2012's Nobel physiology prize goes to Sir John Gurdon and Shinya Yamanaka for a crucial discovery in stem-cell science?—how to make what are known as pluripotent stem cells from ordinary body cells.


  What the citation does not say is that this work also allows clones to be made from adult animals, potentially including people.

  诺贝尔颁奖典礼上的褒奖词没有指出的是,这项成果使得成年动物 的克隆成为可能,也有可能可以克隆人类。

  A stem cell is one that can differentiate into daughter cells specialised for particular functions, and all the cells in a body are thus derived from stem cells.

  干细胞是一种可以分化成姐妹细胞的物质,而姐妹细胞则担当某种特定的功能 ,体内的所有细胞都是来源于干细胞的。

  That includes the stem cells themselves, which derive from ur stem cells found in embryos.


  These embryonic stem cells are the pluripotent cells, meaning they can turn into many other sorts of cell.


  Pluripotent embryonic stem cells are of GREat value to researchers but, if the embryos they came from were human, their use is controversial.


  Also, if such cells are ever to play a useful role in medicine, then they will need to be available in bulk—and ideally in a form whose DNA matches that of the recipient.

  而且,这些细胞在医药方面扮演着如何重要角色, 那么 我们就大量需要这些干细胞了—在理想的情况下,这些干细胞的DNA和接受者的DNA相匹配。

  Sir John and Dr Yamanaka have both conducted work that should help make this possible.


  Sir John's prizewinning study, published half a century ago, in 1962, when he was at Oxford University, was to transplant the nuclei of cells from adults of a frog called Xenopus laevis into enucleated eggs of that species.


  The eggs in question then developed into healthy adults.


  This showed that DNA is not altered during embryonic development, at least in Xenopus.


  It thus suggested it might be possible to get an entire adult cell to perform a similar trick, without involving an egg at all.


  That was what Dr Yamanaka did.


  He and his colleagues at Kyoto University managed to activate four crucial genes in adult mouse cells.


  These genes each encode a protein of a type known as a transcription factor, which controls the expression of DNA.


  Together, they trick the cell in question into thinking it is part of an embryo.


  In the first experiment, conducted in 2005, Dr Yamanaka did not get complete mice, but he did turn the adult cells into pluripotent stem cells. Subsequent work by his group and others then produced embryos which, if transplanted into the womb of a female mouse, will go all the way to adulthood.


  Finally, in 2007, Dr Yamanaka managed to switch on the same four genes in adult human cells, and thus generated pluripotent human stem cells.


  In principle, that opens the door to human cloning, though no one has tried this in practice—and in most countries such an experiment would be illegal.


  It also opens the door, though, to bespoke tissue repair as it would allow cells of whatever type were desired to be grown from, say, a few skin cells and then transplanted back into the donor without risking an adverse reaction from his immune system.


  How well that would work in practice remains to be seen.


  But if it works well then Sir John and Dr Yamanaka may turn out to have been the pioneers of a whole, new field: regenerative medicine.