Mary Schweitzer, a professor of marine, earth and atmospheric sciences, was working with the North Carolina Museum of Natural Sciences attempting to determine the sex of their dinosaur bone specimen when they accidentally discovered preserved dinosaur bone cells.
“In order to study how the bone is laid out ... you have to remove the bone mineral. And so we put it in a mild acid,” Schweitzer said.
However, when the researchers added the acid, disaster struck.
“We weren’t intending to dissolve the whole thing, but the reaction was faster than we planned,” Schweitzer said.
Luckily, this story ended with a surprise discovery instead of with the destruction of a 67 million-year-old Tyrannosaurus Rex bone. After the acid reacted with the bone, the researchers were left with soft tissue-- something that is unheard of when working with fossils.
“[The samples] were stretchy, and they were flexible. We were really, really, really surprised,” Schweitzer said.
The researchers repeated the experiment, starting with modern bones they purchased from the grocery store and working their way backward through the fossil record.
“When we were finally convinced that this was real, not only did we know we had a female dinosaur -- we had soft tissue,” Schweitzer said.
Inside the tissue Schweitzer discovered were preserved ancient osteocytes — cells that produce the protein of the bone.
These osteocytes were definitely dead, but their shapes and the shapes of the proteins inside them were still preserved well enough that the researchers could react them with antibodies from other organisms. They used antibodies from ostriches, as ostriches are hypothesized to be some of the closest living relatives to dinosaurs.
If the antibodies attempted to bind to sites on the osteocytes, the researchers could tell which proteins the cells most likely contained and produced.
“We apply the antibodies and if they don’t find anything there that they recognize, they just wash away. But if they do find the piece that they are designed to recognize, they stick, and we can measure that,” Schweitzer said.
They’ve completed the experiment with several different antibodies, choosing ones that would react to modern day osteocytes and then testing them against the ancient ones to find matches.
One of the first proteins they looked for inside the osteocytes was one called actin, which acts like a skeletal structure inside the cell.
“The actin is arranged in the [ostrich] cell in a thread-like pattern, and our antibodies bind in a similar pattern,” Schweitzer said, supporting the hypothesis that dinosaurs and ostriches are closely related.
The researchers also used an antibody called OB7.3, which binds to a protein involved in bone mineralization.
“The specificity [of OB7.3] is incredibly intense -- it only binds to bird osteocytes. It doesn’t bind to any other cell or osteocytes from any other type of organism,” Schweitzer said.
But OB7.3 did bind to the dinosaur osteocytes in the same way that it bonded to a modern ostrich osteocyte.
“What we’ve shown is that based upon the chemistry … those antibodies recognize spots that are consistent with [the dinosaur specimen] being a close relative of birds,” Schweitzer said.
However, the researchers have been receiving criticism; other members of the scientific community do not believe that proteins could have been preserved so long.
“People tell me that they don’t believe my data – they can’t tell me what’s wrong with it, but they don’t think it’s possible for cells to subsist this long,” Schweitzer said.
This means that a large part of the experiments have just been to build credibility for and improve the new methodology, which according to Schweitzer could be applied to numerous other investigations. While the technology is not advanced enough to synthesize the actual proteins or DNA from a single preserved cell yet, that is the goal.
“It is possible to sequence proteins and DNA from a single cell if you’re not talking about one that’s 80 million years old,” Schweitzer said. “If we can get sequences, we can say a lot not only about the relationship between dinosaurs and other animals, but also we can ask questions like ‘How fast did certain proteins evolve?’”
Improved technology would allow scientists to take a much closer look at molecular evolution — studying the process, potential environmental factors that might cause it, and the rate at which it takes place.
“Once we get over the hump of ‘Can we do this?’ there are about a million questions we can ask,” Schweitzer said.
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