Caenorhabditis elegans is a free-living, transparent nematode (roundworm), about 1 mm in length, which lives in temperate soil environments. Research into the molecular and developmental biology of C. elegans was begun in 1974 by Sydney Brenner and it has since been used extensively as a model organism.
It reproduces with a life cycle of about 3 days under optimal conditions. The animal can be maintained in the laboratory where it is grown on agar plates or liquid cultures with E. coli as the food source. It can be examined at the cellular level in living preparations by differential interference contrast (DIC) microscopy, since it is transparent throughout its life cycle.
Among its many advantages for study are its short life cycle, compact genome, stereotypical development, ease of propagation and small size. The adult bodyplan is anatomically simple with about 1000 somatic cells. C. elegans is amenable to genetic crosses and produces a large number of progeny per adult.
Each worm contains only 302 neurons, virtually all of which have distinct genetic markers, enabling researchers in many cases to express their desired proteins in any neuron of interest. Additionally, a simple system such as C. elegans allows researchers to more easily tease apart the neural networks involved in behaviours such as movement, sensation and learning. Optogenetics has already contributed to several studies in the worm, including: establishing the functional relevance of neural connections and determining whether neurotransmission is a digital ‘all-or-none’ signal or an analogue graded signal.
C. elegans worms are easy to grow, maintain and manipulate, making them excellent models for a variety of genetic and other screens. However, screening ad manipulating large numbers of worms by hand is labour-intensive.
Many homologs of human genes that are targets for mutation in cancer have been found to function at distinct steps within such genetic pathways. This way, studies in C. elegans have provided important clues about the functions of human oncogenes and tumor suppressors.
Developmental processes in the nematode C. elegans are controlled by pathways of gene functions that are analogous to those used in mammals. Hence, genetic studies in C. elegans have helped build the frameworks for these regulatory pathways.
Marie-Anne Felix, PhD, a researcher who studies nematodes at the Monod Institute, began the study by gathering C. elegans from rotting fruit in French orchards. Felix noted that some of her sample worms appeared to be sick. Treatment with antibiotics failed to cure them, so Felix repeated a classic biology experiment that led to the discovery of viruses.
Researchers at Washington University School of Medicine in St. Louis, the Jacques Monod Institute in France and Cambridge University have found that the nematode C. elegans, a millimeter-long worm used extensively for decades to study many aspects of biology, gets naturally occurring viral infections. The discovery means C. elegans is likely to help scientists study the way viruses and their hosts interact.
[Anne Brunet's] team is now looking to see if the results in the worm Caenorhabditis elegans translate to species that are evolutionarily closer to humans, such as fish and mice. The discovery is an example of "epigenetic inheritance", where organisms pass on changes in the way genes are used rather than in the genes themselves.
A study has shown that nematode worms [ Caenorhabditis elegans] can inherit a "memory of longevity" from their parents, even though their genome remains unchanged. It is not clear if the same processes apply to humans, but Anne Brunet from Stanford University, who led the study, noted that some genes that affect the lifespan of nematodes were later found to influence human longevity too. "In several cases, the worm has proved to be a good model for humans, who live 2,000 times longer," she said.