Wednesday, October 22, 2008

Glowing Green with Envy

In all of this election clamor, I forgot to post the winners of the Nobel Prize in Chemistry for this year. The award was split between three scientists for their discovery and development of Green Fluorescent Protein or GFP: Osamu Shimomura, Martin Chalfie, and Roger Y. Tsien.

I think this prize was rightly awarded this year. Their discovery boosted a huge jump in basic science research by pioneering a new tool that could be used to investigate questions about that molecular world. GFP was originally discovered in the jellyfish, Aequorea victoria, and is known to give that iridescent glow to our sea-water friends. This natural sort-of night light is not uncommon in the animal kingdom. It turns out that bioluminescence has evolved independetly about 30 differents times in organisms we see today. Another example is the firefly which uses a protein called luciferase to activate a substrate which will the glow after cleavage. GFP is different, however, because it can fluoresce on its own, with no need for a substrate.

The implications for the discovery of GFP have been far-reaching, and I'll just touch on a few in the biomedical sciences. GFP is a protein coded for by a gene in the jellyfish. Scientists were able to cut this gene out, and put it in other species to make them glow - first, by just making it glow in all the cells for a proof of principle. Then they began to put different promoters in front of the gene, or 'switches' that can control whether or not the gene is on or off. For example, if Gene X is only turned on in the stomach and I want to put GFP only in the stomach, I'll take the 'switch' for Gene X (usually sits right in front of the gene) and put a copy in front of GFP so that it only turns on in the stomach. This way, scientists could label particular organs, tissues, or even single cells to carry out different studies.

But what about more than one cell type? No problem - scientists have tinkered with GFP to make RFP (red), YFP (yellow), BFP (blue), CFP (Cyan), mStrawberry, Tomato, Cherry, Plum, Katushka, Kate, and the names just get better and better. We can label all sorts of cells differently and all at the same time!

What's even cooler, is that we can actually engineer a normal protein that has a normal function in a cell to have GFP at the end of it, literally attached to it. This way we can follow around single molecules inside a cell to see where they go and what other molecules they interact with!

Other strategies have used this type of labeling to sort out cell types from complex tissues using a machine that recognizes the fluorescent color.

These examples just scratch the surface of the kinds of techniques GFP has allowed us to explore. I'll leave you with a picture I took of one of my embryonic mouse gonads using a transgenic mouse line using GFP. This is a picture of an E12.5 mouse testis from an Oct4:EGFP embryo - that means only germ cells are labelled - in this case, I've psuedocolored the GFP positive germ cells to look PINK, so don't be fooled - I've labelled two other molecules: laminin and PECAM.

Behold the power of GFP:


96well: said...

Very nice picture. Actually, I prefer luciferase as a reporter, but I recognize only fluorescent proteins render so well. Have you seen the Brainbow mouse?

I make conversations about reporter development at Reportergene, if you want to join...

Matthew said...

Dude! I have seen Brainbow mouse - it's utterly amazing. Tell me more about reportergene...

96well: said...

Contextual, systems-level measurements of genes, proteins and their cellular functions can facilitate understanding of biological pathways and networks in the context of normal physiology as well as in disease pathology with/out drug treatment.
Theoretically a reporter gene can allow to monitor noninvasively each molecular mechanism. Unfortunately, new developments in such assays comes randomly from historically separated fields like optics, physics, pharmacology, chemistry and medicine; so my idea is to collect transversal informations and providing the trend toward bioassay development.