Simple and Accessible Egg-Hatching Assays in Caenorhabditis elegans: Adaptable Formats for Drug Screening

Summary

This study presents a flexible and standardized egg-hatching assay platform in Caenorhabditis elegans that integrates multiple experimental formats. The approach enhances reproducibility, scalability, and accessibility, enabling robust evaluation of drug effects and developmental processes, while remaining cost-effective and easily adaptable for both research applications and educational settings.

Abstract

Egg-hatching assays (EHA) are widely used to evaluate the effects of chemical compounds on early developmental stages of nematodes, particularly in anthelmintic research. However, existing methodologies vary substantially in format, complexity, and reproducibility, and are often presented as fixed protocols rather than adaptable experimental frameworks. In this study, we establish a simple, accessible, and flexible platform for egg-hatching assays in Caenorhabditis elegans by integrating and directly comparing three experimental configurations: (i) controlled incubation in microcentrifuge tubes followed by seeding on agar plates, (ii) direct exposure on drug-containing agar plates, and (iii) multiwell-based liquid assays. Two representative compounds were used to illustrate the assay: one that inhibits egg hatching and one that has no detectable effect. Each configuration provides distinct advantages in terms of experimental control, throughput, and accessibility. The microcentrifuge tube-based approach enables precise control of drug exposure and supports quantitative pharmacological analyses. Agar-based assays offer a simplified and low-cost alternative suitable for continuous exposure and educational settings. Multiwell formats enable scalable, standardized screening consistent with modern drug discovery pipelines. By directly comparing these formats, we show how methodological choices influence assay reproducibility, drug exposure dynamics, and biological interpretation, particularly in relation to stage-specific factors such as the protective role of the eggshell and developmental variation in molecular target expression. Overall, this work establishes egg-hatching assays in C. elegans as a versatile and scalable platform adaptable to diverse applications, including anthelmintic screening, toxicological assessment, developmental studies, and teaching laboratories, thereby facilitating broader and more rational use of this methodology.

Introduction

Egg-hatching assays (EHA) have long been established as a cornerstone methodology in nematology for evaluating ovicidal activity and early developmental effects of chemical compounds. Originally developed for parasitic nematodes, these assays quantify the inhibition of embryonation or larval emergence under controlled in vitro conditions, providing robust and biologically relevant endpoints such as hatching percentage or concentration–response analysis (e.g., EC₅₀ or IC₅₀)^1,2,3,4,

Protocol

1. Caenorhabditis elegans strains and culture

1. Use the wild-type N2 (Bristol) strain and/or the transgenic strain PD4251 (ccIs4251; dpy-20(e1282)) to develop and validate the methodology^25,26. PD4251 expresses GFP, facilitating visualization and potential imaging applications when required, while showing egg-hatching and developmental responses indistinguishable from those observed in the wild-type N2 strain under the experimental conditions used in this study²⁷.
2. Obtain strains (e.g., wild-type N2 strain) from the Caenorha....

Results

TCA produced clear concentration-dependent inhibition of egg hatching across all experimental formats, as shown in Figure 1. Representative concentration–response curves are presented for each assay configuration: microcentrifuge tubes (Figure 1A), direct exposure on agar plates (Figure 1B), and multiwell plates (Figure 1C).

The estimated IC₅₀ values were 0.19 ± 0.0262 mM in .......

Discussion

This study presents a simple and adaptable platform for egg-hatching assays in Caenorhabditis elegans, structured around three complementary experimental formats that differ in control, exposure dynamics, and scalability. Rather than defining a single optimal protocol, our results support the view that egg-hatching assays should be considered a flexible methodological framework adaptable to specific experimental objectives.

The microcentrifuge tube-based format provides a highly contr.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Bacteriological Agar	Britania	B0101406	should be prepared fresh (1.7 gr in 100 mL H2O)
Bleach solution	N/A	N/A	1.2 % (v/v) NaOH and 0.5 M NaOH
Centrifuge	ThermoScientific.	Sorvall ST16R.
Centrifuge	BiofugePICO to eppendorf tube	Heraeus 75003235
Digital camera	ToupCam	TP605100A	Industrial digital camera. Adjustabe focal length USB 2.0
DMSO	BioBasic	RAS#7-68-5	MW: 78,13
Linalil Acetate	SIGMA	No.CAS: 115-95-7	should be prepared fresh
Lysogeny broth (LB) medium	N/A	N/A	10 g Bacto-tryptone, 5 g yeast extract, 10 g NaCl to 1 L destilled water
M9 Buffer	N/A	N/A	3 g KH2PO4, 6 g Na2HPO4, 5 g  NaCl, 0,25 g MgSO4 to 1 L destilled water
Mini Rotator	BioSan	Bio RS-24
Nematode Growth Medium (NGM)	N/A	N/A	3 g NaCl, 17 g agar, 2,5 g  Bacto-Peptone to 1 L destilled water. Sterilize by autoclaving. Supplemented 1 mL cholesterol (5 mg/mL),  1 mL CaCl2 (1 M) , 25 mL potassium phosphate buffer (1 M, pH 6.0) and 1 mL  MgSO4 (1 M)
Petri Dish (3 - 5 mm)	ThermoScientific. Nunclon DeltaSurface	153066
Petri Dish (90 mm x 15 mm)	ExtraGene	1026160305	For laboratory use only, Polystyrene.
Pipette	Fisherbrand	N/A
SigmaPlot 12.0	Systat Software	N/A	Version 12.0
Stereomicroscope	ARCANO	ZTX-T 1:4 LED	Trinocular stereomicroscope (10x–40x total magnification; LED incident and transmitted illumination)
Sucrose	Laboratorio Cicarelli	Art 841	60 % (v/v) sucrose
Tissue culture plate 96 well	Biofil	TCP 012096	Polystyrene, Low Evaporation Lid.
ToupView	ToupTek Photonics	N/A
Transcinnamaldehyde (TCA)	Santa Cruz Biotechnology	J1712	Should be prepared fresh