British scientist John B Gurdon and his Japanese counterpart Shinya Yamanaka honoured
The Nobel Prize in Medicine for 2012 has been jointly conferred upon British scientist John B Gurdon and Japanese scientist Shinya Yamanaka for their breakthrough work on stem cells.
Stem cells are cells that are endowed with the ability of self-renewal and pluripotency (the ability to differentiate to any cell type), properties that have brought them to the forefront of clinical research.
The two scientists, over a span of more than 40 years between their individual experiments, overturned the long-held belief among biologists that mature or specialised cells (cells that make up various parts of an organism) are incapable of further differentiation into tissue—cells of an embryo are pluripotent but as they grow into specialised tissue, such as liver, nervous, cardiovascular, they lose pluripotency.
In 1962, Gurdon replaced the nucleus of an immature egg cell of a frog with the nucleus from a mature cell in its intestine. The altered egg cell gave rise to a normal frog. Through this and follow-up studies, Gurdon was able to prove that DNA of the mature cell still has all the information needed to develop into all types of cells.
Gurdon’s experiment involved replacing an immature nucleus with a mature one in an egg cell of a frog. He was able to develop a normal tadpole from this cell.
While this proved that the nucleus (which contains DNA) of a mature cell has the genetic capability of specialising further, it did not say anything about how intact, complete mature cells could be reprogrammed into immature cells. More than forty years later, Shinya Yamanaka, in 2006, went a step further.
Yamanaka looked for genes that could keep immature cells. He tested several of these genes to see if any of them could reprogramme mature cells to become pluripotent stem cells. When these genes were introduced in different combinations, into mature cells he found that just four genes could reprogramme the mature cell into immature stem cells.
Gurdon is a distinguished group leader in the Wellcome Trust/CRUK Gurdon Institute in Cambridge, UK. Yamanaka is director of the Center for iPS Cell Research and Application (CiRA) in Kyoto University, Japan.
The Nobel Assembly at Karolinska Institutet, the Swedish body that awards the Nobel Prize in Physiology or Medicine, noted in its press release that the findings “have revolutionised our understanding of how cells and organisms develop.”