October 24, 2012
Ancient Protein Preservation Confirmed In Dinosaur Bone Cells
April Flowers for redOrbit.com - Your Universe Online
A new study from North Carolina State University (NCSU) and the Palo Alto Research Center (PARC) reveals new evidence for the preservation of ancient dinosaur proteins. This new evidence includes reactivity to antibodies that target specific proteins that are normally found in bone cells of vertebrates. Further, the study findings rule out sample contamination, and solidify the case for the preservation of cells and possibly DNA in ancient remains.The first discovery, in 2005, of what appeared to be preserved soft tissue in a 67-million-year-old T. Rex was made by Dr. Mary Schweitzer, professor of marine, earth and atmospheric sciences with a joint appointment at the North Carolina Museum of Natural Sciences. Similar preservation in an even older, 80-million-year-old Brachylophosaurus canadensis was revealed by subsequent research. Schweitzer and her team used chemical and molecular analyses in 2007 and 2009 to confirm that the fibrous material collected from the specimens was collagen.
The team's next step was to find out if the star-shaped cellular structures within the fibrous matrix were bone cells, also called osteocytes. They used a variety of techniques, including microscopy, histochemistry and mass spectrometry, to demonstrate that these cellular structures react to specific antibodies. One such antibody — a protein known as PHEX — is found in the osteocytes of living birds.
The findings of this study were presented last week at the annual meeting of the Society of Vertebrate Paleontology, and appear online in the journal Bone. Funding for the project was obtained by grants from the National Science Foundation and the David and Lucile Packard Foundation.
“The PHEX finding is important because it helps to rule out sample contamination,” Schweitzer says in a news release. “Some of the antibodies that we used will react to proteins found in other vertebrate cells, but none of the antibodies react to microbes, which supports our theory that these structures are surviving osteocytes. Additionally, the antibody to PHEX will only recognize and bind to one specific site only found in mature bone cells from birds. These antibodies don´t react to other proteins or cells. Because so many other lines of evidence support the dinosaur/bird relationship, finding these proteins helps make the case that these structures are dinosaurian in origin.”
Using another antibody that only binds to the 'backbone" of DNA, Schweitzer tested for the presence of DNA in the cellular structures. This antibody reacted to tiny amounts of material in both T. rex and B. canadensis. The team used another antibody that binds histone proteins to rule out the presence of microbes. This antibody binds tightly to the DNA of everything except microbes, and they received a positive result. Two other histochemical stains, which fluoresce when they attach to DNA were tested with positive results. These results strongly suggest that the DNA is original. Without sequence data, however, it is impossible to confirm that the DNA is in fact dinosaurian.
“The data thus far seem to support the theory that these structures can be preserved over time,” Schweitzer says. “Hopefully these findings will give us greater insight into the processes of evolutionary change.”