Sir John B. Gurdon and Shinya Yamanaka

Two pioneers of stem cell research have shared the Nobel Prize for medicine or physiology

John Gurdon from the UK and Shinya Yamanaka from Japan were awarded the prize for changing adult cells into stem cells, which can become any other type of cell in the body.

Prof Gurdon used a gut sample to clone frogs and Prof Yamanaka altered genes to reprogramme cells.When a sperm fertilises an egg there is just one type of cell. It multiplies and some of the resulting cells become specialised to create all the tissues of the body including nerve and bone and skin.

It had been though to be a one-way process - once a cell had become specialised it could not change its fate.

In 1962, John Gurdon showed that the genetic information inside a cell taken from the intestines of a frog contained all the information needed to create a whole new frog. He took the genetic information and placed it inside a frog egg. The resulting clone developed into a normal tadpole.

Forty years later Shinya Yamanaka used a different approach. Rather than transferring the genetic information into an egg, he reset it.

He added four genes to skin cells which transformed them into stem cells, which in turn could become specialised cells.

The discoveries of Gurdon and Yamanaka have shown that specialized cells can turn back the developmental clock under certain circumstances.

These discoveries have also provided new tools for scientists around the world and led to remarkable progress in many areas of medicine.