Researchers have now been able to sequence the entire Denisova genome using 10 MG of a finger bone fragment that was found in the Denisova-Cave in Southern SibEria. Image: MPI for Evolutionary Anthropology |
In
2010, Svante Pääbo and his colleagues presented a draft version of the
genome from a small fragment of a human finger bone discovered in
Denisova Cave in southern Siberia. The DNA sequences showed that this
individual came from a previously unknown group of extinct humans that
have become known as Denisovans. Together with their sister group the
Neandertals, Denisovans are the closest extinct relatives of currently
living humans.
The
Leipzig team has now developed sensitive novel techniques which have
allowed them to sequence every position in the Denisovan genome about 30
times over, using DNA extracted from less than 10 mg of the finger
bone. In the previous draft version published in 2010, each position in
the genome was determined, on average, only twice. This level of
resolution was sufficient to establish the relationship of Denisovans to
Neandertals and present-day humans, but often made it impossible for
researchers to study the evolution of specific parts of the genome. The
now-completed version of the genome allows even the small differences
between the copies of genes that this individual inherited from its
mother and father to be distinguished. This Wednesday the Leipzig group
makes the entire Denisovan genome sequence available for the scientific
community over the Internet.
“The
genome is of very high quality,” says Matthias Meyer, who developed the
techniques that made this technical feat possible. “We cover all
non-repetitive DNA sequences in the Denisovan genome so many times that
it has fewer errors than most genomes from present-day humans that have
been determined to date”.
The
genome represents the first high-coverage, complete genome sequence of
an archaic human group—a leap in the study of extinct forms of humans.
“We
hope that biologists will be able to use this genome to discover
genetic changes that were important for the development of modern human
culture and technology, and enabled modern humans to leave Africa and
rapidly spread around the world, starting around 100,000 years ago” says
Pääbo. The genome is also expected to reveal new aspects of the history
of Denisovans and Neandertals.
The
group plans to present a paper describing the genome later this year.
“But we want to make it freely available to everybody already now” says
Pääbo. “We believe that many scientists will find it useful in their
research”.
The
project is made possible by financing from the Max Planck Society and
is part of efforts since almost 30 years by Dr. Pääbo’s group to study
ancient DNA. The finger bone was discovered by Professor Anatoly
Derevianko and Professor Michail Shunkov from the Russian Academy of
Sciences in 2008 during their excavations at Denisova Cave, a unique
archaeological site which contains cultural layers indicating that human
occupation at the site started up to 280,000 years ago. The finger bone
was found in a layer which has been dated to between 50,000 and 30,000
years ago.
