Glowing Coral Proteins Aid Medical Research

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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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