Caenorhabditis elegans: A Model Organism
C. elegans has been a long standing model organism for multicellular eukaryotes due to its simplistic structure and features which, despite being base in nature, provide highly analogous representations of biological processes in other model organisms. Generally, model organisms must have a set of common traits which allow for ease of use and observation such as rapid maturation and small growth cycles, small size, availability, and tractability. C. elegans is a particularly attractive model organism not only for its adherence to the above criteria but due to several other factors as well.
C. elegans is a transparent, nonparasitic nematode approximately 1mm in length and is found in most temperate soil climates. It is easily sustained in the lab through use of agar plates or liquid cultures at laboratory temperatures. It can feed solely on E. coli, and is hence cheaply cultivated. Its transparency allows for the study of cellular differentiation and tissue mapping via fluorescing proteins. The rapidity with which C.elegans reproduces and the large number of offspring generated per hermaphrodite leads to the production of high numbers of offspring in a short amount of time.
A population of C. elegans is comprised of two sexes: hermaphrodites and males, the former being predominant in any given population. Because of a lack of male-hermaphroditic mating, the genotypes of worms produced in culture remain generally homogenous. While the life span of a worm can be anywhere from 2-3 weeks in length, the worms themselves reach maturation within 3 days. At this point, all expression patterns in their cells are considered adult and the number of somatic cells within the worm remains at a constant of 959 for hermaphrodites and 1031 for males. The expected results of genetic construct microinjection can be detected and tested at this point.
The completely sequenced genome of C. elegans contributes to the organism’s status as a model for genetic engineering study, and as a result, means genetic manipulation techniques within the worm are well tested. Methods of gene manipulation by injection of plasmid vectors into the gonads are standard, as is RNAi gene knockout, for example. Furthermore, transgenes from higher organisms such as humans have been successfully expressed within C. elegans. This was proven with the insertion of human GPCRs (G-protein Coupled Receptors) into C. elegans where interactions between the human receptor and the worm G-protein were successful. These findings led QGEM 2011 to harness the potential of C.elegans through genetic engineering.
Caenorhabditis elegans: Eukaryotic Chassis
QGEM 2010 was the first iGEM team to introduce C. elegans as a chassis for genetic engineering in the iGEM competition. Their project focused on the creation of a C. elegans toolkit whereby other teams may easily perform feats of genetic engineering with the worm. This year, our focus was to build upon that concept, demonstrating the use of having a eukaryotic multicellular organism as a functional iGEM chassis and also a bioremediation tool, among other goals.
While the benefits of working with simpler prokaryotic organisms such as E. coli are not disputed, using eukaryotes as a chassis for genetic engineering has significant advantages as well. As a model eukaryotic organism, succesful manipulation of the C.elegans genome would quantify similar exploits using larger organisms. The portability between the genes of C. elegans and genes of other model organisms is high and, as is seen with the successful insertion of human GPCR transgenes into C. elegans, is proof that despite a largely divergent evolutionary pathways, eukaryotic systems share much in basic biological interactions. By utilizing a eukaryotic chassis, we show that other higher organisms may be manipulated similarly and that the possibilities of genetic engineering are truly endless. Already C. elegans has been instrumental in the study of aging and cancer development in humans.
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