Dinosaur Collagen Points to Chicken Connection
Analysis of amino acids in T. rex femur shows molecular link to birds
THURSDAY, April 12, 2007 (HealthDay News) -- Scientists report they have managed not only to detect collagen protein in a 68-million-year-old dinosaur fossil, but they've also found more evidence that birds might have descended from dinosaurs.
This is the first time that relationships between species have been established from molecular information.
Previously, scientists had believed that protein in fossils completely degraded within 1 million years and, prior to this report, the oldest sequenced DNA was probably Neanderthal, some 30,000 to 50,000 years old.
Science completely changed with the discovery and subsequent analysis of a 68-million-year-old femur from a Tyrannosaurus rex. That bone was shown to contain collagen, the most abundant protein in mammals, investigators report in the April 13 issue of Science. The researchers outlined their findings at a teleconference Wednesday.
John Asara, director of the mass spectrometry core facility at Beth Israel Deaconess Medical School and an instructor in pathology at Harvard Medical School, was lead author of a second paper in Science. He got hold of a sample of the collagen, purified the protein and broke it down into peptides of 10 to 20 amino acids each. These were then fed into an ultra-sensitive ion mass spectrometer.
Seven protein fragments were compared with existing amino acid sequences and found to most closely match amino acid sequences found in the collagen of modern-day chickens.
Other sequences matched newts and frogs.
"Of the seven total sequences, three matched chickens uniquely, another matched frogs and another matched the newt uniquely," Asara said. "This supports previous reports that birds evolved from dinosaurs or are closely related, at least."
Although nothing definitive can be stated, this does suggest that chickens are the most likely species to be related to dinosaurs, unless other as-yet-unsequenced species are closer.
The hypothesis that birds and dinosaurs might be related had been based largely on information about bone architecture.
Researchers from North Carolina State also found that the T. rex bone reacted with antibodies to chicken collagen, again helping to establish a relationship between birds and dinosaurs.
Asara and his colleagues also used mass spectrometry to analyze 70 protein fragments from the bones of an extinct mastodon, 160,000 to 600,000 years old. They found four sequences unique to the prehistoric beast.
"With these sequences, we can start to think about evolutionary biology and start to create relationships between extinct and living organisms based on protein sequences," Asara said.
The new findings and techniques may also have implications for human disease. For instance, the technology may one day be used to sequence proteins that are in low abundance, such as those connected with cancers, said Lewis Cantley, a professor of systems biology at Harvard Medical School and chief of signal transduction at Beth Israel Deaconess Medical Center. He is also a co-author on the Asara paper.
"The exciting thing is that this technology is really in its infancy," Cantley added. "We're going to see it get a lot better."
"We don't know what the possibilities are," said Mary Higby Schweitzer, of North Carolina State University in Raleigh and lead author of the other paper. "We're starting right now with a particular goal in mind, but how this might apply to human health and how this might apply to disease, all of that is yet to be seen. You don't know what the outcome might be. It could be more than you could ever imagine."
Visit University of California Museum of Paleontology for more on T. rex and his cousins.