Kyodo / Reuters

Kyoto University Professor Shinya Yamanaka (left) and John Gurdon of the Gurdon Institute in Cambridge, England, at a symposium on induced pluripotent stem cells in Tokyo in April 2008

In a testament to the revolutionary potential of the field of regenerative medicine, in which scientists are able to create and replace any cells that are at fault in disease, the Nobel Prize committee on Monday awarded the 2012 Nobel in Physiology or Medicine to two researchers whose discoveries have made such cellular alchemy possible.

The prize went to John B. Gurdon of the University of Cambridge in England, who was among the first to clone an animal, a frog, in 1962, and to Shinya Yamanaka of Kyoto University in Japan who in 2006 discovered the four genes necessary to reprogram an adult cell back to an embryonic state.

Sir John Gurdon, who is now a professor at an institute that bears his name, earned the ridicule of many colleagues back in the 1960s when he set out on a series of experiments to show that the development of cells could be reversed. At the time, biologists knew that all cells in an embryo had the potential to become any cell in the body, but they believed that once a developmental path was set for each cell toward becoming part of the brain, or a nerve or muscle it could not be returned to its embryonic state. The thinking was that as a cell developed, it would either shed or silence the genes it no longer used, so that it would be impossible for a cell from an adult animal, for example, to return to its embryonic state and make other cells.

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Working with frogs, Gurdon proved his critics wrong, showing that some reprogramming could occur. Gurdon took the DNA from a mature frogs gut cell and inserted it into an egg cell. The resulting egg, when fertilized, developed into a normal tadpole, a strong indication that the genes of the gut cell were amenable to reprogramming; they had the ability to function as more than just an intestinal cell, and could give rise to any of the cells needed to create an entirely new frog.

Just as Gurdon was facing his critics in England, a young boy was born in Osaka, Japan, who would eventually take Gurdons finding to unthinkable extremes. Initially, Shinya Yamanaka would follow his fathers wishes and become an orthopedic surgeon, but he found himself ill-suited to the surgeons life. Intrigued more by the behind-the-scenes biological processes that make the body work, he found himself drawn to basic research, and began his career by trying to find a way to lower cholesterol production. That work also wasnt successful, but it drew him to the challenge of understanding what makes cells divide, proliferate and develop in specific ways.

In 2006, while at Kyoto University, Yamanaka stunned scientists by announcing he had successfully achieved what Gurdon had with the frog cells, but without using eggs at all. Yamanaka mixed four genes in with skin cells from adult mice and turned those cells back to an embryo-like state, essentially erasing their development and turning back their clock. The four genes reactivated other genes that are prolific in the early embryo, and turned off those that directed the cells to behave like skin.

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Stem Cell Scientists Awarded Nobel Prize in Physiology and Medicine