History of GFP and GFP Antibodies
GFP and Anti-GFP Antibodies: Why we make anti-GFP antibodies and why people want them.
GFP stands for green-fluorescent protein, a protein found in jellyfish, sea pansies, corals, sea anemones, and a few other groups of marine organisms. Discovered by a group at Princeton University (Shimomura and Johnson) in the late 1960’s and characterized in the sea pansy by Bill Ward in the mid 1970’s, GFP is a relatively small protein about half the size of serum albumin and half the size of hemoglobin in the blood stream. Since the mid 1970’s, Professor Ward has published about 100 articles, book chapters, and short papers on GFP and has hosted three international symposia on GFP (1997, 2000, and 2003).
The first natural function discovered for GFP back in the 1970’s (Morin and Hastings) was to turn the bioluminescence flash of hydroids, jellyfish, and sea pansies from blue to green. Since then other functions have been found. In sea anemones, that have fluorescent proteins with more color varieties than just green (pink, for example), the fluorescent protein seems to serve the function of a pigment—the ecological functions of which are still a mystery. This may also be true for corals, as neither anemones nor corals bioluminesce. After many years of research by several groups, primarily at Johns Hopkins, Princeton, Mayo Clinic, and Univ. of Georgia, a group at Columbia University (Chalfie et al) succeeded in cloning the gene for GFP into bacteria and round worms in 1994. That ground-breaking cover story in Science magazine by the Columbia group (Dr. Ward was a co-author) has now become one of the ten most cited papers in all of biotechnology. The reason for the extraordinary popularity of GFP in science research is that GFP is the only fluorescent protein (the only colored protein, in fact) that can be genetically transferred into other cells, tissues, organs, and organisms (and be expressed as a fluorescent protein) after the gene transplant. Many other proteins have brilliant colors and some have fluorescence, but none of these can be cloned, with retention of that color, just by being inserted, via a single gene, into another organism. So GFP is unique.
What the cloning of GFP means to scientists in cell biology, neurobiology, oncology, developmental biology, stem cell research, and a host of other biomedically related fields is that they can now watch what is happening in cells in real time by monitoring a non-invasive, non-toxic fluorescent marker–GFP. Before GFP, the most common way to see what was happening in cells was to kill them, preserve them, and stain them with toxic chemicals. With few exceptions, all studies were post-mortem—a field called cytology. This all changed with GFP, as GFP can report on developmental events and intimate details of cellular metabolism in cells that are still living. Whole organisms (fish, flowers, pigs, mice, rats, and cats) have been transformed with the GFP gene, making every cell in the body green-fluorescent. These transformed organisms go on to lead perfectly happy lives (like the Amazing Hulk or Shreck) and they even have perfectly well-adjusted green-fluorescent babies, some of whom go on to college (well, I did have one student with green-fluorescent hair).
The GFP gene can be linked to cellular control factors (called promoters). In the case of the round worm at Columbia University, the study was one of nerve growth. By linking the GFP gene to the promoter for nerve growth, the Columbia scientists could study what triggers other cells to grow into nerves. Only when the nerves begin to grow do the cells begin to glow green. Since 1994, these kinds of experiments have been performed in tens of thousands of labs all over the world, providing information about the workings of cells that no other tool has been able to uncover. Nature Biotechnology magazine even put a picture of GFP on its magazine cover in the mid 1990’s, calling GFP “The Molecule of the Year.”
Sometimes people want to trap GFP with antibodies. The GFP may have been fused to another protein of interest so that trapping GFP also traps the protein of interest. Perhaps, by trapping and then measuring GFP, a researcher can tell how well a flask of bacteria are growing. Sometimes GFP is used to find out if one cellular protein binds to another cellular protein. Sometimes it is used to mark success with stem cell transplantation. Sometimes GFP marks the onset of cancer metastasis. But, sometimes, when the gene for GFP is expressed in a cell, it is expressed in a non-fluorescent form, because something interfered with the way it was folded. Antibodies can be used to trap the misfolded GFP so that the experimenter can determine at what stage the failure occurred—was there a problem with gene expression, protein synthesis, or protein folding, for example.
We obtained our native GFP through hard work and dedication, collecting huge numbers of jellyfish from the Puget Sound and then isolating and purifying the GFP protein from those jellyfish. We spent 3 weeks each summer for 17 summers (8 persons each working for 21 days) hand-collecting jellyfish (from floating docks at the University of Washington’s Friday Harbor Laboratories) and then hand-dissecting those jellyfish (nearly 2 million of them). Purifying the protein was even more time consuming. It took us more than 8 person-years to purify the protein we extracted from those 2 million jellyfish. As we are the only remaining large, active group in the world to have gone this extraordinarily tedious route (the other three groups to do the same thing are retired, semi-retired, or doing other things), we believe we are the only group with a supply of pure native jellyfish GFP sufficient in quantity and purity to make high quality antibodies
GFP has become so popular in the molecular life sciences that virtually every person in the field has heard of and has read about GFP. A large percentage has actually used GFP or anti-GFP antibodies in experimental research. The abbreviation GFP now has almost as much “name recognition” as ATP. Brighter Ideas, Inc. is one of the world’s largest producers of anti-GFP antibodies raised in rabbits and chickens. In addition, we are designing diagnostics tools, like the protease detection and fingerprinting platform “GFP-on-a-String,” that utilize either GFP or anti-GFP antibodies to deliver sensitive and specific outputs for the molecules they measure.
Dr. William Ward
Founder and President
Brighter Ideas, Inc.