High-throughput RNAi by soaking in Caenorhabditis elegans

Introduction The phenomenon of RNA-mediated interference (RNAi) was first discovered in the nematode Caenorhabditis elegans (Fire et al., 1998), in which introduction of double-stranded RNA (dsRNA) causes specific inactivation of genes with corresponding sequences. RNAi was soon recognized as an experimentally simple and technically undemanding method for gene knockdown in this organism. The emergence of this new technology, which coincided with the completion of the sequencing of the C. elegans genome (The C. elegans Sequencing Consortium, 1998), has brought about a dramatic shift in the experimental strategies adopted in the study of this organism, and greatly expanded our understanding of gene function at the whole-genome level. Our group have established an optimized “soaking method” for dsRNA delivery into worms (Maeda et al., 2001), and applied this technique for large-scale analysis of gene function. In this paper, I describe the characteristics of the “soaking method,” and its application in the study of developmental processes in C. elegans. RNAi in C. elegans After the finding of RNAi in C. elegans, a series of subsequent analyses demonstrated that wide range of animals, plants, and fungi has RNAi-related gene regulatory mechanisms (Cogoni and Macino, 2000). Biochemical and genetic approaches, conducted mainly in C. elegans and Drosophila, have revealed the evolutionarily conserved nature of the molecular mechanism of RNAi (see other chapters in this book for detail). Although the “core RNAi mechanism” appears to be conserved among diverse organisms, some aspects of RNAi observed in C. elegans are not universally found in other species.