Preparation of staged Caenorhabditis elegans embryos using size filtration

The free-living nematode Caenorhabditis elegans has been routinely used to study gene functions, gene interactions, and conserved signaling pathways. Most experiments require that the animals are synchronized to be at the same specific developmental stage. Bleach synchronization is traditionally used to obtain a population of staged embryos, but the method can have harmful effects on the embryos. The physical separation of differently sized animals is preferred but often difficult to perform because some developmental stages are the same sizes as others. Microfluidic device filters have been used as alternatives, but they are expensive and require customization to scale up the preparation of staged animals. Here, we present a protocol for the synchronization of embryos using mesh filters. Using filtration, we obtained a higher yield of embryos per plate than using standard bleach synchronization protocol and at a scale beyond microfluidic devices. Importantly, filtration does not affect downstream larval development assays as much as bleach synchronization does. In conclusion, we have exploited the differences in the sizes of C. elegans developmental stages to isolate embryo cultures suitable for use in high-throughput assays.