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Thursday, April 12, 2007

Harvard team identifies protein from a dinosaur

By Colin Nickerson, Globe Staff

Scientists at Harvard Medical School have for the first time isolated and identified protein from a dinosaur -- a Tyrannosaurus rex that perished in Montana 68 million years ago and was partly preserved under tons of sandstone. Some of the protein identified in the Cretaceous era predator match that of modern-day chickens, the research revealed.

The findings, being published tomorrow in the journal Science, upset the long-held assumption that protein and other basic materials of life could not possibly survive in detectable amounts for more than a few hundred thousand years. They also raise the possibility that scientists might eventually recover DNA from prehistoric beasts, allowing for even more sophisticated analyses of ancient organisms and the processes of evolution.

"People are going to be looking differently at prehistoric bones because now we see they may carry tissue and information that nobody believed could still exist," said Mary H. Schweitzer, a paleontologist at North Carolina State University and a coauthor of both articles.

In all, scientists at Harvard were able to isolate seven tiny strips of collagen protein from soft tissue found in the thigh bone of a Tyrannosaurus rex recovered earlier in the decade from beneath 60 feet of sandstone ledge in Montana's Hell Creek formation.

"At the very least, this breakthrough shows we can look at [protein] sequences that are many, many millions of years old," said John M. Asara, director of the mass spectrometry core facility at Beth Israel Deaconess Medical Center and one of the authors. "That's a first."

Paleontologists not involved in the the T.rex protein research said it represented an astonishing piece of scientific sleuthwork.

"This research might be creating a whole new field of molecular paleontology," said Lawrence M. Witmer, a paleontologist at Ohio University. "This research has opened a door we didn't even suspect was there."

But some scientists doubted whether the experiment will have much practical effect on the study of prehistoric life. Many seemed to believe that the surviving soft tissue found in the Montana T. rex was a fluke -- and that there will never be enough material for the sort of fullbore scientific scrutiny that would allow large conclusions to be drawn about the animals.

"If there were regular opportunities for this kind of matching and comparison, [these] techniques might add important evidence to genuine conundrums -- outstanding questions about the origin and relationships of various vertebrate groups," said Farish A. Jenkins Jr., a Harvard professor of zoology and internationally-recognized expert in vertebrate paleontology. "But the reality remains that finding soft tissues preserved with actual soft tissue structure intact is outside the realm of common expectation, so the applicability of their techniques is very limited."

Similar skepticism was expressed by Mark A. Norell, a paleontologist with the American Museum of Natural History: "This is a very cool experiment. But I don't think curators are going to start grinding up their fossil bones to obtain the really minuscule bits of protein that might be available. There probably just isn't going to be enough of this material" to conduct major research.

"Science requires replication," he said. "You need thousands of comparisons. Not dozens."

Still, buzz surrounded the the mind-boggling findings that protein dating back tens of millions of years can be identified at all. Until now, the oldest positively-identified proteins were recovered from the bones of a wooly mammoth reckoned to be a couple hundred thousand years old, according to Schweitzer. DNA has been taken from the 38,000 year-old bones of a Neanderthal, believed to be a prehistoric relative of modern humans.

Several of the T. rex protein snippets captured at Harvard matched sequences in modern chickens, which the authors of the Science articles say lends more credence to the increasingly accepted view among paleontologists that birds are descended from dinosaurs. "We've added molecular evidence to evidence based on the architecture of bones," said Asara.

The research marked an unusual collaboration between field paleontologists -- famous for rough expeditions to remote places in search of rare fossils -- and medical researchers more familiar with finicky lab equipment and computer readouts than sharp pickaxes, smelly sleeping bags, and battered sifting trays.

Lewis Cantley, professor of systems biology at Harvard Medical School and one of the authors, said the techniques used in sequencing the dinosaur protein from minuscule amounts of material could be useful for researchers who need to find the tiny molecular changes that lead to cancer. "We're creating a cross-discipline of biomedical researchers and paleontologists."

The T. rex femur at the center of the research was found in 2003 by John Horner, a paleontologist with Montana's Museum of the Rockies and reknowned fossil hunter. Schweitzer, analyzing the bone, found evidence that the big bone still contained actual bone and vascular tissue. In most preserved dinosaur remains, minerals have replaced all organic matter, the process known as fossilization.

Scientists were quick to discount any suggestion that the sequencing of protein from a T. rex might represent a toddling first step toward cloning dinousaurs, as in Michael Crichton's novel Jurassic Park and the movies that followed. Cloning would require DNA, which deteriorates more rapidly than protein. Collagen, the sort isolated from the t. rex, is a notably durable protein.

"The idea of cloning prehistoric animals from genetic materials remains science fiction," said Ohio University's Witmer. "But keep in mind, until very, very recently, just the idea of obtaining any genetic material at all from animals so old was dismissed as pure science fiction."

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