Green Flourescent Protein

Green fluorescent protein, or GFP, was originally used in C. elegans by Dr Martin Chalfie. Dr Chalfie worked with the scientist Sidney Brenner - the first scientist to champion the use of C. elegans as a model organism. It is a protein with fluorescent capabilities found in the jellyfish Aequorea victoria and was first isolated as a 238 amino acid protein by Douglas Prasher (Prasher et al, 1992).

Chalfie used the research into the GFP gene (gfp) by Prasher and combined it with the work of Brenner. He used GFP from Prasher in 1992 and expressed it in both E. coli strains and C. elegans, where the GFP was detectable under a blue light. The area Chalfie tagged using GFP was a promoter region regulating beta-tubulin expression which had been found to be present in six touch receptor neurons. The resulting organism expressed GFP from distinct positions at certain times in its development.

The technology has now been advanced to the extent where amino acids in GFP can be substituted to form new fluorescent colours so multiple proteins can now be monitered at the same time.  Current research methods can now view molecules in real time in a live subjuct using Photobleaching methods such as 'Fluorescence recovery after photobleaching' (FRAP), 'fluorescence loss in photobleaching' (FLIP) and inverse FRAP (iFRAP). These methods use a dye to tag the target molecule or protein, parts of which are then bleached using a laser. The intensity of the flourescence in that particular area is then monitored over time.


                          Image of adult C. Elegans expressing GFP tagged promoter of Tyrosinase    
Image property of Mark Blaxter. Image source.


The lineage and morphology of each neuron type has been described in detail and neuronal fate markers exist for virtually all neurons in the form of fluorescent reporter genes for C. elegans

References

The green fluorescent protein: discovery, expression and development
    The Royal Swedish Academy of Science

Study of molecular dynamics using fluorescently tagged molecules in live cells
    C. N. Goulbourne et al 2010

Two-color GFP expression system for C. elegans
    Miller DM 3rd et al 1999