Anupom, Taslim, Laranjeiro, Ricardo, Norouzi Darabad, Masoud, Lesanpezeshki, Leila, Driscoll, Monica, Blawzdziewicz, Jerzy, A. Vanapalli, Siva
[
International Worm Meeting,
2021]
Caenorhabditis elegans has been widely used to study the genetics of behavior and neuromuscular function. Most of the behavioral studies in C. elegans are limited to two-dimensional (2D) assessment of animal locomotion on agar plates (crawling) or in liquid (swimming), and it was not until recently that C. elegans studies began to focus on 3D motion. 3D locomotion where animals burrow through a matrix is known to be physiologically distinct from 2D crawling and swimming (Bilbao et al. 2018) and 3D movement evokes different gene expression responses (Hewitt et al. 2020). We have previously deployed a Pluronic hydrogel environment to assess the burrowing performance of muscle mutants. The stiffness of the gel can be tuned to challenge the animals to burrow through a higher mechanical resistance environment to increase the assay sensitivity (Lesanpezeshki et al. 2019). However, due to the assay geometry being in a well-plate, the full burrowing trajectory was not observable, and the animals could be only visualized at the top surface, precluding evaluation of the burrowing behavior throughout the gel layers. To address the above issues, we have developed a microfluidic platform called a burrowing chip, that enables visualization and assessment of burrowing behavior in the same Pluronic hydrogel environment. The microfluidic format provides excellent control of the chemotactic gradient and animal/gel loading. The shallow depth of the channel enables use of consumer cameras for visualizing and recording burrowing behavior. We show that the device provides a 3D environment to assess the animal's burrowing performance and the animal distribution along the channel during chemotaxis. Next, we identify two burrowing classes of behaviorally slow and fast movement, based on the time it takes animals to reach the attractant. Slow burrowers weakly maintain their direction toward the attractant. We have discovered pause intervals as a novel phenotype for stimulated burrowing animals, as the burrowing animals exhibit long pauses. Finally, we show that the burrowing chip is capable of characterizing the muscle mutants based on their lower burrowing velocity and higher frequency of pauses compared to wild-type animals. We suggest that the burrowing chip can be used to provide insights into the genetic basis of burrowing behavior and to assess the neuromuscular health in C. elegans, paving the road to identify therapeutic targets for age-related diseases and decline.