Behavioral and developmental assays of C. elegans using microfluidic technology
C. elegans is an exciting model organism for neuroscience research. The worm’s body structure is simple but complex enough to carry sophisticated neural circuits such as insulin signalling pathways. The worm can process environmental cues through various sensory neurons. It can sense or respond to temperature, chemical, electrical, and optical signals as well as mechanical and gaseous cues. The study of the worm’s behaviour in the presence of these stimuli is very insightful in determining the locomotory mechanisms as well as the roots and origins of neurodevelopmental disorders.
Nearly one-third of the C. elegans cells are nerve cells. The structural connections of these cells have been mapped. This makes C. elegans an ideal model organism for studying the chemosensory and mechanosensory circuits. Batch studies and population-averaged results cannot help in discovering these circuits. Microfluidic devices made from PDMS enable researchers to use microfluidics to trap worms (single worms or a population) inside micron-sized channels and expose them to various chemical and mechanical stimuli. The behavioural response of the worm can then be monitored in the microfluidic chip and under the microscope. This can be combined with real-time fluorescent microscopy using GCaMP calcium reporter to observe the neural basis of the worm’s response to chemical cues. The effect of ageing on perception and behaviour of the worm in the presence of chemical and mechanical stimuli can be investigated and compared by simply using worms at different life stages. In terms of mechanical stimuli, microfluidic technology helps in exposing the worm to various touching stimuli by compressing the PDMS walls or various optical or stimuli using fibre optics.
Through its inherent circuits, C. elegans can respond to mechanical, thermal, chemical, and electrical signals. The behavioral response of the animal in the presence of various stimuli provides a comprehensive phenotypic map of this model organism. Some of the behavioral responses that are of interest to C. elegans researchers are listed below.
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- Locomotion: The focus here is the motor-response of the worm in presence or absence of stimuli.
- Sleep or wake response: A sleep-state can be induced in the worm and its posture and muscle activity be measured while the worm is in the sleep mode
Ageing and Developmental Assays
The short life span of C. elegans and its quick maturation (72 hr after laying eggs) turns this nematode into a suitable model organism for developmental biology and ageing research. Whether you are interested in investing the behavior of the nerve cells due to ageing, mutants, or neurodegenerative diseases or in monitoring the developmental stages of this nematode, microfluidics can be of help. Microfluidic chips have been used for long term culturing and monitoring of C. elegans with the possibility of precisely changing the media during the life-span. More sophisticated Microfluidics fabrication methods allow the extraction of eggs to ensure a synchronized population in the channel. Details of these microfluidic devices can be found in the reference section at the bottom of the page.
Development and ageing studies of C. elegans can be insightful for neurodegenerative diseases such as Parkinson’s. There are various aspects of the worm that can be studied when it comes to development. Despite the simplicity of C. elegans, it shows complex decision-making processes. The worm can also manifest learning and memorizing behaviours. For example, it can be conditioned in the presence of food to exhibit directional selection.- A uFluidix original article.