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Glowing Coral Proteins Aid Medical Research

John Roach
for National Geographic News
January 12, 2005
 
Tiny proteins that give coral reefs a mysterious glow may be key to keeping coral species alive, according to scientists. Those same proteins, they say, may also help blaze trails to new health cures.

Known as fluorescent protein, the molecules absorb light of one color and emit light of a different color. Scientists are uncertain as to why the proteins do this. But researchers believe the proteins may either help in the production of food or serve as a sunscreen.

Scientists say gaining a better understanding of the proteins' role may help prevent further reef destruction.


"Corals are some of the most endangered organisms on the Earth. There are thousands of different kinds of coral, and many are headed for near extinction," said Vincent Pieribone, an associate professor of cellular and molecular physiology and neurobiology at Yale University School of Medicine in New Haven, Connecticut.

Away from the oceans, the medical community is using fluorescent protein in the lab to monitor and study biological processes associated with AIDS, Alzheimer's disease, cancer, and a host of other diseases.

Researchers can attach the fluorescent molecules to a protein inside a dividing cancer cell or a spreading virus. Then, by shining a light of the appropriate color, scientists can watch as a cell divides or a virus spreads—processes they wouldn't be able to see without the special proteins.

Scientists say the proteins may one day illuminate intricacies of the human nervous system. "Our big goal is to put these [glowing proteins] in the brains of organisms and actually look at what the brain is doing," Pieribone said.

By watching how the brain works—observing what nerves are fired to command a certain action, such as lifting a foot—researchers may find a way to bypass spinal cord injuries, Pieribone said.

Many people with severed spinal cords can create muscle commands in their brains. But damage to nerve tissue prevents brain messages from reaching muscles.

The task for medical researchers is to devise a means to read these brain commands and transfer them to appropriate body tissues, perhaps through robotics.

"We're laying the groundwork to do that sort of thing," Pieribone said. "It could happen 30 or 40 years from now."

First, however, Pieribone and his colleagues are searching global coral reefs for new fluorescent proteins, ones that better shine through bones and muscle tissue.

Fluorescent Jellyfish

Fluorescent proteins were first discovered about 40 years ago in an Aequorea jellyfish that thrives in the coastal waters of the Pacific Northwest. The protein, named green fluorescent protein, or GFP, was shown to play a secondary role in the bioluminescence periodically emitted by the jellyfish.

In the 1990s researchers cloned the fluorescent molecules. Scientists learned how to attach the molecules to cells and proteins inside the bodies of other living animals, including humans. The breakthrough allowed widespread use of fluorescent proteins in biomedical research.

"Once GFP was cloned and became an important biological tool, people felt the need to find more colors of fluorescent proteins," said David Gruber, a graduate student in biological oceanography at Rutgers University in New Brunswick, New Jersey. Gruber collaborates with Pieribone, the Yale cell scientist and neurobiologist, on fluorescent protein research.

Researchers were able to manipulate the DNA of jellyfish GFP to obtain yellow and cyan, or dark blue, colors. However, scientists were unable to engineer red florescent proteins. The color is desirable because it penetrates deeper into living tissue.

In 1999 a team of Russian scientists found a GFP-like protein in a common sea anemone (Anemonia majano) sitting in a Moscow fish tank. The team has since discovered and cloned a handful of other fluorescent proteins from coral-reef species, and the race is on to find more.

"If the Russians found both green and red fluorescent protein from a few fish-tank corals, what discoveries would the most diverse coral ecosystem hold?" Gruber said. "We quickly set off for Australia's Great Barrier Reef to look for new fluorescing proteins."

Coral Conservation

Fluorescent proteins are now known to be common to coral reefs around the world. The largest number to date have been discovered on Australia's Great Barrier Reef.

What the proteins accomplish in coral reefs, however, remains uncertain and is a major focus of biological studies.

Some researchers believe the fluorescent protein may act as a sunscreen for the corals reefs. Another theory is that the proteins provide algae—the main food of many coral species—with light to grow in deeper, darker waters. Algae requires light to live.

"Coral reefs are extremely complex systems, and there is a tremendous amount of information still to be learned," Gruber said.

Regardless of the fluorescent proteins' exact ecological function, research shows that corals shed their covering of algae when water temperatures rise, a process widely known as coral bleaching. When corals bleach, they also alter their fluorescence levels.

"That leads us to believe that fluorescence is important when algae is there," Pieribone said.

Pieribone and other conservationists express alarm at the rapid disappearance of coral species around the world. By some estimates, thousands of coral species may go extinct by the end of the century, primarily owing to rising global temperatures.

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