Ian Wilmut with Dolly the Sheep Credit: Roslin Institute

Nature Reports Stem Cells: Of the early cloned sheep, Megan and Morag were made by nuclear transfer from embryonic stem cells, Dolly from an adult cell, and Polly from a genetically modified adult cell. How hard was it to go from nuclear transfer using stem cells to adult cells to genetically modified adult cells?

Wilmut: The later the stage of development from which you obtain the donor cells the more difficult it is to obtain offspring. For a different reason the culture that is involved in making genetic change also reduces efficiency. We really need cells equivalent to mouse ES cells from livestock, because they tolerate this abuse much better than other cells.

Nature Reports Stem Cells: What was your luckiest day in the lab?

Ian Wilmut: The birth of the cloned lambs including Dolly depended upon the use of donor cells in quiescence. It was chance that we decided to use that cell cycle stage.

Nature Reports Stem Cells: I understand the media response was more than anticipated. Why is Dolly the most famous?

Wilmut: I think that people were both excited and frightened by the new technique. I am sure that the anxiety was increased by the fact that the story was broken prematurely, just before we made a careful announcement. It made it look as though we felt that we had a nasty secret, whereas in fact we were excited and proud of what had been achieved.

Nature Reports Stem Cells: Whose idea was it to name Dolly after Dolly Parton (the buxom country singer)?

Wilmut: Dolly was christened by John Bracken, one of the men who paced anxiously about day and night as we waited for the birth of the lamb. Dolly Parton's manager was reported to have said “There is no such thing as baaaaad publicity”.

Nature Reports Stem Cells: What, scientifically, are the three most important questions about stem cells?

Wilmut: How can we obtain and maintain stem cells from embryos and different tissues? How can we induce them to become the specific tissue that we need? What methods will allow us to move cells from one lineage to another?

Nature Reports Stem Cells: How would you have answered that question 15 years ago?

Wilmut: At that time we wondered if embryo stem cells would ever be derived from livestock or human embryos or were they unique to the mouse. Remember that even in that species ES cells were only available from one inbred strain, and it was suggested that perhaps they could only be obtained from that unique genotype.

Nature Reports Stem Cells: What is the most common misconception about stem cells you encounter with the general public? With scientists?

Wilmut: Sadly, it is that cell therapies are available now, or will be very soon, whereas we know that in the case of most diseases treatment is years away.

Nature Reports Stem Cells: You've been involved in many areas of science: lab, industry, academic administration. What did they teach you?

Wilmut: We should be ambitious in what we try to achieve.