Caenorhabditis Elegans - Laboratory Uses

Laboratory Uses

In 1963, Sydney Brenner proposed using C. elegans as a model organism for the investigation of animal development including neural development. Brenner chose it mainly because it is simple, easy to grow in bulk populations, and convenient for genetic analysis. It is a multicellular eukaryotic organism that is simple enough to be studied in great detail. Strains are cheap to breed and can be frozen. When subsequently thawed, they remain viable, allowing long-term storage. Other desirable properties are:

C. elegans is transparent, facilitating the study of cellular differentiation and other developmental processes in the intact organism. The males can be easily distinguished from hermaphrodites based on the morphology of the tail region.

The developmental fate of every single somatic cell (959 in the adult hermaphrodite; 1031 in the adult male) has been mapped. These patterns of cell lineage are largely invariant between individuals, in contrast to mammals, where cell development from the embryo is more largely dependent on cellular cues.

In both sexes, a large number of additional cells (131 in the hermaphrodite, most of which would otherwise become neurons), are eliminated by programmed cell death (apoptosis). Because of this "apoptotic predictability", it has contributed to the elucidation of some apoptotic genes, mainly through observation of abnormal, apoptosis-surviving nematodes.

It is one of the simplest organisms with a nervous system. In the hermaphrodite, this comprises 302 neurons whose pattern of connectivity, or "connectome", has been completely mapped and shown to be a small-world network. Research has explored the neural mechanisms responsible for several of the more interesting behaviors shown by C. elegans, including chemotaxis, thermotaxis, mechanotransduction, and male mating behavior.

A useful feature is a relatively straightforward method to disrupt the function of specific genes by RNA interference (RNAi). Silencing the function of a gene in this way can sometimes allow a researcher to infer what the function of that gene may be. The nematode can either be soaked in or injected with a solution of double-stranded RNA, the sequence of which is complementary to the sequence of the gene the researcher wishes to disable. Alternatively, worms can be fed genetically transformed bacteria that express the double-stranded RNA of interest.

The study of meiosis is simplified considerably with this organism. As sperm and egg nuclei move down the length of the gonad, they undergo a temporal progression through meiotic events. This progression means every nucleus at a given position in the gonad will be at roughly the same step in meiosis, eliminating the difficulties of heterogeneous populations of cells.

It can also be used in the study of nicotine dependence, as it has been found to exhibit behavioral responses to nicotine that parallel those observed in mammals, including acute response, tolerance, withdrawal, and sensitization.

As for most model organisms, a dedicated online database for the species is actively curated by scientists working in this field. The WormBase database attempts to collate all published information on C. elegans and other related nematodes. A reward of $4000 has been advertised on their website, for the finder of a new species of closely related nematode. Such a discovery would broaden research opportunities with the worm.