Electrical sorting of Caenorhabditis elegans

Abstract

The nematode (worm) C. elegans is one of the widely studied animal model organisms in biology. It develops through 4 larval stages (L1-L4) in 2 to 3 days before becoming a young adult. Biological assays involving C. elegans frequently require a large number of animals that are appropriately staged and exhibit a similar behaviour. We have developed a new method to synchronize animals that relies on the electrotactic response (electric field-induced motion) of C. elegans to sort them in parallel based on their age, size and phenotype. By using local electric field traps in a microfluidic device, we can efficiently sort worms from a mixed culture in a semi-continuous flow manner (with a minimum throughput of 78 worms per minute per load-run) and obtain synchronized populations of animals. In addition to sorting larvae, our device can also distinguish between young and old adults efficiently. Unlike fluorescent based sorting systems that use active imaging based feedback, this method is passive and automatic and uses the innate behaviour of the worm. Considering that the entire procedure takes only a few minutes to run and is cost-effective, it promises to simplify and accelerate experiments requiring homogeneous cultures of worms as well as to facilitate isolation of mutants that have abnormal electrotaxis. More importantly, our method of isolating and separating worms using locomotion as a defining characteristic promises development of advanced microfluidics-based systems to study the neuronal basis of movement-related defects in worms and facilitate high-throughput chemical screening and drug discovery.

An automated microfluidic system for screening Caenorhabditis elegans behaviors using electrotaxis

“…[15][16][17][18][19][20][21][22] In previous work from our group, we designed a simple microfluidic device to examine the swimming behaviors of C. elegans under electric fields, termed electrotaxis, and demonstrated that changes in movement are reliable indicators of neurodegeneration and harmful effects of toxic chemicals on C. elegans health. [23][24][25] However, the inherent manual operation of the devices makes the screening process labor intensive and time consuming, which limits largely the practical application of the method. [23][24][25] In order to enable widespread use of the electrotactic assay, we have addressed the current limitations and developed an entirely new automated microfluidic system, which can perform electrotaxis assay for a batch of worms, without human intervention, one worm at a time while substantially increasing the throughput of analysis.…”

“…[23][24][25] However, the inherent manual operation of the devices makes the screening process labor intensive and time consuming, which limits largely the practical application of the method. [23][24][25] In order to enable widespread use of the electrotactic assay, we have addressed the current limitations and developed an entirely new automated microfluidic system, which can perform electrotaxis assay for a batch of worms, without human intervention, one worm at a time while substantially increasing the throughput of analysis. This system can load, isolate, perform electrotaxis assay, and flush C. elegans in a computer-controlled sequence.…”

Recent Developments in Electrotaxis Assays

“…Rezai et al spatially separated different worms in a simple planar microchannel with a narrowed trap region based on the age-dependent or stagedependent electrotactic responses of worms. 25 In addition, continuous sorting can be achieved in a parallel manner. Han et al proposed another sorting strategy based on the size-dependent motility and electrotaxis of worms in a microstructured channel.…”

Galvanotaxis of Caenorhabditis elegans: current understanding and its application in improving research

“…Using this device, authors sorted the young adult worms from older worms, young adult worms from larval staged worms and wild-type young adult worms from mutant worms. Although the sorter works at a selectivity of ~90% for worms of different age and mutants, multi-stage sorting of worms can potentially overcome this issue [38].…”

“…Handful of devices/setup and microfluidic devices had been introduced to scientific community which can sort worms based on electro-sensation behavior of worm into age, size and locomotion defective groups. Rezai et al (2012) introduced a microfluidic device that can sort worms using differential electrotactic response of the worm at different age. The microfluidic device created contains an electrical trap with narrow microchannel, which enhances the EF in the narrow channel when compared to the wider channel on either side.…”