Neanderthal genome

We have the modern human genome. Now researchers are set to sequence the DNA of our extinct cousins: Neanderthal man.

The Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, in collaboration with 454 Life Sciences Corporation, in Branford, Connecticut, today announce a plan to have a first draft of the Homo neanderthalensis genome within two years.

Comparing the result to modern human and other primate genomes should help to clarify the evolutionary relationship between humans and Neanderthals. It may also illuminate the genetic changes that enabled humans to leave Africa and rapidly spread around the world around 100,000 years ago.

The chimpanzee (Pan troglodytes) has already been sequenced and stands ready to be compared to Neanderthals (see Chimp genome special). The US National Human Genome Research Institute (NHGRI) has set a goal of sequencing the genome of at least one genome from each of the major positions along the evolutionary primate tree, including the rhesus macaque, orangutan, marmoset, northern white-cheeked gibbon and gorilla.

DNA hunt

The announcement comes as scientists gather in Bonn, Germany, this week to mark the 150th anniversary of the discovery of Neanderthal man — made in Germany's Neander Valley. During 21-26 July, experts will debate all aspects of Neanderthal life, from how they migrated across Europe to what effect climate may have had on their evolution. They will also debate how to find more and better samples to work with (see Palaeoanthropology: Decoding our cousins).

Getting clean genetic material out of such ancient bones is a challenging task. The DNA of the bacteria and fungi that degrade a body after it dies tends to get mixed up with the DNA of the host. And what hominin DNA does survive is usually broken up into small bits over time.

But there are ways to reduce these problems — including using skeletons left from cannibalistic societies, where no flesh was left on the bones for bacteria to eat.

"The dream to find Neanderthal DNA started in the early 1980s," says Paabo. "The problems with contamination were difficult; I almost gave up at times. But now we have new technologies and fossils free of contamination."

The Leipzig team has already sequenced about one million base pairs of nuclear Neanderthal DNA from a 38,000-year-old Croatian fossil. That success was reported by Svante Pääbo, director of the Institute's department of evolutionary genetics, at a meeting at Cold Spring Harbor Laboratory in New York this May. But they have a long way to go; the entire genome is thought to be 3 billion letters long.

Mother's own

In addition to Pääbo's work with the Croatian fossil, there have been successes with mitochondrial DNA — a portion of the genome that tends to be better preserved, but which makes up only a tiny fraction of the entire sequence and is passed down only through the female line.

Almost ten years ago, Pääbo succeeded in sequencing Neanderthal mitochondrial DNA. More recently, such DNA was extracted from a 100,000-year-old Neanderthal fossil found in Belgium.

But a map of the nuclear DNA will prove the real prize, revealing much more about the Neanderthal genetic make-up.

The project will extract the nuclear DNA from bones or teeth from both the first Neanderthal specimen ever discovered, and some additional bones found in Croatia.

Source:
news @ nature.com