This story has been corrected to attribute a quote to Raghu Kalluri. ProteoMonitor regrets the error.
In a follow-up to a story that aimed to genetically link Tyrannosaurus rex to chickens, a team of researchers has uncovered and sequenced a set of proteins belonging to the 80-million-year-old remains of a duck-billed hadrosaur.
The authors hope the findings, to be published in the May 1 issue of Science, prove that their T. rex discovery "was not a unique occurrence," co-author John Asara, director of the Beth Israel Deaconess Medical Center Mass Spectrometry Core and an instructor at Harvard Medical School, said in a statement. "This is the second dinosaur species we've examined and helps verify that our first discovery was not just a one-hit wonder."
The research follows up on work done in 2007 that sequenced the proteins found in the soft-tissue of a 68-million-year old T. rex [see PM 04/12/07].
The T. rex findings, however, were met with controversy, including questions about whether contamination had skewed the results. But in the hadrosaur study, Asara and his colleagues were able to identify almost twice as many amino acids as recovered in the T. rex studies.
The new work is based on the femur bone fossil of an 80-million-year old hadrosaur, or Brachylophosaurus Canadensis, discovered by North Carolina State paleontologist Mary Schweitzer, who had also uncovered the T. rex fossil used for the 2007 research, and Jack Horner, a paleontologist at Montana State University's Museum of the Rockies.
Initial observation suggested that the fossil was even better preserved than the T. rex fossil, though it was 12 million years older. After demineralization, bone fragments showed "marked preservation of original tissues and molecules, with microstructures resembling soft, transparent vessels, cells, and fibrous matrix," the researchers said in a statement.
Subsequent immunoblotting and immunochemistry confirmed the presence of collagen, laminin and elastin proteins from the bone. Bone cells and blood vessels were also extracted from the bone.
"Our findings demonstrated that it did contain basement membrane matrix," said Raghu Kalluri, chief of the Division of Matrix Biology at Beth Israel Deaconess and a co-author on the Science study. Basement membranes, which degrade and regenerate during development and wound repair, comprise a continuous extracellular matrix that links endothelial, epithelial, muscle, or neuronal cells and their adjacent stroma.
In situ mass spectrometery independently verified amino acids in dinosaur tissues, including the collagen signature amino acid, hydroxylated proline.
Asara then combined two mass-spec technologies, linear ion trap and hybrid linear ion trap/Orbitrap, to sequence the proteins. The final results: eight collagen peptides and 149 amino acids from four different samples. Multiple validation steps verified the findings, they said.
In a phylogenetic analysis, the hadrosaur was placed on the same family-tree branch with T. rex, in the same group as chicken and ostrich, and more distantly, to alligator and lizard, though not enough sequence data is available to definitively link the two dinosaurs with modern poultry, said Chris Organ, a co-author of the study, and a postdoctoral fellow in organismic and evolutionary biology at Harvard.
A follow-up to this story is available here.