[
WormBook,
2006]
Small GTPases of the Ras superfamily are key regulators of diverse cellular and developmental events, including differentiation, cell division, vesicle transport, nuclear assembly, and control of the cytoskeleton. The C. elegans genome encodes 56 members of the major Ras GTPase subfamilies, including the Ras/Ral/Rap family, the Rho family, the Rab family, Ran, and the Arf/Sar family. Studies in C. elegans have shown that Ras/Rap family members control cell fate specification and differentiation; Rho GTPases control morphogenesis and actin dynamics, including axon pathfinding and cell migration; Rab GTPases control synaptic vesicle trafficking and release and gene expression responses in innate immunity; the Ran GTPase controls nuclear import/export, nuclear reassembly after mitosis, and kinetechore association with microtubules; and Arf/Sar GTPases control morphogenesis and microtubule organization and possibly cilia development. Functions for many of the small GTPases remain to be discovered, and continuing studies in C. elegans will elucidate the roles of these molecules in animal development.
[
1994]
Nematodes have been cultured continuously in the laboratory since 1944 when Margaret Briggs Gochnauer isolated and cultured the free-living hermaphroditic species Caenorhabditis briggsae. Work with C. briggsae and other rhabditid nematodes, C. elegans, Rhabditis anomala, and R. pellio, demonstrated the relative ease with which they could be cultured. The culturing techniques described here were developed for C. elegans, but are generally suitable (to varying degrees) for other free-living nematodes. Whereas much of the early work involved axenic culturing, most of these techniques are no longer in common use and are not included here. In the 1970s C. elegans became the predominant research model due to work by Brenner and co-workers on the genetics and development of this species. An adult C. elegans is about 1.5 mm long, and under optimal laboratory conditions has a life cycle of approximately 3 days. There are two sexes, males and self-fertile hermaphrodites, that are readily distinguishable as adults. The animals are transparent throughout the life cycle, permitting observation of cell divisions in living animals using differential interference microscopy. The complete cell lineage and neural circuitry have been determined and a large collection of behavioral and anatomical mutants have been isolated. C. elegans has six developmental stages: egg, four larval stages (L1-L4), and adult. Under starvation conditions or specific manipulations of the culture conditions a developmentally arrested dispersal stage, the dauer larva, can be formed as an alternative third larval stage. Many of the protocols included here and other experimental protocols have been summarized in "The Nematode Caenorhabditis elegans". We also include a previously unpublished method for long-term chemostat cultures of C. elegans. General laboratory culture conditions for nematode parasites of animals have been described, but none of these nematodes can be cultured in the laboratory through more than one life cycle. Marine nematodes and some plant parasites have been cultured xenically or with fungi. Laboratory cultivation of several plant parasites on Arabidopsis thaliana seedlings in agar petri plates has also been reported.