Caenorhabditis elegans Module

Caenorhabditis elegans Module

C. elegans, a free-living nematode, was chosen by Sydney Brenner in 1963 as an experimental organism because it is transparent, easy to propagate, and is a hermaphrodite capable of selfing as well as outcrossing, which facilitates genetic manipulation. The entire cell lineage of C. elegans, from the zygote to the adult has been determined—hermaphrodite adults contain exactly 959 somatic cells. The worm’s transparency and reproducible anatomy make it possible to identify each cell at all stages of development. These features, coupled with its amenability to forward genetics, reverse genetics, systems-level approaches, and molecular studies, have allowed developmental, physiological, and behavioral events to be identified and characterized. Work on this small worm has led to Nobel Prizes for Physiology or Medicine in 2002 to Sydney Brenner, Robert Horvitz, and John Sulston for their characterization of organ development and programmed cell death, the 2005 award to Andrew Fire and Craig Mello for their characterization of RNAi, and the 2008 Nobel Prize in Chemistry to Martin Chalfie and colleagues (including Osamu Shimomura from Woods Hole!) for their use of the jellyfish green fluorescent protein (GFP) as an experimental reagent.

C. elegans has two sexes: self-fertile hermaphrodites (which produce both sperm and oocytes) and males that can inseminate hermaphrodites. Hermaphrodites can produce large populations without mating; you can generate many worms by placing a single hermaphrodite on a petri dish with sufficient food (worms are grown on a lawn of E. coli). Genetic crosses are performed by mating males with hermaphrodites, with male sperm precedence increasing the likelihood of producing cross progeny over self progeny.

In this module, students will learn how to knock down genes with RNAi, look at protein dynamics with fluorescence recovery after photobleaching (FRAP), conduct experiments with optogenetic approaches, carry out laser ablation of selected cells, conduct analysis of differentiated cell types by fluorescent protein markers, and observe development and behavior in wild-type, mutant, and wild-caught worms. One of the main advantages of C. elegans for genetic studies is its short generation time (3 days). Although the constraints of a short module will not allow sufficient time to perform genetic experiments, you will have the opportunity to take advantage of many reagents and experimental conditions to live image worm development.