Caenorhabditis elegans is a well-established model organism first introduced to the laboratory in the 1960s by Sydney Brenner. Comprised of just 959 cells and maturing in only a few days, these small, transparent nematodes have provided researchers with unique insights into developmental biology. Cell fates have been mapped, but observing all of the transitions from embryo to adult has been challenging because worms are, frankly, squirmy. Images of freely moving larvae can be taken but have lacked single-cell detail, while acquiring high-resolution images requires that the animals be immobilized. Mechanical restriction and paralytic drugs can hold them still long enough to take a decent picture, but prevent feeding. In an organism with such a short life cycle, even minimal disruptions can quickly arrest further development. Visualizing C. elegans at the cellular level over the full course of its development was hypothetically possible, but in need of an improved approach.

To resolve this imaging conundrum, Dutch researchers led by Jeroen van Zon at FOM Institute AMOLF in Amsterdam have developed a new quantitative microscopy technique for tracking C. elegans development (Nat. Commun. 7, 12500; 2016). The team manufactured a 10 x 10 array of microchambers filled with a polyacrylamide hydrogel, which slows the worms down without completely stopping them from moving about. A single embryo was placed in each chamber along with some E. coli for food. LED illumination, short exposure times, and high numerical aperture allowed the researchers to take time-lapse microscopic photographs of the entire chamber while resolving each individual cell. Their images corresponded with established markers such as molting episodes and body length extension—indicating that the set-up did not impede development—yet allowed them to document individual variation for 10 to 20 worms simultaneously every 20 minutes over 48 hours as they matured from embryos to adults.

Credit: Heiti Paves, Getty

The researchers further demonstrated the utility of their microscopy technique by following cell division, cell migration, and gene expression dynamics in wild-type C. elegans as well as various mutants, with the help of fluorescent tags. Each of the processes examined occurs over time-frames too long to be adequately captured by previous techniques but could be suitably imaged in the current study, offering novel insight into C. elegans development. The team hopes that their microscopy technique will be a valuable tool for studying C. elegans in future research.