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Monday, December 10, 2012
Genome sequencing pioneer: How biology entered the information age
STOCKHOLM, SWEDEN—Eric Lander
was one of the leaders behind the effort to sequence the human genome.
He has also continued to work on various follow-up projects through his
involvement with the Broad Institute, a leading sequencing center. So,
Lander makes an excellent choice to provide some perspective about how
the growing availability of genomes has driven the biological sciences
over the last decade. He did just that at a Nobel Week Dialogue talk.
But Lander didn't stop at ten years. Instead, he backed up all the
way to the start of the 20th century and ran through the history of
biology since. His reasoning was that it can take decades for the impact
of scientific discoveries to be clear. And, according to Lander, the
story parallels that of the 20th century as a whole, the rise of the
information age. Information was a theme that pervaded the rest of his
talk, and Lander blamed life itself. "Life was fundamentally about
information."
Biology reaches the information age
At the end of the 1800s, vitalism—the idea that life had features
that were distinct from the rest of the physical world—was still
popular. It was the parallel progress in genetics and biochemistry that
helped bring vitalism to a close. It took until the 1940s for the two
fields to overlap, as researchers started to study the genetics of
biochemical pathways and the biochemistry of heritable material. This is
when the central role of DNA became clear. And that's what inspired
Watson and Crick (plus a number of others) to think that understanding
the structure of DNA would be critical.
The double helix moved biology into the information age, as Lander
put it, since it answered some key questions: how can you store
information, faithfully replicate it, but still allow room for the new
variants that drive evolution? The identification of the genetic code
was the next (and obvious) step in understanding how information was
stored in a string of nucleotides. The problem, Lander said, was that
you couldn't actually read any of this—at least not as it exists in a
cell.
From a biochemical perspective, all DNA was more or less the same, so
you couldn't deal with that information by the standard methodology of
the time. It took the development of molecular biology and recombinant
DNA to start dealing with the actual information content.
"How do you ask how to read DNA?" Lander asked. "You ask the
master—the cell. The cell is in the business of reading the information
in DNA." Molecular biology and biotechnology developed around the
purification and use of the proteins used by the cells themselves to
manipulate DNA.
The next hurdle, according to Lander, was that we had no idea how to
apply the principles of molecular biology to something as big as the
human genome in a systematic way. That problem first started to crack
with the development of RFLP mapping, when human genes were first
associated with a nearby DNA feature that could only be revealed using
the techniques of molecular biology. In principle, these worked. But
Lander said without the genome sequence, each research group had to
essentially start from scratch.
Conceptually, he said the key step was the development of a
hierarchical map. Lay out genetic markers on a map, identify the DNA
associated with those markers, and then dig down into the actual DNA
sequences. The first human genetic map appeared in 1987. That set the
stage for the genome sequencing to kick off in earnest in the 1990s. The
final draft was announced in 2003, on the 50th anniversary of the
Watson and Crick paper.
Maps on tops of maps
Once we had the sequence, we could start making notes about the
specific features of different genome regions, a concept Lander referred
to as mapping. By comparing genomes, you could map the parts of the
genome conserved through evolution; the sites of common human
variations; the sites where proteins bind to DNA to regulate genes; and
so on. These maps have been essential to understanding the meaning of
the sequences that were identified in the genome sequencing project.
All that information helped us start to make some progress in
medicine. Over the last 25 years, we've gone from knowing the causative
mutations behind 20 human diseases to knowing about 3,500. We only knew
something about 1 polygenic disorder, while now we know more about over
2,000.
Having reached the present, Lander joked it was a mistake to ever
talk about the future. But that didn't stop him from trying. He kept his
discussion to problems that are already obvious. One was the challenge
of integrating all the information that's now flowing in such a way that
respects privacy while providing access to researchers. We still don't
know how to consistently translate knowledge about biological systems to
effective medicine. And we're only just starting to learn how to
effectively "write" using the genetic code, to create novel proteins or
combinations of them.
And with that, Lander wrapped up, leaving it for the rest of the speakers to fill in the details of the future.
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