(fc21) mutants was not previously reported. Here,&#160;ZebraLab and WormScan methods were applied to independently quantify the locomotor activity of gas-1(fc21) as compared to wild-type (WT, N2 Bristol) worms, both as a way to validate the methods as well as to demonstrate their comparative utility and efficiency of the experimental protocols and informatics analyses. ZebraLab software allowed rapid quantitation of several concurrent conditions of worm locomotor activity in C. elegans mitochondrial disease models, with potential application for targeted drug screening or validation studies. WormScan analysis, in particular, is well-suited to readily enable high-throughput drug screens of compound libraries and prioritize leads that improve the animal neuromuscular function and the locomotor activity in preclinical C. elegans models of primary mitochondrial disease.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>C. elegans wild isolate</td>
			<td>&#160;Caenorhabditis Genetics Center (CGC)</td>
			<td>N2 Bristol</td>
			<td></td>
		</tr>
		<tr>
			<td>Camera</td>
			<td>Olympus</td>
			<td>DP73</td>
			<td></td>
		</tr>
		<tr>
			<td>gas-1(fc-21)</td>
			<td>CGC</td>
			<td>CW152</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope slides</td>
			<td>ThermoFisher</td>
			<td>4951PLUS</td>
			<td></td>
		</tr>
		<tr>
			<td>Nematode Growth Medium (NGM)</td>
			<td>Research Products International Corp.</td>
			<td>N81800-1000.0</td>
			<td></td>
		</tr>
		<tr>
			<td>OP50 Escherichia coli</td>
			<td>CGC</td>
			<td></td>
			<td>Uracil auxotroph E. coli strain</td>
		</tr>
		<tr>
			<td>Petri dishes (60 mm)</td>
			<td>&#160;VWR international</td>
			<td>25373-085</td>
			<td></td>
		</tr>
		<tr>
			<td>S. Basal</td>
			<td>VWR 5.85 g NaCl, 1 g K2 HPO4, 6 g KH2PO4, and 5 mg cholesterol, in 1 l H2O</td>
			<td>VWR 101175-162, 103467-156, EM1.09828.1000, 97061-660</td>
			<td></td>
		</tr>
		<tr>
			<td>Scanner</td>
			<td>EPSON</td>
			<td>V800</td>
			<td></td>
		</tr>
		<tr>
			<td>Stereomicroscope</td>
			<td>Olympus</td>
			<td>MVX10 microscope</td>
			<td></td>
		</tr>
		<tr>
			<td>96-well flat bottom</td>
			<td>&#160;VWR international</td>
			<td>29442-056</td>
			<td></td>
		</tr>
		<tr>
			<td>WormScan software</td>
			<td>Mathew et al. 45</td>
			<td>S1 Standalone Java platform</td>
			<td>Software for automation of difference image of scanned plates</td>
		</tr>
		<tr>
			<td>ZebraLab software</td>
			<td>ViewPoint</td>
			<td></td>
			<td>Software for automated quantization and tracking of zebrafish behavior, designed by ViewPoint (http://www.viewpoint.fr/en/p/software/zebralab-zebrafish-behavior-screening) and here applied to C. elegans. This system is applicable for high-throughput behavioral analysis</td>
		</tr>
	</tbody>
</table>

comparative analysis of experimental methods to quantify animal activity in caenorhabditis elegans models of mitochondrial disease

Caenorhabditis elegans is widely recognized for its central utility as a translational animal model to efficiently interrogate mechanisms and therapies of diverse human diseases. Worms are particularly well-suited for high-throughput genetic and drug screens to gain deeper insight into therapeutic targets and therapies by exploiting their fast development cycle, large brood size, short lifespan, microscopic transparency, low maintenance costs, robust suite of genomic tools, mutant repositories, and experimental methodologies to interrogate both in vivo and ex vivo physiology. Worm locomotor activity represents a particularly relevant phenotype that is frequently impaired in mitochondrial disease, which is highly heterogeneous in causes and manifestations but collectively shares an impaired capacity to produce cellular energy. While a suite of different methodologies may be used to interrogate worm behavior, these vary greatly in experimental costs, complexity, and utility for genomic or drug high-throughput screens. Here, the relative throughput, advantages, and limitations of 16 different activity analysis methodologies were compared that quantify nematode locomotion, thrashing, pharyngeal pumping, and/or chemotaxis in single worms or worm populations of C. elegans at different stages, ages, and experimental durations. Detailed protocols were demonstrated for two semi-automated methods to quantify nematode locomotor activity that represent novel applications of available software tools, namely, ZebraLab (a medium-throughput approach) and WormScan (a high-throughput approach). Data from applying these methods demonstrated similar degrees of reduced animal activity occurred at the L4 larval stage, and progressed in day 1 adults, in mitochondrial complex I disease (gas-1(fc21)) mutant worms relative to wild-type (N2 Bristol) C. elegans. This data validates the utility for these novel applications of using the ZebraLab or WormScan software tools to quantify worm locomotor activity efficiently and objectively, with variable capacity to support high-throughput drug screening on worm behavior in preclinical animal models of mitochondrial disease.

Analysis of C. elegans locomotor activity in the liquid media could easily capture an integrated phenotype of mitochondrial disease worm models that may not be easily quantifiable on solid media. ZebraLab was used to quantify locomotor activity of the well-established mitochondrial complex I disease gas-1(fc21) strain relative to WTworms in liquid media at the L4 larval stage. The activity of 5 worms in a single liquid drop was recorded over 1 min, with a total of 19 videos (technical replicate...

Watch this Scientific Journal Video about Comparative Analysis of Experimental Methods to Quantify Animal Activity in Caenorhabditis elegans Models of Mitochondrial Disease at JoVE.com

Comparative Analysis of Experimental Methods to Quantify Animal Activity in Caenorhabditis elegans Models of Mitochondrial Disease

This study presents protocols for two semi-automated locomotor activity analysis approaches in C. elegans complex I disease gas-1(fc21) worms, namely, ZebraLab (a medium-throughput assay) and WormScan (a high-throughput assay) and provide comparative analysis among a wide array of research methods to quantify nematode behavior and integrated neuromuscular function.

Comparative Analysis of Experimental Methods to Quantify Animal Activity in Caenorhabditis elegans Models of Mitochondrial Disease

Caenorhabditis elegans is widely recognized for its central utility as a translational animal model to efficiently interrogate mechanisms and therapies of ...

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