Why do we use xenopus frogs?

The xenopus – known more commonly as the clawed frog – is one of the most studied of all amphibians. The frog can be bred and maintained easily in the laboratory, where they can live for as long as 30 years. In its lifetime, a female xenopus can produce between 1,000 and 3,000 eggs, depending on the particular species.

The frog is genetically surprisingly similar to humans, which means that scientists can model human disease in this amphibian and replace the use of higher sentient species.

Unlike humans and other mammals, the xenopus’s offspring grow outside of the body. Although the eggs are initially opaque, within a couple of days they become transparent, enabling researchers to see how the tadpole grows at all stages of development.

What do we study?

Can we obtain heart or brain cells from skin or blood cells?
Professor Sir John Gurdon was awarded the Nobel Prize in Physiology or Medicine 2012 for his work, carried out using xenopus, which showed that it is possible to take a nucleus from another cell (in this case, a tadpole cell), insert it into a frog egg cell and fertilise the egg, and that this would then grow into a healthy offspring – the principle that was later used by researchers to clone Dolly the Sheep from an adult cell.

Now, Professor Gurdon is continuing his work to find ways of obtaining embryo cells from the cells of an adult. The eventual aim is to provide replacement cells of all kinds starting from easily obtainable cells of an adult individual, for example to obtain spare heart or brain cells from skin or blood cells. The important point is that the replacement cells need to be from the same individual, to avoid problems of rejection and hence the need for immunosuppression. His team is trying to identify the molecules and mechanisms by which eggs can reverse the process of specialisation, so as to derive embryo cells from adult skin cells.

Image: Xenopus laevis (Brian Gratwicke)