The Nobel Assembly at Karolinska Institutet on Oct. 8 decided to
award the Nobel Prize in Physiology or Medicine 2012 jointly to
John B. Gurdon and Shinya Yamanaka. The two scientists
discovered that mature, specialized cells can be reprogrammed to
become immature cells capable of developing into all tissues of
the body. Their findings have revolutionized our understanding
of how cells and organisms develop. Gurdon discovered in 1962
that the specialization of cells is reversible. In a classic
experiment, he replaced the immature cell nucleus in an egg cell
of a frog with the nucleus from a mature intestinal cell. This
modified egg cell developed into a normal tadpole. The DNA of
the mature cell still had all the information needed to develop
all cells in the frog. Yamanaka discovered more than 40 years
later, in 2006, how intact mature cells in mice could be
reprogrammed to become immature stem cells. Surprisingly, by
introducing only a few genes, he could reprogram mature cells to
become pluripotent stem ce