This year’s laureates are both stem cell scientists.
Two stem cell researchers have shared the Nobel Prize in Medicine for 2012, an elderly Briton, Sir John B. Gurdon, and a younger Japanese, Shinya Yamanaka. By a serendipitous coincidence, Sir John made his discovery in 1962 — the year of Yamanaka’s birth.
In his classic experiment at the University of Cambridge, Sir John discovered that cell development is reversible. The conventional wisdom was that cells could never change once they had specialized as nerve, skin, or muscle cells. He proved that this was wrong by replacing the nucleus of a frog egg cell with a nucleus from a mature intestinal cell. This modified cell developed into a normal tadpole.
This astonishing development eventually led to the cloning of the first mammal, Dolly the sheep, in 1996. But while the technique worked, no one really understood cell development. The obvious target for research was the embryo. From this ball of undifferentiated cells come each of the body’s specialized cells — more than 200 of them in humans. Surely the answer must lie there. In 1998 an American scientist, James Thomson, of the University of Wisconsin-Madison, isolated and cultivated human embryonic stem cells.
But a one-eyed focus on embryos left stem cell science hostage to ethics. Despite scientists’ bravado, everyone had some qualms about destroying embryos for their stem cells. Even Thomson admitted to the New York Times that “if human embryonic stem cell research does not make you at least a little bit uncomfortable, you have not thought about it enough”.
Still, it seemed the only way forward. But in 2006 there came astonishing news from the University of Kyoto. An orthopaedic surgeon turned stem cell scientist, Shinya Yamanaka, had discovered that skin cells from mature mice could be reprogrammed to become immature stem cells.
Yamanaka found that by introducing only a few genes, specialized skin cells could become pluripotent stem cells, i.e. immature cells that can develop into all types of cells in the body. Until then, creating pluripotent cells without resorting to cloning seemed unlikely. Like Gurdon, Yamanaka had skittled the conventional wisdom.
This was electrifying news for biologists. It was as if commuters on the pot-holed, terrorist-infested road from Baghdad airport to the Green Zone could suddenly detour down a six-lane autobahn at 200km. Many famous scientists dropped human embryonic stem cells and began work on what Yamanaka had termed “induced pluripotent stem cells”. A year later, in November 2007, both he and James Thomson, in separate papers, confirmed that human cells could also be reprogrammed.
The rest is history.
What turned Yamanaka away from the group-think which goaded his colleagues into the swamp of human embryonic stem cell research? Perhaps his ethics. Even Julian Savulescu, the director of the Oxford Uehiro Centre for Practical Ethics, who has no objections to embryo research, recognises this. “Yamanaka has taken people’s ethical concerns seriously about embryo research and modified the trajectory of research into a path that is acceptable for all. He deserves not only a Nobel Prize for Medicine, but a Nobel Prize for Ethics.”
In an interview with the New York Times in 2007, Yamanaka remembered one day years before when he paid a social visit to a friend’s IVF clinic. There, he peered through a microscope. “When I saw the embryo, I suddenly realised there was such a small difference between it and my daughters,” said the father of two. “I thought, we can’t keep destroying embryos for our research. There must be another way.”
Nobel Prize for Medicine
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