Aegarter-Wilmsen, Tinri, Lattmann, Evelyn, Hajnal, Alex, Casadevall i Solvas, Xavier, deMello, Andrew, Berger, Simon, Hengartner, Michael
[
International Worm Meeting,
2017]
Owing to its small size, fecundity and genetical tractability C. elegans has become one of the most widely used model organisms in biology. One major challenge when working with C. elegans however, is its high mobility, making immobilization necessary for the study of most cellular and subcellular processes. Immobilization is usually achieved by simply placing the worms of interest on an agar pad, limiting motion through the pressure exerted on the animal and, if necessary, through addition of chemical tranquilizers. Unfortunately, this process has proven to be a major limitation when trying to follow developmental processes over extended periods of time, as it rapidly causes slowdown or arrest of many such processes. Here we present a novel set of microfluidic devices able to trap, feed and image C. elegans in a variety of developmental stages (L1 to adult), without any of the adverse effects encountered when using conventional immobilization methods. Our immobilization platform is based on a simple PDMS microfluidic device mounted on the back of a coverslip. Operation of the device is readily learned and the microfluidic device can easily be integrated with any type of microscope (inverted or upright), all imaging modalities commonly used (brightfield, epifluorescence and confocal microscopy), and any type of objective (high magnification and high numerical aperture). Thus requiring only small changes to existing microscope setups and microscopy protocols prior to adaptation, enabling the study of a great variety of developmental processes, interference free, in vivo. We demonstrate the platforms capabilities in several case studies. First, we studied long-term viability of adult C. elegans on-chip, readily achieving viabilities exceeding 100 hours while immobilized, all while observing normal feeding and egg laying rates. Optimal quality images of the adult gonad were then acquired, showcasing the platforms capabilities of following complex developmental processes over long time periods. Specifically we studied germ cell apoptosis, a process known to arrest on agar pad within 20 minutes, and factors involved in the cell fate decision by tracking 100 cells over the course of 12 hours. For the first time determining an apoptotic rate of 60% in vivo (n = 100). Secondly we demonstrate that crucial developmental process, e.g. anchor cell invasion and distal tip cell migration, occur normally on-chip in all larval stages assessed, and at rates comparable to on plate culture. Compared to development on agar pads, processes occurred 5-7 times faster and more reliable on-chip, with all worms undergoing normal development. This strongly suggests that our immobilization device has minimal negative effects on sensitive developmental processes, thus making it ideally suited for long-term studies of processes so far inaccessible, all while allowing the capture of high resolution images.