19 December 2011
Scientists turn to protein clues to recreate mammoth DNA
Fossilised bones can be so degenerated that their DNA is unusable by scientists. But for the first time ever scientists at the Centre for Geogenetics at the Natural History Museum of Denmark and the Novo Nordisk Foundation Center for Protein Research at the University of Copenhagen have been able to work backwards by using 126 proteins from a 43,000-year-old bone to recreate the genes of a mammoth. The scientists used a unique proteome method that could have applications in both forensics and paleo-zoology.
DNA uses 20 amino acids to create the stable protein building blocks required for all biological processes. Each amino acid contributes specific biochemical characteristics and makes it possible for proteins to combine to form everything from antigens to adrenalin.
“Fossilised DNA allows us to understand the biology of extinct animals,” says Professor Jesper Velgaard Olsen, of the Novo Nordisk Foundation Center for Protein Research.
“By comparing it with the DNA of modern species – in the case of mammoth DNA, by comparing it with elephant DNA – we can see the mutations have occurred. The problem is that over time, DNA becomes so broken down that we can’t analyse it. Proteins, however, take much longer to break down, and our new method is an important step on the road to being able to recreate DNA using the proteins in fossils.”
Biologically, proteins are a more stable than DNA, and they are more likely to withstand the tests of time. Until now, though, isolating and analysing proteins from fossils has been a demanding and time consuming process that yielded only uncertain results.
“We’ve been able to isolate and analyse more than 10 times as many proteins from fossils than before,” Professor Velgaard Olsen said.
In their improved method based on mass spectrometry the researchers have isolated 126 proteins from a 43,000 year old Siberian mammoth compact bone. Postdoc Enrico Cappellini from Centre for GeoGenetics at the Natural History Museum of Denmark says:
"It is an important step forward in this methodology. Earlier approaches were useful, but limited. The new method has great perspectives and can be applied to a wide range of problems."
"One of the most interesting things in our study is that we found the protein serum albumin. Usually it is found only in blood, but it is also known to accumulate in bone. We found it in the mammoth's femur. If the albumin is intact it can be detected by other methods. But, until now, it has never been sequenced in ancient or degraded samples. One of the possible consequences of this is that in the future we may be able to detect ancient albumin and use it as a marker for extinct species identification, if e.g. the DNA is absent, or too degraded to be sequenced."
Forensic and paleo-zoologic applications
The process of using protein clues to determine the DNA profile of extinct animals also be applied to fossils that are far older than a mammoth’s.
“Nothing stops us from studying bones that are over 100,000 years old. We could even apply the method to million-year-old bones from the Jurassic Period,” Professor Velgaard Olsen says.
Another benefit of the new method is that it’s now possible to study fossils that haven’t been preserved by tundra.
“We’ve been able to analyse proteins from mammoth bones found in temperate climates,” Professor Velgaard Olsen says. “And our technology works fast enough that it could someday even be used by forensic geneticists when they need to determine the identity of bones.”
Postdoc Enrico Cappellini
Centre for GeoGenetik
Natural History Museum of Denmark
Phone: +45 35 32 13 38
Professor Jesper Velgaard Olsen
Novo Nordisk Foundation Center for Protein Research
Mobile: +45 24 42 59 56